The Curious Case of the St Kilda House Mouse

Did you know that the word ‘curious’ comes from the Latin word ‘cura’, which means ‘care’?

The last mammal to go extinct in Britain was the St Kilda house mouse.

St Kilda is an archipelago on the wrong side, as it were, of the Outer Hebrides, making it the most remote place in the British Isles. This did not stop it from being inhabited by humans from the Bronze Age right up until the twentieth century. In that time, the islanders developed their own remarkable culture, which I wholeheartedly advise you to research. It is a place where culture and nature bleed into each other. Indeed, it is the UK’s only UNESCO World Heritage site for both nature and culture, and hosts Britain’s largest seabird colony. 

It was probably the Vikings that got the house mouse to St Kilda. The mice lived exclusively in the human settlements, feeding exclusively off of the detritus that humans tend to leave about them. For a thousand years, no one really bothered about them.

Evolutionarily speaking, a thousand years isn’t a lot, if you are a human. If you are a mouse, however, it is enough time to create the pitter-patter of 5,000 generations of little feet. As is often the case with animals on islands with little competition, it got bigger, because bigger animals are generally more efficient at conserving heat and energy. Not massively so, but big enough to eventually become a subspecies. A human-made subspecies, completely dependant on human food to survive. Little more than a parasite.

St Kilda House Mouse

It is sobering to think that humans can have such a dramatic effect on the genetics of a population of animals as to create a new subspecies. That is, until you look at a dog. Or a cow.

St Kilda is not the most hospitable of places. In fact, it is probably most famous for being decidedly inhospitable. By 1930 things had gotten so bad for the islanders that the whole community asked to be relocated to the mainland, and so the island was deserted. As is often the case with decidedly inhospitable places, the only people who currently bother to go there regularly are the military and a small group of conservationists.

In any case by 1932, within two years of humans leaving, the mouse was extinct. They were not hardy enough to leave the abandoned buildings, and without human food available to pilfer there was nothing for the fat little rodents to eat.

It is a curious story, and a curious creature, and one that I personally feel entirely ambiguous about. Should it have been saved? Is its extinction a great loss for biodiversity? Was there a moral obligation to save the subspecies? Would there have been a moral obligation to save them had they not been classed as a subspecies? Is it a subspecies or a cultural relic or even just a cruel mistake? A wild animal, or a pet, or vermin? People worry about the loss of subspecies of tigers – should they have worried about the loss of the St Kilda house mouse? Does this story belong in the annals of ecology, or history?

If nothing else, the St Kilda house mouse shows us the limitations of the words and ideas that we use to frame the great ecological debates of our age. It blurs the distinctions between wild and domestic, natural and man-made, history and natural history, anthropology and ecology, even between vermin and endangered animal. As such, it can help us to frame fundamental questions about conservation, what we are trying to achieve and why we are trying to achieve it. The St Kilda house mouse should be a rallying call for the curiosity of conservationists; we need to question perceived wisdom, distinctions and definitions and to measure worth and value and meaning. To care for the planet, or even to care about it at all, we need to be curious.

A shame it’s gone then. But the good news is that another ‘man-made’ rodent subspecies, the St Kilda field mouse, is currently thriving. By all accounts it has developed a taste for Mars bars.

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Andy Painting

Writer, I guess.

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1 Response

  1. 25th May 2016

    […] Wildlife Articles: The Curious Case of the St Kilda House Mouse […]

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