Christmas Island red crabs.
Credit: Getty Images

Every year, Christmas Island—a remote Australian island in the Indian Ocean—is overrun by bright red crabs. Forty million fire engine-colored crustaceans pour out of the jungle and fill the island’s streets with red bodies eager to breed. It sounds like the stuff of horror films, but it’s actually just the annual migration of the Red Crab, a natural phenomenon that earns Christmas Island a spot on many travelers’ bucket lists.

An estimated 40 to 50 million crabs leave their homes in the jungle plateau and head to the coast en masse to breed and to allow the female crabs to release their eggs into the sea. The red crabs will only breed during a very specific time frame—very specific, e.g., the high tide of the last quarter of the moon during the rainy season—so when the precise moment comes, the crabs synchronize their move resulting in an island teeming with creatures on the run.

The main crab migration can last up to 18 days with streams of crabs making their way towards the coast, clambering over obstacles to follow routes that have been used for years. And while most modern societies would view the annual migration as a nuisance, the 2,000 or so residents of Christmas Island roll out the red carpet for the red crabs carpeting their home, doing their best to accommodate the hustling crustaceans. They close down roads and construct special fences, tunnels, and even bridges to help keep the crabs safe on their arduous journey to the sea.

Watch the video above for a peek at the migration, or book a last-minute flight to Christmas Island. The next possible spawning date is January 6-8 of 2016, according to the locald tourism board.