The Christmas Island Red crab (Gecarcoidea natalis) is a species of land crab that is endemic to Christmas Island in the Indian Ocean.[1][2] Low numbers are also found on North Keeling Island, thought to be from larvae drifted from Christmas Island and never been observed to breed. Although restricted to a relatively small area, it has been estimated that 43.7 million adult Red crabs once lived on Christmas Island alone,[3] but the accidental introduction of the yellow crazy ant is believed to have killed about 10–15 million of these in recent years.[4] Christmas Island Red crabs are well known for their annual mass migration to the sea to lay their eggs in the ocean.[5]