Dog

Dog

Overview
The domestic dog is a domesticated form of the gray wolf
Gray Wolf
The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...

, a member of the Canidae
Canidae
Canidae is the biological family of carnivorous and omnivorous mammals that includes wolves, foxes, jackals, coyotes, and domestic dogs. A member of this family is called a canid . The Canidae family is divided into two tribes: Canini and Vulpini...

 family of the order Carnivora
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...

. The term is used for both feral
Feral
A feral organism is one that has changed from being domesticated to being wild or untamed. In the case of plants it is a movement from cultivated to uncultivated or controlled to volunteer. The introduction of feral animals or plants to their non-native regions, like any introduced species, may...

 and pet
Pet
A pet is a household animal kept for companionship and a person's enjoyment, as opposed to wild animals or to livestock, laboratory animals, working animals or sport animals, which are kept for economic or productive reasons. The most popular pets are noted for their loyal or playful...

 varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working
Working dog
A working dog refers to a canine working animal, i.e., a type of dog that is not merely a pet but learns and performs tasks to assist and/or entertain its human companions, or a breed of such origin...

, hunting
Hunting
Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...

, and companion animal in human history. The word "dog" may also mean the male of a canine species, as opposed to the word "bitch" for the female of the species.

Dogs were domesticated from gray wolves about 15,000 years ago.
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Encyclopedia
The domestic dog is a domesticated form of the gray wolf
Gray Wolf
The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...

, a member of the Canidae
Canidae
Canidae is the biological family of carnivorous and omnivorous mammals that includes wolves, foxes, jackals, coyotes, and domestic dogs. A member of this family is called a canid . The Canidae family is divided into two tribes: Canini and Vulpini...

 family of the order Carnivora
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...

. The term is used for both feral
Feral
A feral organism is one that has changed from being domesticated to being wild or untamed. In the case of plants it is a movement from cultivated to uncultivated or controlled to volunteer. The introduction of feral animals or plants to their non-native regions, like any introduced species, may...

 and pet
Pet
A pet is a household animal kept for companionship and a person's enjoyment, as opposed to wild animals or to livestock, laboratory animals, working animals or sport animals, which are kept for economic or productive reasons. The most popular pets are noted for their loyal or playful...

 varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working
Working dog
A working dog refers to a canine working animal, i.e., a type of dog that is not merely a pet but learns and performs tasks to assist and/or entertain its human companions, or a breed of such origin...

, hunting
Hunting
Hunting is the practice of pursuing any living thing, usually wildlife, for food, recreation, or trade. In present-day use, the term refers to lawful hunting, as distinguished from poaching, which is the killing, trapping or capture of the hunted species contrary to applicable law...

, and companion animal in human history. The word "dog" may also mean the male of a canine species, as opposed to the word "bitch" for the female of the species.

Dogs were domesticated from gray wolves about 15,000 years ago. Their value to early human settlements led to them quickly becoming ubiquitous across world cultures. Dogs perform many roles for people, such as hunting
Hunting dog
A hunting dog refers to any dog who assists humans in hunting. There are several types of hunting dogs developed for various tasks. The major categories of hunting dogs include hounds, terriers, dachshunds, cur type dogs, and gun dogs...

, herding
Herding dog
A herding dog, also known as a stock dog or working dog, is a type of pastoral dog that either has been trained in herding or belongs to breeds developed for herding...

, pulling loads
Sled dog
Sled dogs, known also as sleigh man dogs, sledge dogs, or sleddogs, are highly trained types of dogs that are used to pull a dog sled, a wheel-less vehicle on runners also called a sled or sleigh, over snow or ice, by means of harnesses and lines.Sled dogs have become a popular winter recreation...

, protection
Guard dog
A guard dog, an attack dog or watch dog is a dog used to guard against, and watch for, unwanted or unexpected people or animals. The dog is discriminating so that it does not annoy or attack familiar people.-Barking:...

, assisting police
Police dog
A police dog, often referred to as a "K-9 dog" in some areas , is a dog that is trained specifically to assist police and other law-enforcement personnel in their work...

 and military
Dogs in warfare
Dogs in warfare have a long history starting in ancient times. From 'war dogs' trained in combat to their use as scouts, sentries and trackers, their uses have been varied and some continue to exist in modern military usage.-History:...

