Gray Fox

Urocyon cinereoargenteus

Summary 3

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 the northern part of South America (Venezuela and Colombia). This species and the closely related Channel Island fox (Urocyon littoralis) are the only living members of the genus Urocyon, which is considered to be among the most primitive of the living canids. Though it was once the most common fox...

Common names 4

More info for the term: tree

common gray fox
grey fox
tree fox
maned fox

Description 5

Gray foxes are adept at climbing trees. They are active at night and during twilight, sleeping during the day in dense vegetation or secluded rocky places. Nursing mothers and pups use a den— a hollow log, abandoned building, tangle of brush, or cracked boulder—for shelter. When she is nursing small pups, the female stays within a few hundred meters of the den, but otherwise adults may range over a 2—5 square km area. Pups begin to forage on their own at about four months of age, and maintain close ties with the mother until they are about seven months old. By about ten months, both males and females are old enough to reproduce, and most females will have a litter annually from then on.

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Distribution 6

The range of common gray fox extends from extreme southern Canada to northern
Venezuela and Columbia, excluding portions of the northern Rocky
Mountain region, the northern Great Plains, and eastern Central America
[16].  Common gray fox range has expanded in the last 50 years to areas
formerly unoccupied and areas where common gray fox had been extirpated
including New England, Michigan, Minnesota, Iowa, Ontario, Manitoba,
North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Utah [9].

Ranges of subspecies follow [16].

U. c. borealis occurs in New England and southern Ontario.

U. c. californicus occurs from southwestern California to northern Baja

U. c. cinereoargenteus occurs from southern Massachusetts and
Connecticut west to Lake Michigan and Illinois; south to central South
Carolina; and west to the Mississippi River.

U. c. floridanus occurs from southern South Carolina south to Florida
and west to eastern Texas; it occurs along the Gulf Coast excluding

U. c. ocythous occurs in Wisconsin and extreme western Illinois; from
Missouri and Arkansas west to Oklahoma, Kansas, Nebraska, South Dakota,
North Dakota, and extreme southern Manitoba and Quebec.

U. c. scottii occurs from western Texas north through northern Colorado
and Utah to the southern half of Nevada; and from California east of the
Sierra Nevada southeast in Mexico to Chihuahua.

U. c. townsendi occurs in northern California and western Oregon.

Food habits 7

Common gray foxes are omnivorous, opportunistic feeders; they prey mainly on
small mammals, but fruit and invertebrates form a substantial portion of
the diet.  In the central United States cottontails (Sylvilagus spp.)
formed the major portion of the common gray fox winter diet.  Other mammals
taken in noticeable numbers include voles (Microtus spp.), mice
(Peromyscus spp.), woodrats (Neotoma spp.), and cotton rats (Sigmodon
spp.).  Invertebrates increase in importance in the spring.  With
seasonally advancing vegetative growth and development, plant material,
particularly fruit, increases in common gray fox diets, sometimes comprising up
to 70 percent by volume [10].  Grasshoppers (Orthoptera), beetles
(Coleoptera), and butterflies and moths (Lepidoptera) are the preferred
invertebrates; plant materials include fruits, nuts, grains, and
grasses.  Carrion is eaten opportunistically [35].  In some areas birds
(nestlings and eggs), particularly ground-nesters, are taken by common gray
foxes; in Texas wild turkey (Meleagris gallopavo) nests were broken up
by common gray foxes [3].

In a riparian area in the Central Valley of California, a common gray fox ate
mostly ring-necked pheasant (Phasianus colchicus), California ground
squirrels (Spermophilus beecheyi), California voles (Microtus
californicus), and berries [11].  In Oregon primary prey items include
mice, pocket gophers (Thomomys and Geomys spp.), kangaroo rats
(Dipodomys spp.), woodrats, ground squirrels (Spermophilus spp.),
chipmunks (Tamias spp.), brush rabbit (Sylvilagus bachmanii), and birds
including domestic poultry.  Other food items include grasshoppers,
beetles, manzanita (Arctostaphylos spp.) berries, juniper cones, and
cascara (Rhamnus purshiana) berries [23].  In the Sonoran Desert the
fruit of the California palm (Washingtonia filifera) forms a substantial
portion of the common gray fox winter diet [2].  In eastern Tennessee plant
foods included persimmon (Diospyros virginiana), black cherry (Prunus
serotina), blackberry (Rubus spp.) , and cancerroot (Conophilus
americana).  The most common vertebrate prey determined in scat analysis
(by volume) was eastern cottontail (Sylvilagus floridana), followed by
white-tailed deer (Odocoileus virginiana), presumably as carrion, and
rodents [14].

