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Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual

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Fahey, B. and P. Myers 2000. "Canidae" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Canidae.html
Bridget Fahey, University of Michigan-Ann Arbor
Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Perception Channels: tactile ; chemical

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Fahey, B. and P. Myers 2000. "Canidae" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Canidae.html
Bridget Fahey, University of Michigan-Ann Arbor
Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Other Physical Features: endothermic ; bilateral symmetry

The Regents of the University of Michigan and its licensors
bibliographic citation
Fahey, B. and P. Myers 2000. "Canidae" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Canidae.html
Bridget Fahey, University of Michigan-Ann Arbor
Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Comprehensive Description

provided by EOL authors

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 ofthe 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 tohabitat 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)

Leo Shapiro
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provided by wikipedia EN

Canidae /ˈkænɪd/[2] (from Latin, canis, "dog") is a biological family of dog-like carnivorans. A member of this family is called a canid.[3] There are three subfamilies found within the canid family, which are the extinct Borophaginae and Hesperocyoninae, and the extant Caninae.[4] The Caninae are known as canines,[5] which includes domestic dogs, wolves, foxes and other extant and extinct species.

Canids are found on all continents except Antarctica, having arrived independently or accompanied human beings over extended periods of time. Canids vary in size from the 2-metre-long (6.6 ft) gray wolf to the 24-centimetre-long (9.4 in) 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 breeds, and a litter of young are reared annually in an underground den. Canids communicate by scent signals and vocalizations. One canid, the domestic dog, long ago entered into a partnership with humans and today remains one of the most widely kept domestic animals.


In the history of the carnivores, the family Canidae is represented by the two extinct subfamilies designated as Hesperocyoninae and Borophaginae, and the extant subfamily Caninae.[4] This subfamily includes all living canids and their most recent fossil relatives.[6] All living canids as a group form a dental monophyletic relationship with the extinct borophagines, with both groups having a bicuspid (two points) on the lower carnassial talonid, which gives this tooth an additional ability in mastication. This, together with the development of a distinct entoconid cusp and the broadening of the talonid of the first lower molar, and the corresponding enlargement of the talon of the upper first molar and reduction of its parastyle distinguish these late Cenozoic canids and are the essential differences that identify their clade.[6]:p6

The cat-like feliformia and dog-like caniforms emerged within the Carnivoramorpha Around 45–42 Mya (million years ago).[7] The caniforms included the fox-like genus Leptocyon, whose various species existed from 34 Mya before branching 11.9 Mya into Vulpini (foxes) and Canini (canines).[6]:174–5

Phylogenetic relationships

Indian wolf at Velavadar (Blackbuck National Park, Gujarat)
Skulls of various canid genera; Vulpes (corsac fox), Nyctereutes (raccoon dog), Cuon (dhole), and Canis (Eurasian golden jackal)

Within the Canidae, the results of allozyme and chromosome analyses have previously suggested several phylogenetic divisions:

  1. The wolf-like canids (genus Canis, Cuon, and Lycaon) include the domestic dog (Canis lupus familiaris), gray wolf (Canis lupus), red wolf (Canis rufus), eastern wolf (Canis lycaon), coyote (Canis latrans), Eurasian golden jackal (Canis aureus), African golden wolf (Canis anthus), Ethiopian wolf (Canis simensis), black-backed jackal (Canis mesomelas), side-striped jackal (Canis adustus), dhole (Cuon alpinus), and African wild dog (Lycaon pictus).[8]
  2. The fox-like canids include the kit fox (Vulpes velox), red fox (Vulpes vulpes), Cape fox (Vulpes chama), Arctic fox (Vulpes lagopus), and fennec fox (Vulpes zerda).[8]
  3. The South American canids include the bush dog (Speothos venaticus), hoary fox (Lycalopex uetulus), crab-eating fox (Cerdocyon thous), and maned wolf (Chrysocyon brachyurus).[8]
  4. Various monotypic taxa include the bat-eared fox (Otocyon megalotis), gray fox (Urocyon cinereoargenteus), and raccoon dog (Nyctereutes procyonoides).[8]

DNA analysis shows that the first three form monophyletic clades. The wolf-like canids and the South American canids together form the tribe Canini.[9] Molecular data imply a North American origin of living Canidae some 10 Mya 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 gray fox and island fox are basal to the other clades; however, this topological difference is not strongly supported.[10]

The cladogram below is based on the phylogeny of Lindblad-Toh et al. (2005),[10] modified to incorporate recent findings on Canis,[11] Vulpes,[12] Lycalopex,[13] and Dusicyon[14] species.

