HomeScienceScience behind why millions of Red Crabs march together in Christmas Island

Science behind why millions of Red Crabs march together in Christmas Island

Each year, millions of red crabs swarm across Christmas Island in a breathtaking migration from forest to sea for spawning.

October 30, 2025 / 16:59 IST
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Science behind why millions of Red Crabs march together (Image: Canva)
Science behind why millions of Red Crabs march together (Image: Canva)

A sea of scarlet sweeps across Christmas Island every year. Millions of red crabs leave their forest burrows and head to the coast. Their goal is reproduction which is a journey guided by rain, moon and tide.

A Forest in Motion

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The red crabs live deep within the island’s tropical rainforest. When the wet season begins, they emerge in waves. The males lead, carving paths through rocks and roads. Females follow later, heavy with eggs.

The migration is perilous under the tropical heat. Crabs travel during cooler hours to avoid dehydration. They rest in shade, conserving moisture as they cross miles of terrain. Local authorities even close roads to protect their passage.