Geographic range 8

Gray foxes occur throughout most of the southern half of North America from southern Canada to northern Venezuela and Colombia. They do not occur in portions of the mountainous northwestern United States, the Great Plains and eastern Central America.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

Habitat 9

Gray foxes are found in deciduous woodlands, but are occasionally seen in old fields foraging for fruits and insects. Unlike Vulpes vulpes, they do not prefer agricultural habitats.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest ; scrub forest

Habitat related fire effects 10

More info for the terms: cover, shrub

Common gray foxes use brush and brushy woods in most areas.  Fire that reduces
brush cover will decrease common gray fox habitat.  Fire usually increases the
productivity of early successional prey species and improves predator
efficiency by reducing hiding cover for prey [21].  In the Southeast
fire produces immediate short-term habitat reduction for prey animals;
prey is concentrated in unburned habitat islands [19].  The most
important common gray fox prey in the Southeast are cottontails and cotton
rats.  Cottontails and cotton rats are not usually killed by fire but
prefer habitats with more cover than is found in immediate postfire
environments.  Both species return to postfire habitats when there is
sufficient vegetation for food and cover.  Fire often reduces fruit
production in the short term, but edges of older burns are usually good
regeneration sites for fruiting shrub species such as blackberries and
blueberries (Vaccinium spp.); gallberry (Ilex glabra) produces the most
fruit a few years after fire pruning [21].

Associated plant communities 11

Common gray foxes occur in a wide variety of forest types; they prefer
woodlands and woodland-brush ecotones over open habitat.  They commonly
occur in eastern and southwestern deciduous forests, but are also found
in mixed and coniferous forests of the northeastern and western states [36].

Common gray foxes are ecologically important members of the oak (Quercus
spp.)-hickory (Carya spp.) ecosystem.  In the Missouri Ozarks mature
oak-hickory stands were the most frequently used (of six habitat types)
by common gray foxes, both at night and during the day.  Old fields were least
used [18].  In North Carolina common gray fox habitats include evergreen redbay
(Persea borbonia) forests, deciduous forests, and streamhead forests.
Common gray foxes were common in the most densely wooded habitats, including
pocosins.  They are often seen running along sandy rims and ridges
between bay and streamhead forests [5].  In central Louisiana common gray foxes
occur in longleaf pine (Pinus palustris)-slash pine (P. elliottii)
stands [25].  Common gray foxes are common in southwestern Wisconsin
oak-hickory forests dominated by white oak (Q. alba), northern red oak
(Q. rubra), black oak (Q. velutina), and shagbark hickory (C. ovata)
with lesser amounts of white ash (Fraxinus americana), green ash (F.
pennsylvanica), maples (Acer spp.), and basswood (Tilia americana) [33].

In Zion National Park, Utah, common gray foxes occur in blackbrush (Coleogyne
ramosissima), shrub-grassland dominated by fourwing saltbush (Atriplex
canescens), and pinyon (Pinus spp.)-juniper (Juniperus spp.) [35].  In
Texas common gray foxes are found in post oak (Q. stellata) woodlands,
pinyon-juniper woodlands, and wooded sections of shortgrass prairie.  In
western states common gray foxes are found in brushy habitat, woods, and
chaparral [36].  In Arizona common gray foxes are relatively rare; they are
typically found in pine (Pinus spp.)-Gambel oak (Q. gambelii) woodlands
at 5,000 to 6,000 feet (1,500-1,800 m) elevation.  They also occur in
pine-fir (Abies spp.), ponderosa pine (P. ponderosa), chaparral, and
desert grassland habitats [6,31].  In California common gray foxes are most
common in mature chaparral at elevations of 1,000 to 3,000 feet (300-900
m) and also occur in open chaparral, riparian areas, and other plant
communities [29].  In riparian zones they have been found in communities
dominated by Fremont cottonwood (Populus fremontii)-northern California
black walnut (Juglans californica var. hindsii), and by large willow
(Salix laevigata) [17].  In northwestern California common gray foxes were
present in Douglas-fir (Pseudotsuga menziesii) forests [39].

