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Urocyon cinereoargenteusgray fox

By Long Vu

Geographic Range

Gray foxes are found in the lower half of the Nearctic and northwestern part of the Neotropics. More specifically, their range spans from southern Canada to Venezuela and Columbia, excluding portions of the Great Plains and mountainous regions of northwestern United States and eastern coast of Central America. (Fritzell and Haroldson, 1982)

Habitat

Gray foxes prefer to live in deciduous forests interspersed with brushy, woodland areas. Many populations thrive where woodlands and farmlands meet; however, red foxes (Vulpes vulpes) are known to frequent agricultural areas more than gray foxes. Proximity to water is a key feature of preferred habitat as well. Dens are usually located in hollow trees or logs, in crevices between and under large rocks, and in underground burrows. Dens have also been found in the lower forest canopy, 10 m above the forest floor, in hollow tree trunks and limbs. Gray foxes are the only member of the Canidae family that can climb trees. They are most often found below 3000 m in elevation. (Brant, 2002)

  • Range elevation
    1000 to 3000 m
    3280.84 to 9842.52 ft

Physical Description

Fully grown gray foxes display a mix of white, red, black and gray fur. However, new born pups tend to be dark brown. Gray foxes are medium-sized canids with elongated bodies and relatively short legs. They usually weigh between 3 and 5 kg, but can weigh up to 9 kg. Individuals at high elevation are slightly larger than their low elevation counterparts. Males are slightly larger than females, and skeletal measurements show that males have longer pelvises and calcanea, wider scapulae and more robust limb bones. In general, gray foxes can grow up to 1 m in length. Their tail makes up approximately one-third of their total body length and has a distinct black stripe along the dorsal surface and a black tip. The top of the head, back, sides, and rest of the tail are gray with the belly, chest, legs and sides of the face being reddish brown. The cheeks, muzzle and throat are white. Gray foxes have oval-shaped pupils and the area around the eyes has a thin black stripe from the outside corner of the eye to the side of the head. Additionally, a thick black stripe runs from the inside corner of the eye, down the muzzle to the mouth. They are sometimes misidentified as red foxes (Vulpes vulpes); however, red foxes have slit-shaped eyes, larger feet, longer legs, and a leaner body. (Davis and Schmidly, 1994; Fritzell and Haroldson, 1982; Postanowicz, 2008; Davis and Schmidly, 1994; Fritzell and Haroldson, 1982; Postanowicz, 2008)

  • Sexual Dimorphism
  • male larger
  • Range mass
    2 to 9 kg
    4.41 to 19.82 lb
  • Range length
    800 to 1125 mm
    31.50 to 44.29 in
  • Average length
    1000 mm
    39.37 in

Reproduction

Gray foxes are solitary animals that socialize only during mating season. They are typically monogamous, although in rare cases polygamy and polyandry occur. For a short period of time after parturition, family groups consisting of male, female, and young exist. Male-female pairings form in the fall with breeding occurring in the winter. During October and September, attracting mates become more competitive and males usually display more aggression while retaining and defending mates. Similar to domestic dogs (Canis lupus familiaris), gray foxes have scent glands just inside the anus. Additional scent glands are found on their face and the pads of their feet. Although these glands are primarily used to demarcate territory, they may also be used to attract potential mates. (Fritzell and Haroldson, 1982; Postanowicz, 2008)

Breeding season varies with geographic region, elevation, and habitat quality. Breeding occurs in yearly cycles, beginning in January through late February, continuing into March. In some areas (e.g., Texas), breeding has been observed as early as December. Parturition occurs after about 2 months of gestation, peaking in April, with an average litter size of 3.8 pups, which weigh about 86 g at birth. Pups are typically weaned by 3 to 4 weeks, but may not be completely weaned until 6 weeks. Both genders are sexually mature by 10 months old, soon after dispersal. Annual onset of spermatogenesis occurs earlier and last longer than estrus. If they have been exposed to significant levels of the synthetic estrogen, diethylstilbestrol, females may experience delayed fertilization. (Fritzell and Haroldson, 1982; Postanowicz, 2008)

