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Nature Notes: Eastern Gray Squirrel

Ed Robinson
January 30, 2023

Please consider a vital question – how can an animal with a brain the size of a walnut be so devilishly clever, defeating nearly every human-designed device and construction to keep him out? If you like to feed the birds, you know exactly what I mean. There are many YouTube videos to prove just how diabolical gray squirrels can be in their unending quest for food. There is also a major industry for “squirrel proof” bird feeders – on Amazon I found over 1,000 listings with dozens that cost over $200!

I make it my practice to avoid being outwitted by animals that weigh just one pound. But Sciurus carolinensis must be one of the most focused, persistent, and clever creatures hopping around on this Earth. If they set their minds on stealing your food or breaking into your cabin, watch out. I have watched them pacing the ground under my feeders, scanning the delectables above them, climbing the posts of my deck, and plotting their next moves to defeat my paltry defenses. They use their sharp incisors to chew through walls or soffits, but sometimes meet an untimely end by chomping on electrical wires. I remember a power outage on our road a few years back that was caused by a squirrel electrocuting itself on a transformer!

gray squirrel stands on leafy ground

Gray squirrel (Tim Hill iStock photo)

Most of the time gray squirrels are the picture of beauty and contentment. As opposed to aggressive red squirrels growling from the trees overhead, gray squirrels are generally social animals who might be seen eating, resting, and grooming quietly in the company of other squirrels. How many times have you seen them chasing each other up and down and around in what appears to be nothing more than play? Gray squirrels are not particularly assertive about defending territories that have considerable overlap among them. Only during breeding season do the males (called bucks) feel the testosterone burn, pursuing females (called does) and running off other males.

Grays are blessed with wonderful climbing ability, one of the few mammals able to descend a tree headfirst. They have great flexibility in their rear ankles that allows the squirrels to rotate their hind feet backwards as necessary. Amazing acrobats, it sometimes seems the squirrels ignore gravity in their pursuit of food, jumping from one branch to another, or perching on tiny twigs that seem too small to support the squirrel’s weight. They seem fearless when launching themselves into space between trees.

Around the year their diets vary considerably as different foods become available. In the spring, buds and flowers are prime foods – on occasion I have seen multiple squirrels perched in large apple trees chomping on nutritious pink blossoms. In summer the squirrels search for berries, fruit, and mushrooms, opportunistically taking fledgling birds, small mammals, amphibians, insects, and their larvae. They can become garden pests, dining on sweet corn and tomatoes. In autumn and winter, the grays focus on nuts and seeds from oak, hickory, walnut, beech, and maple trees, also gnawing on bones and antlers for calcium and other minerals.

Scientists use the term “scatter-gatherer” in referring to gray squirrels. They are highly efficient collectors of food with a compelling drive to cache huge supplies for future needs, especially the next winter. If sufficient food is available, gray squirrels will tuck away thousands of morsels in trees, hollow logs, buried in the ground or in your garage if you are lax in closing the door. The squirrels have excellent memories and noses to find up to 95% of their stored caches, but some of those buried nuts end up sprouting, making the squirrels highly productive partners with trees trying to ensure the survival of their own progeny.

University of Berkeley (CA) professor Mikel Delgado wondered how squirrels evaluate food items in deciding what to eat at once or to set aside in a cache. Delgado’s research assistants were directed to follow gray squirrels with binoculars, stop watches, camcorders and GPS units to document squirrel movements and decision making. It must have been a sight; college kids laden with gear and bags of nuts wandering around campus stalking squirrels!

The researchers learned that squirrels carefully evaluate each food item for perishability, nutritional value, and availability, while considering the competitive landscape. Squirrels were documented eating acorns with weevils rather than burying a nut that might spoil, plus they had the bonus of weevil protein. It was surprising to find that squirrels used deception when hiding food, sometimes hiding in thick cover to mask their actions. At other times, the squirrels would dig up and relocate food items to confuse competitors.