, companionship
Pet
A pet is a household animal kept for companionship and a person's enjoyment, as opposed to wild animals or to livestock, laboratory animals, working animals or sport animals, which are kept for economic or productive reasons. The most popular pets are noted for their loyal or playful...

, and, more recently, aiding handicapped individuals
Service dog
A service dog is a type of assistance dog specifically trained to help people who have disabilities including visual or hearing impairment, and also to help people with mental disabilities including Post Traumatic Stress Disorder and severe depression...

. This impact on human society has given them the nickname "Man's Best Friend" in the Western world. In 2001, there were estimated to be 400 million dogs in the world.

Over the 15,000-year span in which the dog has been domesticated, it has diverged into only a handful of landrace
Landrace
A landrace is a local variety of a domesticated animal or plant species which has developed largely by natural processes, by adaptation to the natural and cultural environment in which it lives. It differs from a formal breed which has been bred deliberately to conform to a particular standard...

s, groups of similar animals whose morphology
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 and behavior have been shaped by environmental factor
Environmental factor
Environmental factor or ecological factor or ecofactor is any factor, abiotic or biotic, that influences living organisms.- Environmental factors inducing diseases :...

s and functional roles. Through selective breeding
Artificial selection
Artificial selection describes intentional breeding for certain traits, or combination of traits. The term was utilized by Charles Darwin in contrast to natural selection, in which the differential reproduction of organisms with certain traits is attributed to improved survival or reproductive...

 by humans, the dog has developed into hundreds of varied breeds
Dog breed
Dog breeds are groups of closely related and visibly similar domestic dogs, which are all of the subspecies Canis lupus familiaris, having characteristic traits that are selected and maintained by humans, bred from a known foundation stock....

, and shows more behavioral and morphological variation than any other land mammal. For example, height measured to the withers
Withers
The withers is the ridge between the shoulder blades of a four-legged animal. In many species it is the tallest point of the body, and in horses and dogs it is the standard place to measure the animal's height .-Horses:The withers in horses are formed by the dorsal spinal processes of roughly the...

 ranges from a few inches in the Chihuahua
Chihuahua (dog)
The ' is the smallest breed of dog and is so named for the state of Chihuahua in Mexico. Chihuahuas come in a wide variety of sizes, head shapes, colors and coat lengths.-History:...

 to a few feet in the Irish Wolfhound
Irish Wolfhound
The Irish wolfhound is a breed of domestic dog , specifically a sighthound. The name originates from its purpose rather than from its appearance...

; color varies from white through grays (usually called "blue") to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patterns; coats
Coat (dog)
The coat of the domestic dog refers to the hair that covers its body. A dog's coat may be a double coat, made up of a soft undercoat and a coarser topcoat, or a single coat, which lacks an undercoat...

 can be short or long, coarse-haired to wool-like, straight, curly, or smooth. It is common for most breeds to shed
Moult
In biology, moulting or molting , also known as sloughing, shedding, or for some species, ecdysis, is the manner in which an animal routinely casts off a part of its body , either at specific times of year, or at specific points in its life cycle.Moulting can involve the epidermis , pelage...

 this coat.

Etymology and related terminology


Dog is the common use term that refers to members of the subspecies Canis lupus familiaris (canis, "dog"; lupus, "wolf"; familiaris, "of a household" or "domestic"). The term can also be used to refer to a wider range of related species, such as the members of the genus Canis, or "true dogs", including the wolf, coyote
Coyote
The coyote , also known as the American jackal or the prairie wolf, is a species of canine found throughout North and Central America, ranging from Panama in the south, north through Mexico, the United States and Canada...

, and jackal
Jackal
Although the word jackal has been historically used to refer to many small- to medium-sized species of the wolf genus of mammals, Canis, today it most properly and commonly refers to three species: the black-backed jackal and the side-striped jackal of sub-Saharan Africa, and the golden jackal of...

s; or it can refer to the members of the tribe
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...

 Canini, which would also include the African wild dog
African Wild Dog
Lycaon pictus is a large canid found only in Africa, especially in savannas and lightly wooded areas. It is variously called the African wild dog, African hunting dog, Cape hunting dog, painted dog, painted wolf, painted hunting dog, spotted dog, or ornate wolf...

