Mouse eradication planned to save island's seabirds


A mass eradication of mice is to take place on Marion Island in order to save the local seabird population.

Marion Island is a small, uninhabited subantarctic island administered by South Africa. It is famed for its breeding seabirds including globally significant populations of 30 species.

However, mice have colonised the island and are decimating the local birdlife, eating chicks in their nests as well as adults. Rough estimates indicate there are more than a million mice on Marion.

As a result, conservationists are planning a mass extermination of the rodents using helicopters and hundreds of tons of poison, which needs to be dropped over every part of Marion's 297 sq km to ensure success.

Wandering Albatross is one of several seabird species that breeds on Marion Island (Rob Hynson).


Mouse-Free Marion

The Mouse-Free Marion project is seen as critical for the ecology of the island and the wider Southern Ocean. It would be the largest eradication of its kind if it succeeds.

The past few decades have been the most significant for the damage the mice have caused, said Dr Anton Wolfaardt, the Mouse-Free Marion project manager. He said their numbers have increased hugely, mainly due to rising temperatures from climate change, which has turned a cold, windswept island into a warmer, drier, more hospitable home.

The scale and frequency of mice preying on seabirds on Marion has risen alarmingly, Wolfaardt said, after the first reports of it in 2003. He said the birds have not developed the defence mechanisms to protect themselves against these unfamiliar predators and often sit there while mice nibble away at them.


Seabirds at risk

Conservationists estimate that, if nothing is done, 19 seabird species will disappear from the island in 50-100 years.

Wolfaardt said four to six helicopters will likely be used to drop up to 550 tons of rodenticide bait across the island. Pilots will be given exact flight lines and Wolfaardt's team will be able to track the drop using GPS mapping.

The bait has been designed to not affect the soil or the island's water sources. It shouldn't harm the seabirds, who feed out at sea, and won't have negative impacts for the environment, Wolfaardt said. Some animals will be affected at an individual level, but those species will recover.


Eradicating rodents

The eradication project is a partnership between BirdLife South Africa and the national Department of Forestry, Fisheries and the Environment, which designated Marion Island as a special nature reserve with the highest level of environmental protection. It has a weather and research station but is otherwise uninhabited and dedicated to conservation.

Wolfaardt said the amount of planning needed means a likely go-ahead date in 2027. The project also needs to raise around $25 million and get final regulatory approvals from authorities.