Christmas Island’s crab conservation success
In recent decades, as many as a third of Christmas Island’s famed large red crabs have been lost to swarms of yellow crazy ants.
But this year Christmas Island National Park’s Chief Ranger is excited to say that he’s seen a swarm of red crabs, the best in at least 25 years.
“When the roads and the beaches and the cliffs turn red with the huge numbers of them, you know that in comparison to other years that it's a big one,” he told ABC.
This red crab return is so spectacular that Sir David Attenborough regards it as one the most “astonishing and wonderful” sights.
The whole island is swarmed by millions of red crabs who’ve emerged from the forests to release their eggs into the sea. Roads are closed and buildings shut to stop crabs getting squashed or becoming lost.
“The crabs all start to come out and it just builds up and builds up and builds up from there over a couple of days. And before you know it you’re running around closing roads and everybody’s out with their cameras,” says Mr Muller.
It’s estimated that over ten million crabs have been lost to the yellow crazy ants. While the ant population has been reduced by regular poisoning, there were concerns about the small numbers of baby crabs returning from the sea to repopulate the forests.
“No one really knows. We assume it’s conditions in the sea, but we don’t know whether it’s water temperature, currents, wave height, how many predators are in the sea – because we get whale sharks come up around the island at this time of the year and a lot of the fish and eels in the sea all like this migration time,” says Mr Muller.
But this year’s flock has Mr Muller in optimistic spirits.
“After a return like this year where more than millions and millions, it’s got to be some billions of little crabs have come out around the island... the population has been well renewed.”
Image credit: Parks Australia
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