Arctic foxes, ermines, snowshoe hares, what do they all have in common? A lustrous, bright white winter coat. Sadly, their sharp winter suits could be putting them in the firing line when it comes to being affected by climate change, as a recent study on white-coated weasels has found out.  

Many animals turn white for winter, replacing their warmer-toned spring-summer brown coats with something that helps them blend effortlessly into the snowy landscape come winter. A sharp white suit may camouflage you when out and about but it will make you stand out like a sore thumb if that snow either melts or doesn’t appear.

Researchers in Poland have found a worrying correlation between the decreasing days of snow cover in Eastern Europe and the decline in the population of white-coated weasels, suggesting that white-furred animals could be at real risk of dying out due to climate change.

Writing in Scientific Reports, the team studied two sub-species of weasel – Mustela nivalis nivalis, which becomes white-pelted in winter and Mustela nivalis vulgaris, which does not – in the Bia?owie?a Forest of Poland. They found that the number of white-coated weasels they captured decreased dramatically between 1997 and 2007 compared to the brown coats. In fact, on days of little snow cover, the number of white weasels they caught fell by 20 percent.

When they looked at the number of permanent snow cover days during this time and saw that the number fell from 80 to 40 days, they realized there was a correlation and decided to test it out.

In the trees, the brown-coated weasel may scurry around undetected, but on the snow-covered ground the white-pelted weasel has the advantage, and up until recently it had been the white coats that were the dominant species. If there isn’t enough snow cover, however, suddenly that white pelt means easy pickings for predators.

Using white and brown toys, they placed the white ones on brown earth and brown ones on snow and then laid a camera a trap to observe if this “camouflage-mismatch” had an effect on local predators. They found the predators could more easily identify the white coats on brown earth than the brown coats on white, which meant more of the white-coated weasels were being picked off.

With snow cover on the ground not lasting as long as it used to in many parts of the world, this isn't good news for any animal that molts to white in winter.

There are around 22 animals known to science that swap to a white coat come winter, including Arctic hares, Siberians hamsters, collared lemmings, and willow ptarmigans. Hopefully, these animals can adapt to the changing climate, but if not we could be faced with losing them as the world's temperatures continue to climb.