CHRISTMAS ISLAND, Western Australia: Each year, a "biblical plague" of 50 million cannibalistic crabs head to the ocean to breed, shutting down roads along the coast on Christmas Island, Western Australia.

The spectacle, considered one of the greatest animal migrations on the planet, sees the bright-red crabs descending on towns through residential areas and tourist hotspots in the winter months.

Some 50 million crabs travel from the forest after rainfall in October or November and head to the ocean to mate each year.

The crabs, which generally eat leaves, fruits, flowers and seeds, have been known to eat their own young when juveniles return from their first ocean migration.

Parks Australia shared photos and video of thousands of crabs scurrying across roads and over specially-constructed bridges.

Due to their sheer numbers on roads, residents of the Drumsite settlement in the northeast were trapped in their homes on Sunday, and workers were forced to rake the crabs off the pavement to keep the island's roads clear.

"With the red crab migration in full swing on Christmas Island, they are turning up everywhere, including at the door of an office block," said a spokesperson for Parks Australia.

National Park acting manager Bianca Priest said the spectacular annual event on Christmas Island, which is popular with travelers, has become an attraction itself.

"World-renowned naturalist Sir David Attenborough described the red crab migration as like a great scarlet curtain moving down the cliffs and rocks towards the sea. Over the years, visitors have traveled from every corner of the world to witness this wildlife phenomenon," she added, as quoted by the New York Post.

The male crabs are the first to make the trip to the water, and are followed by their female counterparts. After mating, they can each produce up to one hundred thousand eggs.