Ocypode quadrata
Atlantic ghost crab

The range of Ocypode quadrata extends from Block Island, Rhode Island to Santa Catarina, Brazil. It has also been found in Bermuda, and larvae have been found as far north as Woods Hole, MA, however no adults have been found at this latitude. Their basic range is 40 degrees N to 30 degrees S on the eastern coasts of North and South America. (Fisher and Tevesz, 1979; Knott, 2010)

Ghost crabs inhabit tropical and subtropical areas and can be found on both oceanic and more protected estuarine beaches. They are found on the supralittoral zone (the area above the spring high tide line) of sand beaches, from the water line up to the dunes. (Branco, et al., 2010; Fisher and Tevesz, 1979; da Rosa and Borzone, 2008)

Ocypode quadrata is small, having a carapace length of about 5 cm (2 inches) at maturity. They are either straw-colored or grayish-white. They have a quadrate carapace, large club-shaped eyestalks, unequal chelipeds (claws) and long walking legs. Males are generally larger than females. (Fisher and Tevesz, 1979)

After hatching from an egg, Ocypode quadrata has five zoea stages and one megalopa stage. The megalopa stage requires at least 35 days for development. The larvae develop in saline water. The megalopa stage of Ocypode quadrata is one of the largest of the brachyuran crabs. Metamorphosis into the first crab stage takes place at the surf-beach interface. (Diaz and Costlow, 1972; McDermott, 2009)

Mating can occur throughout the year. Unlike other crab species, ghost crabs can mate even when the female’s integument is hard, which means that they can mate anytime after sexual maturation. This is an adaptation to terrestrial life. Mating occurs while both the male and the female have a hard shell. Usually mating will occur somewhere in or near the burrow of the male. Often copulatory plugs are found in ghost crabs; the male will release a seminal fluid along with his sperm that will become hard and prevent rival sperm from reaching the female’s ova. (; Burggren, 1988; Rothschild, 2004)

In the Carolinas, ghost crabs spawn from April through July. Females will mature and ovulate in April and again in August. Females reach sexual maturity when their carapace is larger than 25 mm. Males reach sexual maturity when their carapace is larger than 24 mm. This usually occurs when they are about a year old. (Haley, 1969; Haley, 1972; Hobbs, et al., 2008; Portell, et al., 2003; Rothschild, 2004)

The female will carry the eggs beneath her body, which will be released into the surf. While carrying the eggs, she must keep them wet by frequently entering the water. Some females may turn upside down in the water to ventilate their eggs. (Mitchell, 2007; Rothschild, 2004)

The typical lifespan of Ocypode quadrata is about 3 years. (Portell, et al., 2003)

Ocypode quadrata is primarily nocturnal. A crab constructs new burrows or repairs older ones during the morning. In the early afternoon it plugs the burrows and stay in them until after sunset. Burrows range from 0.6 to 1.2 m long and the width of burrows approximates the carapace size of the burrower. The width of the burrow tends to be about equal to the width of the carapace. Younger, smaller crabs tend to burrow closer to the water. While foraging at night, a crab can travel up to 300 m, so it will not return to the same burrow each day. Ghost crabs hibernate in their burrows from October to April. Ocypode quadrata is considered semiterrestrial. It has developed an interesting adaptation for life on land: A crab will occasionally will return to the water to wet its gills; however it can also get water from damp sand. Ghost crabs use fine hairs on the base of their legs to wick water from the sand up onto its gills. (Branco, et al., 2010; Hobbs, et al., 2008; Knott, 2010)

Ghost crab burrows can be found from the high tide line to 400 m shoreward. (Hobbs, et al., 2008)

Ghost crabs communicate using many sounds, including striking the ground with their claws, stridulation (rubbing together) of their legs and making a “bubbling sound”. Males compete in a ritualized matter that avoids the need for physical contact. (Shields, 1998)

Ghost crabs are both predators and scavengers, and they feed at night. Their prey can be influenced by the type of beach they live on. Crabs on oceanfront beaches tend to feed on bean clams (Donax spp.) and mole crabs (Emerita talpoida), while crabs on more protected beaches will feed on the eggs and hatchlings of loggerhead turtles (Caretta caretta). (Knott, 2010)

Ghost crabs have few terrestrial predators. They are largely nocturnal to reduce the risk of being eaten by shorebirds and gulls. When they do leave their burrows during the day, they are able to slightly change their color to match the surrounding sand. Another predator is the raccoon. (Knott, 2010; Mitchell, 2007)

The main role of Ocypode quadrata in its ecosystem is the role of top predator in the filter-feeding based food chain. The majority of their food is live prey, although they are also facultative scavengers. Ghost crabs can consume the majority of the production of both Donax and Emerita talpoida crabs. They are a crucial part of the food chain, playing an important role in the energy transfer from organic detritus and smaller invertebrates to larger predators. (Fisher and Tevesz, 1979)

Ghost crabs have been used as indicators for measuring the impacts of human use on beaches. Their population is relatively easy to monitor; the density of ghost crabs on a beach can be estimated by counting the number of burrows in a certain area. Population densities have declined due to habitat modification and heavy, continuous trampling. Because ghost crabs are apex predators of the habitat, monitoring their population can allow humans to assess the impact of human activity on sandy beach ecosystems. (Hobbs, et al., 2008; Schlacher and Lucrazi, 2009)

There are no known adverse effects of Ocypode quadrata on humans.

Currently, ghost crabs are not considered threatened or endangered. One of the main threats to ghost crabs is off-road vehicles (ORVs). The ORVs can crush or bury the crabs and interfere with their reproductive cycle. ORVs can greatly affect ghost crabs at night when they are feeding. Another threat is a decline in their habitat; construction in the upper intertidal zone for residential or commercial use can caused increased mortality and a potential decline in the population. (Hobbs, et al., 2008; Knott, 2010)

While there is no directly negative influence of ghost crabs on humans, Ocypode quadrata has been shown to have a negative impact on turtle populations. There have been efforts to control ghost crab populations due to their predation on turtle eggs. Studies have found that ghost crabs consume up to 10% of turtle eggs when they prey on a nest, and they have also been known to prey on the hatchlings. Measures to control populations around turtle nesting sites have included destroying burrows and using raccoons that prey on the crabs. (Barton and Roth, 2008)