; or it can be used to refer to any member of the family Canidae, which would also include the fox
Fox
Fox is a common name for many species of omnivorous mammals belonging to the Canidae family. Foxes are small to medium-sized canids , characterized by possessing a long narrow snout, and a bushy tail .Members of about 37 species are referred to as foxes, of which only 12 species actually belong to...

es, bush dog
Bush Dog
The bush dog is a canid found in Central and South America, including Panama, Colombia, Venezuela, Bolivia, Peru , Ecuador, the Guianas, Paraguay, northeast Argentina and Brazil...

, raccoon dog
Raccoon Dog
The raccoon dog , also known as the magnut or tanuki, is a canid indigenous to east Asia. It is the only extant species in the genus Nyctereutes...

, and others. Some members of the family have "dog" in their common names, such as the raccoon dog and the African wild dog. A few animals have "dog" in their common names but are not canids, such as the prairie dog
Prairie dog
Prairie dogs are burrowing rodents native to the grasslands of North America. There are five different species of prairie dogs: black-tailed, white-tailed, Gunnison's, Utah and Mexican prairie dogs. They are a type of ground squirrel, found in the United States, Canada and Mexico...

.

The English word dog comes from Middle English
Middle English
Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

 dogge, from Old English docga, a "powerful dog breed". The term may derive from Proto-Germanic *dukkōn, represented in Old English finger-docce ("finger-muscle"). The word also shows the familiar petname diminutive
Diminutive
In language structure, a diminutive, or diminutive form , is a formation of a word used to convey a slight degree of the root meaning, smallness of the object or quality named, encapsulation, intimacy, or endearment...

 -ga also seen in frogga "frog", picga "pig", stagga "stag", wicga "beetle, worm", among others. Due to the archaic structure of the word, the term dog may ultimately derive from the earliest layer of Proto-Indo-European vocabulary, reflecting the role of the dog as the earliest domesticated animal.

Mbabaram
Mbabaram language
Mbabaram is an extinct Australian Aboriginal language of north Queensland. It was the traditional language of the Mbabaram tribe. Known speakers were Albert Bennett, Alick Chalk, Jimmy Taylor and Mick Burns. Recordings of Bennett and Chalk are held in the Audiovisual Archive of the Australian...

 is famous in linguistic circles for a striking coincidence in its vocabulary to English. When linguist R. M. W. Dixon
R. M. W. Dixon
Robert Malcolm Ward Dixon is a Professor of Linguistics at The Cairns Institute, James Cook University, Queensland, and formerly Director of the Research Centre for Linguistic Typology at La Trobe University, Melbourne, Australia.In 1996, Dixon and another linguist, Alexandra Aikhenvald,...

 began his study of the language by eliciting a few basic nouns among the first of these was the word for "dog" which coincidentally in Mbabaram is dog. The Mbabaram word for "dog" really is pronounced almost identically to the English word (compare true cognates such as Yidiny gudaga, Dyirbal guda, Djabugay gurraa and Guugu Yimidhirr gudaa, for example). The similarity is a complete coincidence: there is no discernible relationship between English and Mbabaram. This and other false cognates are often cited as a caution against deciding that languages are related based on a small number of comparisons.

In 14th-century England, hound
Hound
A hound is a type of dog that assists hunters by tracking or chasing the animal being hunted. It can be contrasted with the gun dog, which assists hunters by identifying the location of prey, and with the retriever, which recovers shot quarry...

(from ) was the general word for all domestic canines, and dog referred to a subtype of hound, a group including the mastiff. It is believed this "dog" type of "hound" was so common it eventually became the prototype of the category “hound”. By the 16th century, dog had become the general word, and hound had begun to refer only to types used for hunting. Hound, cognate to German Hund, Dutch hond, common Scandinavian hund, and Icelandic hundur, is ultimately derived from the Proto-Indo-European *kwon- "dog", found in Welsh
Welsh language
Welsh is a member of the Brythonic branch of the Celtic languages spoken natively in Wales, by some along the Welsh border in England, and in Y Wladfa...

 ci (plural cwn), Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 canis, Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 kýōn, Lithuanian
Lithuanian language
Lithuanian is the official state language of Lithuania and is recognized as one of the official languages of the European Union. There are about 2.96 million native Lithuanian speakers in Lithuania and about 170,000 abroad. Lithuanian is a Baltic language, closely related to Latvian, although they...

