Grey fox (Urocyon cinereogenteus) COSEWIC assessment and update update status report: chapter 5

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Species information

• Name and classification
• Description

Name and classification

Urocyon cinereoargenteus Schreber (grey fox; renard gris) is a member of the family Canidae, a group that includes dogs, wolves, foxes and jackals (DeBlase and Martin 1981). The generic name Urocyon means "tailed dog", and comes from the Greek oura meaning "tail" and kyon meaning "dog". The specific name cinereoargenteus translates as "silvery grey" (Baker 1983). Other common names for U. cinereoargenteus are tree fox, cat fox (Baker 1983), scrub fox (Peterson et al. 1953), zorra, zorra gris and gato de monte (Leopold 1959). Sixteen subspecies of Urocyon cinereoargenteus are recognized (Fritzell and Haroldson 1982), of which three are thought to be found in Canada, U. c. borealis Merriam, U. c. cinereoargenteus (Schreber) and U. c. ocythous Bangs (Banfield 1974).

Description

Urocyon cinereoargenteus (Fig. 1) is similar in appearance to the cross phase of the red fox (Vulpes vulpes); however, there are a number of characteristics that make it possible to reliably differentiate the two species. The grey fox has a dark longitudinal stripe, made up of coarse black-tipped hairs, running the length of its back and tail (Fritzell and Haroldson 1982). The sides and back of its pelage are grizzled grey, caused by individual guard hairs being banded with black, grey and white, and the underfur is buffy (Banfield 1974; Fritzell and Haroldson 1982). There is white fur on the ears, face, throat, chest, belly and hind legs (Fritzell and Haroldson 1982), but the tail is black-tipped, in contrast to the red fox's, which is white-tipped (Baker 1983). Parts of the grey fox's neck, sides and limbs are a cinnamon-rufous colour (Fritzell and Haroldson 1982). There is a distinctive black muzzle patch in front of each eye and on the lower jaw. The grey fox has shorter legs than the red fox, although it is of a similar mass. The grey fox has a shorter muzzle, rounder footprints, larger toe pads and more curved claws than the red fox (Banfield 1974). The grey fox has a tail gland that extends one-third to one-half the length of its tail, making it the largest of the North American Canidae (Seton 1923). Newborn grey foxes are blackish in colour whereas red fox kits resemble domestic pups with white-tipped tails (Peterson 1966). There are usually six mammae instead of eight as in the red fox (Piérard 1983). The grey fox is less vocal, and has a less intense and lower pitched call than the red fox (Peterson 1966).

The tracks of the grey fox are shorter and broader than those of the red fox. Spacing between grey fox prints is also slightly closer than between red fox prints. Grey fox tracks look very similar to domestic cat (Felis catus) tracks except that claw marks show in those of a grey fox (Fritzell 1987).

Figure 1. An adult grey fox, Urocyon cinereoargenteus

Photo from the San Diego Zoological Society, from Nowak 1999.

Members of the genus Urocyon are distinguishable from other canids by having skulls with prominent, widely separated temporal ridges that run posteriorly from the postorbital processes to the occipital crest to form a U-shape (also found in Otocyon), and a dentary that has a unique step or notch near the posterior ventral border (also found in Otocyon and Nyctereutes) (Banfield 1974; Fritzell and Haroldson 1982). The dental formula of the grey fox is: incisors 3/3, canines 1/1, premolars 4/4, and molars 2/3 for a total of 42 teeth (Peterson 1966).

Grey fox average body measurements are as follows: total length 988 mm (range=800-1125 mm), tail length 372 mm (range=275-443 mm), hind foot length 142 mm (range=100-150 mm), ear 75 mm (Banfield 1974), condylobasal length of the skull 110-135 mm and skull width 65-74 mm (Peterson 1966). Males weigh 4.1 kg on average (range=3.6-5.9 kg), females weigh an average of 3.9 kg (range=3.4-5.4 kg) (Peterson 1966).