Canids And Humans
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Canidae (; from Latin, '' canis'', "
dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
") is a biological family of dog-like
carnivora Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like and canidae, dog-like animals, and all descendants of that ancestor. Members of this group are f ...
ns, colloquially referred to as dogs, and constitutes a
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
. A member of this family is also called a canid (). There are three
subfamilies In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
found within the canid family, which are the extinct
Borophaginae The extinct Borophaginae form one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Hesperocyoninae and extant Caninae. Borophaginae, called "bone-crushing dogs", were endemic to North America du ...
and
Hesperocyoninae The extinct Hesperocyoninae are one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Borophaginae and extant Caninae. Taxonomic history Hesperocyoninae are basal canids that gave rise to the o ...
, and the extant Caninae. The Caninae are known as canines, and include
domestic dogs The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...
,
wolves The wolf (''Canis lupus''; plural, : wolves), also known as the gray wolf or grey wolf, is a large Canis, canine native to Eurasia and North America. More than thirty subspecies of Canis lupus, subspecies of ''Canis lupus'' have been reco ...
, coyotes,
fox Foxes are small to medium-sized, omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull, upright, triangular ears, a pointed, slightly upturned snout, and a long bushy tail (or ''brush''). Twelve sp ...
es,
jackals Jackals are medium-sized canids native to Africa and Eurasia. While the word "jackal" has historically been used for many canines of the subtribe canina, in modern use it most commonly refers to three species: the closely related black-backed ...
and other extant and extinct species. Canids are found on all continents except
Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
, having arrived independently or accompanied human beings over extended periods of time. Canids vary in size from the gray
wolf The wolf (''Canis lupus''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly u ...
to the 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, originated from a
symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or parasit ...
relationship with Upper Paleolithic humans and today remains one of the most widely kept
domestic animals This page gives a list of domesticated animals, also including a list of animals which are or may be currently undergoing the process of domestication and animals that have an extensive relationship with humans beyond simple predation. This includ ...
.


Taxonomy

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. This subfamily includes all living canids and their most recent fossil relatives. All living canids as a group form a dental
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
relationship with the extinct borophagines, with both groups having a
bicuspid The premolars, also called premolar Tooth (human), teeth, or bicuspids, are transitional teeth located between the Canine tooth, canine and Molar (tooth), molar teeth. In humans, there are two premolars per dental terminology#Quadrant, quadrant in ...
(two points) on the lower carnassial
talonid The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...
, which gives this tooth an additional ability in
mastication Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, th ...
. This, together with the development of a distinct
entoconid Many different terms have been proposed for features of the tooth crown in mammals. The structures within the molars receive different names according to their position and morphology. This nomenclature was developed by Henry Fairfield Osborn i ...
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 The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
canids and are the essential differences that identify their clade. The cat-like
feliform Feliformia is a suborder within the order Carnivora consisting of "cat-like" carnivorans, including cats (large and small), hyenas, mongooses, viverrids, and related taxa. Feliformia stands in contrast to the other suborder of Carnivora, Caniform ...
ia and dog-like caniforms emerged within the
Carnivoramorpha Carnivoramorpha ("carnivoran-like forms") is a clade of placental mammals that includes the modern order Carnivora and its extinct stem-relatives.Bryant, H.N., and M. Wolson (2004“Phylogenetic Nomenclature of Carnivoran Mammals.”''First Inter ...
around 45–42 Mya (million
year A year or annus is the orbital period of a planetary body, for example, the Earth, moving in its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the hou ...
s ago). The Canidae first appeared in North America during the
Late Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "daw ...
(37.8-33.9 Mya). They did not reach Eurasia until the
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
or to South America until the
Late Pliocene Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...
.


Phylogenetic relationships

This cladogram shows the phylogenetic position of canids within Caniformia, based on fossil finds:


Evolution

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 In biology, phylogenetics (; from Greek language, Greek wikt:φυλή, φυλή/wikt:φῦλον, φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary his ...
relationships. In some species, genetic divergence has been suppressed by the high level of
gene flow In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent a ...
between different populations and where the species have hybridized, large hybrid zones exist.


