Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or brush).

Twelve species belong to the monophyletic "true foxes" group of genus Vulpes. Approximately another 25 current or extinct species are always or sometimes called foxes; these foxes are either part of the paraphyletic group of the South American foxes, or of the outlying group, which consists of the bat-eared fox, gray fox, and island fox.[1]

Foxes live on every continent except Antarctica. The most common and widespread species of fox is the red fox (Vulpes vulpes) with about 47 recognized subspecies.[2] The global distribution of foxes, together with their widespread reputation for cunning, has contributed to their prominence in popular culture and folklore in many societies around the world. The hunting of foxes with packs of hounds, long an established pursuit in Europe, especially in the British Isles, was exported by European settlers to various parts of the New World.


The word fox comes from Old English, which derived from Proto-Germanic *fuhsaz[nb 1]. This in turn derives from Proto-Indo-European *puḱ-, meaning ’thick-haired; tail’.[nb 2] Male foxes are known as dogs, tods or reynards, females as vixens, and young as cubs, pups, or kits, though the last name is not to be confused with a distinct species called kit foxes. Vixen is one of very few words in modern English that retain the Middle English southern dialect "v" pronunciation instead of "f" (i.e. northern English "fox" versus southern English "vox").[3] A group of foxes is referred to as a skulk, leash, or earth.[4][5]

Comparative illustration of skulls of a true fox (left) and gray fox (right), with differing temporal ridges and subangular lobes indicated

Within the Canidae, the results of DNA analysis shows several phylogenetic divisions:

The fox-like canids, which include the kit fox (Vulpes velox), red fox (Vulpes vulpes), Cape fox (Vulpes chama), Arctic fox (Vulpes lagopus), and fennec fox (Vulpes zerda).[6]
The wolf-like canids, (genus Canis, Cuon and Lycaon) including the dog (Canis lupus familiaris), gray wolf (Canis lupus), red wolf (Canis rufus), eastern wolf (Canis lycaon), coyote (Canis latrans), golden jackal (Canis aureus), Ethiopian wolf (Canis simensis), black-backed jackal (Canis mesomelas), side-striped jackal (Canis adustus), dhole (Cuon alpinus), and African wild dog (Lycaon pictus).[6]
The South American canids, including the bush dog (Speothos venaticus), hoary fox (Lycalopex uetulus), crab-eating fox (Cerdocyon thous) and maned wolf (Chrysocyon brachyurus).[6]
Various monotypic taxa, including the bat-eared fox (Otocyon megalotis), gray fox (Urocyon cinereoargenteus), and raccoon dog (Nyctereutes procyonoides).[6]


Foxes are generally smaller than some other members of the family Canidae such as wolves and jackals, while they may be larger than some within the family, such as Raccoon dogs. In the largest species, the red fox, males weigh on average between 4.1 and 8.7 kilograms (9 and 19+1⁄4 pounds),[7] while the smallest species, the fennec fox, weighs just 0.7 to 1.6 kg (1+1⁄2 to 3+1⁄2 lb).[8]

Fox features typically include a triangular face, pointed ears, an elongated rostrum, and a bushy tail. They are digitigrade (meaning they walk on their toes). Unlike most members of the family Canidae, foxes have partially retractable claws.[9] Fox vibrissae, or whiskers, are black. The whiskers on the muzzle, known as mystacial vibrissae, average 100–110 millimetres (3+7⁄8–4+3⁄8 inches) long, while the whiskers everywhere else on the head average to be shorter in length. Whiskers (carpal vibrissae) are also on the forelimbs and average 40 mm (1+5⁄8 in) long, pointing downward and backward.[2] Other physical characteristics vary according to habitat and adaptive significance.
Pelage

Fox species differ in fur color, length, and density. Coat colors range from pearly white to black-and-white to black flecked with white or grey on the underside. Fennec foxes (and other species of fox adapted to life in the desert, such as kit foxes), for example, have large ears and short fur to aid in keeping the body cool.[2][9] Arctic foxes, on the other hand, have tiny ears and short limbs as well as thick, insulating fur, which aid in keeping the body warm.[10] Red foxes, by contrast, have a typical auburn pelt, the tail normally ending with a white marking.[11]

A fox's coat color and texture may vary due to the change in seasons; fox pelts are richer and denser in the colder months and lighter in the warmer months. To get rid of the dense winter coat, foxes moult once a year around April; the process begins from the feet, up the legs, and then along the back.[9] Coat color may also change as the individual ages.[2]


A fox's dentition, like all other canids, is I 3/3, C 1/1, PM 4/4, M 3/2 = 42. (Bat-eared foxes have six extra molars, totalling in 48 teeth.) Foxes have pronounced carnassial pairs, which is characteristic of a carnivore. These pairs consist of the upper premolar and the lower first molar, and work together to shear tough material like flesh. Foxes' canines are pronounced, also characteristic of a carnivore, and are excellent in gripping prey.[12]


In the wild, the typical lifespan of a fox is one to three years, although individuals may live up to ten years. Unlike many canids, foxes are not always pack animals. Typically, they live in small family groups, but some (such as Arctic foxes) are known to be solitary.[2][9]

Foxes are omnivores.[13][14] Their diet is made up primarily of invertebrates such as insects and small vertebrates such as reptiles and birds. They may also eat eggs and vegetation. Many species are generalist predators, but some (such as the crab-eating fox) have more specialized diets. Most species of fox consume around 1 kg (2.2 lb) of food every day. Foxes cache excess food, burying it for later consumption, usually under leaves, snow, or soil.[9][15] While hunting, foxes tend to use a particular pouncing technique, such that they crouch down to camouflage themselves in the terrain and then use their hind legs to leap up with great force and land on top of their chosen prey.[2] Using their pronounced canine teeth, they can then grip the prey's neck and shake it until it is dead or can be readily disemboweled.[2]

The gray fox is one of only two canine species known to regularly climb trees; the other is the raccoon dog.[16]


The male fox's scrotum is held up close to the body with the testes inside even after they descend. Like other canines, the male fox has a baculum, or penile bone.[2][17][18] The testes of red foxes are smaller than those of Arctic foxes.[19] Sperm formation in red foxes begins in August–September, with the testicles attaining their greatest weight in December–February.[20]

Vixens are in heat for one to six days, making their reproductive cycle twelve months long. As with other canines, the ova are shed during estrus without the need for the stimulation of copulating. Once the egg is fertilized, the vixen enters a period of gestation that can last from 52 to 53 days. Foxes tend to have an average litter size of four to five with an 80 percent success rate in becoming pregnant.[2][21] Litter sizes can vary greatly according to species and environment – the Arctic fox, for example, can have up to eleven kits.[22]

The vixen usually has six or eight mammae.[23] Each teat has 8 to 20 lactiferous ducts, which connect the mammary gland to the nipple, allowing for milk to be carried to the nipple.[citation needed]

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