South Africa is preparing the largest eradication campaign against house mice on Marion Island. In our country, they are relatively harmless, but on the island, they kill many seabirds, which are therefore threatened with extinction.
The mice don’t belong on the desert island in the Indian Ocean. In the 19th century, they accidentally came to the island by seal hunters. “Their boats were full of vermin; no wonder a few ended up on the mainland,” says Dirk Adriaens, invasion biologist at the Institute for Nature and Forest Research against De Morgen. “Due to the biting cold on the island, it took a while for the population to flourish. But since our planet is warming up significantly, the mice are multiplying at a breakneck pace.”
And that’s a problem because they are dangerous to plants, invertebrates and even adult seabirds that like to breed on Marion Island. Millions of seabirds, including four species of penguins and a quarter of the world’s albatrosses, come to the island each year to hatch their eggs. If nothing is done about the mice, 18 of the 28 seabird species that breed here will become extinct on the island.
“Seabirds and especially their chicks are very naive. They don’t know that mice are a threat. That makes them an easy victim,” says Adriaens. “It may sound strange for a little mouse to kill a big bird, but seabirds are only made to fly, making them weak. In addition, rodents grow considerably due to their new food source. This way, you get giant mice that look more like rats. We call that killer mice.”
“The need is great for the seabirds,” says the operational manager of the extermination project Keith Springer. “The extermination has clear benefits for the birds and other animals and plants that live here, but the project is also of value outside the island. The seabirds are part of a community that is important to the functioning of the subantarctic region.”
South Africa and organization BirdLife South Africa will bring mouse poison helicopters from South Africa to Marion Island in the summer of 2025. The poison will be spread over 30,000 hectares of the island. This is the only way that has been proven to be successful. In 2018, South Georgia used this method to eradicate mice and rats.