One of the grey squirrels in my garden is black. He’s very cute, and so unusual that people often think he must be a different species, like a red squirrel.

In fact, the black fur is due to a genetic mutation, first seen in Britain in Bedfordshire in 1912. The mutated gene has been spreading through the grey squirrel population since then, so we are seeing more and more black-furred, melanistic individuals like mine.

He’s very nervous and hard to photograph, but I like this snap. It gives us a glimpse of his rich brown tummy.

Genes for colour variants can be linked to other traits, like blue eyes and deafness in white cats. Scientists wonder whether melanism in squirrels might be linked to higher testosterone and so to more aggressive behaviour. For what it’s worth, my black squirrel is pretty shy. His grey relations beat him to the bird-feeder every time!