The Christmas Island red crab, Gecarcoidea natalis, is the most dominant animal species found exclusively on Christmas Island. Their numbers have increased to 50-100 million since the extinction of their natural predator, the Maclear's rat. One of the impressive sights on Christmas Island is the yearly migration of red crabs across the plateau, which can last up to 18 days as the crabs move in broad columns along the same route each year. The biggest threats to the red crabs are direct sunlight, heat, and the invasive Yellow Crazy Ant, whose numbers on the island have been reduced by 99% through an extermination program since 2000.

1. Most Famous Crab Of The Island Is Christmas Island Red Crab
Gecarcoidea Natalis – Dominating Animal Species In Forest, Endemic
Species Met Only On This Island.
In total on island live 50 – 100 million of these crabs what represents unprecedented density of land
crabs in the world.

2. As early settlers have not reported about unusual numbers of these crabs, it is possible that
their number increased after extinction of it’s natural enemy – Maclear’s rat (Rattus macleari).

3. In 19th century these rats were everywhere on the island but went extinct in early 20th century after
invasion of black rat and epidemics.
One of the impressive sights not only for Christmas Island but for whole world is yearly migration of
red crabs.

4. It seems that migration takes place in the time when there is least difference between low and high
tides – then it is safer to lay eggs.

5. Migration starts on plateau, lasts up to 18 days. Crabs gather in broad columns and repeat the same
route each year.

6. They prefer to go in early morning or late afternoon – to avoid direct sunlight.
The biggest danger to them is direct sunlight and heat

7. but the rains and moist overcast conditions make their journey long and difficult too.

8. To save the crabs, on the roads there have been developed special crab crossings and plastic
walls, funneling them to these crossings.

9. Sections of roads where crabs cross in high numbers are closed to vehicles for short periods.
But there is another deadly enemy – invasive Yellow Crazy Ant (Anoplolepis gracilipes).

10. It is the main reason why the number of red crabs is decreasing,
although numerous other species of introduced animals are changing the ecosystem too.
Since 2000 there is on-going extermination of

11. the super-colonies of crazy ants all over the island,
decreasing their number per 99%.

12. Read more: http://trifter.com/asia-pacific/migration-of-red-crab-of-the-christmas-
island/#ixzz1s5Lr20Oz