Members of the family Canidae (dog family) exhibit great flexibility in diet and behavior and complex social organization, with much variation both within and between species. Canids are among the most widely distributed carnivores, with at least one species present on every continent except Antarctica, and one or more canid species can be found from sea level to 5000 meters.
Sillero-Zubiri (2009) recognized 35 extant canid species (37 if the Dingo is treated as a distinct species, Canis dingo, rather than a subspecies of the Gray Wolf, Canis lupus dingo, and if the Eastern North American Wolf is treated as a distinct species, Canis lycaon). South America has 11 species, including nine (mainly Pseudalopex [sometimes known as Lycalopex] foxes) endemic to the continent. Africa has 13 species, including eight endemics. Asia has twelve species, including three endemics. Two species, the Golden Jackal (Canis aureus) and Arctic Fox (Alopex lagopus) are native to three continents (Africa/Europe/Asia and North America/Asia/Europe, respectively).
A few canids have extremely small ranges, the most extreme example being Darwin's Fox (Pseudalopex fulvipes): most of the world population of just a few hundred individuals is found on a single island off Chile, although a small number persist on the mainland. Ethiopian Wolves (Canis simensis) occur only in a few isolated pockets of Afro-alpine grasslands and heathlands above the treeline from around 3200 meters to 4500 meters, where they are found mainly in open areas with short vegetation and feed almost exclusively on Afro-alpine rodents such as Ethiopian African Mole Rats (Tachyoryctes macrocephalus) and Arvicanthis and Otomys murine grass rats, which can be very abundant. At the other extreme, the Red Fox (Vulpes vulpes) has the largest natural range of any carnivore (Larivière and Pasitschniak-Arts 1996), encompassing nearly 70 million km2 and extending across the entire northern hemisphere from the Arctic Circle through Canada and the United States and most of Europe and Asia to North Africa; in addition, Red Foxes were introduced to Australia in the 1800s and their range in the United States was extended through several introductions of European Red Foxes starting in the mid-1700s. The Gray Wolf (Canis lupus) has (or had) a similar distribution, occuring widely in North America, Asia, and Europe. Some canid distributions have changed substantially in historical times. For example, the Coyote (Canis latrans) used to be found mainly in arid parts of the western United States, but is now found in every state, province, and country north of Panama, an expansion that was clearly aided by the extirpation of Gray Wolves from most of the United States in the early 1900s. The Red Fox and Dingo are found in Australia and Oceania, but were brought there by humans. Red Foxes are known to coexist in one region or another with 14 other canid species, Golden Jackals with 13 other canids, and Gray Wolves with 11 other canids.
Although canids generally stick to the ground, Northern Gray Foxes (Urocyon cinereoargenteus) are very capable tree climbers and Blanford's Foxes (Vulpes cana) and Arctic Foxes regularly climb cliffs. Some canids have adaptations allowing them to live in extreme environments, e.g., the Arctic (Arctic Foxes) and deserts (several desert foxes). The Fennec (Vulpes zerda), Rüppel's (Vulpes rueppellii), and Pale Foxes (Vulpes pallida) are found in the Sahara and Sahel and Blanford's Fox occurs in the deserts and mountains of western Asia. Sechuran Foxes (Pseudalopex sechurae) live in the coastal desert of Peru and Ecuador. All these desert foxes are nocturnal and spend much of the hot day in burrows. The Fennec Fox is the smallest canid and the only Saharan carnivore that does not need to drink water. It is so specialized to tolerate high ambient temperatures that it begins to shiver when the temperature drops below 20 C; it begins to pant only above 35 C and dramatically increases its breaths per minute to help lower its body temperature. The Fennec Fox also has proportionately enormous ears (accounting for 20% of its body surface!) that facilitate thermoregulation and are perhaps the most obvious of a whole suite of anatomical, physiological, and behavioral adaptations to extremely hot and dry environments. More than 20 species of canids are clearly associated with open habitats including temperate grasslands, shrublands, and montane habitats. Only four South American species—Bush Dog (Speothos venaticus), Short-eared Dog (Atelocynus microtis), Hoary Fox (Pseudalopex vetulus), and Crab-eating Fox (Cerdocyon thous)—are essentially restricted to tropical forest (the first three of these are among the most poorly known of all canids).
Although many canids are highly carnivorous, they are mostly rather opportunistic (especially the foxes) and the typical diets of some species, especially those with smaller body sizes, may include less than 5% protein. Among the larger canids are several species that live in groups and prey on animals that may exceed their own body size: Gray Wolves across much of the Northern Hemisphere, Dholes (Cuon alpinus) in southern Asia, and African Wild Dogs (Lycaon pictus) in Africa. The Maned Wolf (Chrysocyon brachyurus), which lives in South American savannas, is unusual for a large canid in that it feeds mostly on rodents and fruit. The Bat-eared Fox (Otocyon megalotis) of eastern and southern Africa and the Hoary Fox of Brazil are the only canids that feed largely on insects rather than mammals, feeding especially on Syntermes and Cornitermes harvester termites that emerge from undergound colonies to forage on grasses, as well as on other insects such as adult and larval dung beetles (particularly during the rainy season when termites are less active).