Communication and perception 12

Like all Canidae, gray foxes have excellent senses of sight and smell. They most likely communicate with one another through scent marking, as do other dogs.

Communication Channels: chemical

Other Communication Modes: scent marks

Perception Channels: visual ; acoustic

Cover requirements 13

More info for the term: cover

Common gray foxes tend to escape their enemies by finding cover rather than
depending on speed (as do red foxes) [23].  Dense vegetation is
important as diurnal resting and escape cover [18].  They climb trees
for use as resting and escape cover [23].  Their climbing ability
extends to saguaro (Carnegiea gigantea); one common gray fox was observed
resting 15 feet (4.6 m) above ground on a saguaro limb [6].

Den sites include hollow logs and trees, rock outcrops, underground
burrows (usually the abandoned den of some other species), cavities
under rocks, abandoned buildings, wood or sawdust piles, and brush
[9,23].  Dens have been found up to 20 feet (9.1 m) above ground in tree
hollows.  Underground dens have usually been excavated by animals of
other species, but common gray foxes occasionally dig dens in loose soil [35].

Den Use:  Dens are used throughout the year, but primary use is during
whelping season.  Dens are usually located in brushy or wooded habitats.
In Wisconsin most common gray fox dens were on east-, southeast-, or
south-facing slopes [9].  Leaves, grass, fur, and other soft materials
are added to dens [23].

Known prey organisms 14

Urocyon cinereoargenteus preys on:
Schismus barbatus
seeds of other plants
Chaetodipus penicillatus
Toxostoma curvirostre
Carpodacus mexicanus
Calamospiza melanocorys
Amphispiza belli
Zonotrichia leucophrys
cactus weevils
Oreoscoptes montanus
Turdus migratorius
Anas fulvigula
Anas acuta
Aix sponsa
Gallinula chloropus
Larus canus
Chordeiles minor
Neurotrichus gibbsii
Myotis grisescens
Tamias alpinus
Tamias merriami
Thomomys talpoides
Dipodomys californicus
Dipodomys deserti
Dipodomys venustus
Peromyscus boylii
Peromyscus polionotus
Microtus californicus
Microtus ochrogaster
Reithrodontomys megalotis
Zapus princeps

Based on studies in:
USA: Arizona, Sonora Desert (Desert or dune)
USA: New Mexico, Aden Crater (Carrion substrate)

This list may not be complete but is based on published studies.

Lifespan, longevity, and ageing 15

Maximum longevity: 16.2 years (captivity)

Management considerations 16

Common gray fox pelts are of some value but are not as valued as those of red
fox [23].  Trapping increases and decreases with pelt values; in a 1987
report it was mentioned that sales in the United States had increased
dramatically in the last decade.  The common gray fox has "furbearer"
management status in many states [13,38].

Population Status:  The common gray fox is characterized by widespread, healthy
populations in most areas.  Habitat availability may limit its
distribution, but lack of habitat does not appear to pose an immediate
threat [13].  Common gray foxes are uncommon to common in New England [7].
Reported population densities range from 1 to 27 per square mile [35].

Common gray foxes are considered pests by many farmers who raise domestic
poultry; biologists claim that this damage is usually overstated and
that common gray foxes benefit agriculture by controlling rodent and rabbit
populations [23].  In northern bobwhite (Colinus virginianus) management
areas only a small number of common gray foxes (0.7%) were found to have
northern bobwhite remains in their stomachs [26].

Common gray foxes commonly carry rabies, most frequently in the Appalachian
states (KY, TN, VA, WV) [4].  They also carry tularemia [23] and canine
distemper which is not as virulent in common gray foxes as it is in domestic
dogs (Canis familiaris) [38].

Physical description 17

Gray foxes resemble small, slender dogs with bushy tails. They are distinguished from most other Canidae by their gray upperparts, buff neck and black-tipped tail. Males are slightly larger than females. Gray foxes range from 800 to 1125 mm in length. Their tails measure 275 to 443 mm and their hindfeet measure 100 to 150 mm. They weigh 3.6 to 6.8 kg.

Range mass: 3.6 to 6.8 kg.

Range length: 800 to 1125 mm.

Sexual Dimorphism: male larger

Predation 18

Large carnivores such as lynx canadensis, lynx rufus, and canis latrans may prey on gray foxes, but it has not actually been documented that this is the case.

