Sharks of Onslow County

Category: Other Marine Species

Reading the Stories Written in Onslow County Shells

Walk almost any beach in Onslow County after the tide has gone out, and before long you’ll find yourself looking down.

A tiny orange shell catches your eye. Just inches away lies another, almost perfectly white. Nearby, a third carries shades of lavender and gray. An old, thick oblong shell rests beside them. A smooth round shell glistens in the afternoon sun while the heavy spiral of another waits half buried in the sand.

It feels like someone scattered an artist’s palette of Onslow County shells across the beach.

You notice how they are all so different and wonder why there are so many different colors.

It’s a simple question, but the answer reaches far beyond color.

Every shell on this beach is the product of millions of years of evolution solving the challenges of this particular coastline. Their colors, shapes, textures, thickness, and even the places we find them are all clues left behind by the animals that built them (Vermeij, 1974).

The shell isn’t simply something an animal lived in.

It is a record of how it survived.

And long after the animal is gone, the coast continues adding to that story.

The First Author

Every shell begins with a living animal.

Before a shell becomes a beach treasure, it is the home of a living animal. Hidden beneath the shell’s edge, the mantle quietly writes the shell one layer at a time throughout the animal’s life. | Image credit: A. Mitchell

Hidden just beneath the edge of the shell is a thin layer of tissue called the mantle. If the shell were a book, the mantle would be its author. Throughout the animal’s life, it slowly writes the shell, depositing layer upon layer of calcium carbonate, proteins, pigments, and minerals (Marin, 2012; Lowenstam & Weiner, 1989). As the animal grows, the shell grows with it.

A mollusk’s mantle doesn’t build a shell all at once. As the mantle grows, it continuously deposits new layers of calcium carbonate along the shell’s edge. Small differences in growth over time produce the incredible variety of shell shapes we find along the Carolina coast. | Figure credit: D. Cossins

The process is remarkably slow. The process is remarkably slow. A shell is never built all at once. Instead, it is written over days, months, and often years. Growth may speed up when food is plentiful, slow during winter or periods of stress, and even record repairs after surviving an attack from a predator (Marin, 2012). Every new layer becomes part of the shell’s permanent record.

Those layers preserve more than the shell itself. In many species, they preserve part of the animal’s history. While shells do not record age as neatly as the annual rings of a tree, scientists can often read growth bands to estimate an animal’s age, identify periods of environmental stress, and even reconstruct past water temperatures, salinity, and other environmental conditions from the chemistry locked inside the shell (Caudle et al., 1981).

Those orange, purple, yellow, white, and brown colors are not painted onto the shell after it forms.

The mantle creates them.

The remarkable variety of colors and patterns found in coquina clams begins with the mantle. As the shell grows, pigments deposited layer by layer create the unique combinations that make each shell part of its own story. | Image credit: S. Bland

As it deposits each new layer of shell, it also deposits tiny amounts of pigments. Different species produce different pigments, while genetics determine much of the pattern. Nutrition, water chemistry, and the environment can influence exactly how those colors are expressed, making every shell as individual as the life that built it. Before the shell ever reaches the beach, much of its color has already been written into its structure (Marin, 2012).

Sometimes the shell also records when conditions are less than ideal. Pollution, disease, and changing ocean chemistry can all influence how well a mollusk builds its shell. Ocean acidification, for example, can make it more difficult for some species to produce thick, durable shells, leaving behind thinner walls or irregular growth. The shell becomes more than protection. It preserves clues about the world the animal experienced while it was alive (Marin, 2012).

But color is only one chapter of the story.

The shell’s shape, thickness, texture, strength, and even the way it grows reveal something even more important.

They reveal the problems the animal had to solve.

Different Coastlines Ask Different Questions

At first glance, shells seem wonderfully diverse.

Look a little closer, and a pattern begins to emerge.

No two coastlines ask life to survive in exactly the same way.

A rocky Pacific shoreline presents different challenges than a tropical coral reef. The cold waters of New England ask different questions than the warm Gulf of Mexico. Even along the Atlantic Coast, the barrier islands, estuaries, marshes, and surf zones of coastal North Carolina create conditions unlike almost anywhere else (Riggs et al., 1995).

No two coastlines ask life to survive in exactly the same way. A shell-covered beach in La Jolla, California (left) reflects a different geologic history, wave energy, sediments, and marine communities than the shell-rich shores of Onslow County, North Carolina (right). Over millions of years, those different conditions shaped different evolutionary solutions. | Image credit: TraipseAndTiptoe (left); and T. Ruff (right)

Different predators.

Different sediments.

Different tides.

Different temperatures.

Different food.

Different problems.

Over millions of years, evolution answered those questions with different shells.

What washes onto our beaches is not random.

It is the collection of species whose solutions worked here (Vermeij, 1974).

Those questions have not remained the same. Over the past 66 million years, North Carolina’s shoreline has advanced and retreated countless times as sea levels rose and fell, rivers shifted course, climates warmed and cooled, and ancient oceans repeatedly flooded what is now dry land (Moslow & Heron, 1981; Riggs et al., 1995). Some shell designs disappeared as habitats changed. Others changed surprisingly little because the solutions they evolved continued to work.

Many of the shells we collect today belong to lineages that stretch back millions of years. Although the species themselves may have changed, the challenges of burrowing into sand, clinging to hard surfaces, escaping predators, or hunting beneath the seafloor have remained remarkably familiar. Every shell scattered across our beaches represents another evolutionary solution that succeeded on this coastline (Vermeij, 1974).

One Mineral. Many Solutions.

Every shell you’ll find on our beaches begins with the same basic building material: calcium carbonate.

It is one of the most common minerals used by living organisms, and yet from this single material evolution has produced an astonishing variety of designs (Lowenstam & Weiner, 1989; Marin, 2012).

An eastern oyster (left) and hard clam (right) are built primarily from the same mineral—calcium carbonate. Yet evolution shaped that shared material into two very different solutions for surviving along the Carolina coast. | Image credit: Original creator unknown

Some shells become thick fortresses.

Others become lightweight burrowing tools.

Some protected animals that never move more than a few inches in their lives.

Others belong to predators that spent their days hunting beneath the sand.

The mineral stayed the same.

The problems did not.

Each shell scattered across our beaches represents a different solution to surviving along the Carolina coast.

Oysters

Few animals have shaped North Carolina’s coast more than the eastern oyster (Crassostrea virginica).

An oyster’s greatest challenge is that it cannot run.

Once it settles as a young larva, it cements itself permanently to a hard surface. Every predator, every storm, every changing tide must be faced exactly where it stands. Escape is no longer an option (Grabowski & Peterson, 2007).

Its solution was to build.

Layer upon layer, the mantle produces an irregular shell that grows thicker and stronger over time. Those rough edges, deep ridges, and uneven shapes are not imperfections. They strengthen the shell and help neighboring oysters lock together into reefs far stronger than any one oyster could build alone (Marin, 2012).

That reef becomes one of the most important habitats along our coast. Small fish hide among the crevices. Juvenile shrimp and crabs find shelter between the shells. Countless worms, anemones, barnacles, and other invertebrates settle on its surface, creating an entire community built upon generations of oysters (Beck et al., 2011; Grabowski & Peterson, 2007).

An eastern oyster reef begins one shell at a time. As generations of oysters cement themselves to one another, they create living reefs that shelter fish, crabs, shrimp, worms, and countless other organisms along the Carolina coast. | Image credit: J. Utrup

People often describe oysters as filtering the water.

They do.

But filtering water is simply how an oyster feeds itself.

The reef—the ecosystem we admire—is what emerges from millions of oysters solving the same survival problem together (Grabowski & Peterson, 2007).

The shell reflects that strategy.

Not speed.

Not camouflage.

Permanence.

Coquina Clams

Walk a few hundred yards toward the surf, and the questions change.

Here the sand never stops moving.

Every incoming wave buries.

Every outgoing wave uncovers.

An oyster’s strategy would fail here.

The coquina clam (Donax variabilis) answered a different problem.

Its shell is small, smooth, lightweight, and remarkably varied in color. Instead of resisting the waves, it moves with them, burrowing into wet sand almost as quickly as each wave retreats. The same shifting surf that would bury many animals has become the rhythm that guides its entire life (Baird, 1960; Manning, 2003).

Those endless combinations of oranges, whites, yellows, purples, grays, and intricate patterns are among the most colorful shells found on our beaches. While their exact patterns are largely determined by genetics, that incredible variety may also help break up the outline of individual clams against the constantly changing mosaic of wet sand, shell fragments, and reflected sunlight.

No two coquina clams are exactly alike. The mantle deposits pigments into each new layer of shell, creating the remarkable variety of colors and patterns that make these tiny surf clams among the most recognizable treasures on Carolina beaches. | Image credit: A. Thamodharan

Coquinas don’t build habitat the way oysters do.

Instead, they move energy through the surf.

They filter microscopic algae and organic matter from the water before becoming food for fish, cownose rays, ghost crabs, gulls, and the flocks of sanderlings that race along the edge of the waves. During migration, entire flocks may depend on these tiny clams to fuel journeys spanning thousands of miles (Baird, 1960; Manning, 2003).

The shell reflects that role. Light enough to move with the surf. Strong enough to survive being tumbled by waves. Small enough to disappear beneath the sand in seconds.

Not because evolution intended to feed birds.

But because surviving here required an entirely different solution.

Moon Snails

Not every shell on our beaches belonged to prey.

Some belonged to hunters.

Moon snails (Neverita duplicata) spend much of their lives hidden beneath the sand, slowly searching for buried clams and other shellfish. Their large, muscular foot does most of the digging while their smooth, rounded shell slips easily through loose sediment without catching on sand or shell fragments (Grant, 2024; Witherington & Witherington, 2011).

The smooth, rounded shell of an Atlantic moon snail is more than beautiful. Its shape allows the animal to move easily through loose sand as it searches beneath the seafloor for buried clams and other shellfish. | Image credit: mattkeene1, iNaturalist

Finding prey is only half the challenge.

Opening another shell is the difficult part.

Rather than smashing their prey, moon snails use a remarkable combination of chemistry and patience. Holding the shell securely with their foot, they slowly rasp away the calcium carbonate with a rough tongue called a radula while releasing acidic secretions that soften the shell beneath. Hours later, all that remains is a nearly perfect circular hole (Grant, 2024).

Beachcombers often find these drilled shells without realizing they are looking at the evidence of one mollusk successfully hunting another.

The shell reflects that hidden lifestyle. Rounded instead of angular. Smooth instead of heavily sculptured.

Built not for resisting crashing waves, but for quietly moving through the sand in search of its next meal.

Whelks and Conchs

Some shells tell the story of animals that stayed in one place.

Others belonged to animals that never stopped moving.

Whelks and conchs are active travelers, spending much of their lives crawling across sandy bottoms, oyster reefs, and shallow estuaries in search of food. Their heavy spiral shells protect a surprisingly muscular animal capable of covering far more ground than most people realize (Magalhaes, 1948; Walker et al., 2008).

The long spiral of a lightning whelk shell provided room for a surprisingly muscular animal. Built for an active life spent searching the seafloor, the shell offered both protection from predators and space for the powerful foot and feeding structures that made whelks successful hunters and scavengers. | Image credit: gilbertgrant, iNaturalist

For many whelks, the challenge isn’t finding food.

It’s getting through another shell.

Using a long, extendable feeding tube called a proboscis, many species pry apart or drill into clams, oysters, and other shellfish. Others scavenge animals that have already died, recycling nutrients that would otherwise remain locked away on the seafloor. Along the way, they become prey themselves for larger fish, rays, sea turtles, and even other whelks (Magalhaes, 1948; Askin et al., 2022).

Their shells reflect that roaming lifestyle. Thick walls help defend against predators while the long spiral provides room for a muscular body that can withdraw deeply into the shell when threatened. Even the wide opening allows that powerful foot to extend far enough for steady movement across shifting bottoms.

The shell isn’t simply a home.

It is armor carried wherever the animal goes.

Scotch Bonnet

North Carolina’s state shell rarely washes ashore as often as oysters or coquinas, making each discovery feel a little more special.

The Scotch bonnet (Phalium granulatum) spends much of its life offshore on sandy bottoms where waves are gentler than those crashing onto the beach. There, it hunts worms and other small invertebrates hidden beneath the sediment (Grant, 2024; Witherington & Witherington, 2011).

Its shell reflects a different set of priorities.

Instead of thick ridges or heavy armor, the Scotch bonnet carries a smooth, rounded shell with delicate markings that blend surprisingly well among sand, shell fragments, and scattered gravel. The shell protects the animal while remaining compact enough for a life spent moving slowly across the seafloor (Grant, 2024; Witherington & Witherington, 2011).

North Carolina’s state shell, the Scotch bonnet, reflects a quieter life beyond the breakers. Its smooth, rounded shell protects a predator that spends much of its life moving across sandy seafloors in search of marine worms and other small invertebrates. | Image credit: gilbertgrant, iNaturalist

For many beachcombers, finding a Scotch bonnet feels like finding a rare treasure.

For the animal that built it, the shell was simply another successful solution to living in a quieter part of North Carolina’s coastal waters. One lived beyond the breakers where survival depends less on enduring crashing surf and more on navigating a different world beneath the waves.

Scallops

Not every shell relies on strength.

Some rely on surprise.

Unlike oysters, scallops – the Atlantic bay scallop (Argopecten irradians), Atlantic calico scallop (Argopecten gibbus), and the Atlantic sea scallop (Placopecten magellanicus) – never permanently attach themselves to the bottom. Although they often rest quietly on the seafloor, they can escape danger by doing something few other shellfish can.

They swim (Grant, 2024).

When threatened by sea stars, crabs, or other predators, a scallop rapidly opens and snaps its shell shut. Each clap forces a jet of water from the hinge, propelling the animal through the water in a series of short bursts (Grant, 2024).

The broad, fan-shaped shell makes this possible. Strong muscles close the shell with remarkable force while the evenly shaped valves help direct each burst of water.

The broad, fan-shaped shell of an Atlantic bay scallop reflects one of the most unusual escape strategies among shellfish. Rather than relying solely on armor, scallops can rapidly clap their shells together, jetting water from the hinge to swim away from predators. | Image credit: lmcconachie, iNaturalist

Scallops also possess dozens of tiny blue eyes along the edge of their mantle. Individually, each eye forms only a simple image, but together they help detect movement and approaching predators long before contact is made (Grant, 2024; Palmer et al., 2017).

Their shell reflects a life balanced between resting quietly on the bottom and escaping at precisely the right moment.

Sometimes survival isn’t about building thicker armor.

It’s about knowing when to leave.

Augers

Some predators chase.

Others wait.

Eastern augers (Neoterebra dislocata) spend much of their lives buried beneath the sand with only a small portion of their bodies exposed. From this hidden position they search for marine worms moving through the sediment (Grant, 2024; Witherington & Witherington, 2011).

Their shells are long, narrow, and remarkably slender. That shape isn’t simply beautiful.

The long, tapered shell of an auger snail reflects a life spent beneath the sand. Its slender shape allows the animal to move through loose sediment with little resistance as it hunts marine worms hidden below the surface. | Image credit: gmskupien, iNaturalist

It allows the animal to slip easily into the sand while occupying very little space as it burrows. Instead of pushing aside large amounts of sediment, the shell moves through it with surprisingly little resistance (Grant, 2024; Witherington & Witherington, 2011).

Many augers also possess venom that helps subdue their prey before swallowing it whole. Their role is quiet and rarely seen, yet they help regulate populations of worms living beneath the surface while becoming prey for larger animals in turn (Grant, 2024; Witherington & Witherington, 2011).

Like so many shells on our beaches, the auger’s design reflects an animal most people never realize is there.

Hard Clams (Quahogs)

Not every shell has to choose between staying still and constantly moving.

Hard clams, or quahogs (Mercenaria mercenaria), do both.

Most of their lives are spent buried beneath the estuary bottom with only their siphons reaching the surface. Hidden beneath the sand, they filter microscopic algae and organic matter from the surrounding water while remaining safely out of sight of many predators. But if conditions change, they can slowly pull themselves through the sediment in search of a better place to live (MacKenzie & Tarnowski, 2018).

Their shell reflects that balance.

The thick shell of a hard clam, or quahog, reflects a life spent buried beneath the sand. Strong, tightly closing valves protect the animal from predators while allowing it to remain hidden as it filters microscopic food from the water. | Image credit: rimcdon, iNaturalist

Unlike the thin shell of a coquina built for speed or the irregular fortress of an oyster reef, a hard clam carries a thick, rounded shell designed to withstand pressure from above. Crabs, rays, and whelks all present different dangers, and the clam’s tightly closing valves provide its best defense against them (MacKenzie & Tarnowski, 2018).

That shell also records an unusually long life. Some North Carolina hard clams live for decades, adding new growth each year as the mantle slowly deposits another layer of shell. Scientists can often estimate a clam’s age by studying those growth bands, much as foresters study the rings of a tree, although the story written in a shell is often more complicated than counting one band for every year (Caudle et al., 1981).

Like oysters, hard clams improve water quality simply by feeding.

Their shell reflects patience.

Rather than escaping danger, it protects an animal that survives by remaining hidden beneath the bottom.

Cockles

Some shells solve a different problem altogether.

Instead of burrowing deeply and staying put, cockles, like the giant Atlantic cockle (Dinocardium robustum), live much closer to the surface where waves, shifting sand, and hungry predators are constant challenges (Grant, 2024; Douglass, 1989).

Their answer is written in a shell unlike almost any other.

The deeply ribbed shell of an Atlantic cockle is more than decoration. Its strong ribs add strength without excessive weight, helping the animal withstand shifting sand and the pounding energy of the surf while it lives just beneath the surface. | Image credit: tceaton, iNaturalist

Strong, radiating ribs run from the hinge to the shell’s edge, strengthening the shell without making it excessively heavy. Those ridges act much like the folds pressed into a piece of cardboard, adding remarkable strength while using relatively little additional material. The rounded shape also helps distribute pressure from predators trying to crush the shell (Grant, 2024; Douglass, 1989).

Although cockles can burrow, many rely on quick movements near the sediment surface, even using their muscular foot to hop short distances when threatened.

The shell reflects that lifestyle. Not as smooth as a coquina. Not as heavy as a hard clam.

Instead, it balances strength with mobility in the constantly changing surf and shallow subtidal sands (Grant, 2024; Douglass, 1989).

Lion’s Paw Scallop

Few shells stop beachcombers in their tracks quite like a lion’s paw scallop (Nodipecten nodosus).

With its brilliant orange, red, or deep coral colors and bold knobby ribs, it hardly resembles the quieter shells scattered around it.

The bold ribs and flared spines of a lion’s paw scallop are more than striking. They strengthen the shell while helping it blend among oysters, rocks, and shell-covered bottoms, where this scallop spends its life. | Image credit: ahoppermann, iNaturalist

Its appearance reflects where it lives.

Unlike bay scallops that spend much of their lives on relatively shallow bottoms, lion’s paws are usually found farther offshore in deeper water where they rest among shell bottom, reefs, and hard substrates. Their heavy ribs strengthen the shell while making it more difficult for predators to crush (Rupp et al., 2005).

Like other scallops, lion’s paws can swim by rapidly clapping their shells together, jetting water from the hinge to escape danger. But unlike the delicate bay scallop, the lion’s paw invests more heavily in protection than speed, reflecting the different challenges of life in deeper coastal waters (Grant, 2024; Rupp et al., 2005).

Finding one washed onto an Onslow County beach usually means the ocean has done some of the traveling for it. Storms, strong currents, and changing tides occasionally carry these offshore shells landward, where they become one of the most treasured discoveries a beachcomber can make (Grant, 2024; Rupp et al., 2005).

The shell reflects both rarity and resilience.

Not because the animal evolved to become a collector’s prize.

But because its offshore home demanded a different solution than the shells living closer to shore.

The Coast Becomes the Second Author

The mantle stops writing the moment the animal dies.

The Carolina coast does not.

What remains is no longer simply a shell. It becomes part of an entirely different story, one written by waves, tides, storms, sunlight, other living organisms, and time itself (Kidwell & Bosence, 1991).

In many ways, the shell begins a second life.

Every tide carries it somewhere new. It may tumble through the surf for years before finally washing ashore. It may become buried beneath shifting sand, exposed again by the next storm, or carried into an estuary where the water, chemistry, and even the color of the bottom are entirely different from where the animal once lived (Kidwell & Bosence, 1991).

The shell that catches your eye today may have traveled miles from the habitat where it was first written.

When the Coast Changes the Color

Not every color you see was created by the animal.

Many are added later.

A bright shell left exposed on the open beach gradually fades as sunlight breaks down the pigments once produced by the mantle. Over time, oranges soften, purples become pale, and richly patterned shells may bleach almost completely white (Kidwell & Bosence, 1991).

Carry that same shell into a quiet salt marsh, and the story changes.

The dark mud beneath the marsh is rich in decaying plant material, bacteria, and low-oxygen sediments. As shells rest there, they often become stained shades of gray, brown, or nearly black. Beachcombers are sometimes surprised to find black shells scattered along an estuary, but the color usually comes from the marsh itself rather than the animal that built the shell.

Elsewhere, iron-rich sediments may leave rusty orange stains. Thin films of algae can tint shells green, while mineral deposits and other chemical reactions slowly alter their appearance over months or years (Kidwell & Bosence, 1991).

The mantle wrote the original color into both of these lion’s paw shells. After the animals died, the Carolina coast continued writing the story. Sunlight, marsh sediments, algae, minerals, and other marine organisms gradually changed their appearance long after the shells were formed. | Image credit: nikole14, iNaturalist

Sometimes those changes tell us almost as much as the shell itself.

A bright, colorful shell may have spent little time exposed after the animal died.

A heavily bleached shell may have rolled through the surf for years.

A blackened shell may have rested quietly in marsh mud before tides carried it back onto the beach.

The coast has been editing the story.

Every Scar Has a Story

Color is only one way the coastline leaves its mark.

Look closely and you’ll often find scars, chips, holes, and rough edges that formed long after the animal was gone.

Rolling waves grind shells against sand and one another, slowly rounding sharp edges until they become smooth enough to fit comfortably in the palm of your hand. Storms break larger shells into fragments before carrying them into entirely different habitats (Kidwell & Bosence, 1991).

Barnacles cement themselves onto abandoned shells. Bryozoans spread across their surfaces like delicate lace. Boring sponges and marine worms slowly tunnel through the calcium carbonate, creating tiny chambers where other organisms eventually move in (Kidwell & Bosence, 1991).

Even after death, the shell continues providing shelter. Some become homes for hermit crabs. Others become attachment sites for young oysters beginning reefs of their own. Small fish hide among broken shell piles while countless microscopic organisms colonize every available surface (Kidwell & Bosence, 1991) .

A shell’s story doesn’t end when the animal dies. Empty shells become homes for hermit crabs, extending their usefulness long after the original builder is gone. | Image credit: A. Mitchell

The shell no longer protects the animal that built it.

Instead, it begins supporting an entirely new community.

Eventually, Even Shells Become the Beach

The Carolina coast wastes very little.

As shells continue breaking apart, the fragments become smaller and smaller until many are no longer recognizable as shells at all.

They become part of the sand (Moslow & Heron, 1981; Riggs et al., 1995).

On many North Carolina beaches, tiny pieces of shell are mixed with quartz grains carried from the Appalachian Mountains by rivers over millions of years. Every handful of sand is a mixture of geology and biology, mountains and oceans, living animals and ancient rock (Moslow & Heron, 1981; Riggs et al., 1995).