The dog is believed to be the first domesticated animal, apparently derived from Gray Wolves at least 10,000-15,000 years ago—possibly far longer ago than this and pre-dating the emergence of agriculture. The Domestic Dog is now generally treated as a subspecies of Gray Wolf, Canis lupus familiaris. Dingo-like feral dogs were apparently associated with hunter-gatherer societies of Africa, Asia, and Europe and later with sedentary agricultural societies. Dingoes were brough from mainland Asia to Australia and various Pacific islands as many as 10,000 years ago, perhaps for food, as guard animals, or for warmth and companionship. The Dingoes of Southeast Asia are often known as Pariah Dogs. On various islands, in particular, introduced Dingos, Red Foxes, and Arctic Foxes have decimated populations of some native birds and mammals.
A number of canid species face serious threats to their populations. Gray Wolves, African Wild Dogs, Coyotes, and Dingoes have often been actively persecuted by humans as a result of their predation of livestock (and, to a lesser degree, because of the perception that they pose a direct danger to humans). Some smaller canids—notably the Arctic Fox and some South American foxes—have historically been hunted extensively for the fur trade, although this pressure has declined with the decline of the fur trade. Some species that have been subjected to intense hunting pressure—such as Dingoes, Coyotes, Culpeos (Pseudalopex culpaeus), and Red Foxes—have nevertheless thrived. Today, many canid species seem to be maintaining stable populations and some have even expanded. Coyotes, for example, are now more common and widespread than ever and Golden Jackals have expanded into Western Europe. Gray Wolves are slowly recovering in some portions of their once far greater range. However, nearly a dozen canid species are considered threatened or endangered, some largely because they are naturally rare, with limited geographic distributions, but mostly because of human activities that have led to habitat loss, persecution, and disease, although they have so far been spared the fate of the Falkland Islands Wolf (Dusicyon australis), which was eradicated by humans in the 19th century. Among the most vulnerable species are the narrowly distributed Darwin's Fox in southern Chile, the Island Fox (Urocyon littoralis) on the Channel Islands off southern California (U.S.A.), and the Red Wolf (Canis rufus) of the southeastern U.S.A. (the taxonomic status of the Red Wolf remains controversial). The Red Wolf was extinct in the wild by 1980; introduction efforts have been fairly successful, but many individuals are killed by cars each year and genetic dilution by hybridization with Coyotes poses a serious threat to the persistence of the species. Other endangered or threatened canids include the African Wild Dog (formerly found across much of sub-Saharan Africa, excluding rainforests, but now occurring only in small scattered populations), the Dhole, and the Ethiopian Wolf, among others. Some species are very poorly known so their status is difficult to assess. Sillero-Zubiri (2009) suggests that the failure of attempts to locate and survey populations of some of these species (notably, Bush Dog and Short-eared Dog and Saharan Pale, Ruppell's, and Fennec Foxes) do not bode well for the status of these species.
Human impacts on canid populations may be direct (e.g., hunting of Indian Foxes, Vulpes bengalensis) or indirect (e.g., the local extinction in the Negev Desert in Israel of Rüppell's Fox, which was abundant into the 1960s, possibly as a result of Red Fox populations increasing in association with increased agriculture). Although around half the species of canids are known to have had some use in traditional medicine, demand for body parts or organs for traditional medicine does not appear to pose a major conservation concern (as it does for many other types of animals) since harvesting for medicinal uses is not believed to currently pose a significant threat to any endangered canid (Alves et al. 2010). Rabies, canine distemper, anthrax, and other pathogens have all taken a severe toll on various canid populations (notably Island Foxes, Ethiopian Wolves, and African Wild Dogs) and in some cases these may have been transmitted from domestic dogs. Management efforts for the long-term conservation of several canids, such as the African Wild Dog and Ethiopian Wolf, have shown evidence of some success, but the remaining challenges are great.
(Sillero-Zubiri 2009 and references therein)
- Alves, R.R.N., R.R.D. Barboza, and W.M.S. Souto. 2010. A Global overview of canids used in traditional medicines. Biodiversity and Conservation 19: 1513-1522.
- Larivière, S. and M. Pasitschniak-Arts.1996. Vulpes vulpes. Mammalian Species 537: 1-11.
- Sillero-Zubiri, C. 2009. Family Canidae (Dogs). Pp. 352-446 in: Wilson, D.E. & Mittermeier, R.A., eds. Handbook of the Mammals of the World. Volume 1. Carnivores. Lynx Edicions, Barcelona.