Predators 19

Adult common gray foxes have few predators, but are occasionally taken by
golden eagle (Aquila chrysaetos), coyote (Canis latrans), and bobcat
(Lynx rufus) [35]; pups are taken by bobcat, great horned owl (Bubo
virginianus), and possibly large hawks [23].

Preferred habitat 20

More info for the terms: hardwood, shrub

Common gray foxes are most closely associated with deciduous forest,
particularly where it is in contact with disturbed or brushy habitat
[9,23,35].  They are usually found near surface water [29].  Preferred
habitat includes shrublands and brushy woodlands on hilly or rough
terrain.  In areas where common gray foxes and red foxes occur together, common gray
foxes prefer mixed woods with dense underbrush.  In the absence of red
foxes, common gray foxes prefer other habitats [35].

In New England common gray foxes are associated with dense northern hardwood or
mixed forests, thickets, and swamps.  Preferred habitat includes a
mixture of fields and woods [7].  In Wisconsin common gray foxes were most
abundant near brush-covered bluffs where woods and farmland were well
interspersed [28].  From Virginia to southern Georgia optimal common gray fox
habitat consists of woodland-farmland edge; post oak woodlands are also
good common gray fox habitat [9].  In southern Georgia common gray foxes are most
abundant in mixed woods and cultivated areas, less abundant in pine
savanna, and least common in mixed woods with dense underbrush [35].  On
the Coastal Plain most common gray fox captures occurred in tall
weed-broomsedge (Andropogon virginicus)-dominated habitats and
cultivated areas.  There were relatively few captures on forested sites;
this difference from common gray fox preferences in the majority of its range
was attributed to the absence of red foxes [24].

In the western states common gray fox habitats include rocky hillsides,
mountainsides, and washes [35].  In Oregon common gray foxes prefer mixed
hardwood and mixed conifer-hardwood habitats; they are present in
riparian hardwood, headland prairie, headland shrub, and tanoak
(Lithocarpus densiflorus) habitats [23].  In the Central Valley of
California, one common gray fox spent most of its time in old fields and
human-use areas, one spent most of its time in agricultural areas, and
two spent most of their time in riparian areas.  None of the foxes used
areas of open dirt [11].  In California common gray foxes were most abundant
from 3,800 to 5,000 feet (1,150-1,525 m) elevation [15].  In
northwestern California Douglas-fir forests, common gray foxes were present in
similar abundances in all forest seres, but there were slightly fewer
common gray foxes in mature timber [39].

Home Range:  Common gray foxes tracked from May through August, 1980 and
January through August, 1981, had a monthly average home range of 740
acres (299 ha), and an average composite home range of 1,700 acres (676
ha).  Some individuals occupied the same general area for extended
periods, but home ranges tended to shift from month to month.  Only a
fraction of the home range is used on a given night [18].  The composite
home ranges of four radio-tracked common gray foxes varied from 262 to 425
acres (106-172 ha).  Common gray foxes are apparently solitary in the
nonbreeding seasons [17].  In Wisconsin common gray fox home ranges vary from
0.24 to 1.2 miles (0.40-2 km) in diameter [32].  Lord [22] estimated
common gray fox home range diameter of 1.9 miles (3.2 km).  Trapp [34] reported
an annual home range average of 0.2 square mile (0.52 sq km).

Territoriality:  Common gray fox territoriality is not well defined.
Territories are marked with urine and feces, but in many areas home
ranges overlap considerably.  Family aggregates are formed so that
individual territories overlap; family aggregates do not overlap [18].

Regional distribution in the western united states 21

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

    1  Northern Pacific Border
    2  Cascade Mountains
    3  Southern Pacific Border
    4  Sierra Mountains
    6  Upper Basin and Range
    7  Lower Basin and Range
    9  Middle Rocky Mountains
   10  Wyoming Basin
   11  Southern Rocky Mountains
   12  Colorado Plateau
   13  Rocky Mountain Piedmont
   14  Great Plains

Reproduction 22

Gray foxes are monogamous; each has only a single mate.

Mating System: monogamous

The breeding season of gray foxes varies by location. In Michigan, gray foxes mate in early March; in Alabama, breeding peaks occur in February. Where vulpes vulpes and gray foxes occur together, gray foxes breed 2 to 4 weeks after the red foxes. Pregnancy lasts about 53 days; the average litter size is 3.8 and ranges from 1 to 7. By 3 months, pups begin to hunt with their parents. After four months, the young have their permanent teeth and can forage on their own. The family group remains together until autumn when the young reach sexual maturity and leave their parents.

