Truth or Fiction?
It has been reported that animals that go white in winter are threatened by climate change. Dr Karol Zub reveals the truth.
Are animals that go white in winter threatened by climate change?
IT’S OBVIOUS, ISN’T IT – a species that is predominantly white to blend in with a snowy landscape will be more at risk in a warming planet. More heat leads to less snow cover – and a ‘camouflage fail’ for the animal in question.
But that needn’t necessarily mean the extinction of that species – because some have the option of whether or not to take on a white coat. In the UK there are several that do this – stoats, mountain hares and ptarmigans – but on mainland Europe, some weasels do too, and a new study that was carried out in Poland’s Białowiez˙a Forest has shown they are slowly adapting to a changing climate.
The researchers found that as the number of days with snow cover decreased, the proportion of weasels that moult to give themselves cryptic coloration reduces within the overall population – they believe that the mustelids that remain brown are less vulnerable to predation by foxes, crows and birds of prey.
“It is similar to the peppered moth in an industrial landscape,” says Dr Karol Zub, of the Mammal Research Institute of the Polish Academy of Sciences and the lead author of the study published in the journal Scientific Reports. “Less snow should favour the brown subspecies, though increasing winter temperatures may also cause the delay in the moult of the white morph.”
In fact, this is already happening. In the UK, stoats in Scotland and the north of England turn white in winter, those in the south stay brown, while some become piebald in appearance – and this also happens to some of Białowiez˙a’s weasels.
“Piebald individuals are those which start their moult very late and do not complete the process before spring,” says Zub.
“This happens to our weasels when the autumn is extremely warm, so they don’t start their transition [to white] until late December – in which case, the days are already getting longer before it is complete.”
Crucially, Zub has observed great variation in the time when Białowiez˙a’s weasels moult, offering potential for those that do so later, to outcompete the others. “When the selective pressures are strong enough, we can observe rapid evolutionary changes,” he says.
A new study in Białowieża Forest, Poland, has shown that weasels are adapting to a changing climate.