The eastern gray squirrel (Sciurus carolinensis) is one of the best-known mammals in eastern North America. It can be observed in suburbs, city and state parks, and native forested habitats. It is one of six large tree squirrels (Sciurus spp.) found in North America north of Mexico.  

An expert climber and very athletic, running and jumping from one tree limb to another, the eastern gray squirrel can both descend and ascend trees head first since it can rotate its hind feet 180 degrees to the back. It rarely falls, but if it does, it can survive a drop of 80 or 90 feet.  

The eastern gray squirrel is small, measuring 18 inches long including an eight- to nine-inch tail and weighing three-quarters to one and three-fifths pounds. As its name suggests, it is gray in color, but all-white and all-black specimens are common among eastern grays. 

Though still abundant today, former gray squirrel populations were unusually large. They would migrate en masse from one forested area to another in huge moving blankets containing hundreds of thousands of animals.  

The eastern gray squirrel is found throughout the eastern half of the United States and southernmost Canada. It is most abundant in hardwood forests with dense understories that provide protection while the squirrel is foraging on the ground. These forests must also include a variety of tree species that produce large mast nuts and support hollowed tree dens for nesting and protection. Forests including many species of oak, walnut, and hickory trees produce greater squirrel densities because of greater food availability.  

The gray squirrel eats a variety of foods, including bird eggs, fledglings, amphibians, plant material, insects and their pupae, and occasional carrion. Its most important foods, however, are acorns from many species of oak trees, hickory nuts, hazelnuts, pecans, walnuts, and beechnuts. It makes hundreds of nut caches (burying its haul) all over its range and sometimes cannot remember the locations of all the caches. This makes the eastern gray squirrel a valuable forest conservationist, because the lost nuts often result in new trees.  

Typical home range size is 12.5 acres or less, but some approach 50 acres. Less food abundance equates to larger home ranges. Home range for the male is twice as large as for the female, as this increases the male’s chances for mating. A female uses only half her home range when rearing young. In areas with many squirrels, individual home ranges are smaller. In areas where squirrels are less dense home ranges are larger. Typically, there are one to four gray squirrels per 2.5 acres, although there can be more than 20 squirrels per 2.5 acres in an urban park where forage and nesting opportunities are more abundant. 

The eastern gray squirrel has two breeding seasons per year. Fewer females participate in the first season from December through March. More mate during the second season from May through July. Most females breed once a year, though when food is abundant more than 30 percent of females will breed twice in one year. None will mate if food is scarce. 

During the breeding season a male will chase and attempt to mate with up to six females in the first three hours of the day. Females that are not in estrus are aggressive and will fight the males off. Males will chase females each day so as not to miss the 8- to 20-hour window when females are in estrus and receptive. A male can smell a female in estrus half a mile away and will travel that far to find her.  

The most dominant males are selected to mate by receptive females. All the males within the queue (hierarchy of males in line to mate) fiercely fight each other, with as many as several thousand fights per hour. Males often exhibit oozing bite wounds, dislocated tails, and torn ears during breeding season. 

After successful mating, young are born 44 days later. A litter usually includes two to four young, which start out bald, pink, and helpless. They begin growing hair about 10 days after birth. Their teeth erupt at three to six weeks. By eight to nine months, they look like adults. 

Young mortality is high, as only 25 to 35 percent survive to one year. Predators include raccoons, foxes, bobcats, housecats, dogs, coyotes, rattlesnakes, rat snakes, hawks, owls, and, when in a body of water, largemouth bass. Squirrel densities are influenced more by available food than by predation. 

William R. Cox has been a professional nature photographer and ecologist for more than 35 years. Visit him online at williamrcoxphotography.com.