Article includes images that some readers may find distressing.
With their Mickey Mouse ears and button-black eyes, house mice may look cute and harmless, but in certain situations, they are anything but.
On the sub-Antarctic island of Marion in the Indian Ocean, they are a deadly threat to one of the world’s most iconic seabirds – the wandering albatross, symbol of the Southern Ocean and immortalised in classic literature such as Samuel Taylor Coleridge’s The Rime of the Ancient Mariner.
An estimated 1,800 pairs – about one quarter of all breeding individuals – nest on Marion, but at some point over the past two decades or so, the non-native house mice have discovered a taste for both the chicks and the adults of many of the island’s seabirds, with disastrous impacts.
Extraordinary as it sounds, says Dr Anton Wolfaardt, the Mouse-Free Marion project manager, the omnivorous mice have slowly moved from the island invertebrates as a source of protein to the seabirds, which don’t appear to recognise them as a threat.
“The mice slowly but surely nibble away at the birds, and though they don’t die [from their wounds] immediately, they become fatigued, the wounds become infected, they lose condition and perhaps they are then vulnerable to predation by avian predators or scavengers such as petrels,” Wolfaardt says.
The chick shown here was photographed in July, with bloody marks on its neck, and it died the next day – yet another victim of the house mice that were accidentally introduced to Marion in the early 1800s.
It was about 20 years ago conservationists first realised the mice had begun attacking vulnerable and naive seabirds such as the albatrosses.
It’s believed that climate change has improved conditions for the mice, lengthening their breeding season by several months, leading to a higher density of animals and greater competition for resources.
Wolfaardt and colleagues estimate that wandering albatrosses and 18 other species will disappear as breeding birds on Marion Island should the house mice continue to predate them. Which is why they are planning to remove the mice for good.
Copying the blueprint used on other islands such as South Georgia, where conservationists carried out a huge rat and mice eradication, Mouse-Free Marion will use between four and six helicopters and some 35 staff to spread a specially formulated rodenticide across its 30,000 hectares – about three-quarters the area of the Isle of Wight – to wipe out the mice over the course of one austral winter [ie, summer time in the UK].
“We want to do it in the winter time because many of the seabirds have left and the mice are more desperate for food,” says Wolfaardt. But, as he explains, there are pros and cons to this strategy – days are shorter and the weather more challenging. You could have weeks when you are unable to spread the bait because of adverse weather conditions.
Wolfaardt says there are still some issues to be resolved, and the project has so far raised only one quarter of the $29 million (£23 million) needed, but the intention is to begin the operation in April 2027, just under three years from now.
Main image: wandering albatross on Marion Island. Credit: Michelle Risi
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