Known prey organisms
This list may not be complete but is based on published studies.
Molecular Biology and Genetics
Statistics of barcoding coverage
|Specimen Records:||835||Public Records:||560|
|Specimens with Sequences:||680||Public Species:||20|
|Specimens with Barcodes:||529||Public BINs:||6|
|Species With Barcodes:||17|
Foxes are small-to-medium-sized, omnivorous mammals belonging to several genera of the Canidae family. Foxes are slightly smaller than a medium-size domestic dog, with a flattened skull, upright triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or brush).
12 species belong to the Vulpes genus of "true foxes". Approximately another 25 current or extinct species are always or sometimes called foxes. Foxes are found on every continent except Antarctica. By far the most common and widespread species of fox is the red fox (Vulpes vulpes). 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 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. This in turn derives from Proto-Indo-European *puḱ- ‘thick-haired; tail’. Male foxes are known as dogs, tods or reynards, females as vixens, and young as cubs, pups, or kits. A group of foxes is referred to as a skulk, leash, troop, or earth.
In the wild, the typical lifespan of a fox is 2 to 3 years, although individuals may live up to ten years. Foxes are generally smaller than other members of the family Canidae such as wolves, jackals, and domestic dogs. Male foxes weigh, on average, around 5.9 kilograms (13 lb) while female foxes weigh around 5.2 kilograms (11.5 lb). Fox-like features typically include a triangular face, pointed ears, a long, narrow, sharp muzzle, and a bushy tail. Other physical characteristics vary according to habitat. For example, the fennec fox (and other species of fox adapted to life in the desert, such as the kit fox) has large ears and short fur, whereas the Arctic fox has tiny ears and thick, insulating fur. The red fox, by contrast, has a typical auburn pelt, the tail normally ending with white marking. Litter sizes can vary greatly according to species and environment – the Arctic fox, for example, has an average litter of four to five, with eleven as maximum.
Unlike many canids, foxes are not always pack animals. Typically, they live in small family groups, and are opportunistic feeders that hunt live prey (especially rodents). Using a pouncing technique practiced from an early age, they are usually able to kill their prey quickly. Foxes also gather a wide variety of other foods ranging from grasshoppers to fruit and berries. The gray fox is one of only two canine species known to climb trees; the other is the raccoon dog.
Foxes are normally extremely wary of humans and are not usually kept as indoor pets; however, the silver fox was successfully domesticated in Russia after a 45-year selective breeding program. This selective breeding also resulted in physical and behavioral traits appearing that are frequently seen in domestic cats, dogs, and other animals, such as pigmentation changes, floppy ears, and curly tails.
Canids commonly known as foxes include members of the following genera:
- Alopex: Former genus of the Arctic fox, now considered part of Vulpes.
- Canis: Ethiopian wolf, sometimes called the Semien fox or Semien jackal.
- Cerdocyon: Crab-eating fox.
- Dusicyon: Extinct genus, including the Falkland Islands wolf, sometimes known as the Falklands Islands fox.
- Lycalopex: Six South American species.
- Otocyon: Bat-eared fox.
- Urocyon: Gray fox, island fox and Cozumel fox (undescribed).
- Vulpes: Includes 12 species of true foxes, including the red fox, V. vulpes, Tibetan sand fox, V. ferrilata and their closest kin.
The fennec fox is the smallest species of fox.
Arctic fox curled up in snow.
Crab-eating fox, a South American species.
Foxes are omnivores. The diet of foxes is largely made up of invertebrates such as insects, and small vertebrates such as reptiles and birds, and also can include eggs and plants. 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.
Many foxes adapt well to human environments, with several species classified as "resident urban carnivores" for their ability to sustain populations entirely within urban boundaries. Litter size in urban areas can be smaller than in non-urban areas, but urban foxes can be longer-lived than their non-urban counterparts. Urban foxes are ubiquitous in Europe, where they show altered behaviors compared to non-urban foxes, including increased density, smaller territory, and pack foraging.
Foxes have been introduced in numerous locations, with varying effects on indigenous flora and fauna. Red foxes were introduced into Australia in the early 19th century for sport, and have since become widespread through much of the country. Their impact on native vegetation and animals is subject to much speculation.
Several fox species are endangered in their native environments. Pressures placed on foxes include being hunted for pelts, other trade, or control. Due in part to their opportunistic hunting style and industriousness, foxes are commonly resented as nuisance animals. On the other hand, foxes, while often considered pests themselves, have been successfully employed to control pests on fruit farms while leaving the fruit intact.
Relationships with humans
Foxes are often considered pests or nuisance creatures for their opportunistic attacks on poultry and other small livestock. Fox attacks on humans are not common but have increased in frequency.
