Skip Navigation
Regional News
"Black" Eastern Grey Squirrel in Toronto.
"Black" Eastern Grey Squirrel in Toronto.

Natural Selections: Black squirrels

Listen to this story
Black squirrels are becoming more common throughout the St. Lawrence Valley. They are a normal variation of the more familiar gray squirrel species. Martha Foley and Dr. Curt Stager discuss melanism, an increase in the pigmentation of some species that can be a response to environmental factors.

Hear this

Download audio

Share this


Explore this

Tags

Story location

News near this location

There is abundance of black squirrels along the St. Lawrence River and in Ontario. Though they appear strikingly different than gray squirrels, they are in fact a member of the same species and can interbreed.

There are more black squirrels in Canada than in the northeastern United States. “The black squirrel version of grays seem to be spreading a lot, and the same thing has happened in England too where they’re not native,” said Dr. Curt Stager. In the 1800’s, gray squirrels were introduced to England and began to push native squirrels out. Recently, black squirrels have found their way into that population as well.

It’s not apparent why black squirrels have become more prevalent. Stager said, “The only thing I could find was there's some evidence that the males have higher testosterone levels and it makes them more aggressive maybe.” This could give the black squirrels a competitive edge over their gray counterparts.

Stager explained that, like any variety of a flower or bird, the black coloring is simply a variation that could be caused by a genetic mutation. Black squirrels have more pigment in their fur, which makes them darker. This is occasionally seen in other animals native to the North Country such as foxes.

“It’s not uncommon,” said Stager. He referenced the classic evolutionary biology story concerning peppered moths during the Industrial Revolution. Darker colored moths that blended in with the soot introduced into their environments became more common. “They were one of the first demonstrations of natural selection in the wild, just based on pollution,” said Stager. “They call it industrial melanism.”

Though there is a clear explanation for the moth population’s shift in color, scientists have yet to determine why the squirrels are experiencing a trend towards darker fur.

There is abundance of black squirrels along the St. Lawrence River and in Ontario. Though they appear strikingly different than gray squirrels, they are in fact a member of the same species and can interbreed.

There are more black squirrels in Canada than in the northeastern United States. “The black squirrel version of grays seem to be spreading a lot, and the same thing has happened in England too where they’re not native,” said Dr. Curt Stager. In the 1800’s, gray squirrels were introduced to England and began to push native squirrels out. Recently, black squirrels have found their way into that population as well.

It’s not apparent why black squirrels have become more prevalent recently. Stager said, “The only thing I could find was there's some evidence that the males have higher testosterone levels and it makes them more aggressive maybe.” This could give the black squirrels a competitive edge over their gray counterparts.

Stager explained that, like any variety of a flower or bird, the black coloring is simply a variation that could be caused by a genetic mutation. They have more pigment in their fur, which makes them darker. This is occasionally seen in other animals native to the North Country such as foxes.

“It’s not uncommon,” said Stager. He referenced the classic evolutionary biology story concerning peppered moths during the Industrial Revolution. Darker colored moths that blended in with the soot introduced into their environments became more common. “They were one of the first demonstrations of natural selection in the wild, just based on pollution,” said Stager. “They call it industrial melanism.”

Though there is a clear explanation for the moth population’s shift in color, scientists have yet to determine why the squirrels are experiencing a trend towards darker fur.

Visitor comments

on:

NCPR is supported by:

This is a Visitor-Supported website.