Eastern gray squirrel

Physical Description and Colour Variations

The eastern gray squirrel is a medium-sized rodent with a characteristically large, bushy tail. Its dorsal fur ranges from grizzled dark to pale grey, often with brown spots, streaks, or cinnamon tones, while its underside is a lighter grey to buff or white, exhibiting countershading. The ears are pale grey to white, and the tail is white to pale grey. There is no sexual dimorphism, meaning males and females are identical in size and coloration. A notable feature is the common occurrence of melanism, particularly in northern parts of its range like southeastern Canada. These black squirrels are not a separate species but a colour morph caused by an incomplete dominant mutation of the MC1R gene. Research indicates melanistic squirrels have a higher cold tolerance, showing an 18 percent reduction in heat loss and adjustments in metabolic rate compared to the common grey morph. Albinism is rare across the species' range. The head and body length measures 23 to 30 centimetres, with a tail adding 19 to 25 centimetres, and adult weight varies between 400 and 600 grams.

Distribution and Habitat in Canada

The eastern gray squirrel's native Canadian range includes New Brunswick, southwestern Quebec, throughout southern Ontario, and southern Manitoba. Its presence in Nova Scotia is recorded, though it is unclear if it resulted from natural expansion or introduction. The species is absent from the boreal forest regions of Canada, preferring mature hardwood-conifer or oak-hickory forests covering more than 40 hectares. These woodlands provide essential mast forage like acorns and walnuts that last through winter storage. The squirrel has also been widely introduced outside its native range. A notable introduction occurred in 1966 on Vancouver Island, British Columbia, near Metchosin, where it is now considered a highly invasive threat to local ecosystems and the native American red squirrel. Historically, populations in the midwestern United States faced drastic reductions by 1900 due to human predation and deforestation, a pattern not seen in its core Canadian range.

Diet and Foraging Behaviour

Eastern gray squirrels are omnivores with a diverse and adaptable diet. Their primary foods are mast from trees such as oaks, hickories, walnuts, and beechnuts. They also consume tree buds, flowers, berries, other fruits, bark, and various fungi including truffles and fly agaric mushrooms. They are not strictly herbivorous, as they will also eat insects, bird eggs, frogs, small birds, lizards, and other small rodents, including other squirrels. They gnaw on bones, antlers, and turtle shells, likely to obtain minerals scarce in their normal diet. In urban and suburban settings, they readily scavenge from garbage bins and raid bird feeders for seeds like millet, corn, and sunflower seeds, though processed human foods with sugar and fat are not safe for them. Their foraging involves seed caching, which aids in seed dispersal and forest regeneration. They can cause damage to trees like sycamore and beech by stripping bark to eat the cambial tissue underneath.

Reproduction and Life Cycle

Eastern gray squirrels typically breed twice a year, in December to February and again in May to June, with timing slightly delayed in more northern latitudes. Breeding success is tightly linked to food availability, particularly mast years. In abundant food years, up to 36 percent of females may bear two litters, but none will do so in poor food years. Females may attract up to 34 males from up to 500 metres away when entering estrus, which is indicated by an enlarged pink vulva and usually lasts less than eight hours. Mating involves a polyandrous system where females often mate with multiple males based on a dominance hierarchy established among competing males. Copulation lasts less than thirty seconds. Gestation lasts about 44 days. Litters usually contain one to four young, though up to eight are possible. Newborns, called kits, are blind, hairless except for whiskers, and weigh only 13 to 18 grams. Their skin darkens after 7 to 10 days before juvenile fur grows in. Weaning begins around seven weeks and is complete by ten weeks. Juvenile pelage is lost after weaning, and adult size is reached by eight to nine months. Females can first enter estrus as early as five and a half months but typically do so at a mean age of 1.25 years, with reproductive longevity documented beyond eight years and up to 12.5 years.

Behaviour and Communication

Eastern gray squirrels are diurnal or crepuscular, most active about two hours after sunrise and two to five hours before sunset to avoid midday heat, and they do not hibernate. They are adept climbers, notable for being one of the few mammals that can descend a tree head-first by rotating their hind feet so the claws point backward. They construct spherical nests called dreys in tree forks using leaves, twigs, and insulation like moss, thistledown, and feathers. They also use natural tree cavities as permanent dens, which offer better protection for young than leaf nests, with young in leaf nests surviving 40 percent less. Squirrels may share dreys for warmth in winter and may claim two or three dens simultaneously. Communication involves a varied repertoire of vocalizations, including chatters, squeaks, alarm calls like the 'kuk' or 'quaa' to warn of predators, and an affectionate 'muk-muk' sound used between mother and kits and during courtship. Visual signals include tail-flicking and other gestures. Urban populations may rely more on visual signals due to noise pollution, while squirrels in wooded areas use more vocalizations.

Predators, Parasites, and Diseases

Eastern gray squirrels face predation from a variety of animals. Their primary predators are hawks, owls, and snakes. They are also preyed upon by foxes, bobcats, raccoons, weasels, and domestic or feral cats and dogs. In its introduced range in South Africa, it is hunted by African harrier-hawks. Squirrels use alarm calls to warn others of approaching predators. The species can host and spread several diseases and parasites transmissible to humans, including typhus, plague, and tularemia. They can also carry parasites like fleas, lice, mites, and ticks, which can transmit Lyme disease and Rocky Mountain spotted fever. Mite infestation can cause rough, blotchy skin and hair loss during winter. Squirrels themselves are susceptible to viral diseases like fibromatosis, which causes massive skin tumours, and squirrelpox. These diseases have the potential to kill squirrels, and tumours near the eyes can cause blindness.

