Yellow Crazy Ants and Red Crab
Christmas Island in the Indian Ocean
for millions of years. This remote speck of land has been ruled by crabs.
Their ancestors came from the sea, but most have now adopted a land based existence based.
Given there are so many of them, they get along relatively harmoniously. They're the gardeners and caretakers of a tiny crab utopia.
Once a year, they must all return to the sea to breed. And the march of the red crabs is one of the greatest natural spectacles on earth. And there are 50 million of them. It's an event.
This has brought the island's worldwide fame. But in recent years, millions of red crabs haven't managed to reach the sea.
An invader has occupied this island. Yellow crazy ants.
They escaped from visiting ships and with no predators to control them,
they have now created vast super colonies in the forest.
When migrating, red crabs march into their territory, the ants attack, squirting acid into the crabs, eyes and mouths. The traps have no defense. Blinded and confused, they are doomed. Humans brought these ant invaders here and now. Humans are having to control them. Isolated communities may evolve for millions of years in relative peace.
But when new challenges arise, they can struggle to cope. Of all the species
that have become extinct in recent years, around 80% have been islanders.
Yellow crazy ants (Anoplolepis gracilipes) are indeed a formidable invasive species known for their aggressive behavior and ability to disrupt ecosystems. One of the ecosystems they've significantly impacted is Christmas Island, where they pose a severe threat to the native red crabs (Gecarcoidea natalis).
Red crabs are a keystone species on Christmas Island, playing a crucial role in nutrient cycling and forest health. They migrate in millions from the forest to the sea to breed each year, and their sheer numbers make them an essential part of the island's ecology.
Yellow crazy ants disrupt this delicate balance. They attack the red crabs, spraying formic acid and overwhelming them with their sheer numbers. This can lead to the death of the crabs, either directly from the ant attacks or indirectly from disrupting their normal behavior and ecological roles.
Efforts have been made to control the yellow crazy ant population on Christmas Island to protect the red crabs and the island's unique ecosystem. These efforts include the use of baiting techniques and biological control methods to limit the spread of the ants and mitigate their impact on native wildlife.
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