The red fox (Vulpes vulpes) is the largest of the true foxes and one of the most widely distributed members of the order Carnivora, being present across the entire Northern Hemisphere including most of North America, Europe and Asia plus parts of Northern Africa. It is listed as least concern by the IUCN. Its range has increased alongside human expansion, having been introduced to Australia, where it is considered harmful to native mammals and bird populations. Due to its presence in Australia, it is included on the list of the "world's 100 worst invasive species".

The red fox originated from smaller-sized ancestors from Eurasia during the Middle Villafranchian period, and colonised North America shortly after the Wisconsin glaciation. Among the true foxes, the red fox represents a more progressive form in the direction of carnivory. Apart from its large size, the red fox is distinguished from other fox species by its ability to adapt quickly to new environments. Despite its name, the species often produces individuals with other colourings, including leucistic and melanistic individuals. Forty-five subspecies are currently recognised, which are divided into two categories: the large northern foxes, and the small, basal southern foxes of Asia and North Africa.

Red foxes are usually together in pairs or small groups consisting of families, such as a mated pair and their young, or a male with several females having kinship ties. The young of the mated pair remain with their parents to assist in caring for new kits. The species primarily feeds on small rodents, though it may also target rabbits, game birds, reptiles, invertebrates and young ungulates. Fruit and vegetable matter is also eaten sometimes. Although the red fox tends to kill smaller predators, including other fox species, it is vulnerable to attack from larger predators, such as wolves, coyotes, golden jackals and medium- and large-sized felines.

The species has a long history of association with humans, having been extensively hunted as a pest and furbearer for many centuries, as well as being represented in human folklore and mythology. Because of its widespread distribution and large population, the red fox is one of the most important furbearing animals harvested for the fur trade. Too small to pose a threat to humans, it has extensively benefited from the presence of human habitation, and has successfully colonised many suburban and urban areas. Domestication of the red fox is also underway in Russia, and has resulted in the domesticated red fox.

Description & appearance

The red fox has an elongated body and relatively short limbs. The tail, which is longer than half the body length (70 per cent 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.

Red foxes are the largest species of the genus Vulpes. However, relative to dimensions, red foxes are much lighter than similarly sized dogs of the genus Canis. Their limb bones, for example, weigh 30 percent less per unit area of bone than expected for similarly sized dogs. They display significant individual, sexual, age and geographical variation in size. On average, adults measure 35–50 cm (14–20 in) high at the shoulder and 45–90 cm (18–35 in) in body length with tails measuring 30–55.5 cm (11.8–21.9 in). The ears measure 7.7–12.5 cm (3–5 in) and the hind feet 12–18.5 cm (5–7 in). Weights range from 2.2–14 kg (5–31 lb), with vixens typically weighing 15–20% less than males.

Adult red foxes have skulls measuring 129–167 mm (5.1–6.6 in), while those of vixens measure 128–159 mm (5.0–6.3 in). The forefoot print measures 60 mm (2.4 in) in length and 45 mm (1.8 in) in width, while the hind foot print measures 55 mm (2.2 in) long and 38 mm (1.5 in) wide. They trot at a speed of 6–13 km/h (4–8 mph), and have a maximum running speed of 50 km/h (30 mph). They have a stride of 25–35 cm (9.8–13.8 in) when walking at a normal pace. North American red foxes are generally lightly built, with comparatively long bodies for their mass and have a high degree of sexual dimorphism. British red foxes are heavily built, but short, while continental European red foxes are closer to the general average among red fox populations.The largest red fox on record in Great Britain was a 17.2 kg (38 lb), 1.4-metre (4 ft 7 in) long male, killed in Aberdeenshire, Scotland, in early 2012.

The winter fur is dense, soft, silky and relatively long. For the northern foxes, the fur is very long, dense and fluffy, but is shorter, sparser and coarser in southern forms. Among northern foxes, the North American varieties generally have the silkiest guard hairs, while most Eurasian red foxes have coarser fur. The fur in "thermal windows" areas such as the head and the lower legs is kept dense and short all year round, while fur in other areas changes with the seasons. The foxes actively control the peripheral vasodilation and peripheral vasoconstriction in these areas to regulate heat loss. There are three main colour morphs; red, silver/black and cross (see Mutations). In the typical red morph, their coats are generally bright reddish-rusty with yellowish tints. A stripe of weak, diffuse patterns of many brown-reddish-chestnut hairs occurs along the spine. Two additional stripes pass down the shoulder blades, which, together with the spinal stripe, form a cross. The lower back is often a mottled silvery colour. The flanks are lighter coloured than the back, while the chin, lower lips, throat and front of the chest are white. The remaining lower surface of the body is dark, brown or reddish. During lactation, the belly fur of vixens may turn brick red.[8] The upper parts of the limbs are rusty reddish, while the paws are black. The frontal part of the face and upper neck is bright brownish-rusty red, while the upper lips are white. The backs of the ears are black or brownish-reddish, while the inner surface is whitish. The top of the tail is brownish-reddish, but lighter in colour than the back and flanks. The underside of the tail is pale grey with a straw-coloured tint. A black spot, the location of the supracaudal gland, is usually present at the base of the tail. The tip of the tail is white.

Red foxes have binocular vision,[8] but their sight reacts mainly to movement. Their auditory perception is acute, being able to hear black grouse changing roosts at 600 paces, the flight of crows at 0.25–0.5 kilometres (0.16–0.31 mi) and the squeaking of mice at about 100 metres (330 ft). They are capable of locating sounds to within one degree at 700–3,000 Hz, though less accurately at higher frequencies.Their sense of smell is good, but weaker than that of specialised dogs.