Status as an Invasive Species

While secure in its native North American range, the eastern gray squirrel is a notorious invasive species in regions where it has been introduced. In Europe, it has largely displaced native red squirrels in Britain and competes with them in Ireland. It has also been introduced to Italy, South Africa, and was extirpated from Australia by 1973. Due to its ecological impact, since 2016 it has been listed as an Invasive Alien Species of Union concern in the European Union, prohibiting its import, breeding, transport, trade, or intentional release. In Canada, its introduction to Vancouver Island is a significant conservation concern. There, it threatens local ecosystems and directly competes with the native American red squirrel. Its adaptability, high reproductive rate, and competitive advantage in foraging make it a successful invader that can alter forest composition and outcompete native wildlife. In the United Kingdom, its attraction to bird feeders can reduce access for wild birds and increase local nest predation.

Fossil Record and Evolutionary History

The eastern gray squirrel has a documented Pleistocene fossil record across North America. Specimens are known from at least 18 fossil occurrences across eight different US states, with some fossils dating back to the late Irvingtonian period. A specific fossil specimen from Harleyville, South Carolina, consisting of partial limb bones, is anatomically indistinguishable from modern S. carolinensis and has been dated to between 18,940 and 18,530 years ago, from the Late Pleistocene epoch. The site at that time was likely a hardwood-conifer swamp. Research on body size indicates it increased during the early to middle Holocene before decreasing to the present size seen today. The genus name Sciurus is derived from Greek words for 'shadow' and 'tail', alluding to the squirrel sitting in the shadow of its bushy tail, while the species name carolinensis refers to the Carolinas where it was first recorded.

Interaction with Humans and Urban Ecology

The eastern gray squirrel's tolerance for human proximity has made it a ubiquitous presence in Canadian cities, suburbs, and farmlands. They are commonly seen in parks, backyards, and gardens, where they raid bird feeders and sometimes nest in attics or exterior walls. In these structures, they can be considered pests and fire hazards due to their habit of gnawing on electrical cables. Many people enjoy feeding and watching them, though providing supplementary food can inadvertently increase local squirrel densities. This attraction to feeders can prevent access for wild birds and, as noted in the UK, increase nest predation rates by concentrating squirrel activity. In agricultural areas, they can raid crops like wheat, corn, strawberries, and tomatoes, sometimes eating only the seeds. Their habit of caching seeds, however, contributes to the planting of trees, and their dynamic presence adds to the biodiversity of urban green spaces. Research in Montreal has provided insight into evolutionary pressures, noting the predominance of gray coats throughout the city.

Questions about Eastern gray squirrel

Are black squirrels a different species from grey squirrels?

No, black squirrels are not a different species. They are a colour morph of the eastern gray squirrel, caused by an incomplete dominant genetic mutation of the MC1R gene. Melanism is particularly common in the northern parts of the species' range, including large parts of southeastern Canada. Research shows black squirrels have higher cold tolerance, exhibiting an 18 percent reduction in heat loss and metabolic adjustments compared to the common grey morph.

Where are eastern gray squirrels found in Canada?

In its native range, the eastern gray squirrel is found in New Brunswick, southwestern Quebec, throughout southern Ontario, and in southern Manitoba. There are also breeding populations in Nova Scotia, though their origin is uncertain. It has been introduced to Vancouver Island in British Columbia, where it is considered an invasive species. It avoids the boreal forest regions of the country, preferring mature hardwood forests over 40 hectares in size.

What do eastern gray squirrels eat?

Eastern gray squirrels are omnivores. Their diet primarily consists of seeds and nuts like acorns, walnuts, and hazelnuts. They also eat tree buds, flowers, berries, bark, and fungi like truffles. They consume insects, bird eggs, frogs, small birds, and other small rodents. They gnaw on bones and shells for minerals. In urban areas, they scavenge from garbage and raid bird feeders, though processed human foods are not safe for them.

How long do eastern gray squirrels live?

In the wild, eastern gray squirrels have a high mortality rate, with only about one in four kits surviving its first year. An adult typically lives to about six years, with exceptional individuals reaching 12 years. The maximum documented longevity in the wild is 12.5 years. In captivity, where they are safe from predators and habitat challenges, they can live to be over 20 years old, as recorded for one female.

How do eastern gray squirrels communicate?

Eastern gray squirrels communicate using a variety of vocalizations and visual signals. Their vocal repertoire includes chatters, squeaks, alarm calls like the 'kuk' or 'quaa' to warn of predators, and a coo-purring 'muk-muk' sound used between mother and kits and during courtship. Visual communication includes tail-flicking and other gestures. Communication methods vary by environment, with urban squirrels using more visual signals due to noise pollution.

Sources: Wikipedia and current public reporting, checked by the Your Space Hamilton desk. Last updated 2026-10-21.