Sharks of Onslow County
When the sun sets behind the dunes and the surf begins to whisper, pale shapes flicker across the sand. Their movements are quick, darting, and silent – like apparitions under moonlight. These aren’t the spirits of shipwrecked sailors but the true “ghosts” of our Carolina coast: Atlantic ghost crabs (Oxypode quadrata).
Ghost crabs live in that liminal zone between land and sea – not quite aquatic, not quite terrestrial. They spend most daylight hours deep inside burrows up to four feet long, spiraling down in the cool, moist sand where they can keep their gills damp (Lucrezi & Schlacher, 2014).
At night, they emerge to feed and patrol their territories. Their footprints – delicate, zigzagging tracks across the high tide line – are often the only sign they’ve been there. Scientists describe O. quadrata as a “semi-terrestrial” species, adapted to breath air while still depending on water for respiration (Lucrezi & Schlacher, 2014). Each burrow is unique, shaped like a J or L., with a single opening and a smooth rim that the crab maintains meticulously (Strachan et al., 1999). It’s both a refuge from predators and a fortress against the summer sun.
Despite their spectral charm, ghost crabs are voracious predators. They scavenge for dead fish, clams, and organic debris but will actively hunt small invertebrates and even sea turtle hatchlings (Wolcott, 1978; Call et al., 2024).
In many coastal ecosystems, ghost crabs are top invertebrate consumers, linking marine and terrestrial food webs by recycling nutrients back into the sand (Wolcott, 1978). Yet their own lives are precarious – shorebirds, raccoons, and even humans are a constant threat. A study in Virginia found that burrow abundance correlated with temperature and habitat type, showing how these crabs respond to subtle environmental shifts (Call et al., 2024). They’re not just scavengers – they’re indicators of a beach’s health.
There’s a reason they earned their spectral reputation. Their translucent shells and lightning-fast reflexes make them appear and vanish like spirits. In low light, the fine grains of sand reflecting off their bodies amplify that effect – a built-in camouflage evolved for moonlit hunting. Can you spot them in the images below?
Ghost crabs also possess 360-degree vision from their elevated eye stalks, allowing them to spot threats in any direction (Lucrezi & Schlacher, 2014). And if the idea of “haunted sounds” intrigues you, here’s a Halloween twist: they “growl” by grinding their internal stomach plates – a process called stridulation – to warn off intruders. The sound, faint but distinct, echoes eerily under the dunes.
If you’ve ever walked Topsail Beach under a full moon, you’ve probably seen them: glowing white blurs racing sideways across your flashlight beam. (It’s best to use red or blue light as you search for ghost crabs and sea turtles.) Locally, these crabs are essential dune engineers. Their burrows aerate sand, help control organic decay, can reduce erosion, and maintain the delicate balance between dry and wet zones of the shore.
You might wonder: since ghost crabs dig deep into the sand, do their burrows stabilize the beach and help fend off erosion? The answer is – sometimes, but not always.
You don’t even need to see a ghost crab to know it’s there – just look for the telltale burrow holes scattered along the upper beach. Each one marks a crab’s hiding place, and scientists often estimate ghost crab populations by counting burrow openings rather than the crabs themselves (Call et al., 2024; Lucrezi & Schlacher, 2014). The more holes you find, the healthier the local population – assuming the beach hasn’t been compacted or disturbed by human traffic.
Ghost crabs don’t just dig- they reshape their sandy underworld. Their burrows loosen compacted sediments, which can lower resistance to wind and wave forces (Rinehart et al., 2024). In some species, burrowing stabilizes surface flows, but in ghost crab systems the effect is less predictable – sometimes helping, sometimes hindering.
Unfortunately, they’re also victims of human disturbance. Coastal development, trampling, beach renourishment, and nighttime beach driving can collapse burrows and disrupt populations (Costa, Madureira & Zalmon, 2018). During the COVID-19 lockdown, researchers noticed ghost crab populations rebounding on urban beaches – a reminder that these “ghosts” return quickly when given peace (Costa et al., 2022).
So this Halloween, as you wander along the moonlit sands of Onslow County, remember that the pale forms darting ahead of your footsteps aren’t apparitions – they’re guardians of the dunes, keeping our coasts breathing and balanced.
Every footprint, every scuttle, every faint rustle beneath the stars tells a story of adaptation and resilience. Ghost crabs may look like specters, but they’re among the most living, vital spirits of the beach.
“They vanish without a trace…except for their tracks.” – A. Mitchell
Antunes, G. D., Do Amaral, A. P., Ribarcki, F. P., Wiilland, E. D., Zancan, D. M., & Vinagre, A. S. (2010). Seasonal variations in the biochemical composition and reproductive cycle of the ghost crab Ocypode quadrata (Fabricius, 1787) in southern Brazil. Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 313A(5), 280-291. https://doi.org/10.1002/jez.593
Call, M. N., Pongnon, R. S., Wails, C. N., Karpanty, S. M., Lapenta, K. C., Wilke, A. L., Boettecher, R., Alvino, C. R., & Fraser, J. D. (2024). Biotic and abiotic factors affecting Atlantic ghost crab (Ocypode quadrata) spatiotemporal activity at an important shorebird nesting site in Virginia. PLoSONE, 19(8), e0307821. https://doi.org/10.1371/journal.pone.0307821
Costa, L. L., Machado, P. M., Barboza, C. A., Soares-Gomes, A., & Zalmon, I. R. (2022). Recovery of ghost crabs metapopulations on urban beaches during the COVID-19 “anthropause”. Marine Environmental Research, 180, 105733. https://doi.org/10.1016/j.marenvres.2022.105733
Costa, L. L., Madureira, J. F., & Zalmon, I. R. (2018). Changes in the behaviour of Ocypode quadrata (Fabricius, 1787) after experimental trampling. Journal of the Marine Biological Association of the United Kingdom, 99(5), 1135-1140. https://doi.org/10.1017/s0025315418001030
Gül, M. R.(2019). Energetic Consequences of Human Impacts for Bioindicator Atlantic Ghost Crab (Ocypode Quadrata). (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/5460
Lucrezi, S., & Schlacher, T. A. (2014). The ecology of ghost crabs. Oceanography and Marine Biology, 201-256. https://doi.org/10.1201/b17143-5
Rinehart, S. A., Dybiec, J. M., Walker, J. B., Simpson, L., & Cherry, J. A. (2024). Effects of burrowing crabs on coastal sediments and their functions: A systematic meta‐analysis. Ecosphere, 15(7). https://doi.org/10.1002/ecs2.4927
Strachan, P. H., Smith, R. C., Hamilton, D. A., Taylor, A. C., & Atkinson, R. J. (1999). Studies on the ecology and behaviour of the ghost crab, Ocypode cursor (L.) in Northern Cyprus. Scientia Marina, 63(1), 51-60. https://doi.org/10.3989/scimar.1999.63n151
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
