After the 1903 extinction of the predatory endemic species the Maclear’s Rat, the people of Australia’s Christmas Island found themselves in the path of millions of red crabs.
Every year in the fall, Christmas Island is overcome by a scarlet wave of migrating crustaceans on a mad dash from the forest to the sea. For terrestrial crabs unique to this area, their little red crablings must be born in the ocean or they will not survive. As soon as the humidity is just right—around October or November—the crabs swarm over the island, across roads, through homes and schools, under every foot, every tire, inside unattended shoes and covering every surface available, all 100 million of them.
The locals are very patient and protective of their sideways-scuttling neighbors and are careful to minimize driving, hang “Crabs Crossing” signs on the roads, and even construct ‘Crab Bridges’ to aid in their crossing. Once the masses reach the ocean and go about their business, they return to the forest, first the males, then the females, exhausted and spent, to wait for their offspring to return.
A few weeks later, once the larval hatchlings have grown into their land legs, it’s time for them to make their journey across the island to their woodland home. At 100,000 hatchlings per female, the sheer number of teeny tiny crablets is hard to fathom as they wash back across the roads and buildings like a sea of scarlet spiders, swarming over everything in their path.