Christmas Island is a small island territory of Australia. It’s home to about 1,500 people. Once a year, it’s also home to red crabs—150 million of them.

Like clockwork, they show up around November. Up the beach, through the fields, down the roads—they’re everywhere. And that’s really just the beginning.

The crabs aren’t on vacation. They come to the island to spawn. Each female crab can produce over 100,000 babies.