Red foxes have a pair of anal sacs lined by sebaceous glands, both of which open through a single duct. The anal sacs act as fermentation chambers in which aerobic and anaerobic bacteria convert sebum into odorous compounds, including aliphatic acids. The oval-shaped caudal gland is 25 mm (1.0 in) long and 13 mm (0.51 in) wide, and reportedly smells of violets.The presence of foot glands is equivocal. The interdigital cavities are deep, with a reddish tinge and smell strongly. Sebaceous glands are present on the angle of the jaw and mandible.

Distribution & habitat

The red fox is a wide-ranging species. Its range covers nearly 70 million km2 (27 million sq mi) including as far north as the Arctic Circle. It occurs all across Europe, in Africa north of the Sahara Desert, throughout Asia apart from extreme Southeast Asia, and across North America apart from most of the southwestern United States and Mexico. It is absent in Iceland, Greenland, Arctic islands, the most northern parts of central Siberia, and in extreme deserts. It is not present in New Zealand and is classed as a "prohibited new organism" under the Hazardous Substances and New Organisms Act 1996, which does not allow import.

Hunting & food

Red foxes are omnivores with a highly varied diet. Research conducted in the former Soviet Union showed red foxes consuming over 300 animal species and a few dozen species of plants. They primarily feed on small rodents like voles, mice, ground squirrels, hamsters, gerbils, woodchucks, pocket gophers and deer mice. Secondary prey species include birds (with passeriformes, galliformes and waterfowl predominating), leporids, porcupines, raccoons, opossums, reptiles, insects, other invertebrates and flotsam (marine mammals, fish and echinoderms). On very rare occasions, foxes may attack young or small ungulates.They typically target mammals up to about 3.5 kg (7.7 lb) in weight, and they require 500 grams (18 oz) of food daily. Red foxes readily eat plant material, and in some areas fruit can amount to 100% of their diet in autumn. Commonly consumed fruits include blueberries, blackberries, raspberries, cherries, persimmons, mulberries, apples, plums, grapes, and acorns. Other plant material includes grasses, sedges and tubers.

Red foxes are implicated in the predation of game and song birds, hares, rabbits, muskrats, and young ungulates, particularly in preserves, reserves, and hunting farms where ground nesting birds are protected and raised, as well as in poultry farms.

While the popular consensus is that olfaction is very important for hunting,[62] two studies that experimentally investigated the role of olfactory, auditory, and visual cues found that visual cues are the most important ones for hunting in red foxes and coyotes.

Red foxes prefer to hunt in the early morning hours before sunrise and late evening. Although they typically forage alone, they may aggregate in resource-rich environments. When hunting mouse-like prey, they first pinpoint their prey's location by sound, then leap, sailing high above their quarry, steering in mid-air with their tails, before landing on target up to 5 metres (16 ft) away. They typically only feed on carrion in the late evening hours and at night.They are extremely possessive of their food and will defend their catches from even dominant animals. Red foxes may occasionally commit acts of surplus killing; during one breeding season, four foxes were recorded to have killed around 200 black-headed gulls each, with peaks during dark, windy hours when flying conditions were unfavorable. Losses to poultry and penned game birds can be substantial because of this. Red foxes seem to dislike the taste of moles but will nonetheless catch them alive and present them to their kits as playthings.

A 2008–2010 study of 84 red foxes in the Czech Republic and Germany found that successful hunting in long vegetation or under snow appeared to involve an alignment of the fox with the Earth's magnetic field.

Breeding & mating

Red foxes reproduce once a year in spring. Two months prior to oestrus (typically December), the reproductive organs of vixens change shape and size. By the time they enter their oestrus period, their uterine horns double in size, and their ovaries grow 1.5–2 times larger. Sperm formation in males begins in August–September, with the testicles attaining their greatest weight in December–February. The vixen's oestrus period lasts three weeks, during which the dog-foxes mate with the vixens for several days, often in burrows. The male's bulbus glandis enlarges during copulation, forming a copulatory tie which may last for more than an hour.The gestation period lasts 49–58 days. Though foxes are largely monogamous, DNA evidence from one population indicated large levels of polygyny, incest and mixed paternity litters. Subordinate vixens may become pregnant, but usually fail to whelp, or have their kits killed postpartum by either the dominant female or other subordinates.

The average litter size consists of four to six kits, though litters of up to 13 kits have occurred. Large litters are typical in areas where fox mortality is high. Kits are born blind, deaf and toothless, with dark brown fluffy fur. At birth, they weigh 56–110 g (2.0–3.9 oz) and measure 14.5 cm (5.7 in) in body length and 7.5 cm (3.0 in) in tail length. At birth, they are short-legged, large-headed and have broad chests. Mothers remain with the kits for 2–3 weeks, as they are unable to thermoregulate. During this period, the fathers or barren vixens feed the mothers. Vixens are very protective of their kits, and have been known to even fight off terriers in their defence. If the mother dies before the kits are independent, the father takes over as their provider. The kits' eyes open after 13–15 days, during which time their ear canals open and their upper teeth erupt, with the lower teeth emerging 3–4 days later. Their eyes are initially blue, but change to amber at 4–5 weeks.

Coat colour begins to change at three weeks of age, when the black eye streak appears. By one month, red and white patches are apparent on their faces. During this time, their ears erect and their muzzles elongate. Kits begin to leave their dens and experiment with solid food brought by their parents at the age of 3–4 weeks. The lactation period lasts 6–7 weeks. Their woolly coats begin to be coated by shiny guard hairs after 8 weeks. By the age of 3–4 months, the kits are long-legged, narrow-chested and sinewy. They reach adult proportions at the age of 6–7 months. Some vixens may reach sexual maturity at the age of 9–10 months, thus bearing their first litters at one year of age. In captivity, their longevity can be as long as 15 years, though in the wild they typically do not survive past 5 years of age.