Red fox

• 1. Introduction

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  The red fox, Vulpes vulpes, occupies a range of nearly 70 million square kilometres that stretches north as far as the Arctic Circle. It is the largest of the true foxes. It is also among the most widely distributed members of the order Carnivora. Red foxes live across Europe, in Africa north of the Sahara, over Asia apart from its extreme southeast, and across North America outside most of the southwestern United States and Mexico. They are missing only from the Arctic islands, the northernmost parts of central Siberia and the most extreme deserts.

  The conservation record for this animal is strangely divided. The IUCN Red List classes the species as of least concern. Yet the same animal also appears on a list of the world's 100 worst invasive species, because of the damage it does to native wildlife where people have carried it.

  Three questions run through this documentary. How did a predator of modest size end up in nearly every corner of the Northern Hemisphere? What do its body and its family life reveal about how it copes with new surroundings? And what have people made of an animal that thrives beside them but is too small to threaten them?

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• 2. Deep Ancestry

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  The oldest known red fox fossils were uncovered in Baranya County, Hungary, and date to between 3.4 and 1.8 million years ago. They show a smaller animal than the foxes alive today. Researchers think the species began in Eurasia, possibly descending from Vulpes alopecoides or from the related Chinese V. chikushanensis. Both of those foxes lived during the Middle Villafranchian of the Pleistocene.

  Fossils of the modern species from the mid-Pleistocene turn up alongside middens and refuse left by early human settlements. One theory holds that early people hunted the foxes for food and pelts. Another possibility is that the foxes themselves scavenged from those middens or from butchered carcasses.

  Genetics adds a puzzle. The sister lineage to the red fox is Rüppell's fox, yet mitochondrial DNA places Rüppell's fox inside the red fox lineage. Biologists call such nesting of one species within another paraphyly.

  In North America, fossils from the Sangamonian Stage have been found near the Fairbanks District of Alaska and at Medicine Hat, Alberta. Red foxes colonised the continent in two waves. The first came before and during the Illinoian glaciation, and the second during the Wisconsinan glaciation. Gene mapping shows that North American foxes have been cut off from their Old World relatives for over 400,000 years. That isolation raises the possibility that they are a separate species, and that the older name Vulpes fulva may be valid.

  During the Wisconsinan the foxes ranged far south, and their fossils appear at 25 sites in states including Texas, Ohio and California. Warmer conditions later pushed them north. They have only recently reclaimed their former range, helped by environmental changes that humans caused.

  Genetic testing reveals two refuges that have stayed separate since the Wisconsinan. The northern, or boreal, refuge covers Alaska and western Canada and holds the larger subspecies. The southern, or montane, refuge lies in the subalpine parklands and alpine meadows of the western mountains, from the Rockies to the Cascades and the Sierra Nevada. Its smaller subspecies have been isolated since at least the last glacial maximum and may have developed unusual ecological or physiological adaptations.

  A 2010 study of mitochondrial haplotypes identified the Sacramento Valley red fox, V. v. patwin, as a distinct subspecies, bringing the accepted total from 45 to 46. European foxes were introduced to parts of the United States in the 1900s, but recent research finds no European mitochondrial haplotypes in any North American population. Eastern American foxes brought to California have spread across most of the inland part of the state, yet they have mixed with the Sacramento Valley fox only in a narrow hybrid zone.

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• 3. Body and Senses

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  A red fox standing still lets its tail touch the ground. That tail is fluffy and measures about 70 percent of the head and body length. The animal has an elongated body on relatively short limbs, and its pupils are oval and vertical. The forepaws carry five digits, while the hind feet have four and no dewclaws.

  Size varies widely by region, sex and age. Adults stand 35-50 cm at the shoulder and measure 45-90 cm in body length, with weights from 2.2 to 14 kg. Vixens typically weigh 15-20 percent less than tods. For their size the foxes are light. Their limb bones weigh 30 percent less per unit area of bone than those of similarly sized dogs in the genus Canis.

