In eastern North America, Gray Foxes are associated exclusively with forest habitats. In the West, the species favors brushy vegetation in broken, rugged terrain. All records in Kansas have been associated with riparian habitats and forest. Gray Foxes are nocturnal and crepuscular but occasionally are seen during the day. They presumably are monogamous, and their basic social unit consists of the adult male, female, and their young. Dens are constructed near water in brushy or wooded habitats. Brush piles, hollow logs or trees, rock outcrops, and abandoned buildings are typical locations for dens. Underground burrows sometimes are used, but they usually are dug by animals other than Gray Foxes. Tree dens have been found as high as 7 meters above the ground. Gray Foxes are unique among canids in Kansas in being adept climbers. They run up sloping tree trunks, but also can climb vertical trunks by wrapping the forelimbs around the trunk while pushing with the hind feet, or by using the claws, much like a cat. Gray Foxes may climb trees to reach dens, to escape from dogs or predators, or while searching for food.
Adults may attain the following dimensions: total length 800-1125 mm; length of tail 275-443 mm; length of hind foot 130-150 mm; length of ear 66-78 mm; weight 3 to 7 kg. The probability of a young Gray Fox surviving its first year is about 30%. Thereafter, the expectancy of reaching each successive year-class is about 50%. A Gray Fox that is 6 years old is considered an old fox.
Gray Foxes are opportunistic feeders, and their diets shift seasonally and geographically with the relative abundance of foods. Nevertheless, mammalian flesh is an important component of the diet throughout the year. Known food items include cottontail rabbits, moles, deer mice, cotton rats, pocket gophers, ground squirrels, tree squirrels, apples, grapes, persimmons, acorns, peanuts, hickory nuts, and corn. Domestic animals may be eaten as carrion, but predation is rare.
The most important predator on the Gray Fox is man. Other predators include eagles, coyotes, and bobcats. It is suspected that disease (especially canine distemper) serves to control populations more than other causes of mortality.
Females are monestrous. Breeding usually occurs in February and March. Subsequently the female prepares a den, usually on the surface rather than underground, lined with grass, leaves, or shredded bark. After a gestation period of 51 to 63 days, from 1 to 8 (average 4 or 5) pups are born. The young remain in the den for 4 to 6 weeks, at about which time they are weaned and begin to forage with their parents. They leave the den for good at 10 weeks of age but remain within the home range of their parents until late winter. They then disperse and establish their own ranges. Nearly all gray foxes breed during their first year.