Fox hunting originated in the United Kingdom in the 16th century. Hunting with dogs is now banned in the United Kingdom, though hunting without dogs is still permitted. It is practiced as recreation in several other countries including Australia, Canada, France, Ireland, Italy, Russia and the United States.
There are many records of domesticated red foxes and others, but rarely of sustained domestication. A recent and notable case is the Russian silver fox, which resulted in visible and behavioral changes, and is a case study of an animal population modeling according to human domestication needs. The current group of domesticated silver foxes are the result of nearly fifty years of experiments in the Soviet Union and Russia to domesticate the silver morph of the red fox. Notably, the new foxes became more tame, allowing themselves to be petted, whimpering to get attention and sniffing and licking their caretakers.
In some countries, foxes are major predators of rabbits and hens. Population oscillations of these two species were the first nonlinear oscillation studied, and led to the now-famous Lotka-Volterra equation.
- "Fantastic Mr Fox". ESO Picture of the Week. Retrieved 11 February 2014.
- Cf. West Frisian foks, Dutch vos, and German Fuchs.
- Cf. Hindi pū̃ch ‘tail’, Tocharian B päkā ‘tail; chowrie’, and Lithuanian paustìs ‘fur’. The bushy tail also forms the basis for the fox's Welsh name, llwynog, literally ‘bushy’, from llwyn ‘bush’. Likewise, Portuguese: raposa from rabo ‘tail’, Lithuanian uodẽgis from uodegà ‘tail’, and Ojibwa waagosh from waa, which refers to the up and down "bounce" or flickering of an animal or its tail.
- Walker, Matt; Davies, Ella (7 March 2012). "Are red foxes getting bigger?" BBC News Online. Retrieved 2012-03-07.
- Hildebrand, Milton (1952). "The Integument in Canidae". Journal of Mammalogy 33 (4): 419–428. doi:10.2307/1376014. JSTOR 1376014.
- Trut, Lyudmila N. (1999). "Early Canid Domestication: The Fox Farm Experiment". American Scientist 87.
- Fedriani, J.M.; T. K. Fuller; R. M. Sauvajot; E. C. York (2000-07-05). "Competition and intraguild predation among three sympatric carnivores". Oecologia 125 (2): 258–270. doi:10.1007/s004420000448.
- Fox, David L. (2007). "Vulpes vulpes (red fox)". Animal Diversity Web. University of Michigan Museum of Zoology.
- Iossa, G. et al. A Taxonomic Analysis of Urban Carnivore Ecology, from Urban Carnivores. Stanley Gehrt et al. eds. 2010. p.174.
- Francis, Robert and Michael Chadwick. Urban Ecosystems 2013. p.126.
- See generally Long, John. Introduced Mammals of the World. 2013.
- Ginsburg, Joshua Ross and David Whyte MacDonald. Foxes, Wolves, Jackals, and Dogs. p.58.
- Bathgate, Michael. The Fox's Craft in Japanese Religion and Culture. 2004. p.18.
- McCandless, Linda Foxes are Beneficial on Fruit Farms. nysaes.cornell.edu (1997-04-24)
- Barratt, Sarah and Martin Barratt. Practical Quail-keeping. 2013.
- "Hunt campaigners lose legal bid". BBC News Online. 2006-06-23.
- Singh, Anita (2009-09-18). "David Cameron 'to vote against fox hunting ban'". The Daily Telegraph. London. Retrieved 2010-05-02.[dead link]
- Fox Hunting. North West League Against Cruel Sports Support Group. nwlacs.co.uk
- "Fox Hunting: For and Against".
- "The most affectionate foxes are bred in Novosibirsk". Redhotrussia.com. Retrieved 2014-04-08.
- Kenneth Mason, Jonathan Losos, Susan Singer, Peter Raven, George Johnson(2011)Biology Ninth Edition, p. 423. McGraw-Hill, New York.ISBN 978-0-07-353222-6.
- Sprott, Julien. Elegant Chaos 2010. p.89.
- Komarova, Natalia. Axiomatic Modeling in Life Sciences, from Mathematics and Life Sciences. Alexandra Antoniouk and Roderick Melnik, eds. pp.113-114.
The Canidae //  are the biological family of carnivorans that includes domestic dogs, wolves, foxes, jackals, coyotes, and many other lesser known extant and extinct dog-like mammals. A member of this family is called a canid (//, //). The Canidae family is divided into two tribes: Canini (related to wolves) and Vulpini (related to foxes).
Canids have a long evolutionary history. In the Eocene, about 50 million years ago, the carnivorans split into two lineages, the caniforms (dog-like) and feliforms (cat-like). By the Oligocene, some ten million years later, the first proper canids had appeared and the family had split into three subfamilies, Hesperocyoninae, Borophaginae, and Caninae. Only the last of these has survived until the present day.
