johannesburg — South Africa is planning a massive mouse eradication project on a sub-Antarctic island to try to stop the invasive species from wiping out the precious seabirds that nest there.

Marion Island, in the southern Indian Ocean almost 2,000 kilometers from Cape Town, is a remote and windswept South African territory that’s home to extensive bird life, including the wandering albatross.

But those birds face an unusual threat: predatory mice that have been feasting on their chicks. The mice are an accident of history, but their population has been increased by climate change.

“The mice were introduced accidentally in the early 1800s,” said Anton Wolfaardt, a conservationist who is leading the program to eradicate the mice. “They came ashore – they were essentially stowaways on the vessels of the early seal hunters that visited the island.”

Huge jump in population

As the island has grown warmer and drier because of climate change, it has also grown more favorable for the mice. Now, by the end of the summer, the mouse population will have increased by 500 percent, he said.   

It was only fairly recently that researchers on Marion observed the mice preying on chicks, but the phenomenon has increased. 

The rodents are such a threat now, Wolfaardt said, “that experts predict that 19 of the 29 bird species on Marion Island face local extinction in the presence of mice.” 

Elsa van Ginkel, a researcher who was employed by the University of Pretoria to collect data on the island last year, said the island region was “truly out of this world. Walking among wandering albatross chicks every day and watching them grow into fledglings – wow, just wow, it’s an absolute privilege.”

But they are slowly being wiped out.

“These fledglings have no means of defending themselves from a mouse that actually starts eating it alive,” van Ginkel said. “It’s quite horrific.”

So Birdlife South Africa, a nongovernmental organization, and South Africa’s forest, fisheries and environment department are planning a major intervention to try to save the seabirds and restore the island to its natural state. 

Wolfaardt is heading the initiative, which is still seeking funding and is scheduled to take place in a few years.  

“Very simply, the operation involves broadcasting a specialized rodenticide bait, from bait spreader buckets that are slung beneath helicopters that are guided by GPS technology,” he said.

The pellets of rodent poison won’t negatively affect the rest of the flora and fauna on the island, experts say.  

A similar project has been undertaken before. In the 1940s, feral cats were introduced to Marion Island to try to control the mice, but then the felines started preying on the seabirds.  

The cats were successfully eradicated in the early 1990s, although that, of course, left the mice to flourish.
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