A different kind of "lockdown" happens on Christmas Island, Australia, annually around this time of the year.

A mass migrationof large red crabs begins like clockwork with the first rainfall of the wet season - usually in October or November, but sometimes as late as December or January.

Millions of the bright red crustaceans, which are endemic to the island, emerge from the forest and make their way towards the ocean to breed. They march across town, swarming roads, streams, rocks and beaches, stopping traffic and creating a spectacle for tourists and residents alike. Male crabs lead the pack and are joined by females along the way.

The exact timing and speed of the migration are determined by the phase of the moon. Red crabs always spawn before dawn on a receding high tide during the last quarter of the moon.

There are an estimated 40 million to 50 million crabs living on Christmas Island.

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