Red crabs begin their march from the forest to the sea, where they will reproduce
A female crab expels eggs from her brood pouch
After two weeks of marching, the first wave of crabs reaches the ocean
The weary travellers dip in the ocean to replace body fluids and salts
There are around 120 million crabs on the march
Red crabs are scavengers
During the migration, the island's human inhabitants just have to adapt
Aerial view of Christmas Island
Location of Christmas Island
Christmas Island rainforest
Baby crabs navigate their way into the rainforest ... and the ants
The crabs navigate the same pathways year after year
The eggs hatch immediately on contact with the water