  The frame suits an agile animal. Red foxes can clear fences over 2 m high and swim well. They trot at 6-13 km/h and reach about 50 km/h at full run. The largest on record in Great Britain was a male 1.4 m long that weighed 17.2 kg and was killed in Aberdeenshire in early 2012. British foxes are heavily built but short, while North American foxes are lightly built with long bodies for their mass.

  The subspecies fall into two broad groups. Large, brightly coloured northern foxes sit at one end. At the other are the small southern grey desert foxes of Asia and North Africa, with longer limbs, bigger ears and skulls that look more infantile. The largest of these desert foxes is still smaller than the average northern fox.

  The typical coat is a bright reddish rust with yellowish tints, a white chin and chest, black paws and a white tail tip. Stripes down the spine and across the shoulder blades form a darker cross. Two other main colour morphs exist, called silver or black, and cross. Unusual colourings tend to be steps toward full melanism, and they mostly occur in cold regions.

  Winter fur is dense, soft and silky. On the head and lower legs, known as thermal windows, the fur stays short and dense all year. Foxes tighten and widen the blood vessels in these areas to control how much heat they lose.

  Hearing is the fox's sharpest sense. Red foxes can pick out black grouse changing roosts at 600 paces, crows flying at 0.25-0.5 km, and mice squeaking at about 100 m. They locate sounds to within one degree at frequencies of 700-3,000 Hz. Their eyes respond mainly to movement, and their sense of smell is good but weaker than that of dogs trained for scent work.

  The oval caudal gland at the base of the tail is 25 mm long and 13 mm wide. It reportedly smells of violets.

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• 4. Family and Voice

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  A male red fox raises one hind leg to spray urine ahead of him, while a female squats and sprays between her hind legs. Foxes use up to 12 urination postures, which lets them place a scent mark precisely. They also mark empty cache sites with urine, a reminder that saves them from wasting time checking for food that is already gone.

  Territories usually belong to family groups. Where hunting pressure is low, one or two subordinate foxes may share a territory, and sometimes as many as eight. They are mostly young animals from the previous year, and they help raise the breeding vixen's kits. Non-breeding vixens guard, groom, play with and feed the kits, an example of kin selection.

  Breeding happens once a year in spring. A vixen's oestrus lasts three weeks, and the male mates with her over several days, often in burrows. During mating the male's bulbus glandis swells and forms a copulatory tie that can last more than an hour. Gestation lasts 49-58 days. Litters average four to six kits, though one of 13 has been reported. Large litters are typical where fox mortality is high.

  Foxes are largely monogamous, but DNA evidence from one population showed high levels of polygyny, incest and litters with mixed fathers. Subordinate vixens may become pregnant but usually fail to give birth. Sometimes the dominant female or other subordinates kill their kits just after birth.

  Newborn kits weigh 56-110 g. They are blind, deaf and toothless, with dark brown fluffy fur. Their eyes open after 13-15 days and are blue at first, turning amber at 4-5 weeks. For the first 2-3 weeks the mother stays with them because they cannot regulate their own temperature, and the father or barren vixens bring her food. If she dies, the father takes over as provider. Vixens fiercely defend their young and have been known to fight off terriers.

  Kits begin leaving the den at 3-4 weeks. They reach adult proportions at 6-7 months. In captivity a fox can live as long as 15 years, but in the wild it typically does not survive past 5.

  A fox's burrow runs 0.5-2.5 m deep, with a main passage that can reach 17 m. In spring the fox clears excess soil by rapid movements of its paws, throwing it up to 2 m from the entrance. Once kits are born, the debris is trampled into a patch where they can play and receive food. Unlike badgers, which keep their earths spotless, red foxes habitually leave pieces of prey lying around their dens.

  The voice of a red fox spans five octaves. Analyses have identified 12 different sounds from adults and 8 from kits. The most commonly heard is a barking call of three to five syllables, written as "wow wow wow". It is heard most often from December to February, when it can be confused with the territorial calls of tawny owls. Captive foxes have answered recordings of their pen-mates but not of strangers. Kits start using this call at 19 days old when they want attention.

