Invasion of the Red Crabs!

Christmas Island Crab Invasion

Whilst some species of crabs may seem common on our regular seafood dinner table, this particular species may not be as they are toxic to human beings. The red crabs, Gecarcoidea natalis, are endemic to the forests of Christmas Island, located in north-west of Australia in the Indian Ocean. Their mating season occurs annually during the monsoon season, where they have to migrate to the coast for breeding.

At the coast, the male crab would have to fight with other males to gain the rights to dig a burrow in which mating occurs. This is a demonstration of greater fitness than rivals. The female will be left in the burrow where she brood the eggs in a pouch on her abdomen. The female will release her eggs into the sea after a lapse of 12 days. These eggs hatch immediately into tiny larvae.

In migrating to the coast from the forests, the crabs have to go through obstacles like roads, where vehicles are prevalent. This poses a threat to the crabs as they face the danger of getting crushed by oncoming vehicles. In order to protect the red crabs from getting crushed on the roads by vehicles during the migration period, the local authorities have closed a few roads.

In addition, the migration of the red crabs has become such a phenomenon that it is now used to attract tourists as this spectacular sight is hard to find in other countries.


  1. “Christmas Island Crab,” by BBC Science and Nature, July 2005. URL: on 5 Apr 2010).  
  2.  “Science Screen Report: The Amazing Red Crab of Christmas Island !,” by Allegrosjf YouTube Channel, 25 September 2009 . URL: (accessed on 5 Apr 2010)
  3. “Red Crabs,” by Environment Australia. URL: on 6 Apr 2010)
  4. Agnieszka M. Adamczewska, Stephen Morris, 2001. Ecology and Behavior of Gecarcoidea natalis, the Christmas Island Red Crab, during the Annual Breeding Migration. Biological Bulletin, 200(3): 305-320
  5. “Christmas Island: kingdom of the crab,” by Nick Squires., 21 Oct 2007. URL: xxx (accessed on 6 Apr 2010).

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