Sir David Attenborough called it one of the ‘most astonishing and wonderful sights’. Here’s why!

1. About 50 million red crabs live on Christmas Island – the only place in the world where they are found.

2. The migration begins with the start of the wet season (usually October to December) and is fixed to a particular lunar phase. It can only happen before dawn on a receding high tide during the last quarter of the moon!Red crab migration - tunnel

3. The crabs will only start their migration if there is enough time for them to complete their downward migration, mate, and develop eggs, before the next suitable spawning date.

4. Park staff have built walls and plastic fencing along roads, to funnel crabs to crossings, underpasses, and a bridge.

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5. Some roads are closed during the migration and everyone takes care to avoid crabs on the roads. Many locals carry a rake in their car at this time of year to clear a safe pathway through the crustaceans.

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6. The spawning date – when the eggs are cast into the sea – is fixed to a particular lunar phase. It can only happen before dawn on a receding high tide during the last quarter of the moon!

7. A single female can brood up to 100,000 eggs.

Female red crab with eggs

8. The eggs hatch as soon as they make contact with the water. Clouds of larvae swirl near the shore before being washed out to sea. The crabs can’t swim (only dip) and some females perform some spectacular feats to get their eggs into the water!

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9. It takes the crabs almost two months to make the journey from the forest to the sea and back again.

10. After about a month in the water the larvae have developed into ‘megalopes’- they crowd together at the shorelines, breathing via their gills. Three to five days later they leave the water, and ‘moult’ into air breathing crabs.

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11. Millions, possibly billions, of baby red crabs swarm toward the forest, creating the most stunning sights imaginable!

 

With thanks to Karen Willshaw and Indian Ocean Experiences for use of their images