Canids are found on all continents except Antarctica and vary in size from the 2 m (6.6 ft) gray wolf to the 24 cm (9.4 in) long fennec fox. The body forms of canids are similar, typically having long muzzles, upright ears, teeth adapted for cracking bones and slicing flesh, long legs and bushy tails. They are mostly social animals, living together in family units or small groups and behaving cooperatively. Typically, only the dominant pair in a group breed, and a litter of young is reared annually in an underground den. Canids communicate by scent signals and by vocalizations. One canid, the domestic dog, a subspecies of the gray wolf, long ago entered into a partnership with humans, and today remains one of the most widely kept domestic animals.
- 1 Classification and relationship
- 2 Evolution
- 3 Characteristics
- 4 Social behavior
- 5 Reproduction
- 6 Canids and humans
- 7 Species and taxonomy
- 8 Prehistoric Canidae
- 9 References
- 10 General references
- 11 External links
Classification and relationship
The subdivision of Canidae into "foxes" and "true dogs" may not be in accordance with the actual relations; also, the taxonomic classification of several canids is disputed. Recent DNA analysis shows that there are three monophyletic clades. Two of these, the South American canine group and the wolf group, together form the tribe Canini. The third clade is the fox group, tribe Vulpini. Molecular data imply a North American origin of living Canidae some ten million years ago and an African origin of wolf-like canines (Canis, Cuon, and Lycaon), with the jackals being the most basal of this group. The South American clade is rooted by the maned wolf and bush dog, and the fox-like canids by the fennec fox and Blanford's fox. The grey fox and island fox are basal to the other clades.
Currently, the domestic dog is listed as a subspecies of Canis lupus, C. l. familiaris, and the dingo (also considered a domestic dog) as C. l. dingo, provisionally a separate subspecies from C. l. familiaris; the red wolf, eastern Canadian wolf, and Indian wolf are recognized as subspecies. Many sources list the domestic dog as Canis familiaris, but others, including the Smithsonian Institution and the American Society of Mammalogists, more precisely list it as a subspecies of C. l. familiaris; the red wolf, eastern Canadian wolf, and Indian wolf may or may not be separate species; in the past, the dingo has been variously classified as Canis dingo, Canis familiaris dingo and Canis lupus familiaris dingo. 
The gray wolf can disperse widely, with some animals moving over 1,000 km (625 miles) from their place of birth, but analysis of mtDNA does not support the existence of multiple subspecies; virtually identical genotypes were identified from as far apart as Alaska and southern Canada. Nor could significant genetic differences be detected between widely separated populations of coyotes.
The Canidae includes a diverse group of some 34 species ranging in size from the maned wolf with its long limbs to the short-legged bush dog. Modern canids inhabit forests, tundra, savannahs and deserts throughout tropical and temperate parts of the world. The evolutionary relationships between the species have been studied in the past using morphological approaches but more recently, molecular studies have enabled the investigation of phylogenetic relationships. In some species, genetic divergence has been suppressed by the high level of gene flow between different populations and where the species have hybridized, large hybrid zones exist.
Carnivorans evolved from miacoids about 55 million years ago (Mya) during the late Paleocene. Some five million years later, the carnivorans split into two main divisions: caniforms (dog-like) and feliforms (cat-like). By 40 Mya, the first member of the dog family proper had arisen. Called Prohesperocyon wilsoni, its fossilized remains have been found in what is now the southwestern part of Texas. The chief features which identify it as a canid include the loss of the upper third molar (part of a trend toward a more shearing bite), and the structure of the middle ear which has an enlarged bulla (the hollow bony structure protecting the delicate parts of the ear). Prohesperocyon probably had slightly longer limbs than its predecessors, and also had parallel and closely touching toes which differ markedly from the splayed arrangements of the digits in bears.
The Canidae family soon subdivided into three subfamilies, each of which diverged during the Eocene: Hesperocyoninae (about 39.74-15 Mya), Borophaginae (about 34-2 Mya), and Caninae (about 34-0 Mya). The Caninae is the only surviving subfamily and all present-day canids including wolves, foxes, coyotes, jackals, and domestic dogs belong to it. Members of each subfamily showed an increase in body mass with time, and some exhibited specialised hypercarnivorous diets that made them prone to extinction.:Fig. 1
By the Oligocene, all three subfamilies of canids (Hesperocyoninae, Borophaginae, and Caninae) had appeared in the fossil records of North America. The earliest and most primitive branch of the Canidae was the Hesperocyoninae lineage, which included the coyote-sized Mesocyon of the Oligocene (38-24 Mya). These early canids probably evolved for the fast pursuit of prey in a grassland habitat; they resembled modern civets in appearance. Hesperocyonines eventually became extinct in the middle Miocene. One of the early member of the Hesperocyonines, the genus Hesperocyon, gave rise to Archaeocyon and Leptocyon. These branches led to the borophagine and canine radiations.