Viewed under magnification, beach sand reveals countless tiny shell fragments mixed among mineral grains. Many of the shells we collect today will eventually weather into pieces so small they become part of the next generation of Carolina beaches. | Image credit: A. Mitchell

Even after the shell disappears, it remains part of the coastline.

Its story simply changes again.

Every Shell Has Two Authors

We often collect shells because they are beautiful.

Beauty is usually the first thing we notice. But it is rarely the most interesting thing they have to offer.

Every shell begins with a living animal whose mantle slowly writes a record of its life—its growth, its habitat, its challenges, and the evolutionary solution that allowed it to survive.

After the animal dies, the Carolina coast picks up the story.

Sunlight softens the colors. Marshes stain them. Waves polish them. Other animals bore through them, build upon them, and make them part of their own lives.

What you hold in your hand is no longer simply the remains of a mollusk.

It is a story with two authors.

One wrote the shell. The other never stopped editing it.

The next time you find a shell along the beaches of Onslow County, look beyond its color.

Notice the thickness. The curves. The ridges. The scars. The stains. The tiny holes.

Each one is a clue.

Each one is another sentence in a story that began with a living animal and continues with every tide that reaches our shore.

Every shell scattered across the beach carries two stories: one written by the animal that built it and another written by the Carolina coast long after the animal was gone. Every tide leaves behind another collection of those stories, waiting to be discovered. | Image credit: A. Thamodharan

References

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Williams, A. B., & Porter, H. J. (1971). A ten-year study of Meroplankton in North Carolina estuaries: Occurrence of Postmetamorphal bivalves. Chesapeake Science, 12(1), 26. https://doi.org/10.2307/1350499

Witherington, B., & Witherington, D. (2011). Seashells of Georgia and the Carolinas. Pineapple Press.

July 18, 2026
What’s in Tail? What the Shapes of Caudal Fins can tell us about a fish

Watch fish for more than a few minutes, and something begins to stand out.

They do not all move through the water the same way.

A school of mullet slips across a creek with steady, effortless motion. A red drum twists through flooded marsh grass, turning between oyster clumps where shrimp and juvenile crabs have nowhere left to hide. A southern flounder erupts from the sand where, a moment before, there seemed to be nothing at all. Farther offshore, a little tunny slices through baitfish near the surface, while a cownose ray appears to fly beneath the water with its long tail trailing quietly behind.

The water is the same.

The rules of physics are the same.

But each animal has answered those rules differently.

A fish’s tail is far more than the end of its body. It is a record of how that fish survives. It can reveal where the fish spends its time, how it captures prey, how it escapes predators, how much energy it can afford to spend moving, and the role it fills within the larger ecosystem.

Like wings on birds or feet on mammals, the tail, known as the caudal fin, carries the shape of a life lived in a particular place.

To read a tail is to begin reading how fish use the water differently.

Every Fish Faces the Same Challenge

Moving through water is expensive.

Water is nearly 800 times denser than air (Vogel, 1996). Every sweep of the body pushes against it. Every turn creates resistance. Every burst of speed requires energy that cannot later be used to grow, migrate, reproduce, or avoid becoming another animal’s meal.

No fish escapes those limits.

Instead, each species works within them.

A fish moves as muscles contract in waves along the body, transferring force toward the caudal peduncle, the narrow region where the body meets the tail (Borazjani & Daghooghi, 2013; Sfakiotakis et al., 1999). From there, energy reaches the caudal fin. Each sweep of the tail pushes against surrounding water, creating pressure differences and rotating vortices that help produce forward thrust (Borazjani & Daghooghi, 2013; Maia et al., 2021).

Before the tail ever pushes against the water the body has already done the work. The caudal peduncle is where that power is passed to the tail. | Image credit: Louisiana Department of Wildlife & Fisheries

The tail is where the body’s power meets the water.

Yet the same basic problem has produced many different solutions.

Some fish are built for steady cruising. Others are built for sudden bursts. Some rely on tight turns. Some barely use the tail in the way we expect at all.

There is no perfect fish tail.
There are only tails shaped by different lives.

A fish that spends its life crossing miles of open water faces different problems than one weaving through flooded marsh grass. A predator that depends on surprise needs something different than one chasing baitfish across the surface. Even the bottom itself asks different things of the animals that live there.

Every tail that follows is one answer to those demands.

The Tail Never Works Alone

It is easy to focus on the tail because it is the most visible part of the movement.

But no fish swims with its tail alone.

The body determines how much drag the fish creates. The muscles generate the force. The caudal peduncle channels that force into the tail. Pectoral fins stabilize, steer, brake, or produce lift. Even the stiffness of the body changes how efficiently motion travels through the water.

A tuna is not fast because of its crescent tail alone. Its narrow caudal peduncle, streamlined body, stiff swimming motion, finlets, and powerful muscle arrangement all work together to conserve energy while moving through open water.

A red drum is not shaped for that same kind of movement. Its broader body, muscular peduncle, and less deeply forked tail serve a different purpose in a different landscape.

A flounder’s tail only makes sense after the rest of the fish has flattened into the bottom.

A shark’s tail cannot be understood without its pectoral fins.

The tail is part of a system (Lauder & Drucker, 2004; Sfakiotakis et al., 1999).

And that system is built around how the animal earns its living.

Built to Cross Open Water

Away from oyster reefs, marsh grass, docks, and submerged roots, the water opens.

There are fewer places to hide.

Prey may be scattered across greater distances.

Movement becomes less about turning around obstacles and more about conserving energy across space.

Watch Spanish mackerel feeding from a pier in late summer and they rarely seem to stop moving. The same is true for little tunny exploding through bait schools just beyond the breakers. Their tails were never built for hovering over one patch of water. They were built for finding the next meal, wherever it happens to be.

Spanish mackerel, bluefish, Atlantic bonito, little tunny, and many jacks carry deeply forked or crescent-shaped tails (Lighthill, 1971; Song et al., 2020; Tack & Gemmel, 2022). Their narrow caudal peduncles and relatively stiff bodies limit unnecessary side-to-side motion, directing more of each tail beat into forward movement. The tall, narrow shape of the tail also reduces drag while allowing fish to maintain speed through repeated strokes.

Their speed is impressive.

But efficiency is the deeper story.

Out beyond the marsh and inlets, where prey may be separated by miles rather than feet, every unnecessary movement matters. A tail that saves a small amount of energy with each stroke can eventually become another mile traveled, another school of baitfish reached, another day survived.

In open water, the tail becomes a tool of endurance.

Built for Split-Second Decisions

The marsh asks something different.

As the tide rises, red drum move into flooded Spartina where shrimp, juvenile blue crabs, and small fishes scatter through stems and oyster clusters. Sheepshead pick around pilings and shell edges. Black sea bass patrol reefs where every ledge may conceal prey or danger. Oyster toadfish wait in crevices, relying less on pursuit than on the suddenness of their strike.

These fishes do not all carry identical tails or hunt in exactly the same way.

None of them needs to cross open water all day.

They need control.

Every oyster shell, grass stem, piling, and dock creates another obstacle. The fish that succeeds here is rarely the fastest. It is the one that can change direction before its prey—or predator—does.

Compared with the narrow crescents of open-water cruisers, rounded, truncate, and slightly emarginate tails move their broader bodies through water (Song et al., 2020; Tack & Gemmel, 2022). That creates more drag, but it also allows the fish to push hard against the water at low speeds, accelerate more quickly, stop abruptly, and turn within confined spaces. A broad, muscular caudal peduncle helps deliver power immediately rather than conserving energy over long distances.

Other fins join in. Pectoral fins brake and steer. The body bends around obstacles. The tail supplies the final shove that send the fish around an oyster clump or into a pocket of flooded grass.

In a maze of oyster reefs, roots, pilings and marsh grass, turning one body length tighter can matter far more than maintaining speed over ten miles.

This type of tail reflects that reality.

Built to Become the Bottom

Few fishes rewrite the body plan as dramatically as a southern flounder.

It does not begin life looking like the fish we recognize.

As a larva, it swims upright with one eye on each side of the head, shaped much like other young fishes drifting through the water column. Then the transformation begins.

One eye slowly migrates across the skull (Okada et al., 2003). The body flattens. Pigment concentrates on what becomes the upper surface. The fish settles onto one side and begins living as part of the seafloor (Midway et al., 2024).

Most people notice the eyes.

But the tail changed jobs, too.

A flounder does not need a tail built for constant cruising. It needs one capable of launching a body that has already disappeared. The fish may remain motionless on sand or mud until a shrimp or small fish comes close enough. Then the body bends, the tail snaps, and the flounder surges forward in a short, explosive burst before settling back into the bottom (Midway et al., 2024).

Its tail serves as surprise.

On an open sandy bottom, there may be no grass, reef, or submerged root behind which a predator can wait. The flounder solves that problem by matching the bottom beneath it, sometimes shifting its color and pattern as the surrounding sediment changes.

Rather than finding cover, the flounder became the cover.

Its tail became the spring that launches an attack from a place prey never realized was occupied.

Built for Places Others Cannot Reach

Some fish survive by entering spaces where others cannot follow.

American eels move through tidal creeks, undercut banks, submerged roots, culverts, marsh edges, and dark spaces beneath docks where a stiffer fish body would become a liability.

Their dorsal, caudal, and anal fins merge into one continuous ribbon (Stin et al., 2024). Instead of relying on distinct tail beats alone, waves of motion travel along much of the body, allowing the eel to bend through narrow openings and complex structure.

Speed is not the point.

Access is.

Yet, the same flexible body that lets an eel disappear beneath roots or slip through a flooded marsh also carries it across an ocean.

American eels hatch in the Sargasso Sea and reach the North American coast after drifting within ocean currents as transparent, leaf-shaped larvae (Secor, 2015; Tsukamoto, 2009). They enter estuaries as glass eels and gradually develop the long, muscular bodies that will carry them through tidal creeks, rivers, ponds, and wetlands.,

Years later, mature eels reverse that journey. They leave inland and coastal habitats and return toward the Sargasso Sea to spawn.

They do not cross ocean like tuna. Rather that holding most of the body stiff and driving a narrow tail rapidly from side to side, an eel sends broad waves of motion along its body (Stin et al., 2024). That swimming style creates more resistance at high speeds, but it remains effective over long distances and across changing environments.

One body design solves two very different problems: it allows the eel to move through open water, climb through a watershed, pass beneath roots and around obstructions; and the other allows it to eventually return to sea.

Its strength is not mastery of one kind of water. It is the ability to keep moving as the water changes. Flexibility opens doors that speed never could.

When the Tail Stops Being the Engine

At first glance, rays appear to have dramatic tails.

Atlantic stingrays, southern stingrays, and cownose rays all trail long, whip-like tails behind wide bodies moving through coastal waters, tidal creeks, sounds, and inlets.

But watch one closely and the story changes.

The tail is not doing most of the swimming.

The large pectoral fins are (Rosenberger, 2001).

Watch a cownose ray passing beneath the surface seems to fly through the water. Each pointed wing rises and falls in a smooth stroke, producing the thrust that carries the ray forward. It’s tail follows behind, sometimes so quietly that it appears almost disconnected from the movement of the animal.

Closer to the bottom, Atlantic and southern stingrays use their broad discs differently. Their pectoral fins ripple or undulate as they move over sand and mud, where they can settle into the sediment and wait nearly unseen. Once propulsion shifted from the tail to the expanded pectoral fins, the tail was no longer required to serve as the main engine (Rosenberger, 2001).

But it did not become useless.

These rays carry one or more serrated, venomous spines on or near the base of the tail. The spine is not used to hunt. It is defensive, capable of discouraging a shark or other predator that attacks from behind or above (Maia et al., 2012).

The placement of the tail also reflects how each ray lives. Bottom-dwelling stingrays can lift and swing it when threatened, especially when pressure from above traps the animal against the sediment. Cownose rays spend more time actively swimming with the tail streaming behind their wing-driven bodies.

The engine moved into the wings.

The tail was free to serve another purpose.

When Lift Matters

Sharks carry another kind of solution.

Unlike most bony fishes, sharks do not have a swim bladder to help regulate buoyancy (Maia et al., 2012). Their position in the water depends on several features working together: an oil-rich liver, body shape, pectoral fins, and the tail.

In many sharks, the upper lobe of the caudal fin is longer than the lower lobe. This heterocercal tail helps generate thrust while also influencing lift and body angle as the shark moves forward (Thomson, 1976; Maia et al., 2012). The pectoral fins, and in hammerhead sharks – their heads, help balance those forces, acting like underwater wings that stabilize the animal in the water column.

A shark’s tail and pectoral fins are not separate stories.

They are part of the same swimming system. But that system is adjusted for different lives.

A bull shark moving through a muddy estuary needs power at lower speeds and enough control to follow prey through channels, shorelines, and changing currents. A blacktip chasing anchovies near the breakers depends more heavily on speed and rapid changes in direction as a bait school folds and scatters around it. Atlantic sharpnose sharks remain active over sandy bottoms and within coastal food webs where they pursue fishes, shrimp, squid and other available prey.

Their tails share the same basic shark pattern, but they do not carry identical proportions. Differences in lobe length, stiffness, body shape, and musculature change how each species uses the pattern to transform into movement.

Farther offshore, the thresher shark pushes the design toward an extreme. Its greatly elongated upper tail lobe is not only part of the swimming system; it is also a hunting tool. The shark accelerates toward schooling fish and sweeps its tail through the water, gathering the school into a tighter pod to consume more fish at a time (Oliver et al., 2013).

Even among sharks, the tail is not one solution.

It changes as the shark’s habitat, prey, and method of hunting change with it.

Every Tail Has a Price

If one tail shape were truly best, fish would all look much more alike.

They do not.

Every tail carries a trade-off.

Evolution does not build perfect designs (Lauder & Drucker, 2004; Secor, 2015).

It builds workable compromises.

Every advantage comes with something surrendered. A narrow, deeply forked tail can conserve energy across open water but cannot push against the water at low speeds like a broad, rounded tail. A fish built to spin through marsh grass cannot match the endurance of a pelagic hunter. A flattened body and explosive tail make the flounder a nearly invisible ambush predator, but not a long-distance cruiser. The eel’s flexibility opens routes through an entire watershed, even though it cannot slice through water like a mackerel.

These are not failed versions of some ideal fish. They are specialists. Nature is full of specialists because environments reward specialists.

Each has inherited a way of moving that makes certain opportunities possible while placing others beyond reach. Over generations, the fish that moved well enough to feed, escape, migrate, and reproduce within a particular landscape passed that arrangement forward.

A tail is therefore more than a solution to water resistances. It is a compromise between everything an animal might do and the few things it must do well. Not a movement toward perfection – but towards belonging.

Reading the Water Differently

The next time you look at a fish, try not to begin with color.

Watch how it moves.

A steady glide across open water tells one story. A sudden turn among oyster shells tells another. A burst from the sand reveals a predator that survived by disappearing. A ray moving like a winged shadow reminds us that the tail is not always the engine. A shark’s movement shows how lift, thrust, and balance must work together in an animal without a swim bladder.

Long before we know a fish’s name, its movement has already begun telling us where it lives, how it hunts, how it escapes, and how it fits into the larger food web.

A tail gives us a place to begin..

It is the visible record of problems solved repeatedly: distances crossed, obstacles cleared, prey overtaken, predators avoided, and energy conserved..

Once we recognize these patterns, we no longer only see a fish passing through water.

We begin to see the life that shaped it.

By the time a fish passes from view, its tail has already revealed the story of the life it was built to live. | Image credit: Explore.org, Frying Pan Tower

References

Borazjani, I., & Daghooghi, M. (2013). The Fish tail motion forms an attached leading edge vortex. Proceedings of the Royal Society B: Biological Sciences, 280(1756), 20122071. https://doi.org/10.1098/rspb.2012.2071

Lauder, G., & Drucker, E. (2004). Morphology and experimental hydrodynamics of fish fin control surfaces. IEEE Journal of Oceanic Engineering, 29(3), 556-571. https://doi.org/10.1109/joe.2004.833219

Lighthill, M. J. (1971). Large-amplitude elongated-body theory of fish locomotion. Proceedings of the Royal Society of London. Series B. Biological Sciences, 179(1055), 125-138. https://doi.org/10.1098/rspb.1971.0085

Maia, A. M., Wilga, C. A., & Lauder, G. V. (2012). Biomechanics of Locomotion in Sharks, Rays, and Chimeras. In Biology of Sharks and Their Relatives (2nd ed.). CRC Press.

Midway, S. R., Scharf, F. S., Dance, M. A., Brown-Peterson, N. J., Ballenger, J. C., Beeken, N. S., Borski, R. J., Darden, T. L., Erickson, K. A., Farmer, T. M., Fincannon, A., Godwin, J., Graham, P. M., Green, J. L., Hershey, H., Kiene, D., Lee, L. M., Loeffler, M. S., Markwith, A., … White, S. B. (2024). Southern flounder: Major milestones and remaining knowledge gaps in their biology, ecology, and fishery management. Reviews in Fisheries Science & Aquaculture, 32(3), 450-478. https://doi.org/10.1080/23308249.2024.2341017

Okada, N., Takagi, Y., Tanaka, M., & Tagawa, M. (2003). Fine structure of soft and hard tissues involved in eye migration in metamorphosing Japanese flounder (Paralichthys olivaceus). The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology, 273A(1), 663-668. https://doi.org/10.1002/ar.a.10074

Oliver, S. P., Turner, J. R., Gann, K., Silvosa, M., & D’Urban Jackson, T. (2013). Thresher sharks use tail-slaps as a hunting strategy. PLoS ONE, 8(7), e67380. https://doi.org/10.1371/journal.pone.0067380

Rosenberger, L. J. (2001). Pectoral fin locomotion in Batoid fishes: Undulation Versus oscillation. Journal of Experimental Biology, 204(2), 379-394. https://doi.org/10.1242/jeb.204.2.379

Secor, D. H. (2015). Migration ecology of marine fishes. JHU Press.

Sfakiotakis, M., Lane, D., & Davies, J. (1999). Review of fish swimming modes for aquatic locomotion. IEEE Journal of Oceanic Engineering, 24(2), 237-252. https://doi.org/10.1109/48.757275

Song, J., Zhong, Y., Du, R., Yin, L., & Ding, Y. (2020). Tail shapes lead to different propulsive mechanisms in the body/caudal fin undulation of fish. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 235(2), 351-364. https://doi.org/10.1177/0954406220967687

Stin, V., Godoy‐Diana, R., Bonnet, X., & Herrel, A. (2024). Form and function of anguilliform swimming. Biological Reviews, 99(6), 2190-2210. https://doi.org/10.1111/brv.13116

Tack, N. B., & Gemmell, B. J. (2022). A tale of two fish tails: Does a forked tail really perform better than a truncate tail when cruising? Journal of Experimental Biology, 225(22). https://doi.org/10.1242/jeb.244967

Thomson, K. S. (1976). On the heterocercal tail in sharks. Paleobiology, 2(1), 19-38. https://doi.org/10.1017/s0094837300003286

Thomson, K. S., & Simanek, D. E. (1977). Body form and locomotion in sharks. American Zoologist, 17(2), 343-354. https://doi.org/10.1093/icb/17.2.343

Tsukamoto, K. (2009). Oceanic migration and spawning of anguillid eels. Journal of Fish Biology, 74(9), 1833-1852. https://doi.org/10.1111/j.1095-8649.2009.02242.x

Vogel, S. (1996). Life in moving fluids: The physical biology of flow (2nd ed.). Princeton University Press.

Wilga, C. D., & Lauder, G. V. (2002). Function of the heterocercal tail in sharks: Quantitative wake dynamics during steady horizontal swimming and vertical maneuvering. Journal of Experimental Biology, 205(16), 2365-2374. https://doi.org/10.1242/jeb.205.16.2365

July 11, 2026
How Sharks, Rays, and Ghost Sharks Read an Invisible Ocean

A shadow moves beneath the surface.

At first, it is only a darker shape inside darker water. Then the shape shifts, and the human mind does what it always does. It tries to make sense of what the eyes are seeing.

Fish? Ray? Shark? Something else?

We look harder. We search for a fin, a tail, a clear outline, some familiar clue that lets us name the animal before it disappears again. That is how we enter the ocean. We enter it as visual animals.

We rely on sight first.

On land, that makes sense. We look both ways before crossing a street. We recognize faces. We read signs. We notice color, distance, motion, and shape. Even when our other senses help us understand the world, sight usually leads the way.

But the ocean is not built for human sight.

Light bends and scatters. Sand clouds the water. Storms stir sediment. Tannins darken creeks and estuaries. Waves break the surface into fragments. A fish can vanish into shadow. A ray can disappear beneath one thin layer of sand. A shark can move through water we are staring directly into and still be almost impossible to see.

To us, the ocean often becomes less clear the moment we step into it.

To sharks, rays, skates, sawfish, and chimaeras, that same water is not empty. It is not silent. It is not blank.

It is filled with signals.

These animals belong to a group called chondrichthyans, fishes with skeletons made of cartilage instead of bone. Sharks, rays, skates, sawfish, and chimaeras all belong here. We often separate them by the way they look: sharks with their familiar fins and teeth, rays flattened against the bottom, skates moving quietly over sand, sawfish carrying a toothed rostrum, and chimaeras drifting through deeper water like something half-remembered from another age.

But they are connected by more than cartilage.

They share sensory worlds that are difficult for us to imagine because they include abilities we do not have in the same way. They use sight, smell, hearing, touch, and temperature, but they also read movement through the water with the lateral line. They detect weak electrical fields with ampullae of Lorenzini. They interpret the ocean through pressure, vibration, chemistry, contrast, motion, and life itself (Collin, 2012; Hart & Collin, 2015).

We may look into murky water and see almost nothing.

They may be reading an entire landscape.

The Ocean as a Different Kind of World

Sometimes, we do sense the world in ways that remind us we are not only visual.

A storm approaches, and some people feel pressure before the first drop of rain falls. Sinuses tighten. Migraines build. The air feels different. We walk into a dark room and suddenly sound becomes more important. A creak in the corner, a moving shadow, or a change in the air near our skin, these matter.

We still try to confirm everything with sight, but when sight weakens, the rest of the body steps forward.

Now imagine living in a world where sight is helpful, but never enough.

Water carries information differently than air. A fish swimming does not simply move from one place to another. It pushes water aside. A tailbeat sends movement outward. A struggling animal leaves a different pattern than a calm one. A crab moving under sand may be hidden from view, but its body is still alive. Muscles contract. A heart beats. Nerves fire. Gills pump. Chemicals dissolve and drift.

Every animal changes the water around it.

For chondrichthyans, that matters.

A shark does not have to wait until prey forms a perfect picture in front of its eyes. A ray does not need the seafloor to look busy in order for it to be busy. A skate does not need color to know the bottom is alive. A sawfish does not carry its rostrum only as a weapon. A chimaera in deep water does not move through darkness without information.

Their sensory systems allow them to gather information across different distances and conditions. Smell, hearing, vision, lateral line detection, and electroreception do not work as separate switches. They overlap, reinforce, and sometimes compensate for one another depending on habitat, prey, visibility, and behavior (Gardiner et al., 2014; Hart & Collin, 2015).

Their world is not less detailed than ours.

It is detailed differently.

Their world is not less detailed than ours.

It is detailed differently.

A Shark’s World

A shark moving through shallow water can be almost impossible to see until it is already there.

Its body color may match the shifting bottom. Sunlight breaks over its back. Ripples blur the outline. The water may be green, gray, brown, or blue depending on the tide, weather, and sediment. Even in clear water, the shark can appear as a shadow before it appears as an animal.