 šuõ.

In breeding circles, a male canine is referred to as a dog, while a female is called a bitch (Middle English bicche, from Old English bicce, ultimately from Old Norse bikkja). A group of offspring is a litter
Litter (animal)
A litter is the offspring at one birth of animals from the same mother and usually from one set of parents. The word is most often used for the offspring of mammals, but can be used for any animal that gives birth to multiple young. In comparison, a group of eggs and the offspring that hatch from...

. The father of a litter is called the sire, and the mother is called the dam. Offspring are, in general, called pups or puppies
Puppy
A puppy is a juvenile dog. Some puppies may weigh , while larger ones can weigh up to . All healthy puppies grow quickly after birth. A puppy's coat color may change as the puppy grows older, as is commonly seen in breeds such as the Yorkshire Terrier...

, from French poupée, until they are about a year old. The process of birth is whelping, from the Old English word hwelp (cf. German Welpe, Dutch welp, Swedish valpa, Icelandic hvelpur).

Taxonomy


The domestic dog was originally classified as Canis familiaris and Canis familiarus domesticus by Carolus Linnaeus in 1758, and was reclassified in 1993 as Canis lupus familiaris, a subspecies of the gray wolf Canis lupus, by the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...

 and the American Society of Mammalogists
American Society of Mammalogists
The American Society of Mammalogists was founded in 1919. Its primary purpose is to encourage the study of mammals and professions studying mammals. There are over 4,500 members of this society, and they are primarily professional scientists who emphasize the importance of public policy and...

. Overwhelming evidence from behavior, vocalizations, morphology, and molecular biology
Molecular biology
Molecular biology is the branch of biology that deals with the molecular basis of biological activity. This field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry...

 led to the contemporary scientific understanding that a single species, the gray wolf, is the common ancestor
Common descent
In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor....

 for all breeds of domestic dogs; however, the timeframe and mechanisms by which dogs diverged are controversial. Canis lupus familiaris is listed as the name for the taxon that is broadly used in the scientific community and recommended by ITIS
Itis
Itis may refer to* Integrated Taxonomic Information System, a partnership designed to provide consistent and reliable information on the taxonomy of biological species...

; Canis familiaris, however, is a recognised synonym.

History and evolution


Domestic dogs inherited complex behaviors from their wolf ancestors, being pack hunter
Pack hunter
A pack hunter is a predator belonging to the animal kingdom, which has evolved to hunt its prey by working together with other members of its species. Normally, such animals are closely related. The most commonly known pack hunter is the Gray Wolf, the ancestor of all breeds of domesticated dogs...

s with complex body language. These sophisticated forms of social cognition and communication may account for their trainability, playfulness, and ability to fit into human households and social situations, and these attributes have given dogs a relationship with humans that has enabled them to become one of the most successful species on the planet today.

Although experts largely disagree over the details of dog domestication, it is agreed that human interaction played a significant role in shaping the subspecies. Shortly after domestication, dogs became ubiquitous in human populations, and spread throughout the world. Emigrants from Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...

 likely crossed the Bering Strait
Bering Strait
The Bering Strait , known to natives as Imakpik, is a sea strait between Cape Dezhnev, Chukotka Autonomous Okrug, Russia, the easternmost point of the Asian continent and Cape Prince of Wales, Alaska, USA, the westernmost point of the North American continent, with latitude of about 65°40'N,...

 with dogs in their company, and some experts suggest the use of sled dogs may have been critical to the success of the waves that entered North America roughly 12,000 years ago, although the earliest archaeological evidence of dog-like canids in North America dates from about 9,000 years ago. Dogs were an important part of life for the Athabascan
Athabaskan languages
Athabaskan or Athabascan is a large group of indigenous peoples of North America, located in two main Southern and Northern groups in western North America, and of their language family...