Around 9-10 Mya during the Late Miocene, Canis, Urocyon, and Vulpes genera expanded from southwestern North America, where the canine radiation began. The success of these canines was related to the development of lower carnassials that were capable of both mastication and shearing. Around 8 Mya, the Beringian land bridge allowed members of the genus Eucyon a means to enter Asia and they continued on to colonise Europe.
During the Pliocene, around 4-5 Mya, Canis lepophagus appeared in North America. This was small and sometimes coyote-like. Others were wolf-like in characteristics.Canis latrans (the coyote) is theorized to have descended from Canis lepophagus.
The formation of the Isthmus of Panama, about 3 Mya, joined South America to North America, allowing canids to invade South America, where they diversified. However the most recent common ancestor of the South American canids lived in North America some 4 Mya and the likelihood is that there were more than one incursion across the new land bridge. One of the resulting lineages consisted of the gray fox (Urocyon cinereoargentus) and the now extinct dire wolf (Canis dirus). The other lineage consisted of the so-called South American endemic species, the maned wolf (Chrysocyon brachyurus), the short-eared dog (Atelocynus microtis), the bush dog (Speothos venaticus), the crab-eating fox (Cerdocyon thous) and the South American foxes (Lycalopex spp.). The monophyly of this group has been established by molecular means.
During the Pleistocene, the North American wolf line appeared, with Canis edwardii, clearly identifiable as a wolf, and Canis rufus appeared, possibly a direct descendent of Canis edwardii. Around 0.8 Mya, Canis ambrusteri emerged in North America. A large wolf, it was found all over North and Central America, and was eventually supplanted by its descendant, the dire wolf, which then spread into South America during the late Pleistocene.
By 0.3 Mya, a number of subspecies of the gray wolf (Canis lupus) had developed and had spread throughout Europe and northern Asia. The gray wolf colonized North America during the late Rancholabrean era across the Bering land bridge, there being at least three separate invasions, with each one consisting of one or more different Eurasian gray wolf clades. MtDNA studies have shown that there are at least four extant C. lupus lineages. The dire wolf shared its habitat with the gray wolf but became extinct in a large-scale extinction event that occurred around 11,500 years ago. It may have been more of a scavenger than a hunter; its molars appear to be adapted for crushing bones and it may have died out as a result of the extinction of the large herbivorous animals on whose carcases it relied.
Wild canids are found on every continent except Antarctica, and inhabit a wide range of different habitats, including deserts, mountains, forests, and grasslands. They vary in size from the fennec fox at 24 cm (9.4 in) long, to the gray wolf, which may be up to 2 m (6.6 ft) long, and can weigh up to 80 kg (180 lb).
All canids have a similar basic form, as exemplified by the grey wolf, although the relative length of muzzle, limbs, ears and tail vary considerably between species. With the exceptions of the bush dog, raccoon dog, and some domestic breeds of Canis lupus, canids have relatively long legs and lithe bodies, adapted for chasing prey. The tails are bushy and the length and quality of the pelage varies with the season. The muzzle portion of the skull is much more elongated than that of the cat family. The zygomatic arches are wide, there is a transverse lambdoidal ridge at the rear of the cranium and in some species, a sagittal crest running from front to back. The bony orbits around the eye never form a complete ring and the auditory bullae are smooth and rounded.
All canids are digitigrade, meaning they walk on their toes. The tip of the nose is always naked, as are the cushioned pads on the soles of the feet. These latter consist of a single pad behind the tip of each toe and a more-or-less three-lobed central pad under the roots of the digits. Hairs grow between the pads and in the Arctic fox, the sole of the foot is densely covered with hair at some times of year. With the exception of the four-toed African hunting dog (Lycaon pictus), there are five toes on the forefeet but the pollex (thumb) is reduced and does not reach the ground. On the hind feet, there are four toes, but in some domestic dogs, a fifth vestigial toe, known as a dewclaw, is sometimes present but has no anatomical connection to the rest of the foot. The slightly curved nails are non-retractile and more or less blunt.
The penis in male canids is supported by a bone called the baculum. It also contains a structure at the base called the bulbus glandis which helps to create a copulatory tie during mating, locking the animals together for up to an hour. Young canids are born blind, with their eyes opening a few weeks after birth. All living canids (Caninae) have a ligament analogous to the nuchal ligament of ungulates used to maintain the posture of the head and neck with little active muscle exertion; this ligament allows them to conserve energy while running long distances following scent trails with their nose to the ground. However, based on skeletal details of the neck, at least some Borophaginae (such as Aelurodon) are believed to have lacked this ligament.
