Every year tens of millions of Christmas Island red crabs migrate from the island’s dense forest to the cliffs to spawn. It’s a phenomenon that literally stops traffic and draws tourists from around the world to the tiny Australian territory.

But while there are still tens of millions of red crabs on the island, in recent years their numbers have dipped by around a third as they compete for space with (and struggle to fend off) a recently introduced pest: the yellow crazy ant.

The ants are having a significant impact on the island’s biodiversity, which relies on the red crab to maintain the forest understorey and keep the forest floor clean.

So what can be done to save Christmas Island’s biodiversity from yellow crazy ant supercolonies?

For the past few years a team of scientists have been hatching a plan to introduce a parasitical wasp to the island to cut the ant’s food supply. And in December they got the ball rolling on the delicate process of tipping the scales back in the crabs’ favour.

La Trobe University’s Matt Smith speaks with Peter Green, Head of the Department of Ecology, Environment and Evolution at La Trobe, about the impact of the yellow crazy ant and how his team’s plan to save the Christmas Island red crab is working in the first few months of its implementation.

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Peter Green receives funding from the Department of Environment and Energy.