Red crab migration season has begun on Australia's Christmas Island. 

In footage filmed by David Watchorn this past weekend, the crustaceans scuttle over roadways and infrastructure.

According to Parks Australia, every year millions of the large crabs emerge from the forest heading to the water to breed. The migration starts with the first rainfall of the wet season.

While that's usually in October or November, it can sometimes be as late as January.

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The exact timing and the speed of the migration are determined by the phase of the moon. 

Male crabs that lead the migration are later joined by females.

If it begins to rain too late to make their spawning date, some crabs will migrate the following month.

Once at the shore, the crabs take a dip to replenish moisture before the male crabs retreat to the lower terraces of the island to dig burrows. 

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The female crabs then join the males on the terraces to mate in or near the burrows. 

Each female crab, which remains in the burrow for over two weeks, can produce up to 100,000 eggs.

Male crabs will take a second dip before starting the journey back home.

When the moon reaches its last quarter, the crabs gather on the shoreline, releasing their eggs in the water. 

Red crab larvae hatch from the eggs as soon as they make contact with the water. 

The red crab migration is Christmas Island’s biggest tourist attraction.