Ocypodidae - Fiddler Crabs and Ghost Crabs
Ocypodidae is a family of mostly semi-terrestrial crabs that live in burrows in soft sand or mud within the intertidal stretches of bays and beaches. When the tide goes out, the crabs will come out of their burrows in search for food. While most crabs in this family live intertidally, some live a more aquatic life while others live supratidally in a more terrestrial setting. All must venture back to the water for breeding and normal larval development.
Fiddler crabs are most easily distinguished by the oversized claw of the male. The male uses the enlarged claw for combat and communication. The smaller claw is used for feeding. The motion of the small claw being raised and lowered from the mouth gives the appearance of strumming the larger claw, thus the name fiddler crabs. Once the fiddler is through sifting through a claw full of sand for food, the sand is deposited in the form of a little ball. These balls are typically found outside the burrows of fiddler crabs. When male fiddler waves its larger claw in the air and taps it on the ground, he is displaying a courtship ritual in an effort attract a female.
Ghost crabs have an enlarged claw also, but not quite the extent of the male fiddler. They are called ghost crabs because they are blend into their background and can easily disappear by running in zigzag lines with speeds up to 10 mph. Their stocked black eyes stand erect giving the ghost crabs 360° vision. Their vision is so acute they can spot and grab insects in mid-air. However, they cannot see directly above themselves which make them easy prey for birds. Ghost crabs are nocturnal, being more active at night than during the day. They are mostly found on beaches. Their burrow holes are about the size of a golf ball. Adult males rearrange the sand that is excavated from its burrow into a pile beside the hole. Adult females and juveniles just scatter the sand outside the holes. These tell-tale signs plus crab tracks around the holes indicate the home of a ghost crab.