To us, the shark is barely more than a shadow. To the shark, the water is already full of information — movement, pressure, chemistry, and weak electrical signals that help it read the world before sight alone confirms what is there. | Image credit: D. Remmers

But the shark’s awareness does not begin when our eyes finally notice its shape.

Long before sight confirms what is nearby, other senses may already be gathering information. A fish moving ahead sends pressure changes through the water. A school changing direction creates a pattern of motion. A wounded or stressed animal moves differently than a calm animal. Muscle contractions and heartbeats create weak electrical fields. Odors move through the water as chemical trails.

To us, the ocean may look open.

To a shark, it is full of clues.

The lateral line runs along the body and head and helps detect movement, vibration, and changes in water flow. It is not vision, but it can reveal that something nearby is moving. It can help an animal sense direction, intensity, and disturbance (Webb, 2023).

The ampullae of Lorenzini add another layer. These small, jelly-filled pores are concentrated around the head and snout. They detect weak electrical fields produced by living animals. This is especially useful at close range, when prey is hidden, when light is low, or when the final decision about an object must be made (Bellono et al., 2017; Hart & Collin, 2015).

A hammerhead makes this easier to picture.

Its wide head may look strange to us, but that shape spreads sensory structures across a broader surface. Moving over the bottom, a hammerhead can sweep its head across the sand. A buried ray may be invisible to human eyes. To the shark, the sand may not be silent at all.

This is where our imagination reaches its limit.

We can compare electroreception to the feeling of standing near an electrical charge or sensing the strange energy in the air during an intense lightning storm. But even that comparison is weak. We do not move through the world constantly reading tiny electrical fields from other living bodies.

Sharks do.

Their world is not a human picture with extra details added. It is a different kind of picture altogether.

Sight Still Matters

Sharks have eyes, and those eyes matter.

They detect contrast, motion, light, shadow, and shape. Many sharks are well suited for low-light conditions. Some have reflective structures behind the retina that help make better use of dim light. This is part of why shark eyes may appear to glow when light catches them underwater. Vision is one piece of a broader sensory strategy that changes by species, habitat, and ecological role (Collin, 2012; Hart & Collin, 2015).

But shark vision is not human vision.

Humans rely heavily on color. We use it to separate objects, judge ripeness, read warning signs, choose clothing, and notice differences in our surroundings. Sharks appear to rely less on color and more on contrast, brightness, movement, and shape. They only have one type of cone photoreceptor with many rods. This makes them more likely to be color blind or have very limited color discrimination (Hart et al., 2019).

That does not mean sharks see poorly.

It means color may not be the priority in their world.

In water, color disappears with depth and distance. Red fades quickly. Light changes constantly. Suspended particles blur edges. A fish flashing silver, a silhouette against the surface, or a sudden burst of movement may matter more than whether something is red, green, or blue.

A shark’s visual world may be built more from shadow, contrast, motion, and form than from color.

This is important when we talk about shark-human encounters. A swimmer, surfer, or splashing person at the surface is not being interpreted through human categories. The shark is not thinking “person.” It is receiving a mixture of signals: movement, vibration, silhouette, chemical traces, electrical fields, contrast, and the surrounding activity of fish or bait.

Sometimes, those signals may be confusing.

The phrase “mistaken identity” is often used to explain shark bites, but it should be used carefully. It does not explain every bite. It does not mean sharks are foolish. It does not mean they are unable to tell anything apart. It means that, in some situations, the clues available to the shark may overlap with the clues produced by prey. This is why some human silhouettes at the surface can resemble seal and sea lion prey to a shark, especially when viewed from below and under certain movement conditions (Ryan et al., 2021).

We know a version of this ourselves.

Walk through a dark house at night and hear something move in the corner. Your eyes search for shape. Your ears sharpen. Your body tenses before your mind has enough information. You move closer. Maybe you speak into the darkness. Maybe you reach out with your hand or nudge with your foot.

Then the light turns on, and the intruder becomes a chair with a jacket over it.

You were not hunting the chair.

You were investigating a signal you did not fully understand.

A shark does not have hands. Its fins move it through the water, but they do not investigate the way our fingers do. Its mouth becomes one of the ways it tests the world. That does not make the animal cruel or mindless. It means its body solves a sensory problem differently than ours does.

For people, that difference can be dangerous. An investigative bite can still cause serious injury. But it is not the same thing as a shark deciding humans belong on the menu.

Most of the time, we do not match the full pattern of shark prey.

We smell different. We move differently. We do not behave like fish, rays, turtles, seals, or other natural prey. But in the wrong place, at the wrong time, with the wrong signals around us, we can become part of a confusing sensory scene.

This is why swimming near active fishing, bait, chum, or dense schools of baitfish matters. The shark is not being summoned by evil intent. It is following information.

The ocean is speaking in the language it knows.

The Ocean as Touch and Sound

A school of fish turns all at once.

There is no visible leader. No signal we can see. One moment the school moves in one direction, and the next it shifts like one silver body. Each fish keeps its place without crashing into the others. The turn happens faster than sight alone seems able to explain.

This is one of the easiest ways to understand the lateral line.

Fish do not only see their neighbors. They feel the water their neighbors move. Each tailbeat, each change in direction, each surge away from danger creates tiny changes in water motion. Those changes travel across the bodies of nearby fish.

The lateral line detects those movements.

This sensory system is found in many fishes, not only sharks and rays. It helps animals orient in currents, avoid obstacles, respond to predators, follow prey, and move together in groups. It turns water into a kind of touch-field. The structure and function of the lateral line vary across fishes, but its role in detecting water motion is central to how aquatic animals interpret movement around them (Webb et al., 2023).

In sharks, this sense is closely tied to the way sound and vibration move through water. We often think of hearing as something that happens only through ears, but underwater, the whole body can become part of how an animal detects vibration. The lateral line helps a shark feel nearby water movement across its body, while the inner ear detects sound and orientation. Together, these systems make the shark’s body seem less like a body moving through water and more like an instrument tuned to it (Collin, 2012; Hart & Collin, 2015; Webb, 2023).

For a shark, this means the ocean is never simply open space.

It has texture.

A mullet swimming calmly leaves one kind of disturbance. A frightened fish leaves another. A crab moving across the bottom creates a different pattern than a shrimp flicking backward. Waves break. Boat motors pulse. Rain hits the surface. Feet shuffle through sand. A fish struggles on a line. A school turns.

Each movement changes the water.

We might stand at the edge of an inlet and see only ripples. A shark, ray, or skate moving through that same water may sense layers of motion overlapping one another. Some signals fade into background noise. Others stand out.

A calm fish and a frantic fish do not write the same message.

Along the Onslow County coast, this matters. Our nearshore waters are not always clear. Wind, tide, storms, suspended sand, tannins from creeks, plankton blooms, and wave energy all change visibility. Animals living here cannot depend on sight alone in a world where the water can cloud overnight.

A shark does not need a perfect view to know something is moving.

A ray does not need to see every small animal beneath it to know the bottom is alive.

A fish in a school does not need to wait for its neighbor to bump into it before turning.

Water carries the conversation.

The Hidden Electricity of Living Things

The sandy bottom can look blank.

A flat stretch of seafloor may seem empty to us, especially when nothing obvious moves. But beneath that surface may be worms, clams, crabs, shrimp, small fish, or rays. Some are hiding. Some are resting. Some are feeding. Some are waiting for the tide to shift.

To our eyes, they disappear.

To an animal with electroreception, hidden does not always mean gone.

Ampullae of Lorenzini allow sharks, rays, skates, sawfish, and chimaeras to detect weak electrical fields. These fields are extremely small, but they are part of what living bodies produce. Muscles contract. Hearts beat. Nerves fire. In saltwater, and especially at close range, those signals can become useful information (Bellono et al., 2017; Collin, 2012).

The sand may cover the animal.

It does not erase it.

This is especially important for animals that feed along the bottom. A shark searching a flat may combine smell, movement, vision, and electroreception. A ray may use similar signals to locate prey in sediment. A sawfish carries this ability into one of the strangest-looking structures in the sea.

Electroreception also reminds us that the ocean is not only a visual habitat.

It is a habitat of fields and traces.

We are used to thinking an animal is hidden when we cannot see it. But concealment depends on who is looking, and how.

A crab hidden from a bird may not be hidden from a ray.

A ray hidden from us may not be hidden from a hammerhead.

A fish buried beneath sand may still be detectable to a predator passing overhead.

This does not make the ocean more frightening.

It makes it more alive.

A Ray’s World

A stingray resting in shallow water can vanish beneath a thin covering of sand.

Only the eyes may remain visible. Sometimes even those are difficult to see. The body becomes part of the bottom: a soft outline, a slight rise, a place where the sand seems smoother than the sand around it.

To us, a buried ray may feel like a surprise.

To the ray, the world is still open.

Its eyes sit high on the body, watching the water above. Its mouth is underneath, positioned for feeding along the bottom. Its spiracles allow water to move across the gills while the animal rests or feeds close to the seafloor. Its lateral line and electrosensory system help detect movement and electrical signals nearby (Bedore et al., 2014; Collin, 2012).

The ray does not need to see the world exactly as we do.

It lives in layers.

Above, there may be predators, shadows, swimmers, boats, birds, and changing light. Below and around it, there may be worms, shrimp, crabs, clams, and small fish hidden in or on the sediment. A ray’s flattened body makes sense in this in-between place. It is shaped for bottom life, but it is not cut off from the water column above it.

Its eyes are important, but they are not everything.

Rays can detect contrast, shape, motion, and orientation. Some rays may have stronger color discrimination than sharks. Some also have a reflective layer in the eye, the tapetum lucidum, that helps make better use of dim light (Hart et al., 2019). We often compare this to the eye shine seen in cats and other animals at night.

But a ray buried in sand is not simply waiting with its eyes.

It is reading pressure. It is reading smell. It is reading electrical traces from animals moving nearby. It is receiving information through more than one doorway.

This is why the stingray shuffle matters.

A stingray spine is not used to chase people. It is a defense. When a ray is stepped on or startled from above, the spine can rise quickly. The injury is real, but the behavior is not personal. The ray is responding to pressure and threat in the only way its body allows.

A shuffled foot gives warning.

It tells the hidden animal that something large is moving through the sand and gives it a chance to leave before contact happens.

That small human behavior recognizes something important: the shallow edge is shared space.

We may be wading through it.

The ray may be living in it.

A Skate’s World

Skates are often confused with rays.

From above, the difference may not seem important to a casual observer. Both are flattened. Both move close to the bottom. Both can disappear into the shape and color of the seafloor.

But skates are not simply stingrays without drama.

They are their own kind of bottom reader.

Like rays, skates use sensory systems that help them understand the seafloor without relying only on sight. Their eyes are positioned on top of the body, while the mouth is underneath. Their flattened form allows them to move close to the bottom, where many small animals hide in sand, shell hash, mud, and seagrass.

A skate moving over the bottom is not only looking.

It is sampling the landscape through touch, smell, pressure, and electricity.

This makes the bottom less like a floor and more like a page. Each small animal leaves some sign: a movement, a chemical trace, a disturbance, a weak electrical field, a change in sediment (Bedore et al., 2014).

Skates remind us that not every chondrichthian is built around speed, teeth, and open-water pursuit. Some are built for patience. Some are built for closeness. Some read the world by staying near the place where water meets sediment.

Along our coast, that meeting place matters.

Sand flats, tidal creeks, inlets, oyster edges, and shallow nearshore bottoms are not empty spaces between “real” habitats. They are habitats. They hold the smaller lives that larger animals follow.

To understand the skate or ray, we have to stop seeing the bottom as blank.

A Sawfish’s World

A sawfish looks almost impossible the first time you really consider it.

It has the flattened body of a ray, but extending from the head is a long, tooth-edged rostrum — the “saw” that gives the animal its name. It looks like a weapon, and it can be used that way. Sawfish can swing the rostrum through schools of fish, stunning or injuring prey. It can also help defend the animal.

But the saw is not only a blade.

It is also a sensory surface.

The rostrum contains electroreceptive organs, ampullae of Lorenzini, that help detect weak electrical signals from nearby animals. In other words, the part of the animal that looks most like a weapon is also part of how it reads the world.

That changes the way we see it.

A sawfish is not blindly sweeping through water with a strange tool attached to its face. It is carrying a detector through the habitat ahead of its body. The saw helps locate prey. It helps interpret the space in front of the animal. It turns the water ahead into information (Wueringer et al., 2011; Wueringer, 2012).

This is different from the way we usually imagine rays and skates sensing the bottom.

A ray or skate often reads the world close to and beneath its flattened body. Its mouth is underneath. Its eyes look upward. Its sensory systems help it interpret the bottom as it rests, glides, or feeds along the sediment. A sawfish, however, extends part of that sensory world forward. The rostrum projects into the water ahead of the body, giving the animal information about prey before the prey reaches the mouth or passes beneath the disc.

That changes the animal’s sensory shape.

A sawfish does not only sense what is under it.

It can sense what is ahead of it.

The saw becomes a leading edge of perception. As the animal moves, the rostrum samples the space in front of the body. A fish hidden in murky water, a prey item moving near the bottom, or a school passing just ahead may be detected through electrical signals before the sawfish strikes. The same structure that can stun prey can also help find it (Wueringer et al., 2011; Wueringer, 2012).

That is what makes the sawfish so fascinating.

The feature that looks most dramatic to us is not simply for attack or defense. It is part of the animal’s sensory map. It stretches the invisible world forward.

Smalltooth sawfish were historically found as far north as North Carolina, but today they are generally associated with Florida waters in the United States (NOAA Fisheries, 2025). Seeing one along the Onslow County coast would be unusual. Still, they belong in this story because they show how far the chondrichthian sensory world can go.

A body part we notice for its shape may be important because of what it senses.

The ocean often works that way.

The feature that looks strange to us may be perfectly sensible in the world where the animal lives.

A Chimaera’s World

Far from the beach, beyond the bright shallows and beyond the places most of us will ever swim, chimaeras move through deeper water.

They are sometimes called ghost sharks, though they are not true sharks. They are relatives within the larger chondrichthian group, with cartilage skeletons and a long evolutionary history. Their bodies seem stitched together from familiar parts in unfamiliar ways: large eyes, winglike fins, smooth skin, and tooth plates instead of the replaceable teeth we associate with many sharks.

They look like animals from the edge of imagination.

But their strangeness is not random.

Many chimaeras live in deep, dim environments where sight has limits. In that world, an animal cannot depend on color and daylight the way we do at the surface. Light fades. Pressure increases the deeper you go. The landscape becomes colder, darker, and harder for human senses to understand.

A chimaera still has eyes, and those eyes can be large. But like other chondrichthyans, chimaeras also use sensory structures that detect electrical fields. In deep water, where prey may be sparse and visibility limited, the ability to detect life without needing a clear visual image becomes essential (Bottaro et al., 2022).

A chimaera reminds us that “seeing” does not always mean forming a bright picture.

Sometimes it means detecting what is alive in darkness.

That may be the hardest part for us to imagine. We tend to picture the deep sea as emptiness because our senses fail there. But the animals that live there are not moving through emptiness. They are moving through a world shaped by pressure, chemistry, temperature, vibration, faint light, and electrical traces.

The deep sea is not empty.

It is written in a language we barely read.

Reading the Ocean Instead of Fearing the Shadow

It is easy to turn sharks into symbols.

Fear does that. So do movies, headlines, and stories told from the shoreline after something frightening happens. A fin becomes a threat. A bite becomes proof of intent. A shadow becomes a monster.

But the real animal is more interesting than the symbol.

A shark is not moving through the water thinking like a person. A ray is not buried beneath the sand waiting for a human foot. A skate is not a flat shadow without a story. A sawfish is not only a saw. A chimaera is not only a ghost.

Each animal is built for a sensory world we do not naturally share.

That does not mean we ignore risk. Quite the opposite. Understanding these senses helps us behave with more respect in the water. We can avoid swimming near fishing activity, bait, or chum. We can pay attention when baitfish are schooling near shore. We can shuffle our feet in ray habitat. We can remember that murky water changes the way animals rely on different senses. We can stop assuming that clear human intent matters in an animal’s sensory landscape.

The ocean does not interpret us the way we interpret ourselves.

We may enter the water as swimmers, surfers, paddlers, anglers, or beachgoers. But to the animals already living there, we are also movement, pressure, chemistry, vibration, shadow, sound, and electricity.

We are part of the signal.

That is humbling, and it should be.

Our world is three-dimensional, but it is still mostly built around what we can see. Their world is three-dimensional too, but it includes layers we barely notice.

They are not seeing less of the ocean than we are. They are reading more of it differently. And maybe that is the point.

Standing at the edge of the ocean, we see waves, color, and surface. Beneath that surface, other animals are reading movement, pressure, chemistry, and electrical traces in ways we cannot naturally feel.

The shark may not be looking for us.

The ray may not be hiding from us.

The fish may not be moving randomly.

They are reading the ocean.

We are only beginning to learn the alphabet.

Standing at the edge of the ocean, we see waves, color, and surface. Beneath that surface, sharks, rays, skates, sawfish, and chimaeras read movement, pressure, chemistry, shadow, and electrical traces in ways we cannot naturally feel. | Image credit: A. Mitchell

References

Bangley, C. (2026, January 26). Sharks of NC. Coastwatch. https://ncseagrant.ncsu.edu/coastwatch/the-sharks-of-north-carolina/

Bedore, C. N., Harris, L. L., & Kajiura, S. M. (2014). Behavioral responses of batoid elasmobranchs to prey-simulating electric fields are correlated to peripheral sensory morphology and ecology. Zoology, 117(2), 95-103. https://doi.org/10.1016/j.zool.2013.09.002

Bellono, N. W., Leitch, D. B., & Julius, D. (2017). Molecular basis of ancestral vertebrate electroreception. Nature, 543(7645), 391-396. https://doi.org/10.1038/nature21401

Bottaro, M. (2022). Sixth sense in the deep-sea: The electrosensory system in ghost shark Chimaera monstrosa. Scientific Reports, 12(1). https://doi.org/10.1038/s41598-022-14076-2

Collin, S. P. (2012). The Neuroecology of cartilaginous fishes: Sensory strategies for survival. Brain, Behavior and Evolution, 80(2), 80-96. https://doi.org/10.1159/000339870

Gardiner, J. M., Atema, J., Hueter, R. E., & Motta, P. J. (2014). Multisensory integration and behavioral plasticity in sharks from different ecological niches. PLoS ONE, 9(4), e93036. https://doi.org/10.1371/journal.pone.0093036

Hart, N. S., & Collin, S. P. (2015). Sharks senses and shark repellents. Integrative Zoology, 10(1), 38-64. https://doi.org/10.1111/1749-4877.12095

Hart, N. S., Lamb, T. D., Patel, H. R., Chuah, A., Natoli, R. C., Hudson, N. J., Cutmore, S. C., Davies, W. I., Collin, S. P., & Hunt, D. M. (2019). Visual Opsin diversity in sharks and rays. Molecular Biology and Evolution, 37(3), 811-827. https://doi.org/10.1093/molbev/msz269

NOAA Fisheries. (2025). Smalltooth sawfish. NOAA. https://www.fisheries.noaa.gov/species/smalltooth-sawfish

Ryan, L. A., Slip, D. J., Chapuis, L., Collin, S. P., Gennari, E., Hemmi, J. M., How, M. J., Huveneers, C., Peddemors, V. M., Tosetto, L., & Hart, N. S. (2021). A shark’s eye view: Testing the ‘mistaken identity theory’ behind shark bites on humans. Journal of The Royal Society Interface, 18(183). https://doi.org/10.1098/rsif.2021.0533

Webb, J. F. (2023). Structural and functional evolution of the mechanosensory lateral line system of fishes. The Journal of the Acoustical Society of America, 154(6), 3526-3542. https://doi.org/10.1121/10.0022565

Wueringer, B. E. (2012). Electroreception in elasmobranchs: Sawfish as a case study. Brain, Behavior and Evolution, 80(2), 97-107. https://doi.org/10.1159/000339873

Wueringer, B., Peverell, S., Seymour, J., Squire, Jr., L., Kajiura, S., & Collin, S. (2011). Sensory systems in Sawfishes. 1. The ampullae of Lorenzini. Brain, Behavior and Evolution, 78(2), 139-149. https://doi.org/10.1159/000329515

July 3, 2026
The Marsh’s Quiet Workforce: More Than a Rabbit

More Than Meets the Eye

Spend enough time walking along a salt marsh and you’ll eventually stop noticing the marsh rabbits.

Not because they’ve disappeared.

Because they’ve become part of the landscape.

They feed quietly along the marsh edge, slipping into the grasses when startled before appearing again somewhere you didn’t expect. Some evenings you may count half a dozen. Other days you wonder if there were ever any there at all.

Unlike the brighter cottontails many people are used to seeing, marsh rabbits are darker, with coarse brown to reddish-brown fur, a grayish underside, and a rusty cinnamon patch along the back of the neck. Even the tail gives them away. Instead of flashing bright white, it appears darker and more bluish, one reason marsh rabbits have sometimes been called “bluetails” (Chapman & Trani, 2007; Chapman & Willner, 1981).

Like so much of the marsh, they’re easy to overlook.

A marsh rabbit may look like a familiar backyard visitor, but its role reaches far beyond the grass beneath it. | Image credit: skylarkymalarkey, iNaturalist

For more than a century, naturalists have described marsh rabbits (Sylvilagus palustris) by documenting where they lived, what they looked like, and what they ate (Rhoads & Young, 1897). Those observations gave us our first understanding of the species. Today, ecology invites us to ask a different question.

What happens because marsh rabbits are here?

The answer reaches far beyond the rabbit itself.

We often measure an animal’s importance by how exciting it is to watch.

The marsh doesn’t.

The marsh measures importance by how many lives are connected to one another (Soulé et al., 2003).

Following One Rabbit

If you’ve ever taken a science class, you’ve probably learned the First Law of Conservation of Energy: energy cannot be created or destroyed. It only changes form.

For many of us, that idea remained in a textbook or written across a classroom whiteboard. It became something to memorize rather than something we expected to witness.

Yet every walk beside a salt marsh quietly brings that principle to life.

Standing beside a marsh, it’s easy to underestimate what you’re seeing. From a distance, much of it appears to be little more than grass. Yet every growing season those grasses capture enormous amounts of energy from the sun, making salt marshes among the most productive ecosystems on Earth (Frizzell, 1988).

That productivity, however, cannot remain in the plants.

It has to move.

Imagine following a single marsh rabbit through its life.

Following one marsh rabbit means following the grasses, cover, and hidden pathways that connect it to the larger marsh. | Image credit: jorgenols, iNaturalist

At only about 2.5 to 3.5 pounds, its small body holds energy gathered first by the marsh plants around it (Chapman & Trani, 2007; Chapman & Willner, 1981).The grasses it consumes become muscle, bone, blood, fur, and new life. That rabbit may one day feed a hawk, an owl, a fox, a bobcat, or a snake. Throughout its life it supports parasites. After its death it feeds scavengers, fungi, bacteria, and countless decomposers before eventually returning nutrients to the marsh where another season of growth begins.

Nothing has appeared from nowhere.

Nothing has truly disappeared.

The energy has simply changed form.

Every day, marsh rabbits transform marsh vegetation into something that can support an entirely different community of organisms (Chapman & Trani, 2007; Chapman & Willner, 1981).

The rabbit isn’t the end of the story.

In many ways, it’s where the story begins.

More Than a Meal

Spend a few minutes watching a marsh rabbit and it may not seem particularly busy.

It grazes along the marsh edge, pauses to listen, slips into dense cover, then returns to feeding when the danger seems to have passed. At first glance, it looks like a small animal moving through its day.

But even before a marsh rabbit becomes food for something else, it is already shaping the marsh around it.

