Fox

• 1. Introduction

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  A fox can leap straight up, twist in the air, and land squarely on top of its prey. It crouches low to vanish into the terrain, then drives off its hind legs with great force. With its pronounced canine teeth, it grips the prey's neck and shakes. Foxes are small-to-medium-sized omnivorous mammals in the family Canidae, and they live on every continent except Antarctica. The most common and widespread is the red fox, Vulpes vulpes, with about 47 recognized subspecies. Twelve species form the monophyletic true fox group of genus Vulpes. Another 25 living or extinct species are sometimes called foxes too. What makes an animal a fox rather than a wolf or a jackal? Why has this creature earned a reputation for cunning that stretches across Europe, Persia, East Asia, and Native American cultures alike? And how does a Russian experiment in selective breeding tie into the floppy ears of a domestic dog? The answers run from the shape of a skull to the forests of Chile.

• 2. What Makes A Fox

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  A flattened skull, upright triangular ears, a pointed and slightly upturned snout, and a long bushy tail called a brush. These are the marks of a fox. They are generally smaller than wolves and jackals, yet larger than some canids such as raccoon dogs. In the largest species, the red fox, males weigh between 4.1 and 8.7 kg. The smallest species, the fennec fox, weighs just 0.7 to 1.6 kg. Foxes are digitigrade, walking on their toes, and unlike most members of Canidae they have partially retractable claws. Their black whiskers tell their own story of adaptation. The mystacial vibrissae on the muzzle average 100 to 110 mm long. Whiskers elsewhere on the head are shorter, and the carpal vibrissae on the forelimbs average 40 mm, pointing downward and backward. A fox's dentition matches the rest of the canids: I 3/3, C 1/1, PM 4/4, M 3/2, totalling 42 teeth. The bat-eared fox is the odd one out, with six extra molars for a total of 48. Pronounced carnassial pairs, the upper premolar and the lower first molar, shear through tough flesh, marking the fox clearly as a carnivore.

• 3. Built For The Climate

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  Pearly white to black-and-white to black flecked with white or grey on the underside. Fox coats span a remarkable range, and the differences are not decorative. Fennec foxes and other desert-adapted species, such as kit foxes, carry large ears and short fur to shed body heat. Arctic foxes do the opposite, with tiny ears, short limbs, and thick insulating fur to trap warmth. The red fox wears a typical auburn pelt, its tail usually ending in a white marking. Seasons reshape the coat as much as habitat does. Fox pelts grow richer and denser in the colder months and lighter in the warmer ones. To shed the dense winter coat, foxes moult once a year around April, the process starting at the feet, moving up the legs, then along the back. Coat color can shift again as an individual ages, so no fox wears exactly the same fur for life.

• 4. Life And The Litter

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  One to three years is the typical lifespan of a wild fox, though some individuals reach ten. They are not always pack animals. Most live in small family groups, while some, such as Arctic foxes, are known to be solitary. Their omnivorous diet leans on invertebrates like insects and small vertebrates like reptiles and birds, with eggs and vegetation added in. Most species eat around 1 kg of food a day, and they cache the excess, burying it under leaves, snow, or soil. Reproduction runs on a tight annual clock. In red foxes, sperm formation begins in August and September, with the testicles reaching their greatest weight between December and February. Vixens are in heat for one to six days, giving a reproductive cycle twelve months long. After fertilization, gestation lasts 52 to 53 days. Litters average four to five kits, with an 80 percent success rate in becoming pregnant, though the Arctic fox can have up to eleven. A vixen usually has six or eight mammae, and each teat carries 8 to 20 lactiferous ducts to bring milk to the nipple.

• 5. A Vast Vocabulary

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  A whine made shortly after birth is a fox's first sound, rising in frequency when kits are hungry or cold. The whine stimulates the mother to care for her young, and it can move the male fox to care for his mate and kits too. About 19 days later the whining sharpens into infantile barks called yelps, heard most during play. By roughly one month old, kits can produce an explosive call, a high-pitched howl meant to threaten intruders or rival cubs. That same call matures in adults into an open-mouthed combative call, a sharper bark used in conflict. Adults also growl to tell their kits to feed or come to them, and they bark to warn off intruders and defend themselves. In domesticated foxes, the whine never quite fades, lingering into adulthood as a sign of excitement and submission toward their owners.

