Jenny Dixon

Wharfedale Naturalists Society

“CAST not a clout till May be out”, was a saying much quoted in my childhood. I was puzzled as to whether it meant the month or the blossom – and still am. However, given the violent switches of weather and temperatures during the past few weeks, I think it was good advice.

We’re used to birds’ seasonally changing plumage, but anyone who owns a cat or dog will know that mammals, too, adapt. The shed hair from many a pet goes to line a thrifty bird’s nest as the thick winter pelt is replaced by a cooler, sleeker covering. The appearance of wild creatures can vary quite considerably – not just in the thickness of the pelt but also in colour. Think of fallow deer and how a rather dull brown – matching the dark ground litter in bare winter woodland – changes to the lighter, cream-spotted, fawn that suits the dappled sunlight under spring trees. There are, of course, more dramatic seasonal changes. Mountain hares and ptarmigan that live at high altitudes turn white to blend with their winter environment. When I was young, our local stoats did this too. It must have been even more well known in the distant past, the white fur being much prized as ermine. With recent climate change it’s a rare sight now.

However, there are other factors at work in the colour variation within a species. As with humans, genetics plays its part. There can be natural subtle variation: my sister can recognise individual red squirrels that visit her Scottish garden by how dark or gingery blond they are. More surprising is the colouration due to an aberrant gene in a local population. Most familiar are probably black rabbits. When badger watching on the moor I used to look down into a field where, among the many brown rabbits, there were usually one or two black. As this happened over several years this melanism was clearly “in the genes”. Similarly, at one time we had reports of a white – or silvery-pale grey squirrel in Addingham. Its eyes were dark so not an albino but a leucistic form. Then, last year, a friend sent me photos of a white roe deer – a frequent visitor to her garden in Airedale - a truly mystical beast glimmering against the backdrop of grass and leaves. No wonder white harts and does became part of our folklore: Wordsworth even wrote a poem about “The White Doe of Rylstone”.