 population in North America, and were their only domesticated animal. Dogs also carried much of the load in the migration of the Apache
Apache
Apache is the collective term for several culturally related groups of Native Americans in the United States originally from the Southwest United States. These indigenous peoples of North America speak a Southern Athabaskan language, which is related linguistically to the languages of Athabaskan...

 and Navajo
Navajo people
The Navajo of the Southwestern United States are the largest single federally recognized tribe of the United States of America. The Navajo Nation has 300,048 enrolled tribal members. The Navajo Nation constitutes an independent governmental body which manages the Navajo Indian reservation in the...

 tribes 1,400 years ago. Use of dogs as pack animal
Pack animal
A pack animal or beast of burden is a working animal used by humans as means of transporting materials by attaching them so their weight bears on the animal's back; the term may be applied to either an individual animal or a species so employed...

s in these cultures often persisted after the introduction of the horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...

 to North America.

The current consensus among biologists and archaeologists is that the dating of first domestication is indeterminate. There is conclusive evidence dogs genetically diverged from their wolf ancestors at least 15,000 years ago, but some believe domestication to have occurred earlier. It is not known whether humans domesticated the wolf as such to initiate dog's divergence from its ancestors, or whether dog's evolutionary path had already taken a different course prior to domestication. For example, it is hypothesized that some wolves gathered around the campsites of paleolithic camps to scavenge refuse, and associated evolutionary pressure developed that favored those who were less frightened by, and keener in approaching, humans.

The bulk of the scientific evidence for the evolution of the domestic dog stems from archaeological findings and mitochondrial DNA
Mitochondrial DNA
Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

 studies. The divergence date of roughly 15,000 years ago is based in part on archaeological evidence that demonstrates the domestication of dogs occurred more than 15,000 years ago, and some genetic evidence indicates the domestication of dogs from their wolf ancestors began in the late Upper Paleolithic
Upper Paleolithic
The Upper Paleolithic is the third and last subdivision of the Paleolithic or Old Stone Age as it is understood in Europe, Africa and Asia. Very broadly it dates to between 40,000 and 10,000 years ago, roughly coinciding with the appearance of behavioral modernity and before the advent of...

 close to the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....

/Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

 boundary, between 17,000 and 14,000 years ago. But there is a wide range of other, contradictory findings that make this issue controversial.

Archaeological evidence suggests the latest dogs could have diverged from wolves was roughly 15,000 years ago, although it is possible they diverged much earlier. In 2008, a team of international scientists released findings from an excavation at Goyet Cave in Belgium declaring a large, toothy canine existed 31,700 years ago and ate a diet of horse, musk ox
Musk Ox
The muskox is an Arctic mammal of the family Bovidae, noted for its thick coat and for the strong odor emitted by males, from which its name derives. This musky odor is used to attract females during mating season...

 and reindeer.

Prior to this Belgian discovery, the earliest dog fossils were two large skulls from Russia and a mandible
Mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

 from Germany dated from roughly 14,000 years ago. Remains of smaller dogs from Natufian
Natufian culture
The Natufian culture was a Mesolithic culture that existed from 12,500 to 9,500 BC in the Levant, a region in the Eastern Mediterranean. It was unusual in that it was sedentary, or semi-sedentary, before the introduction of agriculture...

 cave deposits in the Middle East, including the earliest burial of a human being with a domestic dog, have been dated to around 10,000 to 12,000 years ago. There is a great deal of archaeological evidence for dogs throughout Europe and Asia around this period and through the next two thousand years (roughly 8,000 to 10,000 years ago), with fossils uncovered in Germany, the French Alps, and Iraq, and cave painting
Cave painting
Cave paintings are paintings on cave walls and ceilings, and the term is used especially for those dating to prehistoric times. The earliest European cave paintings date to the Aurignacian, some 32,000 years ago. The purpose of the paleolithic cave paintings is not known...

s in Turkey. The oldest remains of a domesticated dog in the Americas were found in Texas and have been dated to about 9,400 years ago.

