August 1, 2022

The Adaptability of the Gray Squirrel

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By Kevin Wright

Photos by the author.

The gray squirrel in Illinois, and much of the United States for that matter, has seen its share of changes over the years. Loss of habitat has been the major contributor to the decline of this species in Illinois. A lover of big timber and heavy tree canopy, the gray squirrel has seen much of that habitat disappear, consequently they have had to adjust their living habits to survive. But first, let us go back in history a bit.

It was once said that a squirrel in Illinois could travel for miles, in the treetops that is, and never touch the ground. That sounds like a good assessment of what things were probably like, but those days are long gone.

A gray squirrel sits on a tree limb hunched over a nut while its tail covers its back. More tree limbs and branches are in the background.

The 1979 booklet Squirrel Hunting in Illinois by Charles M. Nixon, Stephen P. Havera, and Jack A. Ellis, had this to say about the gray squirrel: “The gray squirrel was often known as the migratory squirrel. Documentations from our ancestors reveal the reason for the nickname. Great migrations of squirrels moving southwest from Wisconsin for four weeks were reported in 1842, 1847, 1852 and 1857. In 1848 in the Ohio Valley, gray squirrels were reported moving by the millions from the north to the south, destroying whole fields of corn in a few days. In 1914 in Missouri a huge army of gray squirrels was seen moving westward. This mass of squirrels was so dense that there were always 400 to 500 in sight, and at least one to the square yard. This legion of squirrels was estimated to be a compact brigade about three-fourths of a mile wide and a quarter mile deep.” Now, just think about that for a minute.

In the Lewis and Clark journals, Lewis wrote of the gray squirrel “Observed a number of squirrels swimming the Ohio and universally passing from W. to the east shore, they appear to be making to the south: perhaps it may be the mast or food which they are in search of but I should suppose that it is climate which is their object as I find no difference in the quantity of mast on both sides of the river, it being abundant on both.”

One then could suggest that gray squirrels were in great abundance. We could easily assume then that big, heavy timber was abundant as well. In Illinois it would be the southern portion of that state that held the majority of the big timber with heavy canopies, ideal gray squirrel habitat, and that is evident by the reports suggested in the Squirrel Hunting in Illinois booklet.

Historically, it was reported that squirrel hunting in Illinois was generally greatest in the southern and western portions of the state (best habitat), and poorest in the northeastern counties. Counties in the southern third of the state accounted for about half the annual harvest. These counties were the most heavily forested in Illinois at the time. At that time hunters harvested as many gray squirrels as they did fox squirrels in southern Illinois, but in northern Illinois, 80 percent of the harvest were fox squirrels.

A gray and orange squirrel stands in green grass. To the right of the image of the squirrel is text where one can find more information about squirrel hunting.
Find the Illinois Hunting and Trapping Digest here.

This might suggest that gray squirrels had no desire to make a permanent residence in less desirable habitat. Then, as the highest quality habitat began to disappear, the gray squirrel had to adapt. Despite their secretive nature in the tree tops the gray squirrel had to change up some of their habits to survive. Soon enough they began to seek out what habitat they could, even in big cities, and now have established themselves throughout the state. While in some locations people can see good numbers of grays, in other locales no grays can be seen at all.

Gray squirrels build leaf nests and typically mate in January and again in June or July. Females more than two years of age will typically produce two litters per year with generally two to three young per nesting. For more on the life history of the gray squirrel, visit Wildlife Illinois.

The eastern gray squirrel is about 8 to 11 inches in length with the tail the length of the body. They have a border of white fur on the tail with the belly also being white. A little white will also border the eye as well as the back of the ears.

Color variations in gray squirrels are currently being researched and are thought to be most likely caused by a genetic mutation. The most common variation is all black fur which occurs in fox squirrels as well. Historically, gray squirrels likely benefited from the black color phase in those early days of old growth oak-hickory forests. The darker fur would be helpful to blend in the darkness of the tree canopy, thus keeping them hidden from potential predators. As the big timber slowly began to disappear, the gray squirrel gradually lost the darker coloration, with most individuals bearing the lighter color. Lewis even noted in his journal of the squirrels swimming across the Ohio River “most were black.”

A black squirrel pauses while climbing down a tree trunk. In the background are tree branches.

These days we commonly see black squirrels in some areas of Illinois. By all accounts they are all considered gray squirrels, but are they?

In the Squirrel Hunting in Illinois booklet, the authors suggested that to their knowledge, “there has never been a verified cross between a gray squirrel and a fox squirrel.” Studies now suggest that it is indeed possible for interbreeding between a fox and gray squirrel.

In a study testing DNA from gray and fox squirrels across the U.S. and Canada, Dr. Helen McRobie, Anglia Rusken University, suggested this of the black squirrel “the researchers discovered that other ‘signatures’ on the mutated gene are more closely related to the fox squirrel. This suggests it is highly likely the mutation first arose in the fox squirrel and passed to the gray squirrel through interbreeding.”

What do you think? Is it possible that a black fox squirrel mated with a gray squirrel, sparking the black color phase in that species?

More studies will certainly be done but, in the meantime, we can praise the gray squirrel for its adaptation in today’s world. City life may not be in their blood, but it is there to stay.


Kevin Wright is an award winning outdoor writer and wildlife photographer whose work has been published in a number of publications and websites throughout the country. He lives and works out of central Illinois.

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