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Natural Phenomena

Christmas Island Red Crab Migration

Animal Behavior and Adaptation

An annual mass migration of an estimated 40 to 50 million red crabs across Christmas Island in the Indian Ocean, moving from the island's forest interior to the coast to breed and release their eggs into the sea, timed to the onset of the wet season and the lunar cycle governing high tide before dawn. The migration transforms roads and the island's landscape into a moving carpet of crabs for several weeks each year, and conservation measures including road closures and purpose-built crab bridges have been put in place to protect the migrating population from traffic.

Facts
Periodicity
Annual, beginning with the onset of the wet season (usually October or November) 1
Scale
Estimated total population of 43.7 million red crabs on Christmas Island 1
Identification
Distinguishing Appearance
Large crabs, most often bright red (sometimes orange or the rarer purple), carapace up to 116 millimetres wide 1
Sources
1. Christmas Island red crab, Wikipedia
  • Migration and breeding section
    Each year they migrate to the coast to breed; the beginning of the wet season (usually October/November) allows the crabs to increase their activity and stimulates their annual migration.
  • Population section
    equalling an estimated total population of 43.7 million on Christmas Island.
  • Description section
    Christmas Island red crabs are large crabs with the carapace measuring up to 116 millimetres (4.6 in) wide.
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