  • Breeding interval
    Gray foxes breed once yearly.
  • Breeding season
    December through March.
  • Range number of offspring
    1 to 7
  • Average number of offspring
    3.8
  • Average number of offspring
    4
    AnAge
  • Range gestation period
    53 to 63 days
  • Average gestation period
    59 days
  • Range weaning age
    2 to 6 weeks
  • Range time to independence
    10 to 17 months
  • Average time to independence
    12 months
  • Average age at sexual or reproductive maturity (female)
    10 months
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    345 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    10 months
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    365 days
    AnAge

Both genders take care of offspring in gray foxes. Before birth, males do a majority of the hunting, while females look for and prepare a suitable den. Weaning begins around 2 to 3 weeks of age. Pups begin eating solid food around 3 weeks old, which is primarily provided by the father. Parents teach pups how to hunt at around 4 months old. Until then, both parents prey for food separately, and pups practice their hunting skills by pouncing and stalking, which is primarily taught by the father. Pups depend on their parents for defense until about 10 months old, at which point they become sexually mature and disperse. (Brant, 2002; Fritzell and Haroldson, 1982)

  • Parental Investment
  • precocial
  • male parental care
  • female parental care
  • pre-hatching/birth
    • provisioning
      • male
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

Lifespan for both captive and wild gray foxes ranges from 6 to 8 years. However, the oldest recorded wild gray fox was 10 years old at time of capture, and the oldest captive gray fox lived to be 12 years old. (Davis and Schmidly, 1994; Fritzell and Haroldson, 1982)

Gray foxes generally live for 6 to 8 years. The oldest wild gray fox was 10 years old when captured. The oldest gray fox in captivity lived to be 12 years old. (Davis and Schmidly, 1994; Fritzell and Haroldson, 1982)

  • Range lifespan
    Status: wild
    6 to 10 years
  • Range lifespan
    Status: captivity
    6 to 12 years
  • Typical lifespan
    Status: wild
    6 to 8 years
  • Typical lifespan
    Status: captivity
    6 to 8 years

Behavior

Gray foxes remain solitary for the majority of the year. During winter, gray foxes socialize with their mate and with their offspring after parturition. They are primarily nocturnal, but have been occasionally spotted during daytime. Some of the physical traits unique to gray foxes (e.g., short legs and retractable claws) have lead researchers to suggest that they are one of the more primitive members of the Canidae family. (Fritzell and Haroldson, 1982)

  • Range territory size
    0.8 to 6.8 km^2
  • Average territory size
    2.1 km^2

Home Range

Home ranges vary between 1 and 7 km^2, depending on geographic range, with an average home range size of 2.1 km^2. Gray foxes use only small portions of this range each day. (Fritzell and Haroldson, 1982)

Communication and Perception

Like other members of the family Canidae, gray foxes are able to communicate by barking and growling. Males have been observed trying to attract potential mates by raising their hind leg to show off their genitalia. As juveniles, gray foxes commonly play fight. As adults, they use their scent glands to mark territories and food sources. ("Southwest Wildlife", 2007)

Food Habits

Gray foxes are omnivorous. Although they prey on small vertebrates, fruit and invertebrates also form a substantial part of their diet. Cottontails (Sylvilagus floridanus), mice (Peromyscus), woodrats (Neotoma), and cotton rats (Sigmodon hispidus) form the majority of their winter diet. In the Sonoran Desert, the fruit of the California palm makes up a significant portion of their winter diet. With the onset of spring, fruits become an increasingly important part of their diet, at times making up 70% of its diet. Invertebrates, fruits, nuts, and grains also increase in importance during the spring. Grasshoppers (Orthoptera), beetles (Coleoptera), and butterflies and moths (Lepidoptera) are the preferred invertebrates. When available, gray foxes may also feed on carrion. When gray foxes accumulate an excess amount of food, they cache it by digging a hole with their forepaws and burying it. Immediately afterwards, they mark it with urine or using their scent glands on their paws and tail in an effort to ward off other animals as well as to make it easier to relocate. (Fritzell and Haroldson, 1982; "Southwest Wildlife", 2007)

  • Animal Foods
  • birds
  • mammals
  • eggs
  • carrion
  • insects
  • terrestrial non-insect arthropods
  • Plant Foods
  • roots and tubers
  • seeds, grains, and nuts
  • fruit

