The red fox (Vulpes vulpes) is the largest of the true foxes, and the most widely distributed member of the order Carnivora. It is present across the entire Northern Hemisphere, including most of North America, Europe and Asia, as well as parts of North Africa. Its range has expanded alongside human settlement, with the species having been introduced to Australia, where it preys on native small and medium-sized rodents and marsupials. The red fox is listed as of least concern on the IUCN Red List. Because of its impact on native species, it is included on the list of the "world's 100 worst invasive species".
The red fox originated in Eurasia during the Middle Pleistocene 400,000 years ago and later colonised North America sometime prior to 130,000 years ago. 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 can be divided into two categories: the large northern foxes and the small, basal southern grey desert foxes of Asia and North Africa.
The red fox usually occurs in pairs or in small family groups consisting of a mated pair and their young, or a male with several females related to each other. The young of the mated pair stay with their parents to help care for the new kits. The red fox primarily feeds on small rodents, though it also hunts rabbits, squirrels, game birds, reptiles, invertebrates and young ungulates. It also eats fruit and vegetables. Although it tends to kill smaller predators, including other fox species, it is vulnerable to attack from predators, such as the golden eagle, Eurasian goshawk, Bonelli's eagle, Eurasian eagle-owl, long-tailed weasel, stoat, striped skunk, American mink, snakes, and martens.
The red fox has been extensively hunted as a pest and furbearer for many centuries, and is represented in human folklore and mythology. Due to its widespread distribution and large population, the red fox is one of the most important fur-bearing animals harvested for the fur trade. Too small to pose a significant threat to humans, it has greatly benefited from the presence of human habitation, and has successfully colonised many suburban and urban areas. The domestication of the red fox is also underway in Russia, and has resulted in the domesticated silver fox.
Terminology
Male foxes are called tods or dogs, females are called vixens, and young are known as cubs or kits. Although the Arctic fox has a small native population in northern Scandinavia, and while the corsac fox's range extends into European Russia, the red fox is the only fox native to Western Europe. For this reason, it is simply called "the fox" in colloquial British English.
Etymology The word "fox" comes from Old English, which in turn derived from Proto-Germanic *fuhsaz. Compare with West Frisian foks, Dutch , and German . This, in turn, derives from Proto-Indo-European *puḱ- 'thick-haired; tail'. Compare to the Hindi pū̃ch 'tail', Tocharian B päkā 'tail; chowrie', and Lithuanian 'fur / fluff'. The fox's bushy tail also forms the basis for its Welsh name, , literally 'bushy', from 'bush'. Likewise, from rabo 'tail', Lithuanian from uodegà 'tail', and Ojibwe waagosh from waa, which refers to the up and down "bounce" or flickering of an animal or its tail.
The scientific term vulpes derives from the Latin word for fox, and gives the adjectives vulpine and vulpecular.
Evolution The red fox is Eurasian in origin and may have evolved from either Vulpes alopecoides or the related Chinese V. chikushanensis, both of which lived during the Middle Villafranchian of the Pleistocene Epoch. The earliest fossil red fox specimens were uncovered in Baranya County, Hungary, dating from .PaleoDatabase collection No. 35369, authorized by Alan Turner, Liverpool John Moores University. Entry by H. O'Regan, 8 December 2003 The ancestral red fox was likely more diminutive compared to today's extant foxes, as the earliest red fox fossils have shown a smaller build than living specimens. The earliest fossil remains of the modern red fox date back to the mid-Pleistocene, found in association with middens and refuse left by early human settlements. This has led to the theory that the red fox was hunted by primitive humans as both a source of food and pelts; the possibility also exists of red foxes scavenging from middens or butchered animal carcasses.
The sister lineage to the red fox is the Rüppell's fox, but the two species are surprisingly closely related through mitochondrial DNA markers, with Rüppell's fox nested within the red fox lineage. Such a nesting of one species within another is called paraphyly. Several hypotheses have been suggested to explain this, including (1) recent divergence of Rüppell's fox from a red fox lineage, (2) incomplete lineage sorting, or introgression of mtDNA between the two species. Based on the fossil record, the last scenario seems the most likely. This is further supported by the clear ecological and morphological differences between the two species.