  Aggression has its own sound. Rival males, or vixens rejecting advances, produce a throaty ratchet-like rattle called gekkering, mostly in the courting season. A long, drawn-out "waaaaah" is thought to come from vixens summoning males. Body language adds to the vocabulary. A frightened fox grins in submission, arches its back, crouches and lashes its tail, with its ears pressed flat against its skull.

  When danger is detected, a fox gives a single bark. At close quarters it is a muffled cough, and at long distances it turns sharper.

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• 5. Hunters and Rivals

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  The red fox eats more than 300 animal species. Small rodents lead the menu, followed by rabbits, squirrels, birds, reptiles, insects and other invertebrates. It usually targets mammals up to 3.5 kg and needs about 500 g of food a day. In autumn, fruit can make up 100 percent of its diet in some areas, from blackberries and cherries to grapes and acorns.

  Surplus killing shows the other side of that appetite. During one breeding season, four red foxes were each recorded killing around 200 black-headed gulls. The kills peaked during dark, windy hours when flying conditions were poor. Foxes in southern Italy have been seen eating pond slider eggs dug from nests, and camera traps at an Australian rookery caught them taking flatback sea turtle eggs. Italian researchers documented foxes hunting wolf cubs in 2025.

  A hunting fox prefers the early morning before sunrise and the late evening. Sight guides it most, but when hunting mouse-like prey it first locates the animal by sound. Then it leaps, sails high above the quarry and steers in mid-air with its tail before landing on target up to 5 m away. Success in long vegetation or under snow appears to involve aligning the leap with the Earth's magnetic field.

  A fox seems to dislike the taste of moles. Still, it catches them alive and carries them to its young to play with.

  Other foxes mostly lose to the red fox. Fur companies introduced both red and Arctic foxes to nearly every island from the Aleutian Islands to the Alexander Archipelago between the 1830s and 1930s. The red fox invariably displaced the Arctic fox. One male red fox was reported in 1866 to have killed off every resident Arctic fox on a small island.

  The red fox beats the corsac fox in snow deeper than 10 cm. In Israel, the Blanford's fox avoids it by staying on rocky cliffs and shunning the open plains. The pattern reverses with the gray fox, which dominates the red fox wherever their ranges meet. Deforestation has made those meetings more frequent by letting red foxes move into gray fox country.

  Larger predators are a constant danger. Wolves kill and eat red foxes in disputes over carcasses. Coyotes start most of the aggressive encounters in North America, although the two species have sometimes been seen feeding together. In Israel, red foxes avoid golden jackals, and where jackals are abundant the fox population drops sharply. In Tatarstan, red foxes caused 11.1 percent of the deaths among 54 raccoon dogs, so the fox sometimes plays the aggressor as well.

  Badgers and foxes sometimes share a large burrow. They may tolerate each other because the foxes bring food scraps and the badgers keep the shared burrow clean. Some badgers, however, drive vixens out and destroy their litters. Striped hyenas can tear open carcasses that are too tough for a fox, and a fox may harass a hyena by outrunning its attacks. Some foxes misjudge and are killed.

  The Eurasian lynx chases foxes into deep snow, where its long legs and large paws give it the advantage, especially once the snow passes one meter. In the Velikoluksky District of Russia, foxes are absent or rare wherever lynx hold permanent territories. The golden eagle regularly takes young foxes and will hunt adults if it needs to.

  Disease is a quieter enemy. Red foxes are the most important rabies vector in Europe. The mite Sarcoptes scabiei causes mange, which strips a fox of hair from the tail base forward. In the final stages a fox can lose most of its fur and half its body weight. During an epidemic outbreak it usually takes four months for an infected fox to die.

