Ghost Crab

Quick Take

• Ghost crabs have a hunting habit that puts one of the world's most endangered sea creatures at serious risk. See their hunting diet →
• Ghost crabs have a key physical trait that sets them apart from their closest relatives, and it shows up in a sex you wouldn't expect. Explore their physical traits →
• Ghost crabs got their name for two very different reasons, and only one of them is their color. Discover the name origins →
• Female ghost crabs reproduce in a way that breaks the rules of their entire crab group, a fact that is tied to a surprising lifestyle shift. See how females reproduce →

Ghost crabs are one of the most populous crab species in the world and are found on beaches from Oman to Polynesia, Australia, Florida, Egypt, and Greece. Ghost crabs, also called sand crabs, are known for their boxy shape, sometimes horned eyestalks, and uneven claw size. Although they use eight of their ten legs to walk normally, they only use their first and second pairs of legs when they need to move quickly.

Classification and Scientific Name

Ghost crabs are members of the subfamily Ocypodinae, which is part of the Ocypodidae family. Ocypode comes from Greek and means “swift-footed,” which describes the surprisingly fast way these crabs can scuttle over the sand. There are two genera in this subfamily: Ocypode and Hoplocypode. In the genus Ocypode, there are 21 species, but there’s only one species in Hoplocypode: H. occidentalis.

Appearance

These crabs have a boxy little body, and most species are pale except for species such as Ocypode gaudichaudii, the painted ghost crab. Their name comes not just from their general pallor, but from the fact that they hunt at night.

One characteristic that identifies ghost crabs is that both males and females have claws of different sizes. This differentiates them from their cousins, the fiddler crabs, where unequal-sized claws are found only on the males. The claws of most ghost crabs also have ridges that allow the animal to produce sounds that include bubbling, stridulation, and thumping.

Ghost crabs have large, elongated eyestalks. In some species, the eyestalks are horned or have styli. Their corneas are large and cover the bottom half of each eyestalk.

Their walking legs are longer than the claws. This allows them to move quickly and easily over the sandy beaches where they live.

Distribution, Population, and Habitat

Ghost crabs are found near warmer waters all over the world, like those off the coast of Florida or India. These semi-terrestrial crabs dig burrows in the sand and mud of the intertidal zone on ocean beaches and in estuaries.

There are 22 species of ghost crab. Although their habitat has been disrupted by human activity, their population is fairly healthy. Most ghost crabs are found in the Indo-Pacific region, while a handful of species are found in the Mediterranean, the Pacific coast of North America, and along the Atlantic Ocean from Massachusetts down to Florida and further south to Brazil.

Predators and Prey

Despite their small size, ghost crabs have few predators. One reason is that they can change color to blend in with the surrounding sand.

Other adaptations that help them both hunt and avoid predators include their speed and their nocturnal lifestyle. Still, ghost crabs are taken by shorebirds and raccoons. The crabs themselves prey on leatherback turtle eggs and hatchlings, which is problematic since the leatherback turtle is globally listed as Vulnerable, with many subpopulations considered Critically Endangered. They also eat smaller crabs, other marine arthropods, and insects. In addition to active hunting, ghost crabs also scavenge and cache food in their burrows.

Reproduction and Lifespan

Ghost crabs can mate all year, though there are some species where the female ovulates only in early spring and again in summer. They are unlike other crabs of their infraorder in that the female can mate after her shell has hardened following a molt. This is one of the adaptations the crabs made when they became semi-terrestrial.

Males posture and make sounds to both attract females and challenge other males. Usually, the male crabs avoid making contact, but if one does not submit, the stronger one shoves him out of the way.

Fertilization is internal, and mating usually happens near the male’s burrow. The sperm comes in a fluid that hardens and forms a plug in the female to make sure her eggs are not fertilized by a rival crab. The female can store sperm for a while, but when the eggs are fertilized, they develop and attach to her abdomen. Since the eggs look like berries, a female carrying her eggs this way is referred to as berried. The female makes sure the eggs are kept hydrated and may sometimes swim upside down for this purpose.

When the crab larvae hatch, the female shakes them off into the water. They are so tiny at this stage that they become part of the zooplankton and are swept along on the ocean currents; however, they are among the largest crab larvae during the final larval, or megalopa, stage.

The baby ghost crab has five molts before it reaches the megalopa stage. It stays in that stage for at least 35 days, and the full larval period can last two to three months in the field. If it survives to molt one more time, it leaves the sea for the land. Ghost crabs are ready to mate when they are about a year old and have a lifespan of about three years.

Population, Fishing, and Cooking

The ghost crab population is healthy as of 2021, though it has decreased due to human activity, climate change, and pollution.

Though ghost crabs are edible, they are considered too small to be worth eating.