Red crabs congest in the thousands on Christmas Island as they scuttle to the sea. Image credit: Parks Australia

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Each year on Christmas Island, over 100 million red crabs scurry at once from the forest to the sea to breed and spawn. For the first time tomorrow you can watch the surreal sight live from home.

IT’S AN AWE-INSPIRING sight, and now, for the first time ever, you can watch Christmas Island’s annual red crab migration as it happens live online.

Each year, up to about 120 million red crabs (Gecarcoidea natalis) scuttle to the sea from the forest across Christmas Island in an effort to mate. It is a commute which overwhelms the island – the 135sq.km Australian-owned island, located in the Indian Ocean 2600km northwest of Perth, has just over 2000 human inhabitants.

Workers from National Parks and Wildlife on Christmas Island are supported during the red crab migration by locals as they try their hardest to keep roads clear for cars and buses to pass through. (Image credit: James D. Morgan)

Males lead what is for many crabs a weeks-long journey – when arriving at the sea, they create burrows in the sand which after mating they ɩeаⱱe to the females to lay eggs.

Tomorrow night, after two weeks of nesting – timed with the dawn of high tide during the last lunar quarter – millions of female red crabs will гeɩeаѕe up to 100,000 eggs each into the sea. They then retreat into the forest – after hatching, the young crabs will follow in their claw-steps several days after.

How to watch it

Parks Australia will live stream the expected hatching time at 8.15am AEST on Friday, 25 November (4.15am Christmas Island time).

The stream will focus on Flying Fish Cove, and is expected to go for 15 minutes – depending on the hatching.

To watch, download the Persicope app for your smart phone and follow @Parks_Australia or һeаd to www.periscope.tv/Parks_Australia.

Learn more about the red crab migration with photographer James D. Morgan’s on the ground account.

On Christmas Island, barriers divvy the road between traffic types: cars and red crabs. (Image credit: Parks Australia)

Hatching and the return of the baby crabs

Red crab larvae hatch from the eggs as soon as they make contact with the water. Clouds of larvae swirl near shore before being taken out to sea by waves and the receding tide.

They grow through several larval stages over the next month, eventually developing into prawn-like animals called megalopae. The megalopae gather in pools close to the shore for one or two days until they become fully formed baby crabs and emerge from the water.

Measuring about 5 mm across, the tiny crabs begin marching inland, taking around 9 days to reach the safety of the plateau. There they will stay hidden in rocky outcrops and forest debris for the first three years of their life.

However, the vast majority of larvae never make it out of the water – instead they are eaten by fish, manta rays, and the enormous whale sharks that visit Christmas Island to take advantage of this annual feast.

Most years, no or very few baby crabs will emerge from the sea at all. But once or twice a decade, a huge number will survive, which is enough to maintain the island’s large red crab population.