The Red Crab

The Christmas Island red crab, Gecarcoidea natalis, is a species of land crab that is endemic to Christmas Island and the Cocos (Keeling) Islands in the Indian Ocean. Although restricted to a relatively small area, it has been estimated that 43.7 million adult red crabs lived on Christmas Island alone, but the accidental introduction of the yellow crazy ant is believed to have killed about 10–15 million of these in recent years. Christmas Island red crabs eat mostly fallen leaves and flowers, but will occasionally eat other animals, including other red crabs if the opportunity arises.
The carapace is up to 116 millimeters (4.6 in) wide, rounded, and encloses the gills. The claws are usually of equal size, unless one becomes injured or detached, in which case the limb will regenerate. The male crabs are generally larger than the females, while adult females have a much broader abdomen (only apparent above 3 years of age) and usually have smaller claws.
Christmas red crabs live in burrows for shelter from the sun. Since they breathe through gills, the possibility of drying out is dangerous. They are famous for their annual migration to the sea to lay their eggs in the ocean.