Every bite influences which plants are grazed and which continue growing (Conner & Cherry, 2017). As it moves between the marsh edge, nearby cover, and slightly higher ground, the rabbit is also moving through the boundary between habitats most of us see as separate. The same dense vegetation that protects the rabbit also provides shelter for insects, reptiles, amphibians, birds, and countless other small lives moving through the marsh (Canepuccia et al., 2023; Larsen & Gray et al., 2021; Wigley & Lancia, 1998).

A marsh rabbit browses at the edge, where each ordinary bite helps move energy through the landscape. | Image credit: cadecampbell, iNaturalist

This is why the rabbit matters before the hawk ever appears.

Its value is not limited to becoming prey. Its ordinary life helps move energy, shape vegetation, and connect habitats long before that energy travels farther up the food web (Chapman & Trani, 2007; Chapman & Willner, 1981; Conner & Cherry, 2017).

Perhaps that is the quiet work of a marsh rabbit.

Not simply feeding something else.

But helping hold together the conditions that allow so much else to live there.

Why There Are So Many

Sometimes marsh rabbits seem to be everywhere — in yards, along road edges, near parking lots, and wherever the Spartina meets slightly higher ground.

A young marsh rabbit beside an adult shows the visible side of abundance, but reproduction is only part of the story. | Image credit: Wolfgang, iNaturalist

The easy explanation is that rabbits reproduce quickly. They can produce several litters in a year, often three to seven, with roughly 15 to 20 young produced annually under favorable conditions (Holler & Conaway, 1979).

That is true, but it is not the whole story.

Nature rarely invests heavily in something that does not matter. In a marsh, abundance is not waste. It is part of the system.

Marsh rabbits live under constant pressure. Every choice — where to feed, when to move, when to freeze, and when to disappear into the grasses — is shaped by predators, tides, weather, and the daily balance between finding food and becoming food (Hill et al., 2019; Holler & Conaway, 1979).

Predators influence far more than the animals they catch. Their presence can change where prey feed, how long they remain exposed, and how energy moves through the landscape (Suraci et al., 2019). When predator communities shift, those changes can ripple through the food web in ways that affect many other species (Bransford et al., 2024; Jiménez et al., 2019) .

Seen this way, abundant marsh rabbits are not simply evidence of successful reproduction.

They are evidence of how much work this one ordinary species performs.

The Rabbit You Didn’t See

Perhaps this also explains something you’ve probably noticed yourself.

One moment several marsh rabbits are feeding along the marsh edge.

You look away for only a moment.

When you look back, they’re gone.

They haven’t left the marsh.

Unlike many rabbits people are used to seeing, marsh rabbits are strong swimmers. Water is not simply something they avoid; it is part of the landscape they know how to use. In a place shaped by tides, wet ground, and narrow edges of cover, the ability to move through water helps explain how they can vanish so completely without ever leaving the marsh (Chapman & Trani, 2007; Chapman & Willner, 1981).

The same dense vegetation that feeds them also protects them. Slight changes in elevation, the rhythm of the tides, the angle of the evening sun, and generations of natural selection have shaped an animal that survives by knowing exactly when to be seen — and when not to be (Chapman & Willner, 1981; Holler & Conaway, 1979).

The rabbit disappeared from sight.

Its place in the marsh never did.

Looking at the Marsh Differently

The next time you notice a marsh rabbit quietly feeding along the marsh edge, pause before it disappears.

What once looked like an ordinary rabbit is now something entirely different.

Not because the rabbit has changed.

But because you can now see the countless connections passing through it (Soulé et al., 2003).

And once you see those connections, the marsh becomes harder to overlook.

A marsh rabbit slips back into the edge, leaving only a glimpse of the connections still moving through the marsh. | Image credit: maxnel, iNaturalist

References

Bransford, T. D., Harris, S. A., & Forys, E. A. (2024). Seasonal variation in mammalian Mesopredator spatiotemporal overlap on a barrier island complex. Animals, 14(16), 2431. https://doi.org/10.3390/ani14162431

Canepuccia, A. D., Fanjul, M. S., & Iribarne, O. O. (2023). Global distribution and richness of terrestrial mammals in tidal marshes. Diversity and Distributions, 29(5), 598-612. https://doi.org/10.1111/ddi.13683

Chapman, B. R., & Trani, M. K. (2007). Marsh Rabbit (Sylvilagus palustris). In The Land Manager’s Guide to Mammals of the South (pp. 247-251). Durham, NC: The Nature Conservancy; Atlanta, GA: U.S. Forest Service.

Chapman, J. A., & Willner, G. R. (1981). Sylvilagus palustris. Mammalian Species, (153), 1. https://doi.org/10.2307/3503947

Conner, L. M., & Cherry, M. J. (2017). Considering Herbivory and Predation in Forest Management. In Ecological Restoration and Management of Longleaf Pine Forests (1st ed., p. 12). CRC Press.

Frizzell, E. K. (1988). Mammals and Wetlands. In The Ecology and Management of Wetlands: Volume 1: Ecology of Wetlands (1st ed., pp. 213-226). Croom Helm Ltd.; Timber Press.

Hill, J. E., DeVault, T. L., & Belant, J. L. (2019). Cause‐specific mortality of the world’s terrestrial vertebrates. Global Ecology and Biogeography, 28(5), 680-689. https://doi.org/10.1111/geb.12881

Holler, N. R., & Conaway, C. H. (1979). Reproduction of the marsh rabbit (Sylvilagus palustris) in South Florida. Journal of Mammalogy, 60(4), 769-777. https://doi.org/10.2307/1380192

Jiménez, J., Nuñez-Arjona, J. C., Mougeot, F., Ferreras, P., González, L. M., García-Domínguez, F., Muñoz-Igualada, J., Palacios, M. J., Pla, S., Rueda, C., Villaespesa, F., Nájera, F., Palomares, F., & López-Bao, J. V. (2019). Restoring APEX predators can reduce mesopredator abundances. Biological Conservation, 238, 108234. https://doi.org/10.1016/j.biocon.2019.108234

Larsen-Gray, A. L., Loeb, S. C., & Kalcounis-Rueppell, M. C. (2021). Rodent population and community responses to experimental, large scale, long-term coarse Woody debris manipulations. Forest Ecology and Management, 496, 119427. https://doi.org/10.1016/j.foreco.2021.119427

Macarthur, R., & Levins, R. (1967). The limiting similarity, convergence, and divergence of coexisting species. The American Naturalist, 101(921), 377-385. https://doi.org/10.1086/282505

Rhoads, S. N., & Young, R. T. (1897). Notes on a Collection of Small Mammals from Northeastern North Carolina. Proceedings of the Academy of Natural Sciences of Philadelphia, 49, 303-312. https://www.jstor.org/stable/4062279?seq=1

Soulé, M. E., Estes, J. A., Berger, J., & Del Rio, C. M. (2003). Ecological effectiveness: Conservation goals for interactive species. Conservation Biology, 17(5), 1238-1250. https://doi.org/10.1046/j.1523-1739.2003.01599.x

Suraci, J. P., Clinchy, M., Zanette, L. Y., & Wilmers, C. C. (2019). Fear of humans as APEX predators has landscape‐scale impacts from mountain lions to mice. Ecology Letters, 22(10), 1578-1586. https://doi.org/10.1111/ele.13344

Wigley, T. B., & Lancia, R. A. (1998). Wildlife Communities. In Southern Forested Wetlands (1st ed., p. 32). Routledge.

June 26, 2026
When Every Bird Looks Like a Hawk: Reading the Raptors of Onslow County
A reader recently asked me about five birds he had seen over the sounds of Surf City last weekend. He was convinced they were five different kinds of “sea hawks.”

At first glance, it was an understandable conclusion.

Each bird was large. Each spent time soaring overhead or hesitating up high over the water. Each occupied the same stretch of coastal North Carolina sky.

Yet every photograph and description reflected the same species: an osprey.

Distance has a way of simplifying wildlife. Colors disappear. Markings fade. Details are lost. What remains is a silhouette against the sky.

Most of us learn to recognize birds by their appearance. Raptors are often easier to understand by their behavior.
- What is the bird doing?
- Is it hovering over the water?
- Circling without flapping?
- Perched motionless on a fence post?
- Drifting above a marsh?
- Crossing silently through the trees after sunset?
The answer often reveals more than the feathers.

The skies above Onslow County are shared by a community of predators. Some hunt fish. Some hunt rodents. Some hunt insects. Some hunt other birds. Some hunt only at night. Others serve as nature’s cleanup crew.

At a distance they may look similar.

Spend enough time watching them, however, and the differences become impossible to miss.

Following the Fish

Osprey: The Fisherman

If there is a signature bird of the coast, it may be the osprey (Pandion haliaetus).

You notice one long before you identify it. The bird appears above a creek, river, or stretch of open water, turns into the wind, and suddenly seems to stop moving. For a few seconds it hangs there, suspended above the surface before plunging feet-first toward the water below.

That moment of hesitation is not hesitation at all.

The bird is making a final decision.

Water distorts light. Fish change direction. Wind roughens the surface. What appears obvious from a dock or kayak becomes much more complicated from above. The osprey’s brief hover allows it to judge distance, depth, and movement before committing to the dive (Poole, 1989; Bierregaard et al., 2020).

The splash usually draws everyone’s attention.

The fish often draws the next question.

Watch an osprey leave the water carrying a mullet or menhaden and it is difficult not to wonder how the bird manages to hold onto it. Fish are essentially living bars of soap wrapped in muscle, built to slip through water and escape predators. Osprey solve that problem with feet lined by tiny backward-facing spicules and a reversible outer toe that help secure slippery prey (Poole, 1989; Bierregaard et al., 2020).

Then, almost as soon as the bird becomes airborne, something else happens.

The fish turns.

Within seconds the osprey has repositioned its catch so the fish faces forward. What looks like a small adjustment saves energy over the course of the flight. A fish carried sideways catches air. A fish carried headfirst moves through it. Often the bird gives its catch a vigorous shake as it climbs away from the water, shedding excess water before continuing on its way. Together, these adjustments reduce drag and make transporting a heavy, slippery meal through the air more efficient (Allen et al., 2018; Poole, 1989; Bierregaard et al., 2020).

Around nesting season, however, it is often the noise rather than the fishing that gets people’s attention.

Osprey rarely seem quiet.

Calls echo from nesting platforms, channel markers, dead trees, and utility poles throughout the breeding season. Adults announce arrivals. Mates communicate with one another. Young birds call constantly whenever food appears nearby. What sounds chaotic from a distance is often a family carrying on a conversation (Bierregaard et al., 2020).

By late summer, that family becomes easier to see.

Several birds may gather near a nest, perched along the same stretch of water where they have spent months raising young. Then, without warning, they take to the air together. The younger birds follow the adults across creeks, marshes, and open water, practicing turns, landings, and the flight skills that will eventually carry them south. What appears at first to be a loose gathering of osprey is often a family still learning from one another long after the young birds have left the nest (Poole, 1989; Bierregaard et al., 2020).

To boaters, it is a channel marker in the New River in Jacksonville, NC. To an osprey, it is home. Many coastal nests are rebuilt and expanded year after year, becoming landmarks visible across the water. | Image credit: A. Mitchell

The nests themselves remain long after the birds have departed.

Many osprey return to the same sites year after year, adding sticks, repairing damage, and expanding structures that can eventually become enormous. What begins as a modest nest slowly grows into a landmark visible from hundreds of yards away (Poole, 1989; Bierregaard et al., 2020).

For many coastal residents, those nests become part of the landscape.

And when spring returns, so do the birds that built them.

Bald Eagle: The Opportunist

If you spend enough time around the water, eventually you’ll see it happen.

An osprey leaves the surface carrying a fish. For a few moments, everything appears normal. Then a second bird enters the scene.

Larger.

Heavier.

Built on an entirely different scale.

The bald eagle (Haliaeetus leucocephalus) begins to follow.

What started as a successful fishing trip suddenly becomes a chase.

From below, the interaction can look almost personal. The osprey twists and climbs. The eagle closes the distance. Sometimes the osprey escapes. Sometimes it drops the fish. The eagle wheels downward after the falling meal while the osprey continues on empty-taloned.

Why go through all that trouble?

Because catching a fish requires energy.

An osprey may spend considerable time searching the water, hovering above the surface, adjusting for currents, and committing to a dive before finally securing a meal. An eagle watching from a nearby perch can recognize that success immediately. From the eagle’s perspective, the fish has already been found. The difficult part of the hunt is over (Buehler, 2020).

This often leads people to wonder whether bald eagles are better fishermen than osprey.

The answer depends on how you define fishing.

If the goal is catching fish, the osprey remains the specialist. Nearly every aspect of its anatomy is designed around that task. Its feet grip slippery prey with remarkable efficiency, and its entire hunting strategy revolves around locating fish beneath the water’s surface.

A bald eagle approaches the world differently.

Rather than specializing in a single food source, eagles take advantage of opportunities wherever they find them. Fish remain important, particularly along the New River, Stump Sound, the Intracoastal Waterway, and the countless creeks that thread through coastal marshes. Yet waterfowl, mammals, reptiles, and carrion can also become part of the menu (Buehler, 2020).

A closer look at their feet reveals those differences. Osprey feet are designed to hold fish. Eagle talons are designed to seize and restrain a wider variety of prey. One bird is built around precision. The other is built around versatility (Buehler, 2020).

That versatility helps explain why bald eagles have become increasingly common sights along the Onslow County coast. Open water, abundant prey, expansive marshes, and large trees provide everything they need. Whether soaring above an estuary, perched along a creek, or watching from a pine overlooking the water, eagles occupy a position near the top of the coastal food web (Buehler, 2020).

And every so often, that position allows them to let someone else do the fishing.

The Hunters of Marsh and Forest

Red-shouldered Hawk: The Watcher on the Fence

Not every raptor announces itself from the sky.

Some introduce themselves by showing up in the yard.

You glance out the window and notice a hawk perched on the fence. Hours later it seems to be in exactly the same place. The next morning it is back again.

Eventually curiosity takes over.

What is it watching?

Perched above a yard in Jacksonville, NC, a red-shouldered hawk waits for movement. From elevated vantage points, these woodland hunters watch patiently for opportunities hidden within the landscape below. | Image credit: A. Mitchell

Many people assume the hawk is focused on the house, the dog, or the family moving through the yard.

In reality, the bird is usually paying attention to everything else.

A well-maintained yard often provides excellent hunting habitat. Frogs move through flower beds. Lizards bask along retaining walls. Small snakes hunt beneath shrubs. Mice travel fence lines and wood piles. The red-shouldered hawk watches for movement, waiting for the landscape to reveal itself (Dykstra et al., 2020).

That patient approach reflects the habitats these birds prefer.

Unlike the open-country red-tailed hawk, red-shouldered hawks (Buteo lineatus) are closely tied to places where woods and water meet. Creek corridors, swamp edges, ponds, marshes, and bottomland forests provide the cover and diversity of prey they rely upon (Dykstra et al., 2020).

A red-shouldered hawk feeds on captured prey in a parking lot. While often associated with swamps and wooded wetlands, these adaptable hunters frequently take advantage of opportunities in suburban landscapes. | Image credit: A. Mitchell

Along the coast, those habitats frequently overlap with where people live.

The fence post is simply the best seat in the house.

From there, the hawk can watch an entire ecosystem unfold beneath it.

Red-tailed Hawk: Master of the Open Sky

A red-tailed hawk (Buteo jamaicensis) – and my personal favorite bird – often attracts attention by doing remarkably little.

You notice one circling high above a field.

Several minutes later it is still there.

The wings barely move.

At first, most people wonder how the bird can remain in the air for so long without flapping. The answer lies in the atmosphere itself. As the ground warms, pockets of heated air rise into the sky. Red-tailed hawks locate these invisible thermals and circle within them, gaining altitude while expending very little energy (Kerlinger, 1989; Preston & Beane, 2024).

But staying aloft is only part of the story.

The real question is why the bird wants to be up there in the first place.

The answer becomes clearer when compared to the red-shouldered hawk.

A red-shouldered hawk often hunts by focusing on a particular place. A pond edge. A marsh creek. A backyard. It watches patiently from a perch, waiting for the landscape to reveal movement (Dykstra et al., 2020).

A red-tailed hawk takes the opposite approach.

Rather than concentrating on one corner of the landscape, it climbs high enough to see how all of those pieces connect. Fields blend into hedgerows. Roadsides meet forest edges. Open ground transitions into cover. From above, what appear to be separate places from the ground become a single hunting landscape.

That broader view is the red-tail’s specialty.

What appears to us as an empty field is filled with clues. A rabbit pauses along a fence line. A squirrel breaks from cover. A mouse rustles through the grass. The bird is not searching for a specific animal. It is searching for movement, patterns, and opportunities spread across hundreds of acres (Preston & Beane, 2024).

The thermal keeps the hawk aloft long enough to gather that information. Height becomes an advantage. Distance becomes information.

The bird is not circling because it has nowhere else to be.

It is circling because the sky offers the best view.

And from that vantage point, one movement in the wrong place at the wrong time is often all it takes.

Cooper’s Hawk: The Pursuit Hunter

If you maintain a bird feeder long enough, sooner or later the yard will go silent.

One moment cardinals, doves, and finches are moving between the feeder and nearby trees.

The next, everything disappears.

Then a gray blur streaks through the yard.

The first time you see it happen, it feels almost impossible that a bird that large could move that quickly through such a cluttered space.

Unlike the red-tailed hawk searching from hundreds of feet above the landscape or the red-shouldered hawk watching patiently from a perch, the Cooper’s hawk (Astur cooperii) hunts in motion. It is built for pursuit (Rosenfield et al., 2025).

Its long tail acts like a rudder while relatively short wings allow it to twist, turn, and accelerate through spaces that would seem impossible for most raptors. Branches, fences, shrubs, and backyard obstacles that slow other birds become part of the chase (Rosenfield et al., 2025).

That agility allows the hawk to exploit something many predators cannot.

Confusion.

A flock of birds startled into flight rarely moves in a straight line. Individuals scatter in different directions, darting through vegetation and searching for cover. The Cooper’s hawk follows.

What appears chaotic to us is a hunting opportunity to the hawk.

Yet not every backyard attracts a Cooper’s hawk.

If you’ve ever noticed that these birds seem more common in some neighborhoods than others, the surrounding landscape is often the reason. Cooper’s hawks favor places where trees, forest edges, wooded corridors, and open spaces meet. Those transitions provide both cover and opportunity, allowing the bird to move quickly between concealment and pursuit (Rosenfield et al., 2025).

A bird feeder placed within that landscape can become part of the story, not because the feeder attracts the hawk, but because it concentrates movement. Birds travel between the feeder and nearby cover. The hawk is already watching the area. The feeder simply makes activity easier to find.

Which is why the sudden silence is often the first clue.

Long before most people see the hawk, the birds have already noticed it.

For a few moments, the yard belongs to the fastest hunter in the neighborhood.

The Hunters of the Air

Mississippi Kite: Catching the Wind

At first glance, a Mississippi kite (Ictinia mississippiensis) looks like it should behave like any other hawk.

It drifts overhead with long, pointed wings, barely moving as it rides the summer air. Then it suddenly changes direction, banking sharply, twisting through the sky, and accelerating after something too small for most people to see.

The first time you notice it, the behavior feels strange.

What is that hawk chasing? Is it chasing dragonflies?

The bird banks again, then again, each turn seeming impossibly precise. Whatever it is pursuing appears far too small to interest a raptor. Yet the longer you watch, the clearer the answer becomes.

While many hawks spend their time searching the ground for prey, Mississippi kites have turned the air itself into a hunting ground. Dragonflies, cicadas, beetles, and other flying insects become meals captured directly on the wing. What appears to be effortless wandering is often an active hunt unfolding overhead (Parker, 2020).

That hunting style explains why they seem so different from other raptors.

The red-shouldered hawk watches a particular place. The red-tailed hawk surveys an entire landscape. The Cooper’s hawk chases prey through trees and backyards. The Mississippi kite is hunting somewhere entirely different.

Its long wings and graceful flight allow it to maneuver with remarkable precision, changing direction quickly as insects dart, climb, and shift with the wind (Parker, 2020).

The same warm air currents that help other raptors gain altitude also gather flying insects into concentrated pockets, creating opportunities for a predator adapted to exploit them (Parker, 2020).

The result is a bird that often feels more like a swallow than a hawk.

An osprey may be hunting fish below. A red-tailed hawk may be watching a field nearby. A Cooper’s hawk may be moving along a forest edge. Above them all, a Mississippi kite may be feeding on insects carried by the same air currents that support the rest of the ecosystem.

The bird is not ignoring the landscape beneath it.

It has simply found opportunity in a place most predators never think to look.

For the Mississippi kite, the sky is not a pathway.

It is habitat.

The Cleanup Crew

Turkey Vulture: Death Becomes Renewal

A turkey vulture (Cathartes aura) lands on your roof and suddenly everyone becomes concerned.

To us, it looks like a warning. To the vulture, it is simply another perch from which to read the landscape. | Image credit: A. Mitchell

Some people take it as a bad omen. Others wonder if something nearby has died. Before long, the bird becomes the center of attention despite doing little more than sitting still.

The turkey vulture, meanwhile, is completely unaware of the stories being told about it.

Most of the time, something far less dramatic is happening.

A rooftop provides warmth on a cool morning, a place to dry rain-soaked feathers, or a convenient perch where rising air currents can be reached without much effort. The bird is not predicting death. It is simply taking advantage of the landscape (Kirk & Mossman, 2020).

Yet the association exists for a reason.

Unlike the hawks and eagles we have encountered so far, turkey vultures are searching for something very different. They are not looking for prey. They are looking for what remains after life has already moved on.

A dead fish along the shoreline.

A raccoon hidden in roadside vegetation.

A deer beyond the edge of a forest.

But how do they find it?

Part of the answer can be seen on the bird’s face. If you are fortunate enough to observe a turkey vulture through binoculars or at close range, you may notice something unusual about its nostrils, or nares. Unlike our own noses, the openings pass completely through the beak. In the right light, you can literally see from one side of the nostril to the other (Kirk & Mossman, 2020).

A close comparison of a turkey vulture (top) and black vulture (bottom) reveals one clue to how they read the landscape differently. Turkey vultures use an exceptional sense of smell to locate carrion, while black vultures depend more on vision and the behavior of other vultures. Arrows highlight differences in the nostril openings of the two species. | Image credit: T. Lisney

That adaptation supports one of the most powerful senses of smell in the bird world. While many raptors rely primarily on vision, turkey vultures are able to detect the scent of carrion from remarkable distances, allowing them to locate food sources hidden beneath vegetation and, in some cases, even beneath the soil itself (Grigg et al., 2017; Kirk & Mossman, 2020).

Finding carrion, however, is only part of the challenge.

Consuming it presents an entirely different set of problems.

The turkey vulture’s bald head, which many people find unsettling, is actually an important adaptation. Unlike a feathered head that could trap blood, bacteria, and other organic material, the bare skin can be cleaned much more easily after feeding. What gives the bird its ominous appearance also helps protect it from the very things it eats (Roggenbuck et al., 2018).

The same is true inside the bird.

Turkey vultures possess an extraordinarily acidic digestive system capable of destroying many of the bacteria and pathogens that would make other animals sick. Organisms responsible for diseases such as anthrax, botulism, cholera, and salmonella are often neutralized during digestion, allowing the vulture to safely consume material that would be dangerous for most scavengers (DeVault et al., 2016; Kirk & Mossman, 2020).

Even their hygiene is unusual.