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• 6. Invader Down Under

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  In 2012, estimates put more than 7.2 million red foxes in Australia. The animals reached the continent in the 1830s and 1840s, brought by settlers who wanted to establish the traditional English sport of fox hunting. The earliest introduction was to Van Diemen's Land in 1833. Another followed as early as 1845 in the Port Phillip District of New South Wales.

  On the island of Tasmania, a permanent red fox population never took hold. It is widely believed the foxes were outcompeted by the Tasmanian devil. On the mainland the story went the other way. The fox became an apex predator and spread through most of the continent.

  It is generally less common where dingoes are numerous. It has found room alongside feral dogs and feral cats, mainly through its habit of burrowing. The fox is now counted among the continent's most destructive invasive species.

  The damage falls on small and medium-sized ground-dwelling mammals. The fox has been implicated in the extinction or decline of several native species, particularly members of the family Potoroidae such as the desert rat-kangaroo. Its spread across the southern part of the continent has coincided with the spread of rabbits. It has also coincided with declines in brush-tailed bettongs, burrowing bettongs, rufous bettongs, bilbies, numbats, bridled nail-tail wallabies and quokkas. Most of those animals now survive mainly in places like islands, where foxes are absent or rare.

  Removing the fox has proved hard. Local eradication programs exist, but the fox's denning habits and nocturnal hunting make elimination difficult, so the focus is on management, including state bounties.

  Tasmania illustrates the stakes. According to the Tasmanian government, red foxes were accidentally introduced to the previously fox-free island in 1999 or 2000. They threatened native wildlife such as the eastern bettong, and the Tasmanian Department of Primary Industries and Water launched an eradication program.

  New Zealand has taken the opposite approach. The red fox is classed there as a prohibited new organism under the Hazardous Substances and New Organisms Act of 1996, which forbids its import.

  The Mediterranean island of Sardinia presents a different mystery. Its ichnusae subspecies is absent from the island's Pleistocene deposits. It may have arrived in the Neolithic, brought by people, and repeated introductions from different parts of the Mediterranean could explain its varied appearance.

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• 7. Names and Folklore

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  The English word fox comes from Old English, which descends from Proto-Germanic fuhsaz. The Dutch vos, the German Fuchs and the West Frisian foks are relatives. The root traces back to a Proto-Indo-European word meaning thick-haired or tail. The Hindi word for tail, pūñch, and the Lithuanian pūkas, meaning fur or fluff, are cousins.

  The tail inspired names in many languages. The Welsh llwynog means bushy, from llwyn, bush. The word raposa comes from rabo, tail, and the Ojibwe waagosh draws on a word for the up and down bounce of an animal or its tail. The scientific term vulpes comes from the Latin word for fox, and it gives English the adjectives vulpine and vulpecular.

  Males are called tods or dogs, females are vixens, and the young are cubs or kits. The red fox is the only fox native to Western Europe, even though the Arctic fox has a small native population in northern Scandinavia and the corsac fox ranges into European Russia. That is why colloquial British English simply says "the fox".

  Folklore gave the animal a long record as a trickster. In Greek mythology, the Teumessian fox, or Cadmean vixen, was a gigantic child of Echidna and was destined never to be caught. In the Cotswolds, witches were believed to turn into foxes to steal butter from their neighbours.

  Reynard the Fox became the great fox of European tales. He first appeared as a secondary character named Reinardus in the 1150 poem Ysengrimus. Pierre Saint Cloud's Le Roman de Renart followed in 1175, and Reynard made his English debut in Geoffrey Chaucer's The Nun's Priest's Tale. Many of his adventures may stem from real fox behaviour, since he is an enemy of the wolf and has a fondness for blackberries and grapes.

  In China, folk tales speak of fox-spirits called huli jing that may have up to nine tails, known in Korea as kumiho. Japanese mythology has the kitsune, fox spirits whose magic grows with age and wisdom. Their foremost power is disguising themselves as humans. Some stories show kitsune tricking people, while others portray them as faithful guardians, friends, lovers and wives.

