Christmas Island has a particular species of crabs that is at odds with modern society. Every year, when the wet season begins in the Australian Island, as many as 50 million crabs migrate from the rainforest to the sea in order to breed.
As a result, the crabs have to cross over human-built roads and other structures. The death toll for these crabs at the end of the mating season can be as high as 500,000, just from their deadly encounters with humans.
To solve this problem without having to close roads and interrupt the island's activities, preservationists have devised different methods, like this train bridge that allows them to bypass over the roads safely.