Turkey vultures practice a behavior known as urohidrosis, in which they defecate on their own legs. While it may seem unpleasant from a human perspective, the highly acidic waste helps kill bacteria picked up while walking on carcasses and also provides a cooling effect during hot weather (Arad et al., 1989; Kirk & Mossman, 2020).

Taken together, these adaptations solve a difficult ecological problem. Dead animals can become reservoirs for bacteria, disease, and decay. Turkey vultures have evolved to exploit that resource while avoiding many of the risks associated with it.

Black vultures, which are often seen alongside them, approach the problem differently. Their nostrils are narrower and not open from side to side. Rather than relying so heavily on smell, they depend more on vision and often watch the movements of turkey vultures to help locate food (Buckley et al., 2020).

That relationship creates an interesting partnership. Turkey vultures are often the first to detect a carcass hidden beneath vegetation, while black vultures are quick to notice where the turkey vultures are gathering. One species excels at finding the scent. The other excels at finding the finder (Buckley et al., 2020; Kirk & Mossman, 2020.

Together, the two species accomplish something few other animals can.

They return nutrients to the landscape.

What appears to be an ending becomes the beginning of something else. Energy stored within a fish, a raccoon, or a deer does not simply disappear. Vultures help move those nutrients back into the ecosystem where they become available to countless other organisms (DeVault et al., 2016) .

The bird on your roof is not waiting for something bad to happen.

More often than not, it is part of the reason the landscape remains healthy after it does.

Black Vulture: Following the Leader

A single turkey vulture on a rooftop often attracts attention.

Ten vultures attract concern.

What appears to be a crowd is often an information network. Black vultures frequently roost together, sharing a landscape where opportunities can appear and disappear without warning. | Image credit: jspruill, iNaturalist

Unlike turkey vultures, which are frequently seen soaring alone or in small numbers, black vultures (Coragyps atratus) often seem to arrive as a group, called a committee. One bird becomes five. Five become ten. Before long, an entire rooftop, parking lot, or dead tree appears covered in vultures (Buckley et al., 2020).

The first question is usually the same.

Why are there so many?

Part of the answer lies in how black vultures find food.

While turkey vultures rely heavily on their extraordinary sense of smell, black vultures depend much more on vision and on one another. They watch the landscape, but they also watch other vultures. A turkey vulture dropping toward a hidden carcass can reveal an opportunity that a black vulture might never have discovered on its own (Buckley et al., 2020).

That difference creates an unusual relationship between the two species.

Turkey vultures are often the first to locate carrion concealed beneath vegetation or hidden from view. Black vultures are often the first to notice that the turkey vultures have found something worth investigating (Buckley et al., 2020).

One species excels at finding the scent.

The other excels at finding the finder.

Their social nature extends beyond feeding. Black vultures frequently roost together, travel together, and gather in numbers that can seem surprising to people unfamiliar with them. What appears to be a crowd is often a network of birds sharing information about a landscape filled with unpredictable opportunities (Buckley et al., 2020).

That strategy has served them well.

A dead fish washed onto a shoreline, a raccoon along a roadside, or a deer hidden beyond the edge of a forest represents a resource that appears without warning and disappears quickly. By paying attention to one another, black vultures can exploit those opportunities efficiently.

To most people, the meal is something to avoid. To a black vulture, it is an opportunity. By consuming carrion that would otherwise decay on the landscape, vultures help return nutrients to the ecosystem while reducing the spread of disease. | Image credit: A. Mitchell

Like the turkey vulture, the black vulture plays an important role in returning nutrients to the ecosystem.

It simply approaches the problem differently.

Where the turkey vulture trusts its nose, the black vulture trusts its neighbors.

The Night Shift

As daylight fades, a different group of predators takes over.

The thermals weaken. The soaring hawks settle. Shadows lengthen across marshes and forests.

Then the owls emerge.

Eastern Screech-Owl: Master of Camouflage

Many people have an eastern screech-owl (Megascops asio) living in their neighborhood and never realize it.

Not because the owl is rare.

Because it is exceptionally good at remaining unnoticed.

You might spend years walking past the same tree without ever seeing this small bird tucked inside a cavity or pressed against the bark. Then one evening, just after sunset, a soft trill or whinny drifts through the yard and suddenly you realize there has been an owl nearby the entire time (Gehlbach, 2009; Ritchison et al., 2020).

The discovery often raises an interesting question.

If eastern screech-owls feed on many of the same insects, rodents, reptiles, and amphibians as some daytime raptors, why don’t we see them more often? (Gehlbach, 2009; Ritchison et al., 2020)

Part of the answer is timing.

While hawks spend the day watching fields, marshes, forests, and backyards, the eastern screech-owl waits for darkness. As daylight fades and the daytime hunters settle into roosts, the owl begins its own shift (Ritchison et al., 2020).

But timing alone does not explain its success.

The owl’s real advantage is concealment.

Its mottled gray and brown feathers blend remarkably well with tree bark, allowing it to disappear into the landscape even when it is in plain sight. During the day, many spend hours motionless inside tree cavities or against trunks where they become nearly impossible to detect (Gehlbach, 2009; Ritchison et al., 2020).

That camouflage allows the owl to remain close to people while largely escaping notice.

Neighborhoods, wooded lots, parks, forest edges, and suburban backyards can all provide suitable habitat. The insects drawn to porch lights, the rodents moving along fence lines, and the small reptiles hiding among shrubs create hunting opportunities throughout the night (Gehlbach, 2009; Ritchison et al., 2020).

By the time most people realize an eastern screech-owl is nearby, it has often been there all along.

Its success does not come from being the largest predator in the landscape.

It comes from being the one you never knew was watching.

Barn Owl: Sound Becomes Sight

A pale shape crosses a field at dusk.

For a moment it hardly seems real. The bird appears almost white against the fading light, gliding silently above the grass before disappearing into the darkness beyond.

The first question is often simple.

What did I just see?

For centuries, encounters like that have inspired stories of ghosts, spirits, and things that move through the night unseen. The barn owl’s piercing scream has only reinforced that reputation. Unlike the familiar hoots people associate with owls, barn owls produce calls that can sound startlingly human, often described as shrieks, screams, or cries drifting through the darkness. Heard for the first time from a forest edge or old barn, it is easy to understand how the bird became woven into folklore (Marti et al., 2024).

Yet the call serves a practical purpose.

In darkness, sound becomes one of the most effective ways for American barn owls (Tyto alba pratincola) to communicate with mates, defend territories, and maintain contact with one another. What sounds eerie to us is simply part of life for an owl that spends most of its time hunting when the rest of the landscape is asleep (Marti et al., 2024).

The hunt itself is equally remarkable.

Barn owls are among the most specialized rodent hunters in North America. Their heart-shaped facial disks act like satellite dishes, funneling sound toward asymmetrical ears capable of pinpointing prey with astonishing precision. A mouse rustling through grass can reveal its location long before the owl ever sees it (Payne, 1971; Marti et al., 2024).

That adaptation helps explain another common experience.

Step quietly into an old barn, abandoned building, or large outbuilding and you may discover one or more barn owls perched overhead. They often watch intruders with an intense stare, swaying and bobbing from side to side as they study the unfamiliar visitor below (Marti et al., 2024).

At first glance, the behavior appears nervous or even strange.

In reality, the owl is gathering information. The subtle movements help it judge distance, depth, and position before deciding whether to remain still or slip silently into the darkness.

Fields, agricultural landscapes, marsh edges, and open grasslands provide ideal hunting habitat (Marti et al., 2024). Every mouse captured represents energy transferred from one part of the ecosystem to another, helping regulate populations that might otherwise grow unchecked.

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The pale bird crossing the field is not a ghost.

It is one of the most effective hunters the night shift has to offer.

For the barn owl, sound does not simply reveal the landscape.

It becomes a way of seeing it.

Barred Owl: The Voice of the Swamp

“Who cooks for you? Who cooks for you-all?”

Once you hear it, you rarely forget it.

The call drifts through wooded neighborhoods, swamp edges, and forested wetlands after sunset, often carrying much farther than people expect. Many coastal residents know the sound long before they ever see the bird responsible for making it (Bierregaard et al., 2025).

The question naturally follows.

Who is calling from the darkness?

More often than not, it is a barred owl.

Unlike the barn owl crossing open fields or the eastern screech-owl disappearing into a backyard tree, barred owls (Strix varia) are closely tied to forests and wetlands. Swamps, creek corridors, bottomland hardwoods, and wooded neighborhoods provide the cover, water, and diversity of prey they need (Bierregaard et al., 2025).

The call itself serves several purposes. Barred owls use it to communicate with mates, establish territories, and maintain contact across dense forests where visibility is limited. What sounds like a conversation to us is often exactly that (Bierregaard et al., 2025).

Those forests and wetlands provide hunting opportunities throughout the year. Frogs call from wetland edges. Crayfish move through shallow water. Rodents travel beneath fallen leaves. Snakes, insects, and small birds all become potential prey. Rather than specializing in a single food source, barred owls have learned to take advantage of whatever the swamp provides (Bierregaard et al., 2025).

The swamp, however, does not make hunting easy.

Prey hides beneath vegetation, beneath water, and beneath layers of leaf litter. Fallen logs, tangled branches, and dense understory create countless places to disappear.

Barred owls overcome many of those challenges through silence.

The leading edges of their feathers are specially adapted to break up airflow, reducing the sound of flight to nearly nothing. A mouse rustling beneath leaves, a frog moving along a wetland edge, or a crayfish crossing shallow water may never hear the owl approaching (Bachmann & Wagner, 2016).

For prey, the danger often arrives without warning.

By the time a barred owl commits to an attack, silence has already done much of the work.

That ability helps explain why barred owls are among the most successful predators in the region.

It also reveals something many people do not realize.

Hunting is not simply a switch that turns on when a young owl leaves the nest.

Juvenile barred owls must learn. They practice. They miss opportunities. They refine the skills needed to locate, pursue, and capture prey in a complex environment. In wildlife rehabilitation settings, young barred owls that fail to develop those hunting skills cannot be successfully returned to the wild (Watson et al., 2023).

Instinct provides the foundation.

Experience builds the hunter.

Perhaps that is why barred owls have become such a familiar voice in the coastal night. Their success comes not from mastering a single prey species or hunting strategy, but from learning to adapt to whatever the swamp provides.

For the barred owl, the swamp is more than habitat.

It is a hunting ground, a classroom, and a home.

Great Horned Owl: Ruler of the Night

The night can be surprisingly noisy.

A barred owl calls from the swamp.

Tree frogs answer from the wetlands.

Crickets fill the spaces in between.

Then, sometimes, the woods erupt with alarm calls.

Crows mob during the day. Smaller birds call from hidden roosts after sunset. Even other predators seem suddenly aware that something has changed.

What happened?

Often, a great horned owl (Bubo virginianus) has arrived.

While many predators spend their lives worrying about what might hunt them, the great horned owl occupies a different position in the food web. Rabbits, squirrels, rodents, reptiles, birds, and even other predators can become prey. Where great horned owls occur, few animals completely ignore them (Artuso et al., 2020).

That includes other owls.

Barred owls, screech-owls, and other nocturnal hunters may alter their behavior when a great horned owl is nearby (Artuso et al., 2020). The question is not simply what the owl is hunting.

The question is whether anything wants to become its next opportunity.

Part of that success comes from versatility. Great horned owls hunt forests, wetlands, agricultural fields, suburban neighborhoods, and coastal habitats with equal confidence. Rather than specializing in a single prey species, they take advantage of whatever opportunities the landscape provides (Artuso et al., 2020).

Yet versatility alone does not explain why other animals react when one arrives.

Power does.

A great horned owl’s grip rivals that of a bald eagle. The force generated by its talons can exceed 270 newtons, allowing it to seize and control prey with remarkable efficiency (Ward et al., 2002). Those feet are capable of exerting tremendous force once they close around a target (Ward et al., 2002; Lingham-Soliar, 2014).

Combined with a wingspan approaching five feet, the result is a predator that commands attention even before it leaves the ground (Artuso et al., 2020).

Yet perhaps the most remarkable thing about a great horned owl is how quietly all of that power moves through the landscape.

Like other owls, the leading edges of their feathers break up airflow, reducing the sound of flight to nearly nothing. A bird carrying a wingspan wider than many people are tall can pass overhead with little more than a faint rush of air (Bachmann & Wagner, 2016).

Sometimes not even that.

The first indication that a great horned owl is nearby is often the reaction of everything else around it.

That silence becomes even more effective when paired with another adaptation.

Many people believe owls can rotate their heads completely around.

They cannot.

A great horned owl can rotate its head roughly 270 degrees, allowing it to scan much of the landscape without moving its body (Ward et al., 2002). Unlike our eyes, an owl’s eyes are largely fixed within the skull. To change its view, it must move its head (Ward et al., 2002; Lingham-Soliar, 2014).

For an ambush predator, that matters.

Every movement risks revealing its position. The ability to gather information while remaining nearly motionless allows the owl to watch far more than most animals realize.

And that may be the real reason so many creatures react when one arrives.

The great horned owl combines strength, silence, patience, and awareness in a way few predators can. By the time a rabbit, squirrel, snake, or even another owl realizes it is being watched, the great horned owl has often been watching for quite some time.

Perhaps that is why other animals seem to know when one is nearby.

The great horned owl is not simply another hunter in the night.

It is often the hunter watching the hunters.

Reading the Sky

At first glance, they all appear similar.

Large birds.

Broad wings.

Silhouettes against the sky.

Yet an osprey hovering above the water, a red-shouldered hawk watching from a fence post, a Mississippi kite chasing dragonflies, a vulture riding a thermal, and a barred owl moving through the darkness are not performing the same job.

They are reading the landscape in different ways.

The osprey watches the water.

The red-tailed hawk watches entire fields.

The Cooper’s hawk watches movement between trees.

The Mississippi kite watches the air itself.

Even the vultures, often dismissed as scavengers, are searching for clues that most of us never notice.

The next time a large bird catches your attention, resist the urge to identify it immediately.

Instead, watch what it does.

Does it hover?

Circle?

Perch?

Glide?

Disappear into the trees?

The answer often tells you as much as the feathers.

Because the sky is not filled with birds doing the same thing.

It is filled with specialists solving different problems.

And once you begin to notice those differences, the sky becomes a little easier to read.

At a distance, every raptor can seem like little more than a shape against the clouds. Spend enough time watching, however, and the sky becomes easier to read. | Image credit: A. Mitchell

References

Allen, L. L., Morrison, K. L., Scott, W. A., Shinn, S., Haltiner, A. M., & Doherty, M. J. (2018). Differences between stance and foot preference evident in osprey (Pandion haliaetus) fish holding during movement. Brain and Behavior, 8(11). https://doi.org/10.1002/brb3.1126

Arad, Z., Midtgard, U., & Bernstein, M. H. (1989). Thermoregulation in Turkey vultures. Vascular anatomy, arteriovenous heat exchange, and behavior. The Condor, 91(3), 505. https://doi.org/10.2307/1368103

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June 20, 2026
Where the Sand Breathes: Life Beneath the Tide Line in Onslow County

Most beachgoers look across the shoreline and see a boundary.

The ocean ends. The land begins.

But the strip of sand where waves wash ashore and slide back toward the sea is not really either one. It is a threshold—a place that becomes ocean and land again with every passing wave.

At first glance, this narrow band of wet sand appears empty. There are no marsh grasses, no oyster reefs, and no obvious schools of fish. Yet beneath the surface, the sand is alive with animals digging, filtering, feeding, hunting, and breathing.

This is the swash zone: the constantly shifting seam between ocean and land.

It is one of the most overlooked ecosystems on the North Carolina coast.

The swash zone is the narrow strip of shoreline where waves wash ashore and then retreat back toward the sea. Though it may appear to be little more than wet sand, it supports a diverse community of animals adapted to life between ocean and land. | Image credit: J. Morales

The Beach That Never Stops Moving

Unlike a marsh, oyster reef, or seagrass meadow, the swash zone never stays still.

Each wave pushes seawater into the sand and then pulls it back out again. Water moves through the spaces between sand grains, carrying oxygen, microscopic algae, bacteria, and organic matter. The sand itself acts almost like a living filter, supporting communities of organisms adapted to conditions that change minute by minute (Brown & McLachlan, 2018; McLachlan & Defeo, 2018).

To survive here, animals must tolerate burial, shifting sediments, crashing waves, changing salinity, and predators arriving from both land and sea.

Few species can endure such instability.

Those that do are specialists (Defeo et al., 2009).

The Living Wave Riders: Mole Crabs and Coquina Clams

If you’ve ever noticed the wet sand suddenly shimmer or seem to move as a wave retreats, you’ve likely witnessed two of the swash zone’s most abundant residents.

Atlantic Mole Crabs (Emerita talpoida)

An Atlantic mole crab, in Surf City, NC, briefly exposed at the surface of the swash zone. Within seconds, these specialized crustaceans can bury themselves beneath the sand, where they spend most of their lives filtering food from the surf. | Image credit: johnnybirder, iNaturalist

Known locally as sand fleas, Atlantic mole crabs spend nearly their entire lives buried beneath the surface of the swash zone.

They are not true crabs. Instead, they belong to a group of highly specialized crustaceans adapted for life where waves break on the shore. Their bodies are smooth, streamlined, and shaped almost like a small bean. Using powerful rear legs, they can bury themselves in saturated sand in seconds (Abude et al., 2024).

When waves wash overhead, they extend feathery antennae into the water and filter microscopic plankton and organic particles from the surf (Abude et al., 2024).

Rather than remaining stationary, mole crabs occupy the constantly shifting swash zone, where food and oxygen are delivered by breaking waves. Their abundance makes them one of the most important food sources for shorebirds, fish, and ghost crabs (Abude et al., 2024).

Coquina Clams (Donax variabilis)

Sharing the same habitat is one of the most recognizable shells on Atlantic beaches.

Coquina clams are the tiny, brightly colored shells scattered across the tide line in shades of pink, yellow, purple, blue, orange, and white.

Most people only notice the shells.

The living animal beneath them is remarkably adapted to life in moving sand.

Coquinas live just beneath the surface of the swash zone where they filter microscopic algae and suspended particles from the water. As waves advance and retreat, they repeatedly rebury themselves, using a muscular foot to dig into the sand with astonishing speed (Ellers, 1995).

Like mole crabs, coquinas are adapted to the dynamic conditions of the swash zone. Their abundance provides food for fish, crabs, and shorebirds, making them a critical link between microscopic plankton and larger coastal predators (Wilson, 1999).

Standing at the water’s edge, it is easy to think the beach is motionless.

In reality, thousands of coquinas and mole crabs may be moving beneath your feet with every wave.

The Night Shift: Atlantic Ghost Crabs (Ocypode quadrata)

Higher on the beach, above the reach of most waves, another resident waits.

Atlantic ghost crabs spend daylight hours hidden inside deep burrows excavated into the sand. Their pale coloration blends almost perfectly with the beach, making them difficult to see unless they move.

Atlantic ghost crabs spend daylight hours hidden in burrows above the tide line. Their pale coloration provides excellent camouflage against the sand, making them surprisingly difficult to spot until they move. | Image credit: A. Mitchell

While the swash zone below is dominated by animals filtering food from the surf, ghost crabs are hunters and scavengers.

After sunset, they emerge to patrol the shoreline, feeding on mole crabs, coquina clams, stranded marine organisms, insects, carrion, and whatever other opportunities the beach provides (Wolcott, 1978).

Many beachgoers never see them at all. Instead, they notice the evidence they leave behind. Round burrow openings dot the upper beach. Fresh tracks crisscross the sand overnight and disappear with the next tide. Occasionally, a pale shape darts sideways through the beam of a flashlight before vanishing into darkness.

Those burrows tell a story of their own. Beaches with abundant ghost crab burrows often support richer communities of animals living both above and below the sand, which is why scientists sometimes use ghost crabs as one way of assessing beach condition and disturbance (Schlacher et al., 2016).

The next time you notice a round hole in the upper beach with a pile of freshly excavated sand nearby, you are likely looking at the entrance to a ghost crab burrow—and evidence that the beach is still very much alive after dark.

Between the Grains

The largest residents of the swash zone are only part of the story.

Beneath the surface lies an even larger community that most beachgoers never see. Between individual grains of sand are tiny water-filled spaces that form a hidden habitat known as the interstitial zone. To us, a handful of wet sand looks solid. To these organisms, it is an underwater landscape of tunnels, chambers, and passageways (Higgins & Thiel, 1988).

The beach is layered with hidden communities. From amphipods and ghost crabs higher on the shore to coquina clams and mole crabs at the water’s edge, different species occupy distinct zones shaped by waves, moisture, food availability, and shifting sand. | Image credit: Michel et al., 2016

Amphipods: The Cleanup Crew

The line of seaweed, shells, and debris left behind by the tide may look messy, but it is often one of the busiest places on the beach.

Hidden among the wrack, in the upper intertidal zone, are amphipods, small crustaceans often called Atlantic beach hoppers (Americorchestia longicornis). If you sift through a pile of damp seaweed or drift algae, you may catch a glimpse of them springing away before disappearing back into cover.

Much of what washes ashore eventually becomes food for something else. Amphipods feed on decaying seaweed, dead animals, and other organic material stranded by the tide. In doing so, they help break down material that would otherwise accumulate along the shoreline. They also become food themselves, supporting shorebirds, fish, and other invertebrates that forage along the beach (Dugan et al., 2003).

Polychaete Worms: Engineers Beneath the Sand

Most beachgoers never see the worms living beneath the tide line, but their work is happening constantly beneath the surface.

As polychaete worms burrow through the sand, they create tiny pathways that allow water and oxygen to penetrate deeper into the sediment. In many ways, they perform the same role that earthworms do in a garden, except their garden is the beach itself.

Some species spend their lives feeding on organic material trapped between the sand grains, such as Lugworms (Arenicolidae). Others hunt small crustaceans and worms moving through the sediment such as Bloodworms (Glyceridae) and Paddle Worms / Shimmy Worms (Nephtyidae). As they burrow, feed, and move through the beach, they continually mix the sand and help create conditions that allow countless other organisms to survive there (McLachlan & Defeo, 2018).

Ribbon Worms: Hidden Predators

Not every animal beneath the sand is feeding on algae, bacteria, or decaying material.

Ribbon worms (Nemertea) are predators, though few people ever realize they are there. Hidden beneath the surface, they hunt some of the same tiny animals that share the spaces between the sand grains, including small worms, crustaceans, and other invertebrates moving through the sediment (Thiel & Kruse, 2001).

Many possess a remarkable feeding structure called a proboscis that can be rapidly extended to capture prey (Thiel & Kruse, 2001).

Most beachgoers will never see a ribbon worm, yet they are part of the same hidden food web as the amphipods, copepods, and nematodes surrounding them. Even beneath a seemingly empty stretch of sand, animals are feeding, avoiding predators, and competing for resources every hour of the day.

Nematodes: Life at Microscopic Scale

If you could shrink yourself down and explore a handful of wet sand, the landscape would look very different.

What appears solid to us is actually filled with tiny spaces between the grains. Moving through those water-filled passages are microscopic animals called nematodes (phylum Nematoda).

These tiny roundworms feed on bacteria, algae, fungi, and organic matter coating the sand. Though nearly invisible, they are among the most abundant animals on many beaches and play an important role in breaking down organic material and recycling nutrients throughout the sediment (Coull, 1999; Schratzberger & Ingels, 2018).

Harpacticoid Copepods: Tiny Links in the Food Web

Sharing those same microscopic spaces are harpacticoid copepods (Paraleptastacus wilsoni), tiny crustaceans that spend their lives moving between individual sand grains.

