The annual spectacle of millions of red crabs swarming Christmas Island has begun. Triggered by the season’s first rainfall, the crabs instinctively embark on their migration to the island’s beaches for their mating season.

Up to 100 million red crabs have begun their annual march to the ocean ahead of mating season on the remote Australian island, after dry weather delayed last year's migration.

Millions of red crabs have taken over an Australian island in their annual migration spectacle. The parade of crustaceans can be seen yearly on Christmas Island during the migration season, which starts with the first rainfall of the wet season — usually in October or November but sometimes as late as December or January.