Eocene epoch

Carnivora Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like and canidae, dog-like animals, and all descendants of that ancestor. Members of this group are f ...
ns evolved after the
extinction Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
of the non-avian dinosaurs 66 million years ago. Around 50 million years ago, or earlier, in the
Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...
, the
carnivorans Carnivora is a monophyletic order of placental mammals consisting of the most recent common ancestor of all cat-like and dog-like animals, and all descendants of that ancestor. Members of this group are formally referred to as carnivorans, ...
split into two main divisions: caniforms (dog-like) and feliforms (cat-like). By 40 Mya, the first identifiable member of the dog family had arisen. Named ''
Prohesperocyon ''Prohesperocyon'' ("before ''Hesperocyon''") is an extinct genus of the first canid endemic to North America appearing during the Late Eocene around 36.6 mya ( AEO). Fossil distribution ''Prohesperocyon wilsoni'' was unearthed at the Airstri ...
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 Bulla (Latin, 'bubble') may refer to: Science and medicine * Bulla (dermatology), a bulla * Bulla, a focal lung pneumatosis, an air pocket in the lung * Auditory bulla, a hollow bony structure on the skull enclosing the ear * Ethmoid bulla, pa ...
(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
bear Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Nor ...
s. The canid family soon subdivided into three subfamilies, each of which diverged during the Eocene:
Hesperocyoninae The extinct Hesperocyoninae are one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Borophaginae and extant Caninae. Taxonomic history Hesperocyoninae are basal canids that gave rise to the o ...
(about 39.74–15 Mya),
Borophaginae The extinct Borophaginae form one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Hesperocyoninae and extant Caninae. Borophaginae, called "bone-crushing dogs", were endemic to North America du ...
(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. Members of each subfamily showed an increase in body mass with time and some exhibited specialized
hypercarnivorous A hypercarnivore is an animal which has a diet that is more than 70% meat, either via active predation or by scavenging. The remaining non-meat diet may consist of non-animal foods such as fungi, fruits or other plant material. Some extant exampl ...
diets that made them prone to extinction.


Oligocene epoch

By the
Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...
, 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 ''Mesocyon'' ("middle dog") is an extinct genus of the Hesperocyoninae subfamily of early canids native to North America. It lived from the Oligocene to Early Miocene, 30.3—20.3 Annum, Ma, existing for approximately . Fossils are known from Ore ...
'' of the Oligocene (38–24 Mya). These early canids probably evolved for the fast pursuit of prey in a grassland habitat; they resembled modern viverrids 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 ''Archaeocyon'' ("ancient dog") is an extinct genus of the Borophaginae subfamily of canids native to North America. It lived during the Oligocene epoch 32-24 Ma., existing for approximately . Species of ''Archaeocyon'' are among the earliest k ...
'' and ''
Leptocyon The genus ''Leptocyon'' (Greek: ''leptos'' slender + ''cyon'' dog) includes 11 species and was the first canine. They were small and weighed around . They first appeared in North America around 34 million years ago in the Oligocene at the same ...
''. These branches led to the borophagine and canine
radiations An evolutionary radiation is an increase in taxonomic diversity that is caused by elevated rates of speciation, that may or may not be associated with an increase in morphological disparity. Radiations may affect one clade or many, and be rapid ...
.Martin, L.D. 1989. Fossil history of the terrestrial carnivora. Pages 536–568 in J.L. Gittleman, editor. Carnivore Behavior, Ecology, and Evolution, Vol. 1. Comstock Publishing Associates: Ithaca.


