Beach Phantoms

You can forgive most people for not noticing the flicker of movement or not seeing them at all. Sand-colored, no bigger than the palm of your hand, and fast as hell, ghost crabs are denizens of sandy Atlantic beaches from Rhode Island to Brazil.

Active at night, ghost crabs spend most of their daylight hours in L-shaped burrows up to four feet deep. At dawn or dusk or on overcast days, small gouts of sand periodically erupt from burrows scattered along the beach above the high tide line. Holes range from dime to silver dollar-size, depending on the size of the resident crab. Digging crabs cradle a spoonful or so of sand in the crook of their claws and fling it out to the surface from the entrance marked with a fan of damp sand that may extend up to a foot out. This is like a person tossing a snow shovel-full across down the block.

Ghost crabs are marine animals who have almost made the transition to land dwellers. On warm June evenings, egg-carrying females rush to the edge of the surf and release their eggs into the water. All ghost crabs scamper to the wave line on occasion to fill special sacks beside the gills with oxygenated water. Specialized muscles circulate the water over the gills keeping them working. In a pinch, specialized leg hairs can wick up moisture from the damp sand at the bottom of a burrow and fill the gill sacks.

Ghost crabs are predators and scavengers. They hunt smaller mole crabs, beach fleas, and tiny burrowing coquina clams right up to the strand line at night. They also investigate and devour anything that may wash up. They can pick a fish to bones before dawn and the day shift of scavengers wakes up. Any greedy crab caught far from its burrow in day light risks becoming gull food. Crabs lack the ability to look up and gulls know this, dropping like hawks on the unlucky.

Ghost crabs segregate by size. The youngest and smallest crabs burrow in the damper sand nearer the surf line, while older and bigger crabs move up the beach to the foot of the dunes. . Crabs guard their burrows fiercely, engaging in ritualized combat with individuals of a like size and plain tossing out smaller contenders. Crabs allow another crab into their burrow only during emergencies or for romance—there seems to be a secret handshake (clawshake?) involved. The biggest crabs, mainly older females, burrow into the face of the dune itself where they remain safe from storm tides. Location, location, location

When your eye does catch the movement, feel free to chase and try to catch the crab. You won’t succeed. Mounted on short stalks like twin periscopes, the crab’s eyes are as good as yours for following movement. Tracking you by your shape against the skyline, the crab slides along sideways effortlessly over the sand at 10 miles per hour, as quick as any Olympic sprinter. Keep following though, and the crab will shift direction at full tilt. Neat trick for someone with five times the legs as you. Keep on it, and the crab will do one of two things. Either it will disappear down another crab’s hole, any port in a storm, or it will stop dead in its tracks. Your eyes, following the movement and your brain anticipating the next move, will loose it in the sand. Score one for the crab.

If you happen to be at any beach on the Atlantic not swept by municipal trash collectors, on a June evening with no moon and a falling tide, you may be lucky enough to see hundreds of ghost crabs scampering down to the water’s edge to release their eggs. Females carry hundreds in a large cluster under their abdomen and walk on stilted legs at full term. Reaching the water, they carefully wade in until the waves lap at their bellies and release their eggs to the currents. Some females may actually turn over on their backs to get the eggs out; a risky move since a wave may wash them out and surprisingly enough, ghost crabs can’t swim and will drown. Eggs soon hatch and the larvae are swept into the longshore current paralleling the coast. Crabs on your beach may well have been spawned on a beach further south, ensuring constant mixing of genes and regular recolonization of storm wrecked sands.

Once you see one, you’ll begin to notice them on nearly any beach you visit. On an exotic beach, like Rio or Jamaica, it’s like seeing a friend from home.