Courtesy of Curiosity.com:
“Christmas Island has nothing to do with a big jolly man in a red suit. Instead, it has its own distinct bright red mascot: millions and millions of land crabs. Every year, this Australian island territory is flooded not by the surrounding Indian Ocean, but by an overwhelming wave of scarlet, clawed crustaceans. Trust us, the annual migration needs to be seen to be believed.
Christmas Island has all the makings of a tropical sight-seeing destination: it boosts exotic birds, azure ocean views, untouched beaches, and lush flora. C’mon, almost two-thirds of the place is national parkland. But it’s best known for its crabs, and not in the New England chowder kind of way. Christmas Island is home to an estimated 50 million crabs, all of which make the annual trek from forest to coast. The wet season there, usually late October and early November, is when the adult Gecarcoidea natalis (Christmas Island crabs) shuffle to the seashore in one giant, synchronized breeding ritual. The whole ordeal can last up to 18 pincer-filled days. And when the eggs hatch? Watch out for rivers of bright-red, ant-sized crabbies.
It’s not all crabs, though. The human population of Christmas Island isn’t huge, but it does exist. Just over 2,000 people live there. The idea of a crabocalypse might have you squirming in your seat, but the Christmas Islanders have a different take: They love it. The people of the island have gone out of their way to do what they can to protect the crabs’ journeys to spawn.
The conservation efforts are quite charming, actually. According to the Christmas Island Tourism Association, “crab crossings” are created to help these little guys along: “Points where high numbers of red crabs cross roads have been identified, and tunnels are built under the road for crabs to pass through. Walls that the crabs cannot climb over are built alongside the road to ‘funnel’ the migrating crabs through the tunnels. […] Other conservation measures used by the community are road closures and traffic detours around the major migration paths during peak periods of the migration.”