The breeding season takes place in late winter, although does can enter estrous again in late spring if their initial pregnancy fails or to create a second litter. Mating can be a rambunctious affair with dozens of bucks zeroing in on a doe as she enters estrous. In the days before she is ready to mate the doe will run through multiple territories leaving her hormonal scent behind, and then mating with several bucks to ensure fertilization. The doe builds a nest of sticks and leaves in the crotch of a tree or in a hollow den, lining it with moss, grass, or feathers for insulation. Six weeks after mating between two and eight pups are born blind and nude, just one inch long and weighing less than one ounce. The pups begin leaving the nest after 12 weeks to feed on bark and buds. There are many predators of squirrels including raptors, weasels, raccoons, bobcats, foxes, snakes, dogs, and cats. First year mortality is about 75 percent but in captivity squirrels have survived up to 20 years.

Like many small mammals with little body mass, gray squirrels do not hibernate; rather they sleep for a couple days at a time then wake up to get their blood moving and to feed before they freeze to death. Several squirrels may occupy the winter residence to share body warmth in a grouping called a scurry or a dray.

The squirrels are generally light gray with black highlights and white undersides. There is some color variation from dark gray to reddish-brown. Like birds, squirrels change their wardrobes each year, shedding their worn-out hair and growing a new pelt. This occurs in spring and autumn, although the hair on the tails and ears only changes once. The small town where I grew up hosted a small population of black squirrels – genetically they were gray squirrels but they produced an excess of melanin which gave them striking black pelts.

And then there is the city of Olney, IL where I stopped on a long drive to Wyoming. I happened to pick up a brochure proclaiming the city as “The Home of the White Squirrels.” Rather than leucistic squirrels, who are white due to an absence of pigments, Olney’s squirrels are true albinos that breed more albinos. In the wild, albino squirrels occur perhaps one in one million but in Olney the ratio of white squirrels is about one for every 12 gray-colored squirrels. Since 1902 Olney has nurtured the white squirrels – the critters have the right of way in town, there are restrictions on free-ranging cats and dogs, the police force wears a logo with a white squirrel and woe be unto anyone who harms a white squirrel! Last year’s head count revealed 69 white squirrels, down from the peak of 800. You can order your souvenirs through the Olney Chamber of Commerce or the local White Squirrel Shop.

It can be tempting to feed gray squirrels as some people unwisely feed chipmunks. But this should be avoided since grays are known to bite the hand that feeds them. In addition, the squirrels can be carriers of typhus, plague and tularemia, diseases that may pass to humans. Grays are also hosts to ticks and we all know the dangers from tick-borne diseases. Squirrel hunting is still popular in some parts of the country, and the flesh is quite tasty if prepared well. Health authorities caution against ingesting squirrel brains because the animals may carry the prions that cause Creutzfeldt-Jakob, or mad cow disease.

Of more than 60 types of squirrels in North America, the Eastern gray squirrel has the highest population among them. Their range goes from New Brunswick to southern Manitoba, down to Texas through Florida. The animal has been introduced to several western states and to many countries around the world from England and Western Europe to South Africa and Australia. They were taken to England in the 1870’s as a fashionable import but as with most invasive species, the introduction had unintended consequences. The gray squirrels are more cold-tolerant than the smaller native red squirrels and the grays carried a pox virus for which England’s red squirrels had no defense. Recent reports suggest England’s red squirrels will be extirpated within a decade. Grays also show a tendency to strip bark from some tree species to reach the moist, tender cambium layer underneath, thus damaging parkland forests.

There are no current concerns about gray squirrel populations since they are well adapted to living in close contact with humans and our developments. Sometimes that contact is too close if they gain entry to homes – when mothballs and loud music will not drive them out, call the animal control officer. Squirrel numbers will cycle every few years as the volume of the mast crop varies, affecting the survival rate of young animals. I found a reference to a large migration of squirrels in 1933 when more than 1,000 were observed swimming across the Connecticut River, presumably in search of food. It sounds like a plot worthy of a Hollywood thriller!

If you like Ed Robinson’s writing, check out his two Nature Notes books! Click here for more information.