Gray foxes are medium-sized canids (dogs) with long bodies and relatively short legs. They usually weigh between 3 and 5 kg, but can weigh up to 9 kg. Individuals at high elevations are slightly larger than those at low elevations. Males are slightly larger and are more robust than than females. Males also have a longer pelvis than females. In general, gray foxes can grow up to 1 m in length. Their tail makes up approximately one-third of their total body length.
When they are born, gray foxes are dark brown in color. As adults they have a mix of white, red, black and gray fur. Their tail has a distinct black stripe along the top and a black tip. The top of the head, back, sides, and rest of the tail are gray. The belly, chest, legs and sides of the face are reddish brown. The cheeks, muzzle and throat are white. Gray foxes have oval-shaped pupils. There is a thin black stripe around the eyes from the outside corner of the eye to the side of the head. A thick black stripe also runs from the inside corner of the eye, down the muzzle to the mouth.
Gray foxes are sometimes mistaken as for red foxes, but red foxes and have slit-shaped eyes, larger feet and longer legs and are thinner than gray foxes. (Davis and Schmidly, 1994; Fritzell and Haroldson, 1982; Postanowicz, 2008)
Gray foxes are found from southern Canada, through the United States and south to Venezuela and Columbia. However, they are not found in the Great Plains and mountainous regions of the northwestern United States or the eastern coast of Central America. (Fritzell and Haroldson, 1982)
Gray foxes prefer to live in deciduous forests interspersed with brushy, woodland areas. Many gray foxes live where woodlands and farmlands meet, but their relative red foxes visit agricultural areas more often. Gray foxes prefer ares close to water. Dens of gray foxes 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 species of dogs that can climb trees. They are most often found below 3000 m in elevation. (Brant, 2002)
Gray foxes are solitary animals that socialize only during mating season. Both males and females tend to mate with only one member of the opposite sex, but they have multiple mates on rare occasions. A family group of a male, female, and young exists for a short time after birth. Males and females form pairs in the fall and breed in the winter. During October and September, males are more competitive and aggressive while looking for, retaining, and defending mates. Similiar to domestic dogs, gray foxes have scent glands just inside the anus. They also have scent glands on their face and the pads of their feet. These scent glands are mainly used to mark territory, but they may also be used to attract mates. (Fritzell and Haroldson, 1982; Postanowicz, 2008)
Gray foxes breed at different times of the year depending on geographic region, elevation, and the quality of their habitat. In general, they breed once a year between January and March. After a pregnancy of 2 months, females give birth to a litter of on average 3.8 pups. The majority of births occur in April. Gray foxes weigh about 86 g at birth. Females nurse their young for 3 to 4 weeks and sometimes even for 6 weeks. Both males and females are able to reproduce at about 10 months of age. (Fritzell and Haroldson, 1982; Postanowicz, 2008)
Both male and female gray foxes take care of their offspring. Before birth, males do the majority of hunting, and females look for and prepare a den. Females nurse their young for 2 to 3 weeks. Pups begin eating solid food around 3 weeks of age, and this food is mainly provided by the father. Parents teach pups how to hunt at around 4 months of age. Until then, both parents hunt 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 of age. At this point, they are capable of reproducing and they leave their parents. (Brant, 2002; 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 are generally solitary, but during the winter, they socialize with their mate and their pups. Gray foxes are most active at night, although they are sometimes seen during the day. (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. They prey on small vertebrates, and also consume fruit and invertebrates. During the winter, they mainly eat cottontails, mice, woodrats, and cotton rats. In the Sonoran Desert, they also eat fruit of California palm trees. During the spring, gray foxes eat more fruit, and fruits make up 70% of their diet at this time. During the spring, gray foxes also eat more invertebrates, fruits, nuts, and grains. Grasshoppers, beetles, and butterflies and moths are the preferred invertebrates. When available, gray foxes may also feed on carrion, or dead animals. When gray foxes have extra food, they store it by digging a hole with their forepaws and burying it. Immediately afterwards, they mark the hole with urine or using their scent glands on their paws and tail in order to ward off other animals and to make it easier to relocate. (Fritzell and Haroldson, 1982; "Southwest Wildlife", 2007)
The main predators of gray foxes include bobcats, golden eagles, great-horned owls and coyotes. In the southern region of the United States, gray fox are the most important part of the diet of coyotes. Humans also kill many gray fox through hunting and trapping. Farmers also kill gray foxes that have threatened or eaten their livestock. To escape predators, gray foxes hide under cover like brush piles. They can also 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 considered a problem species by poultry farmers, but red foxes are often mistaken for gray foxes, and red foxes also commonly attack and kill poultry. Gray foxes also carry some diseases that could be a potential health threat to humans (like rabies) and domestic dogs (like tularemia and canine distemper). (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 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.
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.
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.
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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.