Canidae Caninae Canini Canina                

Canis lupus familiaris (domestic dog) Tibetan mastiff (transparent background).png


Canis lupus (gray wolf) Dogs, jackals, wolves, and foxes (Plate I).png


Canis latrans (coyote) Dogs, jackals, wolves, and foxes (Plate IX).png


Canis anthus (African golden wolf) Dogs, jackals, wolves, and foxes (Plate XI).png


Canis simensis (Ethiopian wolf) Dogs, jackals, wolves, and foxes (Plate VI).png


Canis aureus (Golden jackal) Dogs, jackals, wolves, and foxes (Plate X).png


Cuon alpinus (dhole) Dogs, jackals, wolves, and foxes (Plate XLI).png


Lycaon pictus (African wild dog) Dogs, jackals, wolves, and foxes (Plate XLIV).png


Canis adustus (side-striped jackal) Dogs, jackals, wolves, and foxes (Plate XIII).png


Canis mesomelas (black-backed jackal) Dogs, jackals, wolves, and foxes (Plate XII).png


Speothos venaticus (bush dog) Dogs, jackals, wolves, and foxes (Plate XLIII).png


Chrysocyon brachyurus (maned wolf) Dogs, jackals, wolves, and foxes (Plate VII).png


Dusicyon australis (Falkland Islands wolf)


Lycalopex vetulus (hoary fox) Dogs, jackals, wolves, and foxes (Plate XXXI).png


Lycalopex sechurae (Sechuran fox or Peruvian desert fox)


Lycalopex fulvipes (Darwin's fox)


Lycalopex gymnocercus (pampas fox) Dogs, jackals, wolves, and foxes (Plate XVII).png


Lycalopex griseus (South American gray fox or chilla)


Lycalopex culpaeus (culpeo or Andean fox) Dogs, jackals, wolves, and foxes (Plate XIV).png


Cerdocyon thous (crab-eating fox) Dogs, jackals, wolves, and foxes (Plate XV).png


Atelocynus microtis (short-eared dog) Dogs, jackals, wolves, and foxes (Plate XVI).png


Otocyon megalotis (bat-eared fox) Dogs, jackals, wolves, and foxes BHL19827472 white background.png


Nyctereutes procyonoides (raccoon dog) Dogs, jackals, wolves, and foxes (Plate XXXII).png


Vulpes zerda (fennec fox) Dogs, jackals, wolves, and foxes (Plate XXXVI).png


Vulpes cana (Blanford's fox) Blandford's fox.png


Vulpes chama (Cape fox) Dogs, jackals, wolves, and foxes (Plate XXXIII).png


Vulpes vulpes (red fox) Dogs, jackals, wolves, and foxes (Plate XXII).png


Vulpes rueppellii (Ruppell's fox) Dogs, jackals, wolves, and foxes (Plate XXXV).png


Vulpes corsac (corsac fox) Dogs, jackals, wolves, and foxes (Plate XXVII).png


Vulpes ferrilata (Tibetan sand fox) Tibetan sand fox illustration, transparent background.png


Vulpes macrotis (Kit fox) Dogs, jackals, wolves, and foxes (Plate XXV).png


Vulpes lagopus (Arctic fox) Dogs, jackals, wolves, and foxes (Plate XXVI).png


Urocyon littoralis (island fox) Vulpes littoralis transparent background.png


Urocyon cinereoargenteus (gray fox) Dogs, jackals, wolves, and foxes (Plate XX).png



The Canidae today 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 phylogenetics 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.[15]

Eocene epoch

Carnivorans evolved from miacoids about 55 Mya during the late Paleocene.[16] Some 5 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.[17]

The canid 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 are 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 specialized hypercarnivorous diets that made them prone to extinction.[18]:Fig. 1

Evolution of the canids
-65 —
-60 —
-55 —
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-40 —
-35 —
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-15 —
-10 —
-5 —
0 —
First Caninae
Modern-looking dogs
An approximate timescale of key events in canid evolution.
For precise dates, see text.
Axis scale: millions of years ago.

