Island Had to Build Bridge for Legion of 47 Million Crabs

Crabs climb up a cliff on Christmas Island. Image: Stefan Krasowski via Flickr

Christmas Island, a tiny Australian territory in the middle of the Indian Ocean, has a bit of a crab problem.

An estimated 40 to 50 million Christmas Island crabs reside on this 52 square mile island. In comparison, the human population there is only about 2,000.

Each year, these fire-engine red crustaceans make their way from the forest to the ocean to breed and spawn. Once they arrive at the coast, the males will construct burrows to entice the females.

Christmas island red crab
The Christmas Island red crab, Gecarcoidea natalis, is a species of terrestrial crab endemic to Christmas Island in the Indian Ocean. Image: Christmas Island via Wikimedia Commons

Mating takes place in or around the burrows, which the females then take over to incubate the eggs. The female then releases the eggs into the ocean where they will develop. When they’re ready, the juveniles will make their way out of the ocean and back to the forests where their parents came from.

As you can imagine, this creates a traffic jam of sorts as the crabs travel back and forth across busy roads. In fact, residents have had to completely close roads for weeks at a time to allow for this elaborate ritual.

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To solve that problem, rangers at Christmas Island National Park have set up over 12 miles of barriers to direct the migrating crabs out of the roads and into 31 underpasses and onto a 16-foot high crab bridge. 

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This inventive bridge system has become quite an attraction, and tourists flock from all over the world to see the crabs in action.

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We love seeing humans coexisting so peacefully with nature!