Most canids have 42 teeth, with a dental formula of: 18.104.22.168. The bush dog has only only one upper molar with two below, the dhole has two above and two below, and the bat-eared fox has three or four upper molars and four lower ones. As in other members of Carnivora, the upper fourth premolar and lower first molar are adapted as carnassial teeth for slicing flesh, although the bat-eared fox differs in this respect, being largely insectivorous. The molar teeth are strong in most species, allowing the animals to crack open bone to reach the marrow. The deciduous, or baby teeth, formula in canids is 3.1.3, molars being completely absent.
Almost all canids are social animals and live together in groups. In most foxes, and in many of the true dogs, a male and female pair work together to hunt and to raise their young. Gray wolves and some of the other larger canids live in larger groups called packs. African wild dogs have packs which may consist of twenty to forty animals, and packs of fewer than about seven individuals may be incapable of successful reproduction. Hunting in packs has the advantage that larger prey items can be tackled. Some species form packs or live in small family groups depending on the circumstances, including the type of available food. In most species, some individuals live on their own. Within a canid pack, there is a system of dominance so that the strongest, most experienced animals lead the pack. In most cases, the dominant male and female are the only pack members to breed.
Canids communicate with each other by scent signals, by visual clues and gestures, and by vocalizations such as growls, barks, and howls. In most cases, groups have a home territory from which they drive out other conspecifics. The territory is marked by leaving urine scent marks, which warn trespassing individuals. Social behaviour is also mediated by secretions from glands on the upper surface of the tail near its root and from the anal glands.
Canids as a group exhibit several reproductive traits that are uncommon among mammals as a whole. They are typically monogamous, provide paternal care to their offspring, have reproductive cycles with lengthy proestral and diestral phases and have a copulatory tie during mating. They also retain adult offspring in the social group, suppressing the ability of these to breed while making use of the alloparental care they can provide to help raise the next generation of offspring.
During the proestral period, increased levels of estradiol make the female attractive to the male. There is a rise in progesterone during the oestral phase and the female is now receptive. Following this, the level of estradiol fluctuates and there is a lengthy diestrous phase during which the female is pregnant. Pseudo-pregnancy frequently occurs in canids that have ovulated but failed to conceive. A period of anoestrus follows pregnancy or pseudo-pregnancy, there being only one oestral period during each breeding season. Small and medium-sized canids mostly have a gestation period of fifty to sixty days while larger species average sixty to sixty-five days. The time of year in which the breeding season occurs is related to the length of day, as has been demonstrated in the case of several species that have been translocated across the equator to the other hemisphere and experiences a six month shift of phase. Domestic dogs and certain small canids in captivity may come into oestrus more frequently, perhaps because the photoperiod stimulus breaks down under conditions of artificial lighting.
In general, canids are territorial or have a home range and sleep in the open, using their dens only for breeding and sometimes in bad weather. The size of a litter varies,with from one to sixteen or more pups being born. The young are born small, blind and helpless and require a long period of parental care. They are kept in a den, most often dug into the ground, for warmth and protection. When the young begin eating solid food, both parents, and often other pack members, bring food back for them from the hunt. This is most often vomited up from the adult's stomach. Where such pack involvement in the feeding of the litter occurs, the breeding success rate is higher than is the case where females split from the group and rear their pups in isolation. Young canids may take a year to mature and learn the skills they need to survive. In some species, such as the African wild dog, male offspring usually remain in the natal pack, while females disperse as a group, and join another small group of the opposite sex to form a new pack.
Canids and humans
One canid, the domestic dog, a subspecies of the gray wolf, entered into a partnership with humans a long time ago. This partnership is documented as far back as 26,000 years ago, when the footprints of a young boy aged about eight to ten was found in Chauvet Cave in southern France, walking alongside what was identified as a large dog or wolf. The earliest recorded fossil of a dog was found to be around 31,700 years ago in Goyet Cave in Belgium. Even earlier, wolves were found fossilized in the same locations as humans at sites that date back 300,000 years, showing how far back humans and wolves had interactions with one another. Studies using Y-chromosome and mtDNA have shown that the wolf was first domesticated in an area south of the Yangtze River in China. The fact that wolves are pack animals with cooperative social structures may have been the reason that the relationship developed. Humans benefited from the canid's loyalty, cooperation, teamwork, alertness and tracking abilities while the wolf may have benefited from the use of weapons to tackle larger prey and the sharing of food. Humans and dogs evolved together. The bond between humans and dogs can be seen in the burial of dogs with their owners as early as 11,000 years ago in the Americas and 8,500 years ago in Europe.