Miocene epoch

Around 9–10 mya during the
Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...
, the '' Canis'', '' Urocyon'', and ''
Vulpes '' Vulpes '' is a genus of the sub-family Caninae. The members of this genus are colloquially referred to as true foxes, meaning they form a proper clade. The word "fox" occurs in the common names of all species of the genus, but also appears ...
'' genera expanded from southwestern
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
, where the canine radiation began. The success of these canines was related to the development of lower carnassials that were capable of both
mastication Chewing or mastication is the process by which food is crushed and ground by teeth. It is the first step of digestion, and it increases the surface area of foods to allow a more efficient break down by enzymes. During the mastication process, th ...
and shearing. Around 8 Mya, the
Beringia Beringia is defined today as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 72 degrees north latitude in the Chukchi Sea; and on the south by the tip ...
n land bridge allowed members of the genus ''
Eucyon ''Eucyon'' (Greek: : good, true; : dog) is an extinct genus of medium omnivorous coyote-like canid that first appeared in the Western United States during the late Middle Miocene 10 million years ago. It was the size of a jackal and weighed ...
'' a means to enter Asia and they continued on to colonize Europe.


Pliocene epoch

During the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Canis lepophagus ''Canis lepophagus'' (Latin: : 'dog'; : 'hare' or 'rabbit'; suffix : '-eating'; hence hare-eating dog) is an extinct species of canid which was endemic to much of North America during the Early Pliocene. It is notable because its lineage is prop ...
'' 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''. The formation of the
Isthmus of Panama The Isthmus of Panama ( es, Istmo de Panamá), also historically known as the Isthmus of Darien (), is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country ...
, about 3 Mya, joined
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
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 (''Aenocyon dirus''). The other lineage consisted of the so-called South American endemic species; the maned wolf (''Chrysocyon brachyurus''), the
short-eared dog The short-eared dog (''Atelocynus microtis''), also known as the short-eared zorro or small-eared dog,de la Rosa, Carlos L.; and Nocke, Claudia. A Guide to the Carnivores of Central America: Natural History, Ecology, and Conservation. Austin: Uni ...
(''Atelocynus microtis''), the
bush dog The bush dog (''Speothos venaticus'') is a canine found in Central and South America. In spite of its extensive range, it is very rare in most areas except in Suriname, Guyana and Peru; it was first identified by Peter Wilhelm Lund from fossils ...
(''Speothos venaticus''), the crab-eating fox (''Cerdocyon thous''), and the
South American fox The South American foxes (''Lycalopex''), commonly called ''raposa'' in Portuguese language, Portuguese, or ''zorro'' in Spanish language, Spanish, are a genus from South America of the subfamily Caninae. Despite their name, they are not Vulpes, ...
es (''Lycalopex'' spp.). The monophyly of this group has been established by molecular means.


Pleistocene epoch

During the
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
, the North American wolf line appeared, with ''
Canis edwardii ''Canis edwardii'', also known as Edward's wolf, is an extinct species of wolf in the genus ''Canis'' which was endemic to North America three million years ago from the Late Blancan stage of the Pliocene epoch and was extinct by the end of the I ...
'', clearly identifiable as a wolf, and ''
Canis rufus The red wolf (''Canis rufus'') is a canine native to the southeastern United States. Its size is intermediate between the coyote (''Canis latrans'') and gray wolf (''Canis lupus''). The red wolf's taxonomic classification as being a separate s ...
'' appeared, possibly a direct descendant of ''C. edwardii''. Around 0.8 Mya, ''
Canis ambrusteri Armbruster's wolf (''Canis armbrusteri'') is an extinct species that was endemic to North America and lived during the Irvingtonian stage of the Pleistocene epoch, spanning from 1.9 Mya—250,000 years BP.Mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...
, a number of subspecies of the gray wolf (''C. 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, with 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 gone extinct as a result of the extinction of the large herbivorous animals on whose carcasses it relied. 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 The African wolf (''Canis lupaster'') or golden wolf, formerly known as the African golden jackal, is a canine native to North Africa, West Africa, the Sahel, northern East Africa, and the Horn of Africa. It is listed as least concern on the IU ...
). According to a phylogeny derived from nuclear sequences, the Eurasian golden jackal (''Canis aureus'') diverged from the wolf/coyote lineage 1.9 
Mya Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese ...
, 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.