Oligocene epoch

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 members of the Hesperocyonines, the genus Hesperocyon, gave rise to Archaeocyon and Leptocyon. These branches led to the borophagine and canine radiations.[19]

Miocene epoch

Around 9–10 mya during the Late Miocene, the 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.[19] Around 8 Mya, the Beringian land bridge allowed members of the genus Eucyon a means to enter Asia and they continued on to colonize Europe.[20]

Pliocene epoch

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. C. latrans (the coyote) is theorized to have descended from C. lepophagus.[21]

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 more than one incursion across the new land bridge is likely. 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.[20]

Pleistocene epoch

During the Pleistocene, the North American wolf line appeared, with Canis edwardii, clearly identifiable as a wolf, and Canis rufus appeared, possibly a direct descendant of C. 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.[22]

By 0.3 Mya, a number of subspecies of the gray wolf (C. lupus) had developed and had spread throughout Europe and northern Asia.[23] The gray wolf colonized North America during the late Rancholabrean era across the Bering land bridge, with at least three separate invasions, with each one consisting of one or more different Eurasian gray wolf clades.[24] MtDNA studies have shown that there are at least four extant C. lupus lineages.[25] 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 gone extinct as a result of the extinction of the large herbivorous animals on whose carcasses it relied.[22]

In 2015, a study of mitochondrial genome sequences and whole-genome nuclear sequences of African and Eurasian canids indicated that extant wolf-like canids have colonized Africa from Eurasia at least five times throughout the Pliocene and Pleistocene, which is consistent with fossil evidence suggesting that much of African canid fauna diversity resulted from the immigration of Eurasian ancestors, likely coincident with Plio-Pleistocene climatic oscillations between arid and humid conditions. When comparing the African and Eurasian golden jackals, the study concluded that the African specimens represented a distinct monophyletic lineage that should be recognized as a separate species, Canis anthus (African golden wolf). According to a phylogeny derived from nuclear sequences, the Eurasian golden jackal (Canis aureus) diverged from the wolf/coyote lineage 1.9 Mya, but the African golden wolf separated 1.3 Mya. Mitochondrial genome sequences indicated the Ethiopian wolf diverged from the wolf/coyote lineage slightly prior to that.[11]:S1


Comparative illustration of the paws of gray wolf, Eurasian golden jackal, and dhole by A. N. Komarov

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, which may be as little as 24 cm (9.4 in) in length and weigh 0.6 kg (1.3 lb),[26] to the gray wolf, which may be up to 160 cm (5.2 ft) long, and can weigh up to 79 kg (174 lb).[27] Only a few species are arboreal—the gray fox, the closely related island fox[28] and the raccoon dog habitually climb trees.[29][30][31]

All canids have a similar basic form, as exemplified by the gray wolf, although the relative length of muzzle, limbs, ears, and tail vary considerably between species. With the exceptions of the bush dog, the 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 vary 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.[32] Females have three to seven pairs of mammae.[33]

Skeleton of a black-backed jackal (Canis mesomelas) on display at the Museum of Osteology

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 the year. With the exception of the four-toed African wild dog (Lycaon pictus), five toes are on the forefeet, but the pollex (thumb) is reduced and does not reach the ground. On the hind feet 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 not retractile and more-or-less blunt.[32]

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.[34] Young canids are born blind, with their eyes opening a few weeks after birth.[35] All living canids (Caninae) have a ligament analogous to the nuchal ligament of ungulates used to maintain the posture of the head and neckwith 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 of the Borophaginae (such as Aelurodon) are believed to have lacked this ligament.[36]