They graze on algae and microbial films coating the sediment, feeding on resources too small for larger animals to use directly. In turn, they become prey for larger invertebrates and juvenile fishes.

Most beachgoers will never see a harpacticoid copepod. Yet every handful of wet sand may contain a community of animals like these, quietly connecting the microscopic world to the larger food web of the beach (Schratzberger & Ingels, 2018).

Individually, these animals are easy to overlook.

Collectively, they form much of the living foundation of the tide line. The coquinas, mole crabs, ghost crabs, fishes, and shorebirds visible along the shoreline all depend, directly or indirectly, on countless small interactions taking place beneath the sand.

Following the Birds

One of the easiest ways to observe this hidden ecosystem is not by looking down.

It is by looking up.Anyone who spends time on the beach has likely watched sanderlings (Calidris alba) racing along the edge of the surf. They dart forward as a wave retreats, stop suddenly to probe the sand, and then sprint away from the next incoming wave. A little farther up the beach, ruddy turnstones (Arenaria interpres) pick through wrack lines left behind by the tide. Along the surf edge, Eastern willets (Tringa semipalmata semipalmata) walk deliberately through the shallows, searching for movement beneath the water.

To many beachgoers, they are simply birds feeding along the shoreline.

What they are actually doing is reading the beach.

Each probe into the sand is a search for prey hidden beneath the surface. Mole crabs, small worms, amphipods, coquinas, and other invertebrates living within the tide line provide food for these birds (Dugan et al., 2003; Hubbard & Dugan, 2003).

The birds go where the food is.

When shorebirds gather along a stretch of beach, they are often revealing an ecosystem that would otherwise remain invisible. Their presence tells us that the sand beneath them is alive with prey, even if we cannot see it ourselves.

In many ways, shorebirds act as interpreters of the tide line. By watching where they feed, pause, and congregate, we gain a glimpse into the hidden community supporting them below.

Reading the Beach

From a distance, the tide line can seem almost empty. A narrow strip of wet sand separates the ocean from the rest of the beach. Waves arrive, waves leave, and little appears to change.

Spend a few minutes watching, however, and a different picture begins to emerge.

Shorebirds gather where the surf is most active. Tiny shells appear and disappear with the retreating waves. Fresh ghost crab burrows punctuate the upper beach. Even the wrack line left behind by the tide becomes a gathering place for scavengers and foraging birds.

What first appears to be a simple boundary between land and sea begins to look more like a busy shoreline neighborhood.

At first glance, the tide line can appear almost empty. Look a little longer, however, and the clues begin to emerge—feeding shorebirds, scattered shells, and the constant movement of the surf all hint at the hidden community living beneath the sand. | Image credit: A. Mitchell

The animals living here are responding to the same thing: the constant movement of the tide. Food arrives with the surf, becomes available for a brief moment, and is quickly claimed by whatever creature is best adapted to find it. Some filter it from the water. Some collect it from the sand. Others hunt the animals already feeding there.

Because these organisms live so closely tied to the conditions of the beach, changes in their numbers can provide clues about the habitat itself (Defeo et al., 2009). A shoreline where birds are feeding, ghost crab burrows remain active, and life continues to reveal itself at the edge of the surf is often a sign that this narrow strip of beach is supporting the community that depends upon it.

When those communities decline, the change may not be immediately obvious. Yet over time the beach can begin to feel quieter. Fewer birds stop to feed. Fewer burrows appear in the sand. The signs become harder to find. Those changes can ripple outward through the food web, affecting species both on the beach and beyond it (Peterson et al., 2006).

The Threshold

The next time you stand at the edge of the surf, watch where the waves pause before sliding back toward the sea.

It is easy to see this narrow strip of shoreline as a boundary. Ocean on one side. Land on the other.

But the tide line is not really a dividing line at all.

It is a place where both worlds meet.

With every passing wave, food, oxygen, and life arrive from the ocean. Beneath the sand, animals capture it, consume it, recycle it, and pass it on. Shorebirds search for it. Ghost crabs emerge after dark to hunt it. Countless organisms spend their entire lives within a space that is neither fully ocean nor fully land.

Most people walk across this strip of beach without ever noticing it.

Yet it is one of the busiest places along the coast.

The next time you see shells appearing and disappearing in the surf, a flock of sanderlings racing the tide, or ghost crab burrows scattered across the upper beach, remember that these are not separate observations. They are pieces of the same story.

What appears to be an empty stretch of wet sand is actually a living threshold—a place where ocean and land remain connected through countless interactions happening beneath every step.

And once you see it, it becomes difficult to look at the shoreline the same way again.

The tide line in Surf City, NC may appear to be little more than wet sand. Yet beneath every retreating wave lies a hidden community connecting ocean and land through countless interactions, most of them unseen. | Image credit: A. Mitchell

References

Abude, R. R., Lôbo-Hajdu, G., Moreira, D. A., & Cabrini, T. M. (2024). Sandy beach mole crabs (Decapoda: Hippidae: Emerita): A systematic review of the anthropic impacts, populations density, and conservation strategies. Marine Environmental Research, 202, 106745. https://doi.org/10.1016/j.marenvres.2024.106745

Coull, B. C. (1999). Role of meiofauna in estuarine soft‐bottom habitats. Australian Journal of Ecology, 24(4), 327-343. https://doi.org/10.1046/j.1442-9993.1999.00979.x

Defeo, O., McLachlan, A., Schoeman, D. S., Schlacher, T. A., Dugan, J., Jones, A., Lastra, M., & Scapini, F. (2009). Threats to sandy beach ecosystems: A review. Estuarine, Coastal and Shelf Science, 81(1), 1-12. https://doi.org/10.1016/j.ecss.2008.09.022

Dugan, J. E., Hubbard, D. M., McCrary, M. D., & Pierson, M. O. (2003). The response of macrofauna communities and shorebirds to macrophyte wrack subsidies on exposed sandy beaches of Southern California. Estuarine, Coastal and Shelf Science, 58, 25-40. https://doi.org/10.1016/s0272-7714(03)00045-3

Ellers, O. (1995). Behavioral control of swash-riding in the clam Donax variabilis. The Biological Bulletin, 189(2), 120-127. https://doi.org/10.2307/1542462

Hubbard, D. M., & Dugan, J. E. (2003). Shorebird use of an exposed sandy beach in Southern California. Estuarine, Coastal and Shelf Science, 58, 41-54. https://doi.org/10.1016/s0272-7714(03)00048-9

McLachlan, A., & Defeo, O. (2018). The ecology of sandy shores (3rd ed.). Academic Press.

P, H. R., & Thiel, H. (1988). Intro study meiofauna. Smithsonian Books (DC).

Peterson, C. H., Bishop, M. J., Johnson, G. A., D’Anna, L. M., & Manning, L. M. (2006). Exploiting beach filling as an unaffordable experiment: Benthic intertidal impacts propagating upwards to shorebirds. Journal of Experimental Marine Biology and Ecology, 338(2), 205-221. https://doi.org/10.1016/j.jembe.2006.06.021

Pilkey, O. H., Rice, T. M., & Neal, W. J. (2014). How to read a North Carolina beach: Bubble holes, Barking sands, and rippled Runnels. UNC Press Books.

Schlacher, T. A., Lucrezi, S., Connolly, R. M., Peterson, C. H., Gilby, B. L., Maslo, B., Olds, A. D., Walker, S. J., Leon, J. X., Huijbers, C. M., Weston, M. A., Turra, A., Hyndes, G. A., Holt, R. A., & Schoeman, D. S. (2016). Human threats to sandy beaches: A meta-analysis of ghost crabs illustrates global anthropogenic impacts. Estuarine, Coastal and Shelf Science, 169, 56-73. https://doi.org/10.1016/j.ecss.2015.11.025

Schratzberger, M., & Ingels, J. (2018). Meiofauna matters: The roles of meiofauna in benthic ecosystems. Journal of Experimental Marine Biology and Ecology, 502, 12-25. https://doi.org/10.1016/j.jembe.2017.01.007

Thiel, M., & Kruse, I. (2001). Status of the nemertea as predators in marine ecosystems. Hydrobiologia, 456(1-3), 21-32. https://doi.org/10.1023/a:1013005814145

Wilson, J. G. (1999). Population dynamics and energy budget for a population of Donax variabilis (Say) on an exposed South Carolina beach. Journal of Experimental Marine Biology and Ecology, 239(1), 61-83. https://doi.org/10.1016/s0022-0981(99)00027-1

Wolcott, T. G. (1978). Ecological role of ghost crabs, Ocypode quadrata (Fabricius) on an ocean beach: Scavengers or predators? Journal of Experimental Marine Biology and Ecology, 31(1), 67-82. https://doi.org/10.1016/0022-0981(78)90137-5

June 5, 2026
The Fish That Follows the Tide: American Eels Along the Waters of Onslow County

Most people who see an American eel (Anguilla rostrata) for the first time do not think they are looking at a fish at all.

They appear suddenly in shallow blackwater creeks, beneath dock lights, beside culverts after rain, or slipping through spartina grass at dusk. Long and muscular, they move more like a snake than something belonging to a river. In muddy water they are usually seen only in fragments — a curve disappearing beneath tannin-dark current, or a ripple crossing the surface where something alive passed moments earlier.

Along the coast of Onslow County, American eels have likely moved through these waters longer than the marshes themselves have held their present shape. They pass through tidal creeks, estuaries, freshwater streams, flooded ditches, cypress swamps, and inland rivers, connecting habitats that often seem separate to us but function together as one living system.

And almost no one realizes that every eel seen here began life far out at sea.

Born Beyond the Horizon

The American eel’s life cycle spans thousands of miles, linking the Sargasso Sea, Atlantic coast, estuaries, marshes, rivers, and inland lakes through a single migration that can last decades. | Image credit: U. S. Fish and Wildlife Service

Far offshore, beyond the continental shelf and beyond the visible horizon of North Carolina’s beaches, lies the Sargasso Sea — a warm, rotating gyre of Atlantic water bordered by ocean currents rather than land. This is where American eels spawn, though much of their reproduction still remains one of the great biological mysteries of the Atlantic Ocean (Béguer‐Pon et al., 2015).After hatching, eel larvae drift for months within the Gulf Stream. At this stage they do not yet resemble eels. They are thin, transparent, leaf-shaped organisms called leptocephali, nearly invisible against the open ocean (Wang & Tzeng, 2000).

Leptocephali, the larval stage of the American eel, drift within the Atlantic Ocean currents for months before transforming into glass eels and entering coastal estuaries. | Image credit: hunterefs, iNaturalist

As they approach the coastline, their bodies begin to transform. The broad leaf-like shape narrows into the familiar eel form. Their organs reorganize. Their muscles strengthen. By the time they arrive in estuaries along the Atlantic coast, they have become what scientists call glass eels — small, transparent juveniles that move into tidal rivers and marshes under the cover of darkness (Starks, 2026).

Glass eels, the transparent juvenile stage of the American eel, gather along coastlines before moving inland through estuaries, marshes, and rivers. | Image credit: W. O’Connor

At night in late winter and spring, these glass eels enter coastal waters by the thousands. Most people never notice them. But beneath bridge lights and along quiet marsh edges, tiny transparent bodies gather against the current, moving inland on tides that have repeated for thousands of years.

Some settle into estuaries. Others continue far upriver into freshwater creeks and reservoirs. A single eel may spend decades there before returning once again to the open Atlantic.

As they continue growing, American eels pass through a series of color changes that reflect different stages of their life cycle. Newly arrived glass eels are nearly transparent. Within months they develop pigmentation and become elvers, often showing olive, brown, or yellowish coloration. During the longest phase of their lives they are known as yellow eels, displaying yellow-brown to olive sides with lighter undersides while feeding and growing in estuaries, rivers, and wetlands for years or even decades (ASMFC, 2017; Haro et al., 2000). As they mature and prepare for their return migration to the Sargasso Sea, they transform into silver eels. Their bodies darken along the back, their sides become silvery, and their eyes enlarge — adaptations that help prepare them for life in the open ocean and their final spawning migration (Haro et al., 2000; Tesch & White, 2008).

American eels change dramatically throughout their lives, from transparent leptocephali and glass eels to yellow eels in estuaries and rivers before developing the silver coloration of spawning adults returning to the Sargasso Sea. | Image credit: C. Bowser & R. Papish

The Marsh at Night

American eels are largely nocturnal, which means many people living along the coast rarely realize how common they are.

After sunset, they emerge from submerged roots, oyster reefs, marsh undercuts, rock piles, and mud-bottom channels to feed. In tidal creeks around Onslow County, they move through habitats that shift constantly with salinity, rainfall, temperature, and tide.

Unlike many fish that specialize in one narrow environment, eels are remarkably flexible. They can tolerate freshwater, brackish estuaries, and saltwater marsh systems throughout different stages of life (Able, 2005).

This flexibility makes them important ecological connectors between habitats.

An eel feeding in an estuary may consume shrimp, small fish, crabs, worms, insect larvae, and carrion. Larger eels become predators capable of feeding on nearly anything they can overpower. In turn, they become prey themselves for river otters, wading birds, striped bass, sharks, alligators, ospreys, and larger coastal predators (MacGregor et al., 2009).

What appears at first to be a strange solitary fish is actually woven through multiple levels of the food web.

American eels help transfer energy through the ecosystem, linking marsh invertebrates, small fish, and larger predators with the waters of Onslow County. | Image credit: A. Mitchell

Ancient Currents and Modern Coastlines

And in a much deeper sense, eels also connect modern coastal ecosystems to ancient worlds that existed long before humans reshaped shorelines. Their lineage stretches back tens of millions of years, surviving repeated shifts in sea level, climate, and continental geography. Long before beach renourishment projects, before the Outer Banks existed in their present form, and even before many modern mammals evolved, ancestral eels were already moving between oceans and coastal rivers (Inoue et al., 2010).

That timeline overlaps surprisingly well with the broader environmental history explored in my earlier posts. During the Carboniferous Period over 300 million years ago, vast swamp forests covered portions of what would eventually become eastern North America, laying down the organic material that later formed coal deposits (Sahney et al., 2010). The world looked entirely different then, but the shallow coastal environments that support migratory fish today evolved from ancient marine systems shaped across those immense spans of geologic time.

By 66 million years ago — around the end-Cretaceous extinction that eliminated non-avian dinosaurs — early eel relatives already existed in ancient seas (Near et al., 2012). Modern American eels evolved much later, but their migratory strategy reflects something extraordinarily old: the continual exchange between ocean currents, estuaries, rivers, and wetlands.

Fossil eels resembling modern species appear in the geologic record tens of millions of years ago, reflecting a lineage that has persisted through changing oceans, shifting coastlines, and repeated cycles of environmental change. | Image credit: Fossil Forum

Beach renourishment, by contrast, exists on an almost microscopic timescale geologically. Most projects reshape shorelines over years or decades, temporarily altering sediment movement, inlet dynamics, turbidity, and nearshore habitat. Eels are resilient enough to survive natural coastal change — hurricanes, shifting barrier islands, overwash events, and migrating inlets that have continually transformed the Atlantic coast. But human-driven shoreline modification can compress those disturbances into shorter, more frequent intervals that affect how juvenile eels enter estuaries and move inland.

So while beach renourishment itself is modern, the habitats it alters are part of a coastal system assembled over millions of years — one that species like the American eel have been navigating since long before the present coastline existed.

Their ecological importance is recognized even within local fisheries. In many areas, crab pots are now designed with eel escapement openings that allow smaller American eels to exit traps rather than become unintended bycatch. These modifications help reduce eel mortality while acknowledging the species’ role in maintaining healthy estuarine ecosystems.

The Animal That Connects Rivers

Many coastal species remain tied to a single environment. Oyster reefs remain fixed in estuaries. Marsh periwinkle snails cling to grass stems. Flounder shift between nearshore and estuarine waters but remain marine fish.

American eels move between worlds.

A juvenile eel may travel from offshore Atlantic currents into a coastal marsh creek, then into freshwater rivers hundreds of miles inland before eventually returning to the Sargasso Sea years later to spawn. Very few animals along the Atlantic coast connect ecosystems across such enormous distances.

American eels connect ecosystems across the Atlantic Ocean, beginning life in the Sargasso Sea before dispersing into estuaries, rivers, lakes, and wetlands throughout eastern North America. } Image credit: L. Poirier

Because of this, eels transport energy and nutrients between habitats that otherwise remain loosely connected. Predators feeding on eels receive marine-derived nutrients that originated far offshore. When adult eels migrate back toward the Atlantic, they carry inland energy back toward the ocean system (Jessop et al., 2020).

Even freshwater mussels depend upon them.

Several mussel species release microscopic larvae called glochidia that temporarily attach to fish hosts while developing. Research in Mid-Atlantic rivers has shown that American eels are one of the most successful hosts for some native mussel species, helping sustain mussel populations throughout eastern river systems (Schwalb et al., 2013).

So beneath the surface, the eel is doing more than surviving for itself. It is helping move life through the watershed.

What Happens When Eels Decline

Globally, the American eel is listed as “endangered, but stable” on the IUCN Red List because of long-term population declines across much of its range (IUCN, 2023). In the United States, however, the U. S. Fish and Wildlife Service has concluded the species does not currently require federal protection under the Endangered Species Act. The Atlantic States Marine Fisheries Commission determined that their populations are largely depleted in U. S. waters and have recommended continued monitoring of their populations because their life cycle depends upon the health and connectivity of both freshwater and marine environments (ASMFC, 2026).

For centuries, rivers along the Atlantic coast held far larger eel populations than they do today.

In many parts of the eastern United States, dams and hydroelectric turbines block migration routes and kill adults moving back downstream toward the ocean. Those barriers have severely reduced eel access to inland habitat across major river systems (Haro et al., 2000).

Onslow County is different.

The New River estuary is not fed by large mountain rivers or controlled by dams upstream. It is a relatively closed coastal watershed shaped instead by rainfall, groundwater springs, blackwater creeks, tidal exchange, runoff, and low-gradient streams winding through wetlands and forests. Here, eel movement depends less on navigating massive river barriers and more on the health and connectivity of marshes, culverts, floodplains, tidal creeks, and shallow estuarine habitat.

That makes local environmental changes especially important.

Wetland loss, shoreline hardening, stormwater runoff, dredging, declining water quality, and altered tidal flow can fragment the smaller pathways eels rely upon throughout the watershed. Even undersized culverts or poorly designed drainage structures can interrupt movement between creeks and flooded wetlands during critical migration periods.

Barrier islands also shape the system eels enter.

Along the Onslow coast, shifting inlets, overwash events, and beach renourishment projects continually reshape the boundary between ocean and estuary. In some cases, renourishment can temporarily increase turbidity, bury nearshore habitat, or alter tidal exchange patterns affecting juvenile eel recruitment into estuarine creeks. At the same time, healthy barrier islands and functioning marsh systems help buffer salinity extremes, reduce erosion, and maintain the sheltered estuarine habitat young eels depend upon once they arrive from the Atlantic.

Because eels use so many habitats, their decline spreads outward through the ecosystem in ways people may not immediately notice.

River otters lose an important prey source in some waterways. Mussel reproduction declines where host fish disappear. Predators that once relied seasonally on eels shift toward other prey. The disappearance of a species that connects marshes, rivers, estuaries, and offshore currents weakens the ecological ties between those environments.

And unlike species that reproduce quickly, eels recover slowly.

An eel living beneath a dock in coastal North Carolina may already be older than the child fishing above it. Some females remain inland for decades before ever returning to spawn (Haro et al., 2000). Every interruption between inland waters and the sea disrupts a migration pattern older than modern coastlines themselves.

The Fish Most People Never See

On warm summer nights in coastal North Carolina, much of the estuary moves unseen.

Shrimp rise into the water column. Rays cross shallow mudflats beneath darkness. Juvenile fish gather around dock lights. Crabs emerge from oyster beds to forage with the tide.

And somewhere below that shifting water, an eel moves silently between habitats, carrying the Atlantic inland and returning inland waters back toward the sea.

Most people standing along the shoreline will never know it is there.

But the marsh still holds the traces of its passage. So do the river otters weaving through flooded reeds and the herons stalking the quiet creek edges at dusk.

The tidal creeks of Onslow County continue shaping themselves around an animal whose life still stretches beyond much of human observation — from blackwater rivers to the open Atlantic, and back again.

Hidden beneath dark water and shifting tides, American eels remain one of the Atlantic coast’s most remarkable connections between ocean, estuary, and river. | Image credit: E. Smith, iNaturalist

References

Able, K. W. (2005). A re-examination of fish estuarine dependence: Evidence for connectivity between estuarine and ocean habitats. Estuarine, Coastal and Shelf Science, 64(1), 5-17. https://doi.org/10.1016/j.ecss.2005.02.002

ASMFC. (2026). American Eel. Atlantic States Marine Fisheries Commission. https://asmfc.org/species/american-eel/

Béguer-Pon, M., Castonguay, M., Shan, S., Benchetrit, J., & Dodson, J. J. (2015). Direct observations of American eels migrating across the continental shelf to the Sargasso Sea. Nature Communications, 6(1). https://doi.org/10.1038/ncomms9705

Haro, A., Richkus, W., Whalen, K., Hoar, A., Busch, W., Lary, S., Brush, T., & Dixon, D. (2000). Population decline of the American eel: Implications for research and management. Fisheries, 25(9), 7-16. https://doi.org/10.1577/1548-8446(2000)025<0007:pdotae>2.0.co;2

Inoue, J. G., Miya, M., Miller, M. J., Sado, T., Hanel, R., Hatooka, K., Aoyama, J., Minegishi, Y., Nishida, M., & Tsukamoto, K. (2010). Deep-ocean origin of the freshwater eels. Biology Letters, 6(3), 363-366. https://doi.org/10.1098/rsbl.2009.0989

Jessop, B. M. (2020). Oceanic environmental effects on American eel recruitment to the east river, Chester, Nova Scotia. Marine and Coastal Fisheries, 12(4), 222-237. https://doi.org/10.1002/mcf2.10121

MacGregor, R., Casselman, J. M., Allen, W. A., Haxton, T., Dettmers, J. M., Mathers, A., LaPan, S., Pratt, T. C., Thompson, P., Stanfield, M., Marcogliese, L., & Dutil, J. D. (2009). Natural Heritage, Anthropogenic Impacts, and Biopolitical Issues Related to the Status and Sustainable Management of American Eel: A Retrospective Analysis and Management Perspective at the Population Level. American Fisheries Society Symposium, 69, 713-740. https://www.thelandbetween.ca/wp-content/uploads/2014/06/Anacat_Final_Final-reprint_-macgregor.pdf

Near, T. J., Eytan, R. I., Dornburg, A., Kuhn, K. L., Moore, J. A., Davis, M. P., Wainwright, P. C., Friedman, M., & Smith, W. L. (2012). Resolution of ray-finned fish phylogeny and timing of diversification. Proceedings of the National Academy of Sciences, 109(34), 13698-13703. https://doi.org/10.1073/pnas.1206625109

Pike, C., Casselman, J., Crook, V., DeLucia, M. B., Jacoby, D., & Gollock, M. (2023). Anguilla rostrata. The IUCN Red List of Threatened Species. https://dx.doi.org/10.2305/IUCN.UK.2023-1.RLTS.T191108A129638652

Sahney, S., Benton, M. J., & Falcon-Lang, H. J. (2010). Rainforest collapse triggered Carboniferous tetrapod diversification in Euramerica. Geology, 38(12), 1079-1082. https://doi.org/10.1130/g31182.1

Schwalb, A. N., Cottenie, K., Poos, M. S., & Ackerman, J. D. (2011). Dispersal limitation of unionid mussels and implications for their conservation. Freshwater Biology, 56(8), 1509-1518. https://doi.org/10.1111/j.1365-2427.2011.02587.x

Starks, C. (2026). Interstate Fisheries Management Program Overview: American Eel (May 2026). Atlantic States Marine Fisheries Commission. https://asmfc.org/wp-content/uploads/2025/11/4.AmericanEel_May-2026.pdf

Tesch, F. W., & White, R. J. (2008). The eel (5th ed.). John Wiley & Sons.

