Tens of millions of red crabs are crawling their way to the ocean as part of their annual migration on Christmas Island.

On the island is a much smaller human population that uses leaf blowers and garden rakes to help the crabs on their way.

Christmas Island National Park acting manager Alexia Jankowski said Thursday there were up to 200 million of the endemic crabs, also known as Gecarcoidea natalis, on the tiny Australian island territory in the Indian Ocean.

Up to 100 million were expected to make their way from their forest burrows to the shoreline where they breed.

The start of the Southern Hemisphere summer rains last weekend triggered the annual odyssey.

Jankowski said early mornings and late afternoons bring about a vast, slow blanket of crustaceans that moves to the coast over roads and gardens.

Their 1,200 human neighbors on the island generally do what they can to clear the red carpet of crustaceans off the roads.

"Some people might think they’re a nuisance, but most of us think they’re a bit of a privilege to experience," she added.

On the shores, the male crabs dig burrows where the females spend two weeks laying and incubating eggs.

The females are all expected to release their spawn into the ocean at high tide on November 14 or November 15, during the last quarter of the moon.

The young spend a month riding the ocean currents as tiny larvae before returning to Christmas Island as small crabs.

"When they’re little babies only about half the size of your fingernail, we can’ rake them, because you’d crush them. So instead we use leaf blowers," Jankowski said.