At the start of the wet season upwards of 50 million red crabs begin their mass migration, marching from the forests to the coast to breed and lay their eggs. Often hailed as one of the world's most impressive wildlife migrations; the eggs are only released by the females in conjunction with a precise lunar phase and at the turn of the high tide. At this time, the sea level at the base of the cliffs and on the beaches, where the eggs are released has the least amount of variation allowing for the safe release of eggs. There may be fluctuations in the time of year of the migration but all migrations retain the same lunar harmony. After about a month at sea, the baby crabs return to the island to begin their march inland, back to the forest.
Christmas Island’s rich ecology is still considered intact. However, many terrestrial species have recently come under threat due to the introduction and spread of yellow crazy ants.