Among canids, only the gray wolf has widely been known to prey on humans. Nonetheless, at least two records have coyotes killing humans, and two have golden jackals killing children. Human beings have trapped and hunted some canid species for their fur and, especially the gray wolf, coyote and the red fox, for sport. Canids such as the dhole are now endangered in the wild because of persecution, habitat loss, a depletion of ungulate prey species and transmission of diseases from domestic dogs.
Species and taxonomy
FAMILY CANIDAE (Extant and recently extinct species)
- True dogs - Tribe Canini
- Genus Canis
- Gray wolf, Canis lupus 2.723 Mya to present)
- Coyote, Canis latrans (also called prairie wolf)
- Ethiopian wolf, Canis simensis (also called Abyssinian wolf, simien fox and simien jackal)
- Golden jackal, Canis aureus
- Side-striped jackal, Canis adustus
- Black-backed jackal, Canis mesomelas
- Genus Cuon
- Genus Lycaon
- Genus Atelocynus
- Genus Cerdocyon
- Genus Dusicyon †
- Genus Lycalopex (Pseudalopex)
- Genus Chrysocyon
- Genus Speothos
- Genus Canis
- True foxes - Tribe Vulpini
- Genus Vulpes
- Arctic fox, Vulpes lagopus
- Red fox, Vulpes vulpes (1 Mya to present)
- Swift fox, Vulpes velox
- Kit fox, Vulpes macrotis
- Corsac fox, Vulpes corsac
- Cape fox, Vulpes chama
- Pale fox, Vulpes pallida
- Bengal fox, Vulpes bengalensis
- Tibetan sand fox, Vulpes ferrilata
- Blanford's fox, Vulpes cana
- Rüppell's fox, Vulpes rueppelli
- Fennec fox, Vulpes zerda
- Genus Urocyon (2 Mya to present)
- Genus Vulpes
- Basal Caninae
- Tribe Canini
- Genus Canis
- Canis adoxus †
- Canis ameghinoi †
- Canis apolloniensis ( ) †
- Canis armbrusteri ( ) †
- Canis arnensis (3.4 Mya, †)
- Canis cautleyi †
- Canis cedazoensis ( ) †
- Canis dirus (Dire wolf), ( ) †
- Canis donnezani (4.0-3.1 Ma †, probably ancestor of wolves)
- Canis edwardii ( ) †, first species of wolf in North America)
- Canis (Eucyon) cipio (8.2 Mya †, probably first species of Canis genus)
- Canis etruscus (3.4 Mya †)
- Canis ferox ( ) †
- Canis gezi †
- Canis lepophagus ( )†
- Canis michauxi †
- Canis mosbachensis (0.787 Mya †)
- Canis nehringi †
- Genus Cynotherium †
- Genus Theriodictis ( )†
- Genus Protocyon †
- Genus Dusicyon †
- Genus Cerdocyon
- Genus Speothos
- Genus Nurocyon †
- Nurocyon chonokhariensis †
- Genus Xenocyon †
- Genus Canis
- Tribe Vulpini
- Basal Caninae
- First Caninae
- Tribe Phlaocyonini ( ) †
- Genus Cynarctoides ( ) †
- Genus Phlaocyon (30-19 Mya)
- Tribe Borophagini ( ) †
- Genus Cormocyon ( ) †
- Genus Desmocyon ( ) †
- Genus Metatomarctus ( ) †
- Genus Eulopocyon (18-16 Mya)
- Eulopocyon brachygnathus (16 Mya)
- Eulopocyon spissidens (18 Mya)
- Genus Psalidocyon (16 Mya)
- Psalidocyon marianae (16 Mya)
- Genus Microtomarctus ( ) †
- Genus Protomarctus (18 Mya)
- Protomarctus optatus (18 Mya)
- Genus Tephrocyon (16 Mya)
- Tephrocyon rurestris (16 Mya)
- Subtribe Cynarctina †
- Subtribe Aelurodontina ( ) †
- Subtribe Borophagina ( ) †
- Genus Paratomarctus ( ) †
- Genus Carpocyon ( ) †
- Genus Protepicyon (16 Mya)
- Protepicyon raki (16 Mya)
- Genus Epicyon ( ) †
- Genus Borophagus ( ) †
† (Mya = million years ago)
- Genus Cynodesmus (32-29 Mya)
- ?Genus Caedocyon
- Genus Ectopocynus (32-19 Mya)
- Genus Enhydrocyon (29-25 Mya)
- Genus Hesperocyon (39.74-34 Mya)
- Genus Mesocyon (34-29 Mya)
- Genus Osbornodon (32-18 Mya)
- Genus Paraenhydrocyon (30-25 Mya)
- Genus Philotrox (29 Mya)
- Philotrox condoni (29 Mya)
- Genus Prohesperocyon (36 Mya)
- Prohesperocyon wilsoni (36 Mya)
- Genus Sunkahetanka (29 Mya)
- Sunkahetanka geringensis (29 Mya)
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