Predation

Gray foxes primary predators include bobcats (Lynx rufus), golden eagles (Aquila chrysaetos), great-horned owls (Bubo virginianus) and coyotes (Canis latrans). In the southern region of the United States, gray fox abundance is highly dependent on coyote abundance. Other than death by natural causes, humans may be responsible for the greatest number of deaths and therefore may be their largest threat. Hunting, trapping and retaliatory killings by livestock ranchers are not uncommon. Unlike red foxes (Vulpes vulpes), which evade predators by using their superior agility, gray foxes escape by hiding under cover (e.g., brush piles). When escaping terrestrial predators, gray foxes can use their retractable claws to climb trees. (Davis and Schmidly, 1994; Fritzell and Haroldson, 1982; Postanowicz, 2008)

Ecosystem Roles

Gray foxes have a small, but important role in our ecosystems. Their feeding habits allow them to influence small rodent (Rodentia) populations by maintaining a steady predator-prey relationship. They serve as a host to many parasitic arthropods, including fleas (Siphonaptera), lice (Phthiraptera), ticks (Ixodida), chiggers (Trombidiformes), and mites (Acari). Gray foxes are also host to a number of internal parasites including nematodes (Nematoda), flukes (Trematoda), tapeworms (Cestoda), and acanthocephalans (acanthocephala) (Fritzell and Haroldson, 1982)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Gray foxes are hunted and trapped for their pelt. Compared to red fox (Vulpes vulpes), gray fox pelts are less desirable because the hairs are coarser and shorter. Gray foxes may also help control the abundance of certain agricultural pests, including rodents (Rodentia) and rabbits (Leporidae). (Fritzell and Haroldson, 1982; Quinn, 2006)

  • Positive Impacts
  • body parts are source of valuable material
  • controls pest population

Economic Importance for Humans: Negative

Gray foxes are considered a problem species by poultry farmers. However, red foxes (Vulpes vulpes) are commonly misidentified as gray foxes, and commonly attack and kill poultry as well. In addition, gray foxes carry zoonotic diseases that could be a potential health threat to humans (e.g., rabies) and domestic dogs (Canis lupus familiaris; e.g., tularemia and canine distemper). (Fritzell and Haroldson, 1982)

Conservation Status

Gray foxes are abundant throughout most areas in the lower two-thirds of North America. They have no special conservation status at this time. Although they are trapped and hunted by humans, there does not appear to be any immediate threat.

Contributors

Long Vu (author), University of Michigan-Ann Arbor, John Berini (editor), Animal Diversity Web Staff, Gail McCormick (editor), Animal Diversity Web Staff, Phil Myers (editor), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

insectivore

An animal that eats mainly insects or spiders.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

male parental care

parental care is carried out by males

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

nomadic

generally wanders from place to place, usually within a well-defined range.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

scavenger

an animal that mainly eats dead animals

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

stores or caches food

places a food item in a special place to be eaten later. Also called "hoarding"

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

Southwest Wildlife. 2007. "Southwest Wildlife" (On-line). The Gray Fox. Accessed March 29, 2009 at http://southwestwildlife.org/pdf/foxindepth.pdf.

Brant, S. 2002. "Gray Fox" (On-line). Accessed March 29, 2009 at http://www.blueplanetbiomes.org/grey_fox.htm.

Campbell, C. 2006. "Urocyon cinereoargenteus - Grey fox" (On-line). World of the Wolf. Accessed March 29, 2009 at http://www.naturalworlds.org/wolf/canids/Urocyon_cinereoargenteus.htm.

Davis, W., D. Schmidly. 1994. "The Mammals of Texas - Online edition" (On-line). Common Gray Fox. Accessed March 29, 2009 at http://www.nsrl.ttu.edu/tmot1/uroccine.htm.

Fritzell, E., K. Haroldson. 1982. Urocyon cinereoargenteus. Mammalian Species, 189: 1-8.

Postanowicz, R. 2008. "Lioncrusher's Domain" (On-line). Grey Fox. Accessed March 29, 2009 at http://www.lioncrusher.com/animal.asp?animal=18.

Quinn, P. 2006. "Illinois Department of Natural Resources" (On-line). Accessed March 29, 2009 at http://www.dnr.state.il.us/orc/wildlife/furbearers/gray_fox.htm.

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