The exact time when red crabs travel from the forest to the ocean is determined by rainfall and moon phases. The male crabs take the lead in the parade, and the females then join in. After reaching the ocean, they mate and lay eggs, and each female is able to lay up to 100,000 eggs. However, most of the baby crabs never return to the forest because they are eventually eaten by fish and whale sharks, a veritable feast for them. To make matters worse, crab larvae that successfully reach the beach are often eaten by returning adult crabs of the same species, hence their name – piranha crabs.
The annual migration of red crabs has brought traffic to a standstill on an Australian island. Apart from the epic journey, the species is also notorious for eating its own young.
Tens of millions of crustaceans are swarming Canberra-governed Christmas Island, which is almost a thousand miles northwest of the Australian mainland. Parks Australia, a government body in charge of wildlife conservation on the island, has deployed its staff to manage traffic, rake crabs off roads and provide advisories to local residents regarding road closures. Authorities are well-prepared to deal with the epic crab march as it repeats every year, usually in October and November. There are even special bridges and tunnels in place, built over and under busy roads so as to minimize the number of crabs crushed by cars. The sight of millions of these creatures making their perilous trek has become one of Christmas Island’s main tourist attractions.
![Australia's Red Crab Bridge, one of the most famous wildlife safety passages, is a dedicated lane for tens of millions of red crabs[fig]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)