Each year, over 40 million red crabs on Christmas Island migrate from the forest to the coast, turning the landscape into a moving crimson carpet.

The Christmas Island red crab migration (Gecarcoidea natalis) is a biological phenomenon driven by the lunar cycle and the onset of the wet season, typically occurring in October or November. This synchronized movement involves millions of crabs traveling up to 5 kilometers from the island's central plateau to the Indian Ocean. The timing is critical because the crabs must reach the shoreline precisely during the high tide of the lunar last quarter to ensure their eggs are successfully swept into the sea.During this period, the Australian government and Parks Australia implement rigorous conservation measures. They have constructed over 30 kilometers of temporary plastic fencing to funnel crabs away from traffic and toward 31 purpose-built underpasses. One of the most famous features is a 5-meter-high 'crab bridge' designed specifically to allow the crustaceans to cross busy roads safely. These efforts are vital because the crabs face significant threats from vehicles and the invasive yellow crazy ant.Once at the shore, the females remain in burrows for about two weeks to allow their eggs to develop. On the night of the spawning, they enter the water and vibrate their bodies to release the larvae. A single female can produce 100,000 eggs, yet only a tiny fraction survives the month-long development in the ocean to return to land as 'baby crabs.' This migration is considered one of the most significant ecological events on the planet, drawing researchers and tourists from around the world.