Every fall, Christmas Island is overcome by a red wave of migrating crustaceans, on a mad dash from the forest to the sea. Terrestrial crabs that are unique to this area, their offspring must be born in the ocean or they will not survive. As soon as the humidity is just right, around October or November, they swarm the island.
The locals are protective of their sideways-scuttling neighbors, and are careful to minimize driving, hang “Crabs Crossing” signs on the roads, and watch their feet during the migration, but a few million become casualties every year to vehicles, other animals, and clumsy tourists not accustomed to carefully watching their steps. Once they 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, the hatchlings have grown into their land legs, and it’s time for them to journey across the island to their woodland home. With 100,000 hatchlings per female, the magnitude is hard to imagine as they wash back across the roads and buildings like a sea of red spiders, swarming over everything in their path. The islanders do their best to help them along , but it’s a losing battle. There is nothing to do but work around them as much as possible, and try to ignore the invasion.
To be able to see this you have to hurry, because of the accidental introduction of the aggressive “yellow crazy ant” the numbers of the red crabs are declining at an alarming rate. The highly invasive insect has wreaked havoc on the ecology of the island, their excretion is poisoning the crabs as well as several other species unique to Christmas Island. Over a quarter of the red crab population has been wiped out so far, and the crabs now face extinction.