Black squirrels are wicked cool creatures and may eventually be the primary type of squirrel that we see. The black fur on these squirrels is caused by a genetic variation in common grey and fox squirrels. However, along with a different colored fur these squirrels appear to have superior abilities to deal with cold weather.
Let’s take a look at what might make Black Squirrels the squirrel of the future!
Photo Credit: DaPuglet on Flickr
What Is A Black Squirrel?
Black squirrels are genetic variants that are found for both Grey and Fox squirrels. The melanistic genetic mutation has been studied extensively in the Grey squirrel. A study published in 2019 suggests that the mutation may have originated in Fox squirrels and was passed to Grey squirrels through interspecies breeding.
There are three color variants of the Grey squirrel, grey, black a brownish black. The colors are determined by the different amount of eumelanin and pheomelanin pigments in the hair. The melanocortin 1 receptor (MC1R) plays a central role in regulating eumelanin and pheomelanin production and the mutation most likely occurs in this gene.
In regular grey squirrels the fur is a mix of black, grey and brown hairs. Studies suggest that the black squirrel mutation is a missing piece of DNA that prevents the production of grey or brown hair.
The mutation must be inherited from both parents. However as a female squirrel will mate with multiple males while in estrus it is possible to have black and grey squirrels born in the same litter.
Is Color The Only Difference?
There are indications that black squirrels might have more differences from greys than just color.
There is some questions about whether or not black squirrels are more aggressive than their grey counterparts. One article on the black squirrel stated, “Researchers will study whether the faulty gene, which is also found in white blood cells, makes the black squirrel more aggressive, as it does in other species.” Another study published in American Midland Naturalist examined the behavioral patterns of black and grey squirrels in an urban environment and did not observe any differences in aggression.
While the question of enhanced aggression has not been answered it has been determined that black squirrels are better adapted to cold weather. Researchers have determined that black squirrels can generate 11% more body heat in cold weather and retain body heat 18% better than the grey color variants. The ability to better withstand the cold has been postulated as the reason that black squirrels are becoming more populous in northern climates. In harsh winters grey squirrels may freeze to death while black squirrels can survive.
The dominance of black squirrels has been observed in the United Kingdom where they are slowly but steadily displacing grey squirrels. This could result in a complete color change for squirrels in the region as the grey squirrel has been aggressively displacing the Eurasian red squirrels in the region. Its amazing to think that the color of squirrels in the UK could flip from Red to Black in the span of a few hundred years!
An interesting phenomenon is that the concentrations of black squirrels is often reported to top out at around 25% of the total squirrel population. One reason that the black population reaches a limit has been speculated that while black squirrels are better adapted to the cold that their black coat makes them easier for predators to spot. However this is not a universal rule as in some areas of the UK black squirrels now make up about 75% of the total squirrel population.
Where Did They Come From And Where Are They Going?
Black squirrels were introduced to the United States in 1902 when they were gifted to the National Zoo in Washington DC from Ontario’s Department of Crown Land. The squirrels were released into the wild and have established a healthy community. By the 1980s the black variants were routinely spotted in Virginia as they slowly migrated.
Other strong populations of black squirrels have been intentionally created. The Kellogg family introduced black squirrels to Battle Creek, Michigan. Squirrels from this population were later trapped and used to establish colonies on the Michigan State campus.
Black squirrels were imported to Kent State University from Canada in 1961 and are now the unofficial university mascot.
There are several other pockets of black squirrel populations and it is not always clear if they were artificially introduced or naturally occurring.
Some naturally occurring populations include the black squirrels in the UK which were first spotted in Bedfordshire in 1912 and was a natural mutation of the grey squirrels that were introduced to the country in the 1870s. The black Fox squirrels of Mississippi and South Carolina are also naturally occurring.
Squirrels migrate as population pressures them to find new food sources and nesting locations. The migration of black squirrels has been study on a small scale in Indiana .
In the UK, where squirrels are taken quite seriously, it has been determined that they travel a half mile per year.