Africa: Plan Underway to Save Seabirds From Killer Mice On Remote South African Island

Conservationists have launched an ambitious project to save albatrosses and other threatened seabirds on a remote island off the coast of South Africa from a plague of killer mice who eat the chicks alive. At least 18 out of the 27 species of bird on Marion Island are at risk of local extinction.

The mice were accidentally introduced to Marion Island, more than 2,000 kilometres south-east of Cape Town, in the early 1800s by sealers who brought them ashore on boats.

Over the last few decades, as the climate has become warmer and drier, mouse numbers on Marion Island — which is about twice the size of Paris — have exploded. In the southern hemisphere winter, as plant and insect food on the island runs low, the mice have turned to feeding on the flesh of seabird chicks with increasing frequency.

Birds that nest in burrows, like petrels and prions, are especially vulnerable.

“They eat the eggs and chicks, and the parent has no defence mechanism against this behaviour,” said Guy Preston, vice chairman of the Mouse-Free Marion Project, a South African non-profit. “For the mice they become ‘sitting ducks’.”

At least 18 out of the 27 species of bird that live and breed on the island — which is also home to colonies of king penguins — risk local extinction if the mice aren’t dealt with. These include birds like the Wandering albatross, whose worldwide population is vulnerable due to declining numbers.

‘Scalping’ albatross chicks

The conservationists are working towards dropping poisoned mouse bait across the island in mid-2023, during winter in the southern hemisphere. Mice stop breeding in winter, and most of the island’s resident birds are away foraging for food.

Both South Africa’s department of forestry, fisheries and the environment, and conservation group BirdLife South Africa are backing the project.

Evidence of the devastation wrought by the mice emerged in 2003. Researchers began to find bloody wounds on the chicks of Wandering albatrosses, one of four species that nest on the island. Similar head and neck wounds have more recently been recorded on the chicks of Grey-headed, Sooty and Light-mantled albatrosses. Scientists refer to the head wounds as “scalping”. Many of the chicks go on to die from their injuries.

There was also evidence that mice burrowing into the base of Wandering albatross nest cups for warmth caused some nests to collapse, killing the chicks.