Breeding interval: Grey foxes breed once per year.

Breeding season: The breeding season of grey foxes varies by location.

Range number of offspring: 1 to 7.

Average number of offspring: 3.8.

Range gestation period: 51 to 63 days.

Average gestation period: 53 days.

Range weaning age: 84 to 120 days.

Average time to independence: 6 months.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average birth mass: 95 g.

Average number of offspring: 4.

Average age at sexual or reproductive maturity (male)
Sex: male:
365 days.

Average age at sexual or reproductive maturity (female)
Sex: female:
345 days.

Male and female gray foxes both provide protection for their offspring. Female gray foxes nurse their young until the young are able to hunt for themselves, when they are about four months old.

Parental Investment: altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Protecting: Male, Female); extended period of juvenile learning

Size in north america 23

Sexual Dimorphism: None

Range: 800-1,130 mm

Range: 3-7 kg

Taxonomy 24

Comments: Has been placed in the genus Canis or in the genus Vulpes by some authors (as recently as the 1970s). Urocyon cinereoargenteus and U. littoralis have been regarded as possibly conspecific by some authors; treated as distinct species by Jones et al. (1992) and Wozencraft (in Wilson and Reeder 2005).

Timing of major life history events 25

More info for the terms: cover, litter

Diurnal Activity:  Common gray foxes are more active at night and at dusk than
during the day.  Activity levels decrease sharply at sunrise, and
increase at sunset [17,18].  Common gray foxes usually leave their daytime rest
area shortly before sunset, investigate the immediate area, and then
move purposefully to a foraging area.  Close to sunrise they usually
move back to a daytime resting area.  Common gray foxes usually change resting
sites every day once vegetative cover is abundant in late spring; sites
are reused in winter [17].

Breeding Season:  Common gray foxes usually breed from late winter to early
spring; dates of mating activity vary with latitude and elevation.  In
southern Illinois breeding occurs from late January to February; in
Wisconsin breeding occurs from late January to March [9], and in Oregon
mating occurs from mid-February to March [23].  Where common gray fox is
sympatric with red fox (Vulpes vulpes), common gray foxes breed 2 to 4 weeks
later than red foxes.  Common gray foxes are assumed to be monogamous, but
direct evidence is lacking [9].  There is only one litter per year [35].

Gestation and Development of Young:  Gestation periods have been
variously reported as ranging from 53 to 63 days; Fritzell [10] reported
gestation in captivity lasted 59 days.  Mean litter size is 3.8, ranging
from 1 to 7.  Development has not been well studied [9].  Young are born
blind and nearly naked.  Eyes open about 9 days after birth.  The pups
nurse for over 3 weeks.  Solid food is fed to the pups before they are
completely weaned with the male beginning to bring food to the pups at
about 2 to 3 weeks.  Pups begin to fend for themselves at about 3
months; families disperse in late summer and autumn [23].

Population Structure:  Root and Payne [33] determined that the majority
of animals in a southwestern Wisconsin common gray fox population were under 1
year old.  They concluded that common gray foxes are "an annual crop."  The
majority of female common gray foxes breed their first year [33].

Mortality and Longevity:  In the Central Valley of California, two of
four radiotracked common gray foxes were killed by cars [11].  In east-central
Alabama, a population of common gray foxes was tagged and monitored for causes
of mortality.  Canine distemper was the most frequent cause of death,
followed by trapping, automobile collision, and infectious canine
hepatitis.  Canine distemper was probably a localized cause of mortality
in this area; it is not expected that most common gray fox populations suffer
the same rate of distemper deaths [27].  Maser and others [23] stated
that collision with automobiles is rare in Oregon; the major causes of
common gray fox mortality are hunting and trapping.  They listed a probable
maximum longevity in the wild of 6 years.  The oldest captive common gray fox
lived less than 8 years [23].

Use of fire in population management 26

Hon [19] and Landers [21] suggest that in the Southeast, burning fields
and slash pine forests on 3-year rotations would create desirable
furbearer habitat; areas supporting fire-sensitive fruit-bearing plants
should be protected from fire.

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  15. (c) Joao Pedro de Magalhaes, some rights reserved (CC BY),
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