Page 25 - How It Works - Book Of Amazing Answers To Curious Questions, Volume 05-15

Environment

‘Crab crossings’ are set
up to reduce the number of
crabs crushed by vehicles
during the migration period

Red crabs regularly
invade local golf courses
on their way to the coast

What’s behind

Christmas Island’s

red crab invasion?

Discover the amazing migration of 120 million crabs

nce a year on Christmas Island, quick dip in the sea to replenish any body into larvae. In the water, the larvae grow into
Australia, tens of millions of red moisture lost during their journey. They then prawn-like creatures called megalopae,
Ocrabs descend from the rainforest, start to dig burrows in the sand and, once the which breathe through gills. Those that
turning the island into a sea of red as they females arrive, they enter the burrows to manage to survive the harsh ocean currents
make their way to the coast to breed. The begin mating. After mating, the males make and marine predators emerge from the sea
migration begins with the wet season, their return journey, leaving the females in four weeks later to shed their outer skin and
typically around October or November, and is the burrows to develop up to 100,000 eggs. become baby crabs. The infants, measuring
linked with the phases of the Moon and About 12 to 13 days later, before dawn at high just 5mm (0.2cm) across, begin their march
therefore the tide. tide, the females emerge from the burrows inland to live on the forest floor, then after © Corbis; Rex Features
The males leave their forest burrows first, and go to sea. Once they reach the water they four years, they progress to join the migrating
and once they reach the shore they have a deposit their eggs, which immediately hatch herds for breeding.

How It Works 25