The red fox (Vulpes vulpes) is the largest of the true foxes and one of the most widely distributed carnivorans.
The red fox has an elongated body and relatively short limbs. The tail, which is longer than half the body length (70 percent of head and body length), is fluffy and reaches the ground when in a standing position. Their pupils are oval and vertically oriented. Nictitating membranes are present, but move only when the eyes are closed. The forepaws have five digits, while the hind feet have only four and lack dewclaws. They are very agile, being capable of jumping over 2-metre-high (6 ft 7 in) fences, and swim well. Vixens normally have four pairs of teats, though vixens with seven, nine, or ten teats are not uncommon. The testes of males are smaller than those of Arctic foxes.
Their skulls are fairly narrow and elongated, with small braincases. Their canine teeth are relatively long. Sexual dimorphism of the skull is more pronounced than in corsac foxes, with female red foxes tending to have smaller skulls than males, with wider nasal regions and hard palates, as well as having larger canines. Their skulls are distinguished from those of dogs by their narrower muzzles, less crowded premolars, more slender canine teeth, and concave rather than convex profiles.
Social and territorial behavior
Red foxes either establish stable home ranges within particular areas or are itinerant with no fixed abode. They use their urine to mark their territories. A male fox raises one hind leg and his urine is sprayed forward in front of him, whereas a female fox squats down so that the urine is sprayed in the ground between the hind legs. Urine is also used to mark empty cache sites, used to store found food, as reminders not to waste time investigating them. The use of up to 12 different urination postures allows them to precisely control the position of the scent mark. Red foxes live in family groups sharing a joint territory. In favourable habitats and/or areas with low hunting pressure, subordinate foxes may be present in a range. Subordinate foxes may number one or two, sometimes up to eight in one territory. These subordinates could be formerly dominant animals, but are mostly young from the previous year, who act as helpers in rearing the breeding vixen's kits. Alternatively, their presence has been explained as being in response to temporary surpluses of food unrelated to assisting reproductive success. Non-breeding vixens will guard, play, groom, provision and retrieve kits, an example of kin selection. Red foxes may leave their families once they reach adulthood if the chances of winning a territory of their own are high. If not, they will stay with their parents, at the cost of postponing their own reproduction.
Outside the breeding season, most red foxes favour living in the open, in densely vegetated areas, though they may enter burrows to escape bad weather. Their burrows are often dug on hill or mountain slopes, ravines, bluffs, steep banks of water bodies, ditches, depressions, gutters, in rock clefts and neglected human environments. Red foxes prefer to dig their burrows on well drained soils. Dens built among tree roots can last for decades, while those dug on the steppes last only several years. They may permanently abandon their dens during mange outbreaks, possibly as a defence mechanism against the spread of disease. In the Eurasian desert regions, foxes may use the burrows of wolves, porcupines and other large mammals, as well as those dug by gerbil colonies. Compared to burrows constructed by Arctic foxes, badgers, marmots and corsac foxes, red fox dens are not overly complex. Red fox burrows are divided into a den and temporary burrows, which consist only of a small passage or cave for concealment. The main entrance of the burrow leads downwards (40–45°) and broadens into a den, from which numerous side tunnels branch. Burrow depth ranges from 0.5–2.5 metres (1 ft 8 in–8 ft 2 in), rarely extending to ground water. The main passage can reach 17 m (56 ft) in length, standing an average of 5–7 m (16–23 ft). In spring, red foxes clear their dens of excess soil through rapid movements, first with the forepaws then with kicking motions with their hind legs, throwing the discarded soil over 2 m (6 ft 7 in) from the burrow. When kits are born, the discarded debris is trampled, thus forming a spot where the kits can play and receive food. They may share their dens with woodchucks or badgers. Unlike badgers, which fastidiously clean their earths and defecate in latrines, red foxes habitually leave pieces of prey around their dens. The average sleep time of a captive red fox is 9.8 hours per day.
Red fox body language consists of movements of the ears, tail and postures, with their body markings emphasising certain gestures. Postures can be divided into aggressive/dominant and fearful/submissive categories. Some postures may blend the two together. Inquisitive foxes will rotate and flick their ears whilst sniffing. Playful individuals will perk their ears and rise on their hind legs. Male foxes courting females, or after successfully evicting intruders, will turn their ears outwardly, and raise their tails in a horizontal position, with the tips raised upward. When afraid, red foxes grin in submission, arching their backs, curving their bodies, crouching their legs and lashing their tails back and forth with their ears pointing backwards and pressed against their skulls. When merely expressing submission to a dominant animal, the posture is similar, but without arching the back or curving the body. Submissive foxes will approach dominant animals in a low posture, so that their muzzles reach up in greeting. When two evenly matched foxes confront each other over food, they approach each other sideways and push against each other's flanks, betraying a mixture of fear and aggression through lashing tails and arched backs without crouching and pulling their ears back without flattening them against their skulls. When launching an assertive attack, red foxes approach directly rather than sideways, with their tails aloft and their ears rotated sideways. During such fights, red foxes will stand on each other's upper bodies with their forelegs, using open mouthed threats. Such fights typically only occur among juveniles or adults of the same sex.
Red foxes have a wide vocal range, and produce different sounds spanning five octaves, which grade into each other. Recent analyses identify 12 different sounds produced by adults and 8 by kits. The majority of sounds can be divided into "contact" and "interaction" calls. The former vary according to the distance between individuals, while the latter vary according to the level of aggression.
- Contact calls: The most commonly heard contact call is a three to five syllable barking "wow wow wow" sound, which is often made by two foxes approaching one another. This call is most frequently heard from December to February (when they can be confused with the territorial calls of tawny owls). The "wow wow wow" call varies according to individual; captive foxes have been recorded to answer pre-recorded calls of their pen-mates, but not those of strangers. Kits begin emitting the "wow wow wow" call at the age of 19 days, when craving attention. When red foxes draw close together, they emit trisyllabic greeting warbles similar to the clucking of chickens. Adults greet their kits with gruff huffing noises.
- Interaction calls: When greeting one another, red foxes emit high pitched whines, particularly submissive animals. A submissive fox approached by a dominant animal will emit a ululating siren-like shriek. During aggressive encounters with conspecifics, they emit a throaty rattling sound, similar to a ratchet, called "gekkering". Gekkering occurs mostly during the courting season from rival males or vixens rejecting advances. Both tamed and domesticated foxes have been observed making sounds similar to laughter, which is believed to be used as a contact call when communicating with human owners and handlers.
Another call that does not fit into the two categories is a long, drawn-out, monosyllabic "waaaaah" sound. As it is commonly heard during the breeding season, it is thought to be emitted by vixens summoning males. When danger is detected, foxes emit a monosyllabic bark. At close quarters, it is a muffled cough, while at long distances it is sharper. Kits make warbling whimpers when nursing, these calls being especially loud when they are dissatisfied.