Annual Red Crab Migration On Christmas Island
Last Updated ( Monday, 09 July 2012 )
Christmas Island is a small Australian island in the Indian Ocean, 2,600
kilometers northwest of the city of Perth, that is home to many species of
animal and plant.
The island is particularly noted for its prodigious populations of Christmas
Island red crabs, a species of land crab that is endemic to the island,
and their spectacular migration from the forest to the coast each year during
the breeding season.
At the beginning of the wet season (which is usually October / November), over
50 million adult red crabs suddenly start migrating from the forest to the coast
to breed. The migration is usually synchronized all over the island. The males
lead the first wave of the migration and are joined by females as they progress.
The crabs take about five to seven days to reach the sea. The rains and moist
overcast conditions make their journey to the sea long and difficult.
During peak migration times, sections of roads where crabs cross in high numbers
are closed to vehicles for short periods of time. The bright red carapaces and
sheer density of crabs make their routes to the sea observable from the air.
After mating the females release their eggs into small burrows on the sea where
the hatch, and the young larvae develop into tiny small crabs. After remaining
about a month in the ocean, the young crabs, only five millimeters across,
accompanied by the adults make their long trek back home. Upon reaching the
inland, the crabs disappear into rocky outcrops, fallen tree branches and debris
on the forest floor for the next three years.
Human activities have led to increased numbers of red crabs being killed during
their annual migration. The crabs risk dehydration when they are forced to cross
areas cleared of forest cover and many thousands of adults and young are crushed
by vehicles as they cross the roads. To protect the crabs from being crushed by
vehicles, staff of Christmas Island National Park some roads are also
temporarily closed off and crab crossing signs erected at places. Walls and
plastic fencing along the roads are also built to funnel the crabs to the 'crab
crossings' and 'crab bridges' where they may safely cross.
The crab migration and the crab bridges have become a great tourist attraction.