Every year millions of bright red crabs leave their burrows in Australia's Christmas Island and head toward the sea. The 18-day-long journey known as the red crab swarm migration has been a popular tourist sight for years, which is why the trek was featured in CNN's 10 most spectacular wildlife migrations for 2013.
The journey, which takes place in November or December, coincides with the turning of high tide and the arrival of the waning moon, CNN noted.