The Christmas Island red crab is a species of land crab that is endemic to Christmas Island and Cocos Islands in the Indian Ocean. It is under the jurisdiction of Australia. Christmas Island’s mass red crab migration is one of the most incredible natural processes on Earth.

The migration starts with the first rainfall of the wet season. This is usually in October or November, but can sometimes be as late as December or January. Red crabs all over the island leave their homes at the same time and start marching towards the ocean to mate and spawn.  Male crabs lead the migration and are joined by females along the way. The exact timing and speed of the migration is determined by the phase of the moon.

The larger male crabs usually arrive at the sea first but are soon outnumbered by females. The female crabs then join the males to mate. They produce eggs within three days of mating. Each can produce up to 100,000 eggs.

The migration starts as soon as the wet season rains have established usually Oct/Nov. When the moon reaches its last quarter, the egg-laden crabs leave for the shoreline. When the high tide starts to turn before dawn, the crabs move into the sea and release their eggs before returning to the forest.  The eggs hatch in the water and after a month or two return as baby crabs and find their way to the mountains.

The roads become a “living red carpet” as millions of red crabs emerge from the forest and make their way to the ocean to breed. As a result some sections of roads may close for vehicular traffic. Main roads will have a barrier built on both sides of the road to prevent crabs crossing the road. Crab bridges and tunnels are built at certain intervals for the crabs to cross the road