DNA studies


DNA studies have provided a wide range of possible divergence dates, from 15,000 to 40,000 years ago, to as much as 100,000 to 140,000 years ago. These results depend on a number of assumptions. Genetic studies are based on comparisons of genetic diversity
Genetic diversity
Genetic diversity, the level of biodiversity, refers to the total number of genetic characteristics in the genetic makeup of a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary....

 between species, and depend on a calibration date. Some estimates of divergence dates from DNA evidence use an estimated wolf-coyote divergence date of roughly 700,000 years ago as a calibration. If this estimate is incorrect, and the actual wolf-coyote divergence is closer to one or two million years ago, or more, then the DNA evidence that supports specific dog-wolf divergence dates would be interpreted very differently.

Furthermore, it is believed the genetic diversity of wolves has been in decline for the last 200 years, and that the genetic diversity of dogs has been reduced by selective breeding
Selective breeding
Selective breeding is the process of breeding plants and animals for particular genetic traits. Typically, strains that are selectively bred are domesticated, and the breeding is sometimes done by a professional breeder. Bred animals are known as breeds, while bred plants are known as varieties,...

. This could significantly bias DNA analyses to support an earlier divergence date. The genetic evidence for the domestication event occurring in East Asia is also subject to violations of assumptions. These conclusions are based on the location of maximal genetic divergence
Genetic divergence
Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes through time, often after the populations have become reproductively isolated for some period of time...

, and assume hybridization does not occur, and that breeds remain geographically localized. Although these assumptions hold for many species, there is good reason to believe that they do not hold for canines.

Genetic analyses indicate all dogs are likely descended from a handful of domestication events with a small number of founding females, although there is evidence domesticated dogs interbred with local populations
Introgression
Introgression, also known as introgressive hybridization, in genetics is the movement of a gene from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species...

 of wild wolves on several occasions. Data suggest dogs first diverged from wolves in East Asia, and these domesticated dogs then quickly migrated throughout the world, reaching the North American continent around 8000 BC. The oldest groups of dogs, which show the greatest genetic variability
Genetic variability
Genetic variability is a measure of the tendency of individual genotypes in a population to vary from one another. Variability is different from genetic diversity, which is the amount of variation seen in a particular population. The variability of a trait describes how much that trait tends to...

 and are the most similar to their wolf ancestors, are primarily Asian and African breeds, including the Basenji
Basenji
The Basenji is a breed of hunting dog that was bred from stock originating in central Africa. Most of the major kennel clubs in the English-speaking world place the breed in the Hound Group; more specifically, it may be classified as belonging to the sighthound type...

, Lhasa Apso
Lhasa Apso
The Lhasa Apso is a non-sporting dog breed originating in Tibet. It was bred as an interior sentinel in the Buddhist monasteries, who alerted the monks to any intruders who entered...

, and Siberian Husky
Siberian Husky
The Siberian Husky is a medium-size, dense-coat working dog breed that originated in north-eastern Siberia. The breed belongs to the Spitz genetic family...

. Some breeds thought to be very old, such as the Pharaoh Hound
Pharaoh Hound
The Pharaoh Hound is a breed of dog and the national hound of the Mediterranean nation of Malta. Its native name is Kelb tal-Fenek in Maltese, which means "rabbit hound". The dog is the traditional hunting companion of Maltese outdoorsmen. The breed has no conclusive links with Ancient Egypt and...

, Ibizan Hound
Ibizan Hound
The Ibizan Hound , pronounced "I-bee-zan" or "I-beeth-an", is a lean, agile dog of the hound family. There are two hair types of the breed: smooth and wire. The more commonly seen type is the smooth...

, and Norwegian Elkhound
Norwegian Elkhound
The Norwegian Elkhound is one of the ancient Northern Spitz-type breed of dog and is the National Dog of Norway. The Elkhound has served as a hunter, guardian, herder, and defender. In a land of subzero temperatures, deep snow, thick forests, and rugged mountains, only the hardiest of the breeds...

, are now known to have been created more recently.

There is a great deal of controversy surrounding the evolutionary framework for the domestication of dogs. Although it is widely claimed that "man domesticated the wolf," man may not have taken such a proactive role in the process. The nature of the interaction between man and wolf that led to domestication is unknown and controversial. At least three early species of the Homo genus began spreading out of Africa roughly 400,000 years ago, and thus lived for a considerable time in contact with canine species. Despite this, there is no evidence of any adaptation of canine species to the presence of the close relatives of modern man. If dogs were domesticated, as believed, roughly 15,000 years ago, the event (or events) would have coincided with a large expansion in human territory and the development of agriculture. This has led some biologists to suggest one of the forces that led to the domestication of dogs was a shift in human lifestyle in the form of established human settlements. Permanent settlements would have coincided with a greater amount of disposable food and would have created a barrier between wild and anthropogenic canine populations.

