To protect one of the world’s most important seabird populations, conservationists have announced a bold plan to eradicate invasive mice on Marion Island, a remote South African territory about 1,250 miles southeast of Cape Town.
The island’s unique ecosystem is under serious threat as an overpopulation of mice has begun hunting albatrosses and other seabirds, eating their eggs and even attacking birds.
“The density of mice has literally increased by about 500 percent in the last 30 years,” said Anton Wolfaardt, project leader of the Mouse-Free Marion project Newsweek.
“The seabirds have no evolutionary defense mechanism against this new predator. And so they literally just sit on their nests while the mice nibble on them night after night, eventually tiring them out and dying for various reasons.”
Ben Dilley
The island’s bird residents include the wandering albatross, known for its impressive 3.5-meter wingspan – the largest of any bird in the world. About a quarter of the world’s population of this species nests on Marion Island, making the situation even more critical.
Among the gruesome evidence presented at a recent BirdLife South Africa meeting were images of bloody birds with severe injuries, some with the flesh eaten from their heads.
If left unchecked, these attacks could contribute to the extinction of 19 of the 29 seabird species that breed on the island, according to the Mouse-Free Marion Project.
The plan – a joint effort between South Africa’s Department of Environment, Forestry and Fisheries and environmental group BirdLife South Africa – involves using helicopters to drop 600 tonnes of pesticide-laced pellets over the island.
The operation is expected to cost around $29 million, but only about a quarter of the necessary funds have been raised so far.
Using hundreds of tons of poison on a remote island is risky. There is a possibility that some birds could eat the poisoned mice and be harmed as a result.
Nevertheless, Wolfaardt remains “convinced of the environmental benefits” and says steps have been taken to minimize unintended consequences.
For example, the poison used is not water-soluble, so it cannot contaminate the island’s water sources. In addition, the eradication operation is planned for winter, when the mice are most vulnerable and many of the seabirds that breed in summer have already left the island.
“Based on experience from previous operations, we know that the majority of mice – possibly 85 to 90 percent – die in their underground burrows, where they are obviously less accessible to carrion birds,” Wolfaardt said.
“There really is a massive imperative to protect the environment, and we believe there is also an ethical imperative.”
However, conducting the operation during the harsh sub-Antarctic winter presents significant challenges.
“When you have to deal with strong winds and poor visibility, you have to take that into account when planning,” said Wolfaardt.
If all goes according to plan, the project will begin in 2027 and could take between four and six months to complete. Experienced helicopter pilots and sophisticated GPS technology will be used to carry out the task.
The unprecedented situation on Marion Island has been exacerbated by climate change, which has led to higher temperatures on the island, allowing the mice to reproduce more frequently and for longer periods of time.
The mouse population was introduced by humans in the early 19th century and has been out of control ever since. Cats were once introduced to control the mouse population, but their presence caused further ecological disruption and by 1991 they were eradicated.
“Unlike most conservation initiatives I have been involved in, which only result in incremental changes over long periods of time, this type of action is a measure where the problem is solved once and for all with a single decisive intervention,” said Wolfaardt.
If successful, the Mouse-Free Marion Project could not only save the birds on the island itself, but also set a precedent for other species conservation projects around the world.
“Every project provides lessons for subsequent projects (…) and we expect other projects to learn from ours,” said Wolfaardt.
Do you have a tip for a science story that Newsweek should cover? Have a question about seabirds? Let us know at [email protected].