Wang, C., & Tzeng, W. (2000). The timing of metamorphosis and growth rates of American and European eel leptocephali: A mechanism of larval segregative migration. Fisheries Research, 46(1-3), 191-205. https://doi.org/10.1016/s0165-7836(00)00146-6

May 29, 2026
When the Water Turns Gelatinous: The Hidden Filter Feeders of Onslow County

Sometimes the estuary changes before people notice why.

The water may look normal from shore, but drifting just beneath the surface are long ribbons of translucent gelatin — soft strands that gather along marsh edges, collect in eddies, or drift through the current like mucus suspended in the tide. In Surf City this week, people described them as “whale snot.”

Gelatinous material collected from Murrells Inlet, South Carolina at the low tide edge. Such suspended material may include colonial tunicates, salps, mucus-rich plankton aggregates, and other organic matter associated with productive estuarine conditions. | Image credit: J. Mattevi

They are more likely colonial tunicates or salps, gelatinous filter-feeders that can appear suddenly when conditions in the water favor rapid plankton growth (Bone, 1998; Madin & Deibel, 1998).

What matters is not only the organisms themselves, but what their appearance says about the estuary around them.

The drifting forms

These blooms often form when the water column becomes temporarily stable and productive (Madin, 1982). Warmer temperatures, calmer conditions, reduced wave turbulence, and elevated plankton concentrations create an environment where filter-feeding gelatinous organisms can reproduce rapidly. Water moving through the inlets may also transport offshore plankton communities into the estuary, concentrating them in tidal creeks and slower-moving surface water (Bone, 1998; Madin, 1982).

In these calmer stretches, the water column begins separating into layers. Suspended plankton remains concentrated near the surface while weaker turbulence allows fragile gelatinous colonies to persist long enough for blooms to form. What would normally disperse through wave action instead remains suspended within the estuary itself (Madin, 1982).

To most people, they look like debris.

Ecologically, they are processing the estuary in real time.

Salps and colonial tunicates continuously pump water through their bodies, removing suspended phytoplankton, bacteria, and organic particles from the water column. During bloom periods, enormous volumes of water can be filtered each day (Madin, 1982; Sutherland et al., 2010). In effect, the estuary briefly develops a drifting layer of living filtration suspended between the surface and the bottom.

Each colony filters continuously. Thousands moving through a tidal creek or marsh edge at once can collectively filter enormous volumes of suspended material over short periods of time, temporarily altering the clarity and composition of the surrounding water (Riisgård & Larsen, 2010).

That shift affects everything around them.

When these blooms are abundant, water clarity can temporarily improve as suspended particles are removed. Organic material becomes concentrated into mucus-rich waste pellets and decaying gelatinous tissue that sink toward the bottom, transferring energy from the surface into benthic food webs below (Madin & Deibel, 1998). Microbes, worms, crustaceans, and scavengers begin responding almost immediately (Madin, 1982; Madin & Deibel, 1998).

Instead of remaining suspended near the surface, nutrients and organic matter begin settling downward through the water column. What had been dispersed through open water becomes concentrated along the bottom, where deposit-feeding worms, small crustaceans, microbes, and scavengers begin incorporating that material into the estuary below (Madin, 1982).

The bloom itself becomes food.

The drifting masses also create temporary structure within otherwise open water. Small fish gather along their edges. Tiny invertebrates gather within folds and strands of gelatinous tissue. Predators begin responding not only to the bloom itself, but to the concentration of life forming around it (Bone, 1998; Madin & Deibel, 1998).

Small fish and invertebrates feed around the edges of these drifting masses. Juvenile fishes may remain near these drifting masses as food becomes concentrated around them. Sea turtles, some fishes, and other gelatinous predators may increase feeding activity where blooms become dense enough to concentrate prey (Bone, 1998).

But like many ecological events, balance matters.

If too few filter-feeders are present during periods of elevated nutrients, water grows murkier and oxygen conditions become less stable, particularly during heat and nighttime respiration. But filtration at the opposite extreme can also reshape the food web. Too many gelatinous filter-feeders, however, may strip large amounts of plankton from the water column, altering food availability for larval fishes and other plankton-dependent organisms higher in the food web (Petersen & Riisgård, 1992).

Most blooms are temporary.

Currents disperse them. Heat and bacteria break them apart. Waves fragment the colonies into nearly invisible strands that disappear back into the system as quickly as they arrived. Even in collapse, the bloom continues feeding the estuary. Decaying tissue is broken apart by bacteria, consumed by scavengers, and recycled back into the same nutrient pathways that allowed the bloom to form in the first place (Madin, 1982).

But for a short period, the estuary reveals something normally hidden: the water between the marsh and the bottom is not empty space. It is an active habitat, filled with organisms that filter, recycle, transport, and redistribute energy through the coastal ecosystem (Bone, 1998; Madin, 1982).

The attached forms

Not all tunicates remain suspended in the water column. Some attach themselves directly to the surfaces that hold still long enough for life to accumulate—dock pilings, oyster shell, ropes, marsh grass roots, floats, and the shaded undersides of piers where current continues moving but turbulence drops away.

Along the estuaries of Onslow County, these attached forms become part of what looks, at first glance, like simple buildup.

The surfaces beneath docks rarely stay bare for long (Wahl, 1989; Lindeyer & Gittenberger, 2011). Marine scientists often describe these layered growths as fouling communities, but along the estuary they appear simply as the layer of life that forms on anything left in the water long enough. First comes a film too thin to notice, then algae, then colonies of organisms layered over one another until wood, shell, and rope begin carrying part of the estuary itself.

Sea squirts and other attached filter-feeders beneath a dock in Surf City, North Carolina. | Image credit: A. Mitchell

Tunicates are part of that layer.

Along this coast, attached tunicates can include solitary species like the pleated sea squirt (Styela plicata) and the sea grape (Molgula manhattensis), as well as colonial species such as Clavelina oblonga and sea pork (Aplidium stellatum) (Van Name, 1945; Lambert, 2007).

Some grow individually, attached like soft sacs with openings at the top. Others spread as colonial sheets or clustered lobes, sharing a common outer covering while continuously filtering water moving past them. Around pilings and floating docks, entire communities can form this way—sponges beside hydroids, bryozoans layered against tunicates, all responding to current, salinity, temperature, and suspended food moving through the tide (Wahl, 1989).

To most people, these surfaces register as slime.

Ecologically, they are filtration, habitat, and nutrient transfer occurring simultaneously (Wahl, 1989).

Sea squirts

The organisms most people recognize first are usually sea squirts. They appear as rubbery sacs attached beneath docks or clustered along ropes, and shell. Press one accidentally and water jets outward through small siphons near the top of the body, giving rise to the common name.

A sea squirt partially coated in algae and sediment beneath shallow estuarine water in Surf City, North Carolina. The two siphon openings are part of the continuous filtration process occurring beneath docks and marsh edges. | Image credit: A. Mitchell

Species such as the pleated sea squirt (Styela plicata) often develop thick, wrinkled outer coverings ranging from tan and off-white to purple, while the sea grape (Molgula manhattensis) forms smaller rounded bodies attached within the layered communities growing beneath docks and along estuarine structure — what marine scientists often call fouling communities (Van Name, 1945).

What looks like a reaction is actually the visible end of a process already underway.

Sea squirts continuously pull water inward through one siphon, filter out phytoplankton, bacteria, and suspended particles from the water, then expel the filtered water back into the estuary through another opening. The animal does not begin filtering when disturbed. It has been filtering the entire time (Riisgård & Larsen, 2010).

In productive estuarine water, thousands of these organisms may be pumping simultaneously (Riisgård & Larsen, 2010).

That filtration matters.

As suspended particles are removed, nutrients become concentrated into waste and biomass that can be transferred downward into bottom communities. Water clarity may improve locally (Riisgård & Larsen, 2010). Microbial activity shifts around them. Small invertebrates begin using the folds and surfaces their bodies create.

Their presence also signals something about the surrounding water.

Sea squirts tend to cluster where flow remains steady enough to deliver oxygen and suspended food continuously, but not so violent that colonies are torn free. Around tidal creeks, dock edges, and quieter stretches of the Intracoastal Waterway, their abundance often reflects a system carrying enough suspended productivity to sustain constant filtration (Barros, 2009).

Sea pork

Some tunicates take a different form entirely.

One of these is sea pork, commonly associated with colonial tunicates such as Aplidium stellatum, which spread outward as shared gelatinous colonies rather than isolated individuals (Van Name, 1945).

Sea pork, a colonial tunicate, washed ashore along Surf City, North Carolina. Though it appears as a single gelatinous mass, it is made up of thousands of tiny filter-feeding animals embedded within a shared outer layer. | Image credit: D. Miles

Sea pork spreads across submerged surfaces in thick, rubbery colonies that look less like individual animals and more like flesh-colored mats attached beneath floats and pilings. Depending on the species and age of the colony, the surface may appear muted pink, tan, orange, or almost translucent beneath the waterline.

Most people don’t realize they are looking at colonies made up of thousands of tiny individual filter-feeding bodies embedded together within a shared outer layer.

The colony functions collectively (Van Name, 1945).

Water moves continuously through countless small openings across the surface, carrying suspended plankton and organic particles into the colony while waste and filtered water move back outward into the surrounding estuary (Riisgård & Larsen, 2010).

That structure changes the surface around it.

Sea pork colonies trap sediment and create small protected surfaces where microorganisms and invertebrates begin to accumulate between folds and protected edges. Tiny crustaceans move across them. Worms and microbial films develop within the folds and protected spaces between colonies. What appears smooth from above becomes, at smaller scales, complex terrain (Wahl, 1989).

Like other filter-feeding communities along this coast, sea pork helps transfer suspended energy from the water column into the attached world beneath docks and marsh edges.

And once that layered habitat forms, other organisms begin responding to it—including the nudibranchs moving slowly across its surface.

Nudibranchs

At low tide along the edges of the sound—where pilings hold a thin skin of life and oyster shells stack into uneven ridges—the water sometimes carries color that doesn’t belong to the sand or the grass. It moves slowly, almost deliberately, across surfaces that most people step over without noticing. What looks like a fragment of drifting algae or a soft piece of shell resolves, if you stop long enough, into something alive.

These are nudibranchs.

They are not fish, not worms, not plants. They are marine gastropods—relatives of snails—but without shells (Valdés et al., 2006). Along the coast of Onslow County, they appear in the quiet places: beneath docks in the Intracoastal Waterway, along the edges of Topsail Island marsh creeks, and on the submerged surfaces where current slows just enough for growth to take hold.

Along shallow estuarine structure in this region—beneath docks, across pilings, and within the layered growth attached to ropes and shell—nudibranchs may include species such as the striped nudibranch (Cratena pilata), the Brazilian aeolid sea slug (Spurilla braziliana), the fringeback dondice (Dondice occidentalis), Thecacera pennigera, Berghia rissodominguezi, and the brackish-water species Tenellia adspersa (Marcus, 1972; Valdés et al., 2006).

Most people never see them. But they are there, working through the same system that shapes everything else along this coast.

A nudibranch collected near Morehead City, North Carolina, viewed under magnification. The cerata along its back increase surface area for respiration and, in some species, store defensive stinging cells obtained from prey. | Image credit: marineinvertgirl, iNaturalist

Built for sensing, not speed

A nudibranch’s body is built for sensing and feeding, not speed. The two structures at the front—rhinophores—sample the water chemically, reading it the way a shoreline bird reads the wind. Along their backs, many species carry cerata, small extensions that look ornamental but function as both respiration and defense.

In aeolid nudibranchs like Spurilla braziliana, Cratena pilata, and Berghia rissodominguezi, these cerata become important sites for both respiration and defensive storage of stinging cells obtained from prey (Goodheart et al., 2018).

The Brazilian aeolid sea slug (Spurilla braziliana) moving across submerged structure near Morehead City, North Carolina. The cerata lining its back function in respiration and can store defensive stinging cells obtained from prey such as anemones and hydroids. | Image credit: wonglab, iNaturalist

They move slowly because they can afford to. Their food doesn’t run.

Sponges, hydroids, bryozoans—these are the surfaces most people would describe as “growth” on docks or shells. To a nudibranch, those surfaces are structure, habitat, and food all at once (Valdés et al., 2006).

The work they do (even when no one’s watching)

Along this coastline, growth is constant. Give any hard surface—an old piling, a piece of shell, a boat hull—enough time in the water and it becomes layered. First a film, then algae, then invertebrates. The system builds upward and outward, creating what scientists call structural complexity, but what you actually see is texture: roughness where there used to be smoothness (Wahl, 1989).

Along shallow estuarine bottoms, algae, shell, and attached growth begin forming the layered habitat that supports juvenile fish, crabs, filter-feeders, and the organisms moving through the estuary food web. | Image credit: A. Mitchell

Nudibranchs move through that texture selectively.

Many species feed on a single type of prey. One may specialize in a particular sponge. Another tracks hydroids, those delicate branching animals that resemble tiny underwater ferns. Species such as Dondice occidentalis, Cratena pilata, and Tenellia adspersa are commonly associated with hydroids and other organisms growing across submerged pilings, docks, ropes and shell in shallow coastal environments (Marcus, 1972; Valdés et al., 2006). This selectivity matters more than their size suggests. They are not removing everything. They are removing specific pieces of the system.

That kind of feeding does not flatten the landscape—it shapes it.

Where one organism begins to dominate, nudibranchs can limit its spread. Where surfaces would otherwise become uniform, their grazing introduces variation. Over time, this helps maintain the uneven habitat small fish, shrimp, and juvenile invertebrates depend on (Wahl, 1989).

Growth that begins as algae quickly becomes habitat. Along shallow estuarine edges, layered vegetation and attached organisms create shelter for crabs, juvenile fish, shrimp, and other small life moving through the system. | Image credit: A. Mitchell

It’s easy to miss because nothing dramatic happens. There’s no visible clearing, no sudden absence. But the balance of what grows, and where, shifts quietly in response to their presence.

Borrowed defenses, redistributed energy

Some nudibranchs do something that seems improbable until you see it up close: they take the defenses of what they eat and keep them.

Hydroids and certain cnidarians carry stinging cells—nematocysts—that function as protection. When a nudibranch feeds on them, those cells pass through the digestive system intact and are stored within the cerata along its back. The nudibranch doesn’t just consume its prey; it incorporates part of its defense (Goodheart et al., 2018).

This changes how energy moves through the system.

Instead of defenses being lost when prey is consumed, they are transferred upward. The nudibranch becomes both grazer and deterrent, a small organism that is less likely to be eaten because of what it has already eaten.

You can see the result in their coloration. Many are bright, almost out of place against the muted tones of sand and shell. That color is not decoration—it’s a signal (Avila, 1995). Along this coast, where predation pressure is constant, visibility can function as warning rather than risk.

Where they sit in the trophic cascade

They are not apex predators. They don’t regulate fish populations or move through the system in ways that draw attention. But they occupy a position that connects the base of the food web to everything above it.

They feed on organisms that build habitat.

Those organisms—sponges, hydroids, bryozoans—form the living surface that supports small invertebrates and juvenile fish. Those smaller organisms, in turn, become prey for larger fish, which then connect to the predators people are more familiar with along this coast—species like blacktip shark (Carcharhinus limbatus) and Atlantic sharpnose shark (Rhizopriodion terranovae) that move along the breakers and through the sounds.

Remove the visible predators, and people notice quickly.

Remove something like a nudibranch, and what changes is slower, but it moves in the same direction. Surfaces become dominated by fewer species. Habitat becomes more uniform. The small organisms that rely on variation lose space. That change works its way upward, not as a single event, but as a shift in the system’s capacity to support diversity.

Even small organisms attached to pilings and submerged structure become part of much larger coastal food webs. Scientific food-web models show nudibranchs, hydroids, bryozoans, worms, shrimp, and fishes linked together through the transfer of energy across the ecosystem.

Generalized food web showing how organisms associated with sponge and attached invertebrate communities connect upward through coastal ecosystems. Nudibranchs, hydroids, bryozoans, worms, shrimp, and fishes all participate in the transfer of energy through these layered habitats. Adapted from Archer et al. (2020).

Why they stay hidden

There’s a reason most beachgoers never encounter them.

They live where water movement slows just enough to allow growth to accumulate, but not so still that oxygen drops away. Around docks, inside creeks, along the quieter edges of the New River estuary, they remain attached to the surfaces that feed them.

Out in the open surf, where sand shifts constantly and hard structure is buried and exposed with each change in wind and tide, there’s less for them to hold onto and less for them to eat. The breakers are a moving environment (Wahl, 1989). Nudibranchs belong to the places that hold still just long enough for complexity to form.

What changes if they’re gone

Nothing you would notice in a single afternoon at the beach.

But over time, the surfaces beneath the waterline would begin to simplify. One or two fast-growing organisms would spread further, covering space that would otherwise remain shared. The small sheltered spaces used by larval fish, juvenile shrimp, and small crabs would begin to thin out.

That loss doesn’t stay at the bottom.

It moves upward, changing how much life the system can support, and how evenly that life is distributed. By the time it reaches the fish people see from the shore, the cause is no longer visible. But it started here, in the slow movement of something small across a surface most people never look at twice.

Nudibranchs don’t reshape the coastline in ways that draw attention. They don’t mark their presence with absence or disturbance. Instead, they work within what’s already there—adjusting, redistributing, and maintaining the uneven structure that makes this coast function.

If you happen to see one, it won’t be moving fast. It won’t need to.

What they’re feeding on (and why it looks familiar)

Along the docks and pilings of Onslow County, the surfaces most people notice first aren’t fish at all. They’re the things attached to everything.

The branching, plant-like fuzz that brushes your hand when you reach into the water—those are hydroids. The firm, uneven coatings that look like they’re part of the structure itself are often sponges or bryozoans.

It’s easy to group all of it together as buildup. Something slimy, something in the way.

But that “squirt” people laugh about isn’t random. A tunicate pulls water in, filters out plankton and suspended particles, and then expels that water back out. What looks like a reaction is just the visible end of constant filtration. They are processing the water column—removing particles, cycling nutrients, and clarifying the water in small, continuous ways (Riisgård & Larsen, 2010).

Hydroids are doing something different. They are predators at a scale most people don’t consider, capturing microscopic prey drifting past. Sponges filter continuously as well, pulling bacteria and organic matter from the water and converting it into biomass that other organisms can use.

A sea anemone beneath shallow estuarine water in Surf City, North Carolina. Organisms like these become part of the layered communities that nudibranchs, tunicates, hydroids, and other invertebrates move through beneath the surface. | Image credit: A. Mitchell

This is the surface layer of the ecosystem.
And it doesn’t stay unchecked.

The ones moving across the surface

Species like the Brazilian aeolid sea slug (Spurilla braziliana) often feed directly on anemones associated with these same submerged communities, while smaller species such as Tenellia adspersa are frequently associated with hydroids in brackish and estuarine waters (Valdés et al., 2006).

The nudibranchs moving across these surfaces are not all the same, and what they eat tells you what role they’re playing.

Some of the small, leaf-like sea slugs in this region—species in the genus Elysia—feed on algae and can even retain the chloroplasts from what they consume, briefly using sunlight as part of their energy system. They blur the line between grazing and something closer to plant-like function (Valdés et al., 2006).

Others, like Cratena pilata and Dondice occidentalis, track hydroids specifically. Where hydroids begin to spread across a piling, these nudibranchs follow, feeding in a way that limits how dense those colonies can become (Marcus, 1972).

Species such as Thecacera pennigera are often associated with the layered communities growing beneath docks and harbor structure, while Berghia rissodominguezi and Spurilla braziliana move through shallow cnidarian-rich habitat where anemones and hydroids provide both food and defensive material (Valdés et al., 2006).

Heavier-bodied nudibranchs—often in groups like Doris—tend to feed on sponges. Not all sponges, and not everywhere, but selectively enough that no single form easily dominates a surface for long.

Even their eggs reflect this connection. The ribbon-like spirals sometimes seen attached to docks are laid directly where food is available. The next generation doesn’t disperse randomly—it begins where the system is already functioning.

Beneath the surface layer

Most of the time, these organisms go unnoticed.

People see the drifting ribbons and call them whale snot. They scrape tunicates from pilings without thinking about what those colonies were filtering from the water. They brush past hydroids and sponges growing beneath docks without realizing those surfaces are part of the estuary’s food web just as much as the fish moving above them.

But the water between the marsh and the bottom is never empty.

It carries suspended plankton, drifting larvae, dissolved nutrients, bacteria, predators, scavengers, and colonies of organisms filtering continuously through the tide. Along the quieter edges of Onslow County—beneath floats, around oyster shells, beside marsh grass roots, and inside the slower water of creeks and sounds—entire communities form within that suspended layer (Wahl, 1989; Lindeyer & Gittenberger, 2011).

Some drift. Some attach. Some graze slowly across the surface consuming the organisms beneath them.

Together, they reshape the estuary constantly.

The gelatinous ribbons appearing this week are not separate from the rest of the system. They are one visible moment in a larger cycle of filtration, growth, decay, grazing, and redistribution that normally happens out of sight (Bone, 1998; Madin, 1982). For a short time, the estuary simply becomes easier to see.

What appears empty from above often contains layered communities of algae, filter-feeders, invertebrates, and microorganisms quietly redistributing energy through the estuary. Surf City, North Carolina. | Image credit: A. Mitchell

References

Avila, C. (1995). Natural products of opisthobranch molluscs: A biological review. In Oceanography and marine biology: An annual review (33rd ed., pp. 487-559). UCL Press.

Barros, R. (2009). Human-mediated global dispersion of Styela plicata (Tunicata, Ascidiacea). Aquatic Invasions, 4(1), 45-57. https://doi.org/10.3391/ai.2009.4.1.4

Bone, Q. (1998). The biology of pelagic tunicates. Oxford University Press on Demand.