• 6. The Family Tree

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  DNA analysis splits the Canidae into several phylogenetic divisions, and the foxes do not all sit together. The fox-like canids include the kit fox, red fox, Cape fox, Arctic fox, fennec fox, and the bat-eared fox. The wolf-like canids form a separate branch, the genus Canis, Cuon, and Lycaon, holding the dog, gray wolf, coyote, golden jackal, the Ethiopian wolf, the dhole, and the African wild dog. The South American canids gather the bush dog, hoary fox, crab-eating fox, and maned wolf into yet another group. The gray fox stands apart in genus Urocyon as a monotypic taxon, and it shares a rare habit. It is one of only two canine species known to regularly climb trees, the other being the raccoon dog. The word itself reaches back through Old English to Proto-Germanic fuhsaz and Proto-Indo-European puḱ, meaning thick-haired or tail. Males are called dogs, tods, or reynards. Females are vixens, a word that keeps the Middle English southern v sound rather than the f. Young are cubs, pups, or kits, not to be confused with the kit fox itself.

• 7. Foxes Among Us

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  Resident urban carnivores is the label given to several fox species able to sustain whole populations inside city limits. Their omnivorous diet lets them live on discarded food waste, and their skittish, often nocturnal nature helps them avoid detection. Urban foxes in Europe show altered behavior compared to their rural kin, with higher population density, smaller territories, and foraging in packs rather than alone. They can live longer in cities, yet often have smaller litters. The relationship with people is uneasy. Foxes are resented as nuisance animals for opportunistic attacks on poultry and small livestock, and urban foxes are seen as threats to cats and small dogs. Yet they have also been employed on fruit farms to control pests while leaving the fruit intact. Fox attacks on humans are not common. The history of fox hunting runs deep, originating in the United Kingdom in the 16th century. Hunting with dogs is now banned there, though hunting without dogs is still permitted. Red foxes were introduced into Australia in the early 19th century for sport, and they have spread through much of the country, driving down native species and preying on new lambs. The mathematics of foxes and their prey left a mark on science as well. Population oscillations of foxes against rabbits and hens were the first nonlinear oscillation studied, leading to the Lotka-Volterra equation.

• 8. Endangered And Engineered

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  A 95 percent decline since 1993 nearly erased the island fox of the California Channel Islands. The cause was an outbreak of canine distemper virus from 1999 to 2000 and predation by non-native golden eagles. With so few animals left, the population fell into an Allee effect, where fitness drops once density gets low enough. Conservationists pulled healthy breeding pairs into captivity and removed nonnative grazers so native plants could regrow and shelter the foxes from eagles. Darwin's fox tells a parallel story of a species pinned to a shrinking map. Once considered critically endangered with around 250 mature individuals, the IUCN downgraded it to endangered in its 2016 assessment after finding a wider distribution. On the Chilean mainland its range is limited to Nahuelbuta National Park and the surrounding Valdivian rainforest, yet 90 percent of Darwin's foxes live on Chiloé Island. Deforestation favors its competitor, the chilla fox, and pet dogs bring diseases it cannot fight. Researchers propose protecting the forests linking Nahuelbuta National Park to the coast and on to Chiloé, a linear distance of more than 400 km. Not every human shaping of foxes ends in loss. In the Soviet Union and Russia, nearly fifty years of experiments set out to domesticate the silver morph of the red fox from scratch. The selective breeding produced traits seen in domestic cats and dogs, including pigmentation changes, floppy ears, and curly tails. The new foxes grew tame, letting themselves be petted, whimpering for attention, and licking their caretakers. The same animal that gave folklore its trickster, the nine-tailed fox of Chinese myth and the shape-shifting spirit of East Asian tales, also rides the night sky as the constellation Vulpecula.