Colonisation of North America
Red foxes colonised the North American continent in two waves: before and during the Illinoian glaciation, and during the Wisconsinan glaciation about 130,000 years ago. Gene mapping demonstrates that red foxes in North America have been isolated from their Old World counterparts for over 400,000 years, thus raising the possibility that speciation has occurred, and that the previous binomial name of Vulpes fulva may be valid. In the far north, red fox fossils have been found in Sangamonian Stage deposits near the Fairbanks District, Alaska, and Medicine Hat, Alberta. Fossils dating from the Wisconsinan are present in 25 sites across Arkansas, California, Colorado, Idaho, Missouri, New Mexico, Ohio, Tennessee, Texas, Virginia, and Wyoming. Although they ranged far south during the Wisconsinan, the onset of warm conditions shrank their range toward the north, and they have only recently reclaimed their former North American ranges because of human-induced environmental changes. Genetic testing indicates that two distinct red fox refugia exist in North America, which have been separated since the Wisconsinan. The northern refugium occurs in Alaska and western Canada, and consists of the larger subspecies V. v. alascensis, V. v. abietorum, V. v. regalis, and V. v. rubricosa. The southern (or montane) refugium occurs in the subalpine parklands and alpine meadows of the west, from the Rocky Mountains to the Cascades and the Sierra Nevada ranges, consisting of the smaller subspecies V. v. cascadensis, V. v. macroura, V. v. necator, and V. v. patwin. The latter clade has been isolated from all other red fox populations since at least the last glacial maximum and may have developed unique ecological or physiological adaptations.
Although European foxes (V. v. crucigera) were introduced to parts of the United States in the 1900s, genetic research suggests that there are no European fox mitochondrial haplotypes present in any North American populations. Additionally, introduced eastern North American red foxes have colonised most of inland California, from Southern California to the San Joaquin Valley, Monterey and north-coastal San Francisco Bay Area (including urban San Francisco and adjacent cities). In spite of the red fox's adaptability to city life, they are still found in somewhat greater numbers in the northern portions of California (north of the Bay Area) than in the south, as the wilderness is more alpine and isolated. The eastern red foxes appear to have mixed with the Sacramento Valley red fox (V. v. patwin) only in a narrow hybrid zone. In addition, no evidence is seen of interbreeding of eastern American red foxes in California with the montane Sierra Nevada red fox (V. v. necator) or other populations in the Intermountain West (between the Rocky Mountains to the east and the Cascade and Sierra Nevada Mountains to the west).
Subspecies The third edition of Mammal Species of the World listed 45 subspecies as valid. In 2010, a distinct 46th subspecies, the Sacramento Valley red fox (V. v. patwin), which inhabits the grasslands of the Sacramento Valley, was identified through mitochondrial haplotype studies. Castelló (2018) recognized 30 subspecies of the Old World red fox and nine subspecies of the North American red fox as valid.
It is known that substantial gene pool mixing occurs between different subspecies. For example, British red foxes have crossbred extensively with red foxes imported from Germany, France, Belgium, Sardinia and possibly Siberia and Scandinavia. However, genetic studies suggest very little differences between red foxes sampled across Europe. Lack of genetic diversity is consistent with the red fox being a highly agile species, with one red fox covering in under a year's time.
Heptner & Naumov (1998) divide subspecies in Eurasia and North Africa into two categories based on morphological features: are large and brightly coloured. include the Asian subspecies V. v. griffithi, V. v. pusilla, and V. v. flavescens. These foxes display transitional features between the northern foxes and other, smaller fox species; their skulls possess more primitive, neotenous traits than the northern foxes and they are much smaller; the maximum sizes attained by southern grey desert foxes are invariably less than the average sizes of northern foxes. Their limbs are also longer and their ears larger. Red foxes living in Middle Asia show physical traits intermediate to the two.