Hoards of Mice on Marion Island are preying on Endangered Seabirds; That’s About to Change.

NBC reports: On remote Marion island near Antarctica, mice are breeding out of control. They are eating seabirds and causing major harm 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 needs to be dropped over every part of Marion Island’s 115 square miles (297 square kilometers) to ensure success. If even one pregnant mouse survives, their prolific breeding ability means they will quickly repopulate.

Sky News notes that Marion island is home to globally significant populations of nearly 30 bird species and a rare undisturbed habitat for wandering albatrosses – with their 10-foot wingspan – and many others.

But two incidents of human agency have changed the fact that the birds are no longer predator free and the mice have taken their place as those who are the prey.

First, during the 1800s, whaling and seal hunting ships in the area carried with them stowaway mice who became the island’s first mammal predators. Second, climate change warmed the island and its waters making the cold inhospitable island more mammal friendly with warmer and drier clients.

Per NBC, mice can reproduce from about 60 days old and females can have four or five litters a year, each with seven or eight babies. Rough estimates indicate there are more than a million mice on Marion Island. They are feeding on invertebrates and, more and more, on seabirds — both chicks in their nests and adults.

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.

This is not the first time the eradication approach has been tried. The previous approach involved Marion Island’s feral cats. Mice were a pest for researchers in the 1940s, so five domestic cats were introduced to prey upon the mice. By the 1970s, there were around 2,000 feral cats on the island, killing half a million seabirds per year. The cats were eliminated by introducing a feline flu virus and hunting down any survivors.