Melanistic Red Squirrels

Wildlife doesn’t always follow the rules, and despite their name, Red Squirrels are sometimes black. PEI has a higher-than-average number of black-furred Red Squirrels (such as this one photographed by Dave Campbell), so let’s take a look at this phenomenon!

In mammals, skin and hair colour are determined by how much and what type of melanin is produced. Genetics controls melanin production, and most individuals within a species have similar colours: for example, Skunks are various combinations of black and white, while Mink are brown. But genetic mutations can produce animals with no melanin at all – albinos – as well as those with an excess of pigment, called melanistic.

PEI’s melanistic Red (aka Silver) Foxes are famous, but other local mammals show this genetic variation as well. In addition to Foxes and Squirrels, the Island has many melanistic Snowshoe Hares (which don’t turn white in winter) along with some Raccoons; I expect melanism occurs in most of our mammals from time to time.

In some species, melanism seems to have advantages. For example, in the northern part of their range, Eastern Grey Squirrels are melanistic far more commonly than they are further south. It’s thought that the black fur may keep the animals warmer in winter and so is being favoured by natural selection. But climate wouldn’t explain the differences in proportions of melanistic Red Squirrels here on PEI (where dozens have been reported over the years) versus Nova Scotia, where only a couple of reports are known.

It’s more likely that the Island itself is a factor. Genetic mutations can increase within populations that are isolated, as PEI is from the mainland. Our Red Squirrels see few (if any) new arrivals from elsewhere to add new genes to the pool. Within this ‘closed pool’, the melanistic mutation is passed around and is able to increase by chance alone rather than because it’s beneficial. This may also explain our abundance of melanistic Snowshoe Hares as compared to elsewhere, though not our melanistic Red Foxes: those are more common because of selective breeding associated with our history of fur farming.

Melanistic Red Squirrels are otherwise the same as their tawny kin, just black from nose to tail. Keep your eye open for these unusual members of PEI Untamed!