AppearanceThe gray fox is mainly distinguished from most other canids by its grizzled upper parts, black-tipped tail and strong neck, while the skull can be easily 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 females being slightly smaller than males. The gray fox ranges from 76 to 112.5 cm in total length. The tail measures 27.5 to 44.3 c of that length and its hind feet measure 100 to 150 mm.
The gray fox typically weighs 3.6 to 7 kg, though exceptionally can weigh as much as 9 kg. It is readily differentiated from the red fox by the lack of "black stockings" that stand out on the latter and the stripe of black hair that runs along the middle of the tail. In contrast to all ''Vulpes'' and related foxes, the gray fox has oval pupils.
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 many predators, such as the domestic dog or the coyote, or to reach tree-bound or arboreal food sources.
It can climb branchless, vertical trunks to heights of 18 meters and jump from branch to branch. It descends primarily by jumping from branch to branch, or by descending slowly backwards as a domestic cat would do.
The gray fox is nocturnal or crepuscular and makes its den in hollow trees, stumps or appropriated burrows during the day. Such gray fox tree dens may be located 30 ft above the ground.
NamingThere are 16 subspecies recognized for the gray fox:
⤷ ''Urocyon cinereoargenteus borealis''
⤷ ''Urocyon cinereoargenteus californicus''
⤷ ''Urocyon cinereoargenteus cinereoargenteus''
⤷ ''Urocyon cinereoargenteus costaricensis''
⤷ ''Urocyon cinereoargenteus floridanus''
⤷ ''Urocyon cinereoargenteus fraterculus''
⤷ ''Urocyon cinereoargenteus furvus''
⤷ ''Urocyon cinereoargenteus guatemalae''
⤷ ''Urocyon cinereoargenteus madrensis''
⤷ ''Urocyon cinereoargenteus nigrirostris''
⤷ ''Urocyon cinereoargenteus ocythous''
⤷ ''Urocyon cinereoargenteus orinomus''
⤷ ''Urocyon cinereoargenteus peninsularis''
⤷ ''Urocyon cinereoargenteus scottii''
⤷ ''Urocyon cinereoargenteus townsendi''
⤷ ''Urocyon cinereoargenteus venezuelae''
ReproductionThe 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 approximately 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 that they are four months old, the kits will have developed their permanent dentition and can now easily forage on their own. The family group remains together until the autumn, when the young reach sexual maturity, then they disperse.
FoodThe gray fox is an omnivorous, solitary hunter. It frequently preys on the eastern cottontail in the eastern U.S., though it will readily catch voles, shrews, and birds. In California, the gray fox primarily eats rodents, followed by lagomorphs, e.g. jackrabbit, brush rabbit, etc.
In some parts of the Western United States, the gray fox is primarily insectivorous and herbivorous. Fruit is an important component of the diet of the gray fox and they seek whatever fruits are readily available, generally eating more vegetable matter than does the red fox.
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