Encarnação, J., Seyer, T., Teodósio, M. A., & Leitão, F. (2020). First record of the nudibranch Tenellia adspersa (Nordmann, 1845) in Portugal, associated with the invasive hydrozoan Cordylophora caspia (Pallas, 1771). Diversity, 12(6), 214. https://doi.org/10.3390/d12060214

Goodheart, J. A., Bleidißel, S., Schillo, D., Strong, E. E., Ayres, D. L., Preisfeld, A., Collins, A. G., Cummings, M. P., & Wägele, H. (2018). Comparative morphology and evolution of the cnidosac in Cladobranchia (Gastropoda: Heterobranchia: Nudibranchia). Frontiers in Zoology, 15(1). https://doi.org/10.1186/s12983-018-0289-2

Korshunova, T., Lundin, K., Malmberg, K., Picton, B., & Martynov, A. (2018). First true brackish-water nudibranch mollusc provides new insights for phylogeny and biogeography and reveals paedomorphosis-driven evolution. PLOS ONE, 13(3), e0192177. https://doi.org/10.1371/journal.pone.0192177

Lambert, G. (2007). Invasive sea squirts: A growing global problem. Journal of Experimental Marine Biology and Ecology, 342(1), 3-4. https://doi.org/10.1016/j.jembe.2006.10.009

Lindeyer, F., & Gittenberger, A. (2011). Ascidians in the succession of marine fouling communities. Aquatic Invasions, 6(4), 421-434. https://doi.org/10.3391/ai.2011.6.4.07

Madin, L. P. (1982). Production, composition and sedimentation of salp fecal pellets in oceanic waters. Marine Biology, 67(1), 39-45. https://doi.org/10.1007/bf00397092

Madin, L. P., & Deibel, D. (1998). Feeding and energetics of Thaliacea. The Biology of Pelagic Tunicates, 81-104. https://doi.org/10.1093/oso/9780198540243.003.0005

Marcus, E. D. (1972). On Some Opisthobranchs from Florida. Bulletin of Marine Science, 22(2), 284-308. https://www.ingentaconnect.com/content/umrsmas/bullmar/1972/00000022/00000002/art00002

Petersen, J., & Riisgard, H. (1992). Filtration capacity of the ascidian Ciona intestinalis and its grazing impact in a shallow fjord. Marine Ecology Progress Series, 88, 9-17. https://doi.org/10.3354/meps088009

Riisgård, H., & Larsen, P. (2010). Particle capture mechanisms in suspension-feeding invertebrates. Marine Ecology Progress Series, 418, 255-293. https://doi.org/10.3354/meps08755

Sutherland, K. R., Madin, L. P., & Stocker, R. (2010). Filtration of submicrometer particles by pelagic tunicates. Proceedings of the National Academy of Sciences, 107(34), 15129-15134. https://doi.org/10.1073/pnas.1003599107

Valdés, Á., Behrens, D. W., & DuPont, A. (2006). Caribbean Sea slugs: A Field guide to the opisthobranch mollusks from the tropical Nortwestern Atlantic. Sea Challengers Natural History Books.

Van Name, W. G. (1945). The North and South American Ascidians. Bulletin of American Museum of Natural History, 84, 1-476. http://hdl.handle.net/2246/1186

Wahl, M. (1989). Marine epibiosis. I. Fouling and antifouling: Some basic aspects. Marine Ecology Progress Series, 58, 175-189. https://doi.org/10.3354/meps058175

May 16, 2026
Where Wings Meet Water: Reading Birds Along the Edges of Onslow County

At the Line Where Air Meets Water

On a late spring morning along Surf City, the first movement is often above the water, not within it. Brown pelicans travel low and steady just beyond the breakers, their wingtips nearly touching the surface as they follow a line that seems invisible from shore. Farther out, a group of terns holds in place against the wind, hovering, adjusting, then dropping sharply into the water before rising again. Closer to the sound side of Topsail Island, an osprey circles once, then folds into a dive toward a channel edge that looks, at first glance, no different than the water around it.

Nothing about these movements is random. They are responses to structure that exists beneath the surface—structure shaped by tide, wind, and the movement of other organisms. What appears as scattered bird activity is, in practice, a map of where the water is concentrating life.

For someone standing at the edge of it, that movement is one of the most accessible ways to read what cannot be seen directly.

What Birds Are Following Beneath the Surface

The birds that move along this stretch of coast are not searching broadly; they are tracking concentration. Along barrier island systems like those in Onslow County, physical processes—tidal exchange through inlets, wind-driven surface currents, and subtle differences in bottom shape—create zones where small fish, shrimp, and other prey accumulate (Peterson & Peterson, 1979; Piersma, 1997).

When the tide moves through places like New River Inlet, water does not flow evenly across the landscape. It accelerates through constrictions, slows along marsh edges, and bends around sandbars and channels. These shifts in speed and direction compress organisms into tighter spaces, particularly along boundaries where moving water meets something that resists it—an edge, a drop-off, or a change in depth (Wright et al., 1985).

Small schooling fish respond to that compression by tightening their formation. In doing so, they become more visible and more vulnerable. Larger fish—bluefish, Spanish mackerel, and juvenile coastal sharks—often move in from below, using that same concentration to feed. The pressure from below pushes prey upward, sometimes all the way to the surface.

Coastal birds feeding where prey has been concentrated near the surface along the breakers. | Image credit: A. Mitchell

What appears overhead depends on which part of that concentration each species is built to exploit.

Terns hovering and diving are often responding to prey that has been driven upward by predatory fish (Safina & Burger, 1985). Brown pelicans, which rely on plunge-diving, tend to follow more stable schools of fish that remain near the surface for longer periods (Shields, 2014). Ospreys, in contrast, depend on clear water and individual fish they can visually isolate, which is why their activity often aligns with calmer conditions and defined channel edges (Poole et al., 2002).

Each species is not simply feeding in the same place; each is reading a different layer of the same system.

When Surface Activity Signals Pressure Below

From the shoreline, bird activity can appear as isolated events—one dive, then another, then a sudden shift down the beach. Watched over time, a pattern emerges. A cluster of terns may concentrate in one location for several minutes, then disperse abruptly, reforming farther along the shoreline. Pelicans may align along a narrow band just beyond the breakers, following it as it drifts.

These shifts often reflect changes in how prey is being compressed and released beneath the surface. When predatory fish move through a bait school, the school tightens, rises, and becomes briefly accessible from above. When that pressure dissipates, the school spreads out again, and the birds move on.

This movement of energy—from smaller organisms to larger predators, and upward through the water column—is one visible expression of a trophic cascade. The term itself is often used to describe longer chains of ecological influence, but along the coast it can be observed in compressed moments, where the effects of predation become visible within seconds (Heithaus et al., 2008).

Birds do not initiate this process. They respond to it. Their presence marks where the system has already intensified.

Indicator Species at the Water’s Edge

From the beach, the difference is subtle. The water does not change color dramatically, and the waves continue to break as they did before. The level of activity shifts within that band—first visible in the air, then inferred below– marking places where the system has tightened, energy is moving through multiple layers at once, and the distance between surface and depth has, for a time, narrowed (Heithaus et al., 2008; Estes et al., 2011).

For someone entering the water, these differences in bird behavior can offer practical information, not in a predictive or absolute sense, but as indicators of what is happening just below the surface.

Brown pelicans traveling low in a consistent line often indicate schools of fish moving parallel to shore. Terns repeatedly diving in a tight area suggest smaller prey being pushed upward, frequently by larger fish feeding below. Ospreys focusing on a specific channel edge reflect clearer water and individual prey availability, rather than broad schooling events. Along the shoreline, shorebirds probing the sand at low tide are responding to invertebrates exposed by receding water, signaling a different layer of the system entirely—one tied to sediment and tidal timing rather than active predation (Colwell, 2010; Piersma, 1997).

None of these signals point directly to a specific species beneath the surface. What they indicate is concentration, and concentration is what draws larger predators closer to shore.

Along the coast of North Carolina, nearshore and juvenile shark presence is often associated with areas of high prey density, particularly where schooling fish aggregate (Heupel & Hueter, 2002). These conditions are not constant, and they shift with tide, temperature, and time of day. Birds make those shifts visible in real time.

At times, that activity stretches into lines that run the length of the breakers.

For someone stepping into the water, that narrowing matters. Not as a warning in the abstract, but as a recognition that the conditions supporting visible feeding above often extend below, linking organisms that are rarely seen together into the same moving structure.

Where the System Tightens

The patterns become easier to see near places where the water is forced to narrow, turn, or accelerate. The most consistent bird activity along this coast tends to occur where water movement is constrained and redirected. Inlets, marsh edges, sandbars, and the transitions between the Intracoastal Waterway and adjacent sounds create these zones (Wright et al., 1985).

At New River and its inlet, tidal flow compresses water into narrow channels before releasing it into broader areas, creating gradients in speed and depth. Along these gradients, prey accumulates, predators follow, and birds gather above.

These are not fixed points. As tide rises and falls, and as wind reshapes surface conditions, the locations of these compression zones shift. The birds move with them, tracing patterns that are constantly changing but not random.

For someone watching from shore, these movements can be read as lines, clusters, and absences—places where activity intensifies, and places where it suddenly drops away.

Standing Within It

Entering the water along this coast means stepping into a system already in motion. The surface may appear uniform, but the activity above it often reveals where that motion is focused.

Birds diving repeatedly in a confined area, or tracking a narrow band just beyond the breakers, indicate where prey is concentrated. Those same conditions are what draw larger predators into closer proximity to shore, not as an anomaly, but as part of the same process.

Watching the birds does not eliminate risk, and it does not provide certainty about what is beneath the surface. What it offers is context—a way to recognize when the water is more active, more compressed, and more connected across its layers.

What appears as feeding from above is part of a larger structure moving through the water. The birds do not create it, and they do not remain once it passes. They mark it, briefly, making visible what is otherwise difficult to see.

Bird movement along the shoreline often draws attention toward activity that remains unseen beneath the surface. | Image credit: A. Mitchell

References

Castro, J. I. (1993). The shark nursery of bulls Bay, South Carolina, with a review of the shark nurseries of the southeastern coast of the United States. Environmental Biology of Fishes, 38(1-3), 37-48. https://doi.org/10.1007/bf00842902

Colwell, M. A. (2010). Shorebird ecology, conservation, and management. University of California Press.

Estes, J. A., Terborgh, J., Brashares, J. S., Power, M. E., Berger, J., Bond, W. J., Carpenter, S. R., Essington, T. E., Holt, R. D., C. Jackson, J. B., Marquis, R. J., Oksanen, L., Oksanen, T., Paine, R. T., Pikitch, E. K., Ripple, W. J., Sandin, S. A., Scheffer, M., Schoener, T. W., & Wardle, D. A. (2011). Trophic downgrading of planet Earth. Science, 33(6040), 301-306. https://doi.org/10.1126/science.1205106

Heithaus, M. R., Frid, A., Wirsing, A. J., & Worm, B. (2008). Predicting ecological consequences of marine top predator declines. Trends in Ecology & Evolution, 23(4), 202-210. https://doi.org/10.1016/j.tree.2008.01.003

Heupel, M. R., & Hueter, R. E. (2002). Importance of prey density in relation to the movement patterns of juvenile blacktip sharks ( Carcharhinus limbatus ) within a coastal nursery area. Marine and Freshwater Research, 53(2), 543-550. https://doi.org/10.1071/mf01132

Peterson, C. H., & Peterson, N. M. (1979). Ecology of intertidal flats of North Carolina: A community profile (79/39). FWS/OBS. https://pubs.usgs.gov/publication/fwsobs79_39

Piersma, T. (1997). Do global patterns of habitat use and migration strategies Co-evolve with relative investments in Immunocompetence due to spatial variation in parasite pressure? Oikos, 80(3), 623-631. https://doi.org/10.2307/3546640

Poole, A. F., Bierregaard, R. O., & Martell, M. S. (2002). Osprey (Pandion haliaetus). In The Birds of North America (1st ed.). Cornell Lab of Ornithology.

Safina, C., & Burger, J. (1985). Common tern foraging: Seasonal trends in prey fish densities and competition with bluefish. Ecology, 66(5), 1457-1463. https://doi.org/10.2307/1938008

Shields, M. (2014). Brown Pelican (Pelecanus occidentalis). In Birds of North America (1st ed.). Cornell Lab of Ornithology.

Wright, L., Short, A., & Green, M. (1985). Short-term changes in the morphodynamic states of beaches and surf zones: An empirical predictive model. Marine Geology, 62(3-4), 339-364. https://doi.org/10.1016/0025-3227(85)90123-9

May 9, 2026
Slough Mud: The Gooey, Stinking Ecosystem Beneath Onslow County’s Shoreline

Where the Ground Doesn’t Hold

There are places along the edges of the water in Onslow County where the ground stops behaving like ground.

You find them along the sound side, at the margins of tidal creeks, and in the quieter edges of channels that drain toward New River Inlet. Places like the shallows near Soundside Park or the creek edges around Kenneth D. Batts Family Park look ordinary when the tide is in—flat water, sometimes with a darker tone beneath the surface, but otherwise unremarkable.

As the tide pulls away, that surface is left behind, exposed in a way that suggests continuity, as though it will hold underfoot the same way sand does along the open beach.

It holds just long enough to believe that.

Then it gives way.

A step sinks past the ankle before there is time to adjust, and the next carries deeper, the sediment tightening around your leg—not suddenly, but with a steady resistance that makes each movement slower than expected, until pulling free requires more effort than the surface first suggested and the footing you thought you had no longer offers anything solid to push against.

Sometimes the mud keeps what you brought with you.

It holds—until it doesn’t. | Image credit: Florida Tech

Each step releases a faint, unmistakable sulfur smell from below, brief but distinct, rising as the sediment shifts and settling again as it closes around the space you’ve displaced.

Nothing about it suggests stability, and yet nothing about it is still.

Where It Forms: Water That Slows Down

If you step back—onto firmer ground, where your footing holds—the pattern begins to show itself.

These places gather along edges where water loses momentum. Along the sound side, there are no breaking waves to constantly overturn the bottom. Water moves in, spreads thin across the flats, and then drains back through the same narrow paths, slowing as it goes.

When that movement slows, what the water was carrying no longer stays suspended.

Fine silts and clays begin to settle. Fragments of marsh grass drift down. Microscopic shells and organic particles—too small to notice while they are moving—collect layer by layer until the bottom changes character (Folk, 1980; Riggs et al., 2008).

Much of that material begins only a few feet away.

Where the water slows, what it carries begins to settle. | Image credit: A. Mitchell

Along the edges of these creeks, smooth cordgrass—Spartina alterniflora—holds the shoreline in place. When it dies back, it doesn’t disappear. It breaks apart, and with each tide, that material moves outward. What looks like loss becomes movement—organic matter carried away from the marsh and into these quieter edges (Odum, 1980).

Where the water lingers, that material accumulates.

And over time, accumulation becomes something you can step into.

The Surface: What Almost Holds

From above, it can look continuous.

In certain light—especially when the sun is low—there is a faint sheen across the surface, something smoother and more uniform than water alone would create. It can appear firm enough to cross, at least for a step or two.

That thin layer is not just sediment.

It settles just enough to look stable—until the weight shifts. | Image credit: A. Mitchell

Microscopic organisms—diatoms and cyanobacteria—spread across the surface, forming a film that binds particles together. They produce substances that hold grains in place, creating a surface that can briefly support weight before it gives way beneath it (Rimmer et al., 2025).

It is just enough structure to mislead you.

Just enough to suggest that what lies beneath it will behave the same way.

Why It Gives Way: Structure Without Support

Once that surface breaks, the difference becomes immediate.

The particles here are small enough to trap water between them, and once that water is there, it does not drain the way it does through sand. The sediment remains saturated, and when pressure is applied, the water has nowhere to go.

Instead of holding its shape, the ground shifts.

There is a way to describe how well a surface resists that kind of movement—shear strength. Sand has enough of it to support your weight.

This does not (Folk, 1980).

There’s form here, but no support—only water and loosened sediment. | Image credit: A. Mitchell

And beneath the surface, the structure is already interrupted. Burrows open and collapse. Small voids form and disappear. Gas collects in pockets that shift when disturbed. What looks continuous from above is already moving below.

So when your foot sinks, it is not breaking through something solid.

It is entering something that was never still to begin with.

Below the Surface: Where the Air Runs Out

The smell arrives as soon as the surface opens.

It rises quickly, sharp and distinct, and then fades again as the mud closes.

Just beneath the surface, oxygen is used up rapidly by microorganisms breaking down the organic material that has accumulated there. Below that thin layer, the sediment becomes anoxic—oxygen is no longer present (Fenchel & Riedl, 1970; Jørgensen & Nelson, 2004).

But the process doesn’t stop.

Bacteria continue to break material down, using sulfate from seawater instead of oxygen. That shift produces hydrogen sulfide gas, which remains trapped until the sediment is disturbed (Kasten & Jørgensen, 2000).

Each step releases it.

The smell is not separate from the system. It is evidence that the breakdown is still happening—just without air.

And because it is happening without oxygen, it happens more slowly.

What Stays Behind

If that same plant material were left exposed to air, it would break down quickly. Most of what it contains would return to the atmosphere as carbon dioxide.

Here, much of it does not.

The organic material that settles into this mud—marsh grass, algae, microscopic debris—is buried into a system where oxygen disappears almost immediately. Without that oxygen, decomposition slows, and a portion of that carbon remains stored in the sediment instead of returning to the air (Chmura et al., 2003).

It does not stop changing.

It is broken down, reworked, and shifted. But it is not fully released.

Layer after layer builds beneath the surface—material that was once living, now held within the mud you step into.

What smells like decay is also storage.

The Surface Is Breathing

Even without oxygen below, the surface is not sealed.

If you stand still long enough, you begin to see small openings, slight movements, places where the mud seems to shift or pulse.

Water moves in and out with the tide. Burrows connect the surface to what lies below. Worms, shrimp, and crabs pull oxygenated water downward as they move through the sediment (Aller, 1982; McCave, 1976).

And the plants at the edge are part of it too.

Marsh grasses do not just sit in the mud. They move oxygen from the air above down into their roots. Some of that oxygen leaks into the surrounding sediment, creating small zones where oxygen briefly exists before it is used up again.

It is uneven. Temporary. Constantly shifting.

At the surface, gases move both ways.

Oxygen enters. Carbon dioxide leaves. Small amounts of other gases—products of what is happening below—escape when the sediment is disturbed or when pressure changes with the tide.

The boundary is thin.

But it is active.

Movement You Don’t See

If you stop looking for stable ground and begin watching the surface itself, other patterns start to emerge.

What looks still is already in use. | Image credit: A. Mitchell

Small openings appear—round, spaced in ways that suggest something below rather than something left behind. Around them, slight mounds form and disappear as the mud dries and softens again.

These are not marks left on the surface. They are the surface expression of what is moving through it.

Polychaete worms pass through the sediment, ingesting it and depositing what remains behind them (Rhoads, 1974). Burrowing shrimp and amphipods maintain tunnels that allow water—and with it, oxygen—to move deeper into the mud than it otherwise could (Aller, 1982).

Crabs hold the edges.

Fiddler crabs open and close their burrows with the tide. Blue crabs move through when water returns, feeding within the same soft substrate that gives way underfoot. Mud crabs remain within it, emerging only when conditions allow.

Bivalves stay buried beneath it all, filtering water when submerged, holding position when exposed.

Sometimes you don’t see them until you feel them.

A sharp edge beneath your foot where the mud shifted just moments before.

The surface does not tell you everything that is there.

When the Water Returns

Then the water comes back.

It fills the same space that resisted your footing, covering the surface without changing what lies beneath it. The ground that gave way becomes part of a shallow, moving system again.

Fish arrive with the water.

Killifish move into these margins first, tolerating the low oxygen conditions that remain in the sediment. Flounder settle directly onto the bottom, their bodies flattening, their coloration shifting until they disappear against it.

Juvenile blue crabs move through these same areas, using them as nursery habitat—protected, shallow, and full of food (Bilkovic et al., 2020).

They are not just using the space. They are feeding on what the mud is processing.

Detritus, microbes, and organic material move through the system below the surface, supporting what arrives above it.

Other species follow.

Stingrays glide over the surface, feeding on what is buried below. Croaker move through slightly deeper channels. Along exposed flats near The Point at Topsail Beach, shorebirds track the retreating tide—probing, picking, following the movement of water as it exposes and covers the same ground again.

As the water returns, the surface changes—and life moves with it. | Image credit: A. Mitchell

What looked still becomes active.

Not because it changed.

But because the conditions around it did.

What Comes From the Marsh

At the edge where your footing gave way, the connection is already there.

The marsh does not end where the grass stops. It extends outward through what it releases.

This isn’t separate from the marsh—it’s what the marsh leaves behind. | Image credit: A. Mitchell

The grasses along the shoreline slow the water, trapping sediment and holding the edge in place. During storms, they absorb energy that would otherwise move inland, reducing erosion and limiting how much material is carried away (Barbier, 2012).

But they also export material.

As grasses break down, they move with the tide—out of the marsh, into the creeks, and into these quieter margins where the water slows again.

What settles here is not separate from the marsh.

It is what the marsh becomes once it begins to move—and what it leaves behind when it does.

What Changes, and What Doesn’t

The ground beneath you is not fixed.

Periods of calm allow fine sediments to build, thickening the layer and increasing the amount of organic material held within it. Warmer temperatures increase microbial activity, accelerating what is happening below the surface.

A storm can undo that quickly.

Sediment lifts back into the water, moves elsewhere, and settles in new places. Edges shift. Channels deepen or fill. What held you in place one week may not exist in the same way the next (Pilkey et al., 2014).

Other changes move more slowly.

Development alters how water flows. Marsh edges are reduced or hardened. Invasive plants like Vitex rotundifolia change how sediment is captured and released.

The system continues.

But the way it moves through the landscape can change.

Standing at the Edge of It

Standing at the edge of one of these places, it is easy to focus on the moment your footing failed—the way the ground gave way when it seemed like it shouldn’t.

But nothing about it failed.

What felt unstable is a working layer—one that gathers what the marsh releases, slows its return to the air, supports what can move within it, and disappears beneath the water as the tide returns.

The same ground that held you in place becomes part of something continuous again, connected to marsh, creek, sound, and ocean.

It does not hold because it is not meant to.

It holds because it is already in motion.

Nothing here failed—it’s doing exactly what it’s meant to do. | Image credit: A. Mitchell

References

Able, K., Manderson, J., & Studholme, A. (1999). Habitat quality for shallow water fishes in an urban estuary:the effects of man-made structures on growth. Marine Ecology Progress Series, 187, 227-235. https://doi.org/10.3354/meps187227

Aller, R. C. (1982). The effects of Macrobenthos on chemical properties of marine sediment and overlying water. Topics in Geobiology, 53-102. https://doi.org/10.1007/978-1-4757-1317-6_2

Barbier, E. B. (2012). Progress and challenges in valuing coastal and marine ecosystem services. Review of Environmental Economics and Policy, 6(1), 1-19. https://doi.org/10.1093/reep/rer017

Bilkovic, D., Isdell, R., Stanhope, D., Angstadt, K., Havens, K., & Chambers, R. (2021). Nursery habitat use by juvenile blue crabs in created and natural marshes. Ecological Engineering, 170(106333). https://doi.org/10.1016/j.ecoleng.2021.106333

Chmura, G. L., Anisfeld, S. C., Cahoon, D. R., & Lynch, J. C. (2003). Global carbon sequestration in tidal, saline wetland soils. Global Biogeochemical Cycles, 17(4). https://doi.org/10.1029/2002gb001917

Fenchel, T. M., & Riedl, R. J. (1970). The sulfide system: A new biotic community underneath the oxidized layer of marine sand bottoms. Marine Biology, 7(3), 255-268. https://doi.org/10.1007/bf00367496

Folk, R. L. (1980). Petrology of sedimentary rocks (2nd ed.). Hemphill Publishing Company.

Jørgensen, B. B., & Nelson, D. C. (2004). Sulfide oxidation in marine sediments: Geochemistry meets microbiology. Sulfur Biogeochemistry – Past and Present. https://doi.org/10.1130/0-8137-2379-5.63

Kasten, S., & Jørgensen, B. B. (2000). Sulfate Reduction in Marine Sediments. In Marine Geochemistry (pp. 263-264). Springer, Berlin, Heidelberg.
https://doi.org/10.1007/978-3-662-04242-7_8

McCave, I. N. (1976). Organism-Sediment Relationships. In The Benthic Boundary Layer (pp. 273-295). Plenum Press.

Odum, E. P. (1980). The status of three ecosystem-level hypotheses regarding salt marsh estuaries: Tidal subsidy, outwelling, and detritus-based food chains. Estuarine Perspectives, 485-495. https://doi.org/10.1016/b978-0-12-404060-1.50045-9

Pilkey, O. H., Rice, T. M., & Neal, W. J. (2014). How to read a North Carolina beach: Bubble holes, Barking sands, and rippled Runnels. UNC Press Books.

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April 25, 2026