Urocyon cinereoargenteus
gray fox

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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.