The Gray Fox (Urocyon cinereoargenteus) is a mammal of the order Carnivora ranging throughout most of the southern half of North America from southern Canada to northern Venezuela and Colombia. This species and the closely related Island Fox are the only living members of the genus Urocyon, which is considered to be among the most primitive of the living canids.
The Gray Fox is distinguished from most other canids by its grizzled upper parts, buff neck and black-tipped tail, while the skull can be distinguished from all other North American canids by its widely separated temporal ridges that form a U-shape. There is little sexual dimorphism, save for the males being slightly larger than females. The Gray Fox ranges from 800 to 1125 mm (31.5 to 41.3 inches) in length. Its tail measures 275 to 443 mm (10.8 to 17.5 inches) and its hind feet measure 100 to 150 mm (4.9 to 5.9 inches). It weighs 3.6 to 6.82 kg (7.9 to 15 lbs).
The Gray Fox's ability to climb trees is shared only with the Asian Raccoon Dog among canids. Its strong, hooked claws allow it to scramble up trees to escape predators such as the Domestic Dog or the Coyote, or to reach tree-bound or arboreal food sources. It descends primarily by jumping from branch to branch, or by descending slowly backwards as a House Cat. The Gray Fox is nocturnal or crepuscular and dens in hollow trees, stumps or appropriated burrows during the day.
The Gray Fox is monogamous. The breeding season of the Gray Fox varies geographically; in Michigan, the Gray Fox mates in early March, in Alabama, breeding peaks occur in February. The gestation period lasts about 53 days. Litter size ranges from 1 to 7. Kits begin to hunt with their parents at the age of 3 months. By the time they are 4 months old, the kits have developed their permanent dentition and can forage on their own. The family group remains together until autumn when the young reach sexual maturity and disperse.