Urocyon cinereoargenteus (Schreber, 1775)

Don E. Wilson & Russell A. Mittermeier, 2009, Canidae, Handbook of the Mammals of the World – Volume 1 Carnivores, Barcelona: Lynx Edicions, pp. 352-446 : 432-433

20.

Northern Gray Fox

Urocyon cinereoargenteus

French: Renard gris / German: Graufuchs / Spanish: Chacalillo gris

Other common names: Tree Fox

Taxonomy. Canis cinereoargenteus Schreber, 1775 ,

eastern North America.

Sufficiently distinct from vulpine foxes to warrant recognition as a separate genus. The Northern Gray Fox often clusters genetically with two other ancient lineages, the Raccoon Dog and the Bat-eared Fox, but the exact relationship is unclear. Urocyon is currently considered a basal genus within the Canidae and has only two surviving members, the Northern Gray Fox and Island Fox (U. lttoralis). Up to sixteen subspecies are recognized.

Subspecies and Distribution.

U. c. cinereoargenteus Schreber, 1775 — E USA.

U. c. borealis Merriam, 1903 — SE Canada and USA (New England).

U. c. californicus Mearns, 1897 — SW USA (S California).

U. c. costaricensis Goodwin, 1938 — Costa Rica.

U. c. flornidanus Rhoads, 1895 — Gulf of Mexico.

U. c. fraterculus Elliot, 1896 — Mexico (Yucatan).

U. c. furvus G. M. Allen & Barbour, 1923 — Panama.

U. c. guatemalae G. S. Miller, 1899 — S Mexico S to Nicaragua.

U. c. madrensis Burt & Hooper, 1941 — Mexico (S Sonora, SW Chihuahua & NW Durango).

U. c. nigrirostris Lichtenstein, 1830 — SW Mexico.

U. c. ocythous Bangs, 1899 — USA (Central Plains) and adjoining S Canada.

U. c. orinomus Goldman, 1938 — S Mexico (Isthmus of Tehuantepec).

U. c. perunsularis Huey, 1928 — NW Mexico (Baja California).

U. c. scottit Mearns, 1891 — N Mexico and SW USA.

U. c. townsend: Merriam, 1899 — W USA (California & Oregon).

U. c. venezuelae]. A. Allen, 1911 — Colombia, Venezuela.

Descriptive notes. Head-body 56-66 cm for males, 54-57-8 cm for females,tail 33-3 44-3 cm for males, 28-0-40-7 cm for females; weight 3-4-5-5 kg for males and 2-3-9 kg for females. Medium-sized with a stocky body, moderately short legs and medium-sized ears. Coat grizzled gray on the back and sides with a dark longitudinal stripe on top of a black-tipped tail. Conspicuous cinnamon-rusty color on its neck, sides and limbs. Face with dark and white markings. There is also white on its ears, throat, chest, belly and hind limbs. The tail is thick and bushy, and the fur has a coarse appearance. The dental formula is 13/3, C 1/1, PM 4/4, M 2/3 = 42. The posterior ventral border of the dentition has a prominent notch or “step”, and on the cranium, the temporal ridges are separated anteriorly but connect posteriorly to form a distinctive “U” shape.

Habitat. Closely associated with deciduous and southern pine forests interspersed with old fields and scrubby woodlands in eastern North America. In the west, commonly found in mixed agricultural, woodland, chaparral, riparian landscapes, and shrub habitats. In Central America, occupies forested areas and thick brush habitats, and in South America forested montane habitats. Northern Gray Foxes occur in semi-arid areas of the south-western USA and northern Mexico where cover is sufficient. They also live at the margins of some urban areas.

Food and Feeding. Omnivorous. During winter, prey consists largely of rabbits (Sylvilagus spp-) and rodents. In spring and summer it diversifies to include insects (e.g. grasshoppers), birds, and sometimes carrion. Northern Gray Foxes also feed on natural fruits and nuts, often consuming more of these foods in the fall as their availability increases.

Activity patterns. Mostly nocturnal.