Wild canids are found on every continent except Antarctica, and inhabit a wide range of different habitats, including deserts,

mountains A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. Although definitions vary, a mountain may differ from a plateau in having a limited summit area, and is usually higher th ...
, forests, and
grassland A grassland is an area where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur natur ...
s. They vary in size from the fennec fox, which may be as little as in length and weigh , to the gray
wolf The wolf (''Canis lupus''; : wolves), also known as the gray wolf or grey wolf, is a large canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, and gray wolves, as popularly u ...
, which may be up to long, and can weigh up to .Heptner, V. G.; Naumov, N. P. (1998)
Mammals of the Soviet Union Vol. II Part 1a, Sirenia and Carnivora (Sea cows; Wolves and Bears)
Science Publishers, Inc. USA., pp. 166–176,
Only a few species are arboreal—the gray fox, the closely related
island fox The island fox (''Urocyon littoralis'') is a small fox that is endemic to six of the eight Channel Islands of California. There are six subspecies, each unique to the island it lives on, reflecting its evolutionary history. They are generally do ...
and the raccoon dog habitually climb trees. 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 dog breeds, 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 arch In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomati ...
es are wide, there is a transverse
lambdoidal The lambdoid suture (or lambdoidal suture) is a dense, fibrous connective tissue joint on the posterior aspect of the skull that connects the parietal bones with the occipital bone. It is continuous with the occipitomastoid suture. Structure Th ...
ridge at the rear of the
cranium The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
and in some species, a
sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptiona ...
running from front to back. The bony orbits around the eye never form a complete ring and the auditory bullae are smooth and rounded. Females have three to seven pairs of mammae. All canids are
digitigrade In terrestrial vertebrates, digitigrade () locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (metatarsals) touching the groun ...
, 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. The penis in male canids is supported by a
baculum The baculum (also penis bone, penile bone, or ''os penis'', ''os genitale'' or ''os priapi'') is a bone found in the penis of many placental mammals. It is absent from the human penis, but present in the penises of some primates, such as the ...
and contains a structure called the
bulbus glandis The bulbus glandis (also called a bulb or knot) is an erectile tissue structure on the penis of canid mammals. During mating, immediately before ejaculation the tissues swell up to lock ('' tie'') the male's penis inside the female. The locking i ...
, which creates a
copulatory tie Canine reproduction is the process of sexual reproduction in domestic dogs, wolves, coyotes and other canine species. Canine sexual anatomy and development Male reproductive system Erectile tissue As with all mammals, a dog's penis is made up of ...
that lasts for up to an hour during mating. 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 of the Borophaginae (such as ''
Aelurodon ''Aelurodon'' is an extinct canid genus of the subfamily Borophaginae which lived from the Barstovian land mammal age () of the middle Miocene to the late Miocene epoch ().
Dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolo ...
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 Canine may refer to: Zoology and anatomy * a dog-like Canid animal in the subfamily Caninae ** ''Canis'', a genus including dogs, wolves, coyotes, and jackals ** Dog, the domestic dog * Canine tooth, in mammalian oral anatomy People with the surn ...
, 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 Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified f ...
that are used together in a scissor-like action to shear the muscle and tendon of prey. 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 canid's dietary adaptation. On the lower carnassial, the
trigonid The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, ...
is used for slicing and the
talonid The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone to ...
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. Because of its low variability, the length of the lower carnassial is used to provide an estimate of a carnivore's body size. 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 The dingo (''Canis familiaris'', ''Canis familiaris dingo'', ''Canis dingo'', or ''Canis lupus dingo'') is an ancient (Basal (phylogenetics), basal) lineage of dog found in Australia (continent), Australia. Its taxonomic classification is de ...
(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. Most canids have 42
teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...
, 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 The bat-eared fox (''Otocyon megalotis'') is a species of fox found on the African savanna. It is the only extant species of the genus ''Otocyon'' and considered a basal canid species. Fossil records indicate this canid first appeared during th ...
has three or four upper molars and four lower ones. 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.