Roles with humans



Early roles


Wolves, and their dog descendants, would have derived significant benefits from living in human camps—more safety, more reliable food, lesser caloric needs, and more chance to breed. They would have benefited from humans’ upright gait that gives them larger range over which to see potential predators and prey, as well as color vision that, at least by day, gives humans better visual discrimination. Camp dogs would also have benefitted from human tool use, as in bringing down larger prey and controlling fire for a range of purposes.

Humans would also have derived enormous benefit from the dogs associated with their camps. For instance, dogs would have improved sanitation by cleaning up food scraps. Dogs may have provided warmth, as referred to in the Australian Aboriginal expression “three dog night” (an exceptionally cold night), and they would have alerted the camp to the presence of predators or strangers, using their acute hearing to provide an early warning. Anthropologists believe the most significant benefit would have been the use of dogs' sensitive sense of smell to assist with the hunt. The relationship between the presence of a dog and success in the hunt is often mentioned as a primary reason for the domestication of the wolf, and a 2004 study of hunter groups with and without a dog gives quantitative support to the hypothesis that the benefits of cooperative hunting was an important factor in wolf domestication.

The cohabitation of dogs and humans would have greatly improved the chances of survival for early human groups, and the domestication of dogs may have been one of the key forces that led to human success.

As pets


“The most widespread form of interspecies bonding occurs between humans and dogs” and the keeping of dogs as companions, particularly by elites, has a long history. However, pet dog populations grew significantly after World War II as suburbanization increased. In the 1950s and 1960s, dogs were kept outside more often than they tend to be today (using the expression “in the doghouse” to describe exclusion from the group signifies the distance between the doghouse and the home) and were still primarily functional, acting as a guard, children’s playmate, or walking companion. From the 1980s, there have been changes in the role of the pet dog, such as the increased role of dogs in the emotional support of their owners. People and dogs have become increasingly integrated and implicated in each other’s lives, to the point where pet dogs actively shape the way a family and home are experienced.

There have been two major trends in the changing status of pet dogs. The first has been the ‘commodification’ of the dog, shaping it to conform to human expectations of personality and behaviour. The second has been the broadening of the concept of the family and the home to include dogs-as-dogs within everyday routines and practices.

There are a vast range of commodity forms available to transform a pet dog into an ideal companion. The list of goods, services and places available is enormous: from dog perfumes, couture, furniture and housing, to dog groomers, therapists, trainers and care-takers, dog cafes, spas, parks and beaches, and dog hotels, airlines and cemeteries. While dog training
Dog training
Dog training is the process of teaching skills or behaviors to a dog. This can include teaching a dog to respond to certain commands, or helping the dog learn coping skills for stressful environments. Dog training often includes operant conditioning, classical conditioning, or non-associative...

 as an organized activity can be traced back to the 18th century, in the last decades of the 20th century it became a high profile issue as many normal dog behaviors such as barking, jumping up, digging, rolling in dung, fighting, and urine marking became increasingly incompatible with the new role of a pet dog. Dog training books, classes and television programs proliferated as the process of commodifying the pet dog continued.
The majority of contemporary dog owners describe their dog as part of the family, although some ambivalence about the relationship is evident in the popular reconceptualisation of the dog-human family as a pack. A dominance model of dog-human relationships has been promoted by some dog trainers, such as on the television program Dog Whisperer
Dog Whisperer
Dog Whisperer with Cesar Millan is a reality television series that features Cesar Millan's work with problem dogs. In the United States, the program airs exclusively on the Nat Geo WILD channel with season 8 expected to premiere in 2012....

. However it has been disputed that "trying to achieve status" is characteristic of dog–human interactions. Pet dogs play an active role in family life; for example, a study of conversations in dog-human families showed how family members use the dog as a resource, talking to the dog, or talking through the dog, to mediate their interactions with each other. Another study of dogs’ roles in families showed many dogs have set tasks or routines undertaken as family members, