The common Eastern Gray Squirrel (scientific name sciurus carolinensis) is one type of wildlife familiar to every city dweller. But how much do you really know about this fascinating creature that often does even better in suburbs and cities than in its natural forest habitat?
Although native to eastern North America, the gray squirrel has also been introduced on the west coast of the U.S. and Canada, as well as Great Britain, Italy, and South Africa. (They were also introduced to Australia but later eradicated.) They are usually considered a pest where they have been introduced, because they compete with native species, or when they get into houses, where they may destroy electrical wiring and woodwork. Their population density in cities is much higher than in wilder, wooded areas, where each squirrel has a territory about one acre in size. In New York City, small parks such as Union Square may have as many as 20 squirrels per acre!
Squirrels have well-defended territories that they mark with scent. They collect nuts and bury them in caches—a single squirrel can make thousands of caches. It is thought that they find these caches later by memory, landmarks, and smell. This makes squirrels important in the forest ecology because the buried and forgotten nuts sprout into new trees. Squirrels have also been observed pretending to bury an object, while actually keeping it hidden it their mouths, if they think they are being watched! Besides nuts, squirrels may eat seeds, bark, flowers, catkins, buds, insects, bird eggs, and fungi—including the fly agaric, which is extremely poisonous to humans. Urban squirrels forage for nuts and acorns, but also raid bird feeders, unattended strollers, and trash cans for food, and often are fed directly by people.
The gray squirrel is one of only a few mammals that can descend a tree head-first, which it does by turning its hind feet so that the claws can grip the bark. Squirrels build large nests of leaves, called “dreys,” in the crotches of branches, usually at least 25 feet above the ground, during the summer, and also line holes in trees with leaves. Where abundant fallen leaves are not available, they have been known to use paper bags instead. In winter, several squirrels may hole up together for warmth, however, they do not truly hibernate and will emerge on sunny days to forage for food and water.
Squirrels are often seen chasing each other. This behavior is related to social hierarchy, and also to the mating season, which is in mid-winter and again in late spring. The males chase females both in trees and on the ground, and the males may fight with each other. After a 44-day gestation, the female squirrel gives birth to two to four blind, hairless babies in a tree cavity or drey. They are weaned at about eight or nine weeks of age, when the mother abandons them. There are usually two litters per year, one in February to March and the second in July to August. Squirrels reach adult size at about nine months and breed at 15 months, on average. Squirrels range from about 15-21″ in length, which is almost half tail, and from 12 to 26 ounces in weight. They have 22 teeth, and their lifespan is about eight to ten years, although in captivity they can live as long as 20.
As diurnal creatures, squirrels communicate using visual cues as well as sounds. They flick their tails in ways that are meaningful to other squirrels. Squirrel vocalizations include mating and warning calls, squeaks, chirps, chattering, and birdlike sounds. Urban squirrels rely more on visual signals due to their noisy, but fairly open, environment, while forest squirrels rely more on sound due to limited visibility. Although country squirrels are most active at dusk and dawn in order to avoid predators, and are extremely wary of humans, urban squirrels are more active during the day, when they are most likely to get food from people. Squirrels in city parks will search the grass for food while people walk all around them, but if a dog appears in the distance, the squirrels will all move close to trees, in order to make a fast escape if necessary. Woodland squirrels are preyed on by various species of weasel, foxes, raccoons, snakes, and birds of prey, and are also hunted and eaten by humans. (In some states, squirrel hunting has a multi-million-dollar economic value.) In the city and suburbs they may be run over by vehicles, or preyed on by domestic or feral cats and dogs and by birds of prey such as red-tailed hawks.
Despite its name, the Eastern Gray Squirrel is not all gray, having white underparts and often a cinnamon or reddish tinge on its back and tail. Males and females are very similar. Some gray squirrels are solid black; for unknown reasons, these “melanistic” squirrels are becoming increasingly common in several urban areas, including parts of New York City, notably around Stuyvesant Town. Albino (white) individuals have also been seen in the city, but are rare.