by CAPE TOWN, South Africa (AP) – Mice accidentally introduced to a remote island near Antarctica 200 years ago are breeding out of control due to climate change, eating seabirds and causing widespread damage in a special nature reserve with “unique biodiversity. “
Now conservationists are planning a mass extermination using helicopters and hundreds of tons of rodent poison, which must be dropped over all of Marion Island’s 115 square miles (297 square kilometers) to ensure success.
If even one pregnant mouse survives, their prolific breeding ability means it can be unexpected.
The Marion Gan Luch project – large-scale pest control – is seen as vital to the ecology of the uninhabited territory of South Africa and the wider Southern Ocean. It would be the largest eradication of its kind if successful.
The island is home to globally significant populations of almost 30 bird species and a rare undisturbed habitat for wandering albatross – with their 10 foot wingspan – and many others.
Unperturbed, at least, until house mice arrived on seal-hunting ships in the early 1800s, introducing the island’s first mammalian predators.
It is the most significant in recent years for the damage done by the mice, said Dr. Anton Wolfaardt, Marion Gan Luch project manager. He said their numbers have increased dramatically, mainly due to rising temperatures due to climate change, which has turned a cold, frigid island into a warmer, drier and more welcoming home.
“They are probably one of the most successful animals in the world. They’ve gone to all kinds of places,” Wolfaardt said. But now on Marion Island, “their breeding season has been extended, and the mouse densities have increased tremendously as a result.”
Mice do not need to be stimulated. They can reproduce from around 60 days of age and females can have four to five litters per year, with seven or eight babies each.
Rough estimates indicate that there are more than a million mice on Marion Island. They feed on invertebrates and, increasingly, on seabirds – both chicks in their nests and adults.
One mouse will eat a bird over and over again. Conservationists took a photo of one perched on the bloody head of a wandering albatross chick.
The phenomenon of mice eating seabirds has only been recorded on a handful of islands in the world.
The scale and frequency of mice preying on seabirds on Marion has increased alarmingly, Wolfaardt said, since the first reports of it in 2003. He said the birds have not developed the defense mechanisms to protect themselves. against these rare predators and that they often sit there and mice. nibble out on them. Sometimes multiple mice swarm over a bird.
Conservationists estimate that if nothing is done, 19 species of seabirds will disappear from the island in 50 to 100 years, he said.
“This extremely important island has a very poor future as a seabird sanctuary because of the impact of the mice,” said Wolfaardt.
The eradication project is a solitary measure, and there is not enough vehicle to make an error. The increasing number of mice and rats has caused problems for other islands. South Georgia, in the south Atlantic, was declared rodent-free in 2018 after an eradication, but that was a multi-year project; the one on Marion may be the single largest intervention.
Wolfaardt said four to six helicopters are likely to be used to drop up to 550 tonnes of rodent bait across the island. Pilots will be given precise flight lines and Wolfaardt’s team will be able to track the fall using GPS mapping.
The bait has been designed so that it does not affect the soil or water sources of the island. It should not harm the seabirds, which feed at sea, and it will not have a negative impact on the environment, Wolfaardt said. Some animals will be affected on an individual level, but those species will recover.
“There is no perfect solution to these types of things,” he said. “Nothing that zaps but mice and nothing else.”
The eradication project is a partnership between BirdLife South Africa and the National Department of Forestry, Fisheries and Environment, which has designated Mauritius as a special nature reserve with the highest level of environmental protection. There is a weather and research station but it is uninhabited and dedicated to conservation.
The department said the eradication of the mice was “necessary if the island’s unique biodiversity is to be preserved”.
Wolfaardt said the amount of planning required means it will likely break ground in 2027. The project also needs to raise about $25 million – part of which is funded by the South African government – and receive final regulatory approvals from the authorities.
Scientists have tried to control Marion’s mice in the past.
They were already a pest to researchers in the 1940s, so five domestic cats were introduced. By the 1970s, there were about 2,000 feral cats on the island, killing half a million seabirds a year. The cats were eliminated by introducing a feline flu virus and hunting any survivors.
Islands are critical to conservation efforts, but fragile. The Island Conservation organization says they are “extinction epicenters” and that 75% of all extinct species lived on islands. About 95% of those were bird species.
“This is really an ecological restoration project,” Wolfaardt said. “It’s one of those rare conservation opportunities where you solve a conservation threat once and for all.”
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