Diagram of a wolf skull with key features labelled

Dentition relates to the arrangement of teeth in the mouth, with the dental notation for the upper-jaw teeth using the upper-case letters I to denote incisors, C for canines, P for premolars, and M for molars, and the lower-case letters i, c, p and m to denote the mandible teeth. Teeth are numbered using one side of the mouth and from the front of the mouth to the back. In carnivores, the upper premolar P4 and the lower molar m1 form the carnassials that are used together in a scissor-like action to shear the muscle and tendon of prey.[37]

Canids use their premolars for cutting and crushing except for the upper fourth premolar P4 (the upper carnassial) that is only used for cutting. They use their molars for grinding except for the lower first molar m1 (the lower carnassial) that has evolved for both cutting and grinding depending on the candid's dietary adaptation. On the lower carnassial, the trigonid is used for slicing and the talonid is used for grinding. The ratio between the trigonid and the talonid indicates a carnivore's dietary habits, with a larger trigonid indicating a hypercarnivore and a larger talonid indicating a more omnivorous diet.[38][39] Because of its low variability, the length of the lower carnassial is used to provide an estimate of a carnivore's body size.[38]

A study of the estimated bite force at the canine teeth of a large sample of living and fossil mammalian predators, when adjusted for their body mass, found that for placental mammals the bite force at the canines was greatest in the extinct dire wolf (163), followed among the modern canids by the four hypercarnivores that often prey on animals larger than themselves: the African wild dog (142), the gray wolf (136), the dhole (112), and the dingo (108). The bite force at the carnassials showed a similar trend to the canines. A predator's largest prey size is strongly influenced by its biomechanical limits.[40]

Most canids have 42 teeth, with a dental formula of: The bush dog has 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.[32] 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, molars being completely absent.[32]

Life history

Social behavior

Almost all canids are social animals and live together in groups. In general, they are territorial or have a home range and sleep in the open, using their dens only for breeding and sometimes in bad weather.[41] 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 20 to 40 animals and packs of fewer than about seven individuals may be incapable of successful reproduction.[42] 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.[43]

Red foxes barking in Pinbury Park, Gloucestershire, England.

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.[44] Social behavior is also mediated by secretions from glands on the upper surface of the tail near its root and from the anal glands.[43]


A feral dog from Sri Lanka nursing her puppies

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 dioestral 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.[45]

During the proestral period, increased levels of oestradiol 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 oestradiol fluctuates and there is a lengthy dioestrous 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 50 to 60 days, while larger species average 60 to 65 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.[45]

The size of a litter varies, with from one to 16 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.[32] 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.[46] Young canids may take a year to mature and learn the skills they need to survive.[47] 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.[48]

Canids and humans

Traditional English fox hunt

One canid, the domestic dog, entered into a partnership with humans a long time ago. The dog was the first domesticated species.[49][50][51][52] The archaeological record shows the first undisputed dog remains buried beside humans 14,700 years ago,[53] with disputed remains occurring 36,000 years ago.[54] These dates imply that the earliest dogs arose in the time of human hunter-gatherers and not agriculturists.[55][56]

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 may have evolved together.[57]

Among canids, only the gray wolf has widely been known to prey on humans.[58] Nonetheless, at least two records of coyotes killing humans have been published,[59] and at least two other reports of golden jackals killing children.[60] Human beings have trapped and hunted some canid species for their fur and some, especially the gray wolf, the coyote and the red fox, for sport.[61] 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.[62]

See also


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Canidae: Brief Summary

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Canidae /ˈkænɪdiː/ (from Latin, canis, "dog") is a biological family of dog-like carnivorans. A member of this family is called a canid. There are three subfamilies found within the canid family, which are the extinct Borophaginae and Hesperocyoninae, and the extant Caninae. The Caninae are known as canines, which includes domestic dogs, wolves, foxes and other extant and extinct species.

Canids are found on all continents except Antarctica, having arrived independently or accompanied human beings over extended periods of time. Canids vary in size from the 2-metre-long (6.6 ft) gray wolf to the 24-centimetre-long (9.4 in) 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 breeds, and a litter of young are reared annually in an underground den. Canids communicate by scent signals and vocalizations. One canid, the domestic dog, long ago entered into a partnership with humans and today remains one of the most widely kept domestic animals.

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