Movements, Home range and Social organization. Monogamy with occasional polygyny is probably most typical. The basic social unit is the mated pair and their offspring of the year; it is not known whether breeding pairs remain together during consecutive years. Offspring typically disperse at 9-10 months of age, and although long-distance dispersal (over 80 km) has been reported, young foxes may also return to and settle down near their natal ranges. Gray Foxes exhibit some territoriality, as home ranges of adjacent family groups may overlap, but core areas appear to be used exclusively by a single family. Home range size varies from 0-8 km? to 27- 6 km?. Foxes increase their home ranges during late fall and winter, possibly in response to changes in food resource availability. Scent marking consists of urine and feces depositions in conspicuous locations. The foxes communicate vocally with growls, alarm barks, screams, and “coos” and “mewing” sounds during greetings. Northern Gray Foxes engage in allogrooming, adults grooming juveniles and each other.

Breeding. Northern Gray Foxes reach sexual maturity at ten months of age, although not all females breed in their first year. Breeding generally occurs from January to April, with gestation lasting about 60 days. Litter size average is 4, ranging from 1-10. Pups accompany adults on foraging expeditions at three months and forage independently at four months. Pups are fed mainly by females, but males may also participate in parental care. Northern Gray Foxes give birth and rear their pups in earthen dens, which they either dig themselves or modify from other species. They will also den in wood and brush piles, rock crevices, hollow logs, hollows under shrubs, and under abandoned buildings. They may even den in hollows of trees up to nine meters above the ground. In eastern deciduous forests, dens are in brushy or wooded areas, where they are less conspicuous than the dens of sympatric Red Foxes. Use of dens diminishes greatly during non-reproductive seasons, when Northern Gray Foxes typically rest in dense vegetation during the day.

Status and Conservation. CITES notlisted. Classified as Least Concern on The [UCN Red List. Common where it occurs, but appears to be restricted to locally dense habitats where it is not excluded by Coyotes and Bobcats. Reported densities range from 0-4/km?® in California to 1-5/km? in Florida. The Gray Fox is legally protected as a harvested species in Canada and the USA. Trapping is legal throughout much of its range, and is likely to be the most important source of mortality where it occurs and probably limits populations locally.

Bibliography. Chamberlain (2002), Chamberlain & Leopold (2000), Cohen & Fox (1976), Davis & Schmidly (1994), Eisenberg (1989), Farias, V. (2000), Follman (1973, 1978), Fox (1970), Fritzell (1987), Fritzell & Haroldson (1982), Fuller & Cypher (2004), Greenberg & Pelton (1994), Grinnell et al. (1937), Hall (1981), Harrison (1997), Nicholson (1982), Nicholson & Hill (1981), Nicholson et al. (1985), Sullivan (1956), Trapp & Hallberg (1975), Wayne et al. (1997), Wood (1958), Yearsley & Samuel (1982).

Figures

On following pages: 16. South American Gray Fox (Pseudalopex griseus); 17. Pampas Fox (Pseudalopex gymnocercus); 18. Sechuran Fox (Pseudalopex sechurae); 19. Hoary Fox (Pseudalopex vetulus); 20. Northern Gray Fox (Urocyon cinereoargenteus); 21. Island Fox (Urocyon littoralis).

Subspecies and Distribution. U. c. cinereoargenteus Schreber, 1775 — E USA . U. c. borealis Merriam, 1903 — SE Canada and USA (New England ). U. c. californicus Mearns, 1897 — SW USA (S California). U. c. costaricensis Goodwin, 1938 — Costa Rica . U. c. flornidanus Rhoads, 1895 — Gulf of Mexico. U. c. fraterculus Elliot, 1896 — Mexico (Yucatan). U. c. furvus G. M. Allen & Barbour, 1923 — Panama . U. c. guatemalae G. S. Miller, 1899 — S Mexico S to Nicaragua . U. c. madrensis Burt & Hooper, 1941 — Mexico (S Sonora, SW Chihuahua & NW Durango). U. c. nigrirostris Lichtenstein, 1830 — SW Mexico. U. c. ocythous Bangs, 1899 — USA (Central Plains) and adjoining S Canada . U. c. orinomus Goldman, 1938 — S Mexico (Isthmus of Tehuantepec). U. c. perunsularis Huey, 1928 — NW Mexico (Baja California). U. c. scottit Mearns, 1891 — N Mexico and SW USA . U. c. townsend: Merriam, 1899 — W USA (California & Oregon). U. c. venezuelae]. A. Allen, 1911 — Colombia , Venezuela .