The weekend rain has triggered the annual march of the red crabs! Christmas Island’s red crab migration is one of the most incredible natural phenomenons on Earth, and one that Sir David Attenborough described as among his all-time greatest television moments.

Over the coming weeks we can expect red crabs all over the island to leave their homes and march towards the ocean to mate and spawn.

The exact timing and speed of the migration is 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. Incredibly, they know exactly when to leave their burrows to make this lunar date. But because they have to wait until the first rainfall to start their trek, they sometimes have to rush the process.

If it begins raining too close to the optimal spawning date (21-23 December) they may stay in their burrows and migrate next month instead. We estimate the next optimum spawning date will be 19-21 January 2020.

Learn more about it here - Red crab migration