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. 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. 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 behavior is also mediated by secretions from glands on the upper surface of the tail near its root and from the
anal gland Anal may refer to: Related to the anus *Related to the anus of animals: ** Anal fin, in fish anatomy ** Anal vein, in insect anatomy ** Anal scale, in reptile anatomy *Related to the human anus: ** Anal sex, a type of sexual activity involving s ...
s,
preputial gland Preputial glands are exocrine glands that are located in the folds of skin front of the genitals of some mammals. They occur in several species, including mice, ferrets, rhinoceroses, and even-toed ungulates and produce pheromones. The glands play ...
s, and
supracaudal gland A Rhodesian Ridgeback (sex unknown) with "stud tail": the violet gland lost hair and appears as a dark dimple The violet gland or supracaudal gland is a gland located on the upper surface of the tail of certain mammals, including European badgers ...
s.


Reproduction

Canids as a group exhibit several reproductive traits that are uncommon among mammals as a whole. They are typically
monogamous Monogamy ( ) is a form of Dyad (sociology), dyadic Intimate relationship, relationship in which an individual has only one Significant other, partner during their lifetime. Alternately, only one partner at any one time (Monogamy#Serial monogamy, ...
, 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 Alloparenting (also referred to as alloparental care) is a term used to classify any form of parental care provided by an individual towards young that aren't its own direct offspring. These are often referred to as "non-descendant" young, even th ...
they can provide to help raise the next generation of offspring. Most canid species are spontaneous ovulators, although maned wolves are induced ovulators. During the proestral period, increased levels of estradiol make the female attractive to the male. There is a rise in
progesterone Progesterone (P4) is an endogenous steroid and progestogen sex hormone involved in the menstrual cycle, pregnancy, and embryogenesis of humans and other species. It belongs to a group of steroid hormones called the progestogens and is the m ...
during the estral phase when female is receptive. Following this, the level of estradiol 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
anestrus The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormones in most mammalian therian females. Estrous cycles start after sexual maturity in females and are interrupted by anestrous p ...
follows pregnancy or pseudo-pregnancy, there being only one oestral period during each breeding season. Small and medium-sized canids mostly have a
gestation Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...
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 Photoperiodism is the physiological reaction of organisms to the length of night or a dark period. It occurs in plants and animals. Plant photoperiodism can also be defined as the developmental responses of plants to the relative lengths of light a ...
stimulus breaks down under conditions of artificial lighting. 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. 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, entered into a partnership with humans a long time ago. The dog was the first domesticated species. The archaeological record shows the first undisputed dog remains buried beside humans 14,700 years ago, with disputed remains occurring 36,000 years ago. These dates imply that the earliest dogs arose in the time of human
hunter-gatherer A traditional hunter-gatherer or forager is a human living an ancestrally derived lifestyle in which most or all food is obtained by foraging, that is, by gathering food from local sources, especially edible wild plants but also insects, fungi, ...
s and not
agriculturists An agriculturist, agriculturalist, agrologist, or agronomist (abbreviated as agr.), is a professional in the science, practice, and management of agriculture and agribusiness. It is a regulated profession in Canada, India, the Philippines, the U ...
. 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. Among canids, only the gray wolf has widely been known to prey on humans. Nonetheless, at least two records of coyotes killing humans have been published, and at least two other reports of golden jackals killing children. 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. Canids such as the dhole are now
endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...
in the wild because of persecution, habitat loss, a depletion of ungulate prey species and transmission of diseases from domestic dogs.


See also

*
Largest wild canids This is a list of the species of Canidae ordered by average and maximum reported mass in the wild. It does not include canid hybrids or any domesticated animals. Only wild species of canids are included, all of which are described as species by ...
* Canid hybrid *
Free-ranging dog A free-ranging dog is a dog that is not confined to a yard or house. Free-ranging dogs include street dogs, village dogs, stray dogs, feral dogs, etc., and may be owned or unowned. The global dog population is estimated to be 900 million, of w ...


References


Bibliography

*


External links

* {{Authority control Mammal families Bartonian first appearances Extant Eocene first appearances Taxa named by Gotthelf Fischer von Waldheim