  Arab folklore sees the fox as a cowardly, deceitful animal that feigns death by filling its abdomen with air. The Bible uses the word fox for false prophets in Ezekiel 13:4 and for the hypocrisy of Herod Antipas in Luke 13:32. In Native American stories Fox is often the constant companion of Coyote, and often steals his food. In the Achomawi creation myth the two together create the world. An Inuit story casts Fox as a beautiful woman who tricks a hunter into marriage and leaves after he offends her.

  A Yurok story tells that Fox, in a fit of anger, captured the Sun and tied him to a hill, and the Sun burned a great hole in the ground.

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• 8. Hunted, Worn, Tamed

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  A seal dated to 350 BC shows a Persian horseman spearing a fox, and it is among the earliest records of fox hunting. Alexander the Great is known to have hunted foxes. Xenophon, who thought hunting was part of a cultured man's education, urged killing foxes as pests because they distracted hounds from hares. By AD 80 the Romans were hunting foxes as well.

  In the Dark Ages foxes were a secondary quarry, though they slowly rose in importance. Cnut the Great reclassified them as Beasts of the Chase, a lower category than Beasts of Venery. By the late 1200s Edward I kept a royal pack of foxhounds and a specialised fox huntsman. Hunters increasingly chased foxes above ground with hounds rather than digging them out with terriers. Edward, Second Duke of York, raised the animal's standing further in his book The Master of Game.

  By the Renaissance, fox hunting was a traditional sport of the nobility. The English Civil War reduced deer populations, and fox hunting grew more popular. By the mid-1600s Great Britain was divided into fox hunting territories, and the first club, the Charlton Hunt Club, formed in 1737. The sport reached its peak in Britain during the 1700s.

  In 1730, prosperous tobacco planters imported English red foxes to Virginia and Maryland for sport, even though the continent already had native red foxes. They found the red fox more sporting than the grey. One account of those hunts says, "The grays furnished more fun, the reds more excitement." The grays kept to circuits near home, while an old red might lead the dogs for thirty miles.

  Persecution continues today. Human-caused deaths remain one of the main causes of fox mortality. Annual kills recorded around 2000 included about 600,000 in Germany, 58,000 each in Austria and Sweden, and between 21,500 and 25,000 in the United Kingdom.

  The fur trade has valued red foxes heavily. Pelts become trimmings, scarfs, muffs, jackets and coats. Furriers prize silver morphs most, then cross morphs, then plain red ones. In the early 1900s over 1,000 American red fox skins were imported to Great Britain each year, while Germany and Russia exported 500,000 annually. The worldwide trade in wild red foxes in 1985-86 reached 1,543,995 pelts. Red foxes made up 45 percent of United States wild-caught pelts, worth $50 million.

  Origin matters for price. Northern Alaska produces pelts with silky guard hairs that allow unrestricted mobility after dressing. Pelts from southern Alaska's coast and the Aleutian Islands are extremely coarse and rarely fetch more than a third as much. North American wholesale auction prices averaged $39 in 2012 and $65.78 in 2013.

  A wild fox makes a poor pet. Many kits are adopted each spring by well-meaning people who assume they were abandoned, although vixens rarely abandon young. Suckling kits need milk every four hours, day and night. Captive foxes that are friendly when young become fearful of everyone but their handlers by 10 weeks of age. Tame foxes were once used to draw ducks close to hunting blinds.

  Fur farms raised foxes ranging from white to black as "silver foxes". In the second half of the 20th century, the Russian geneticist Dmitry Belyayev used them for a breeding experiment over 40 years. He kept breeding only the individuals that showed the least fear of humans, and later only those with the most positive response. After about 10 generations the foxes had lost all fear of people, and they often wagged their tails and licked their caretakers.

  Their bodies changed too. The foxes developed piebald coats, floppy ears in kits and curled tails, the same traits that separate domestic dogs from grey wolves. The team had selected only for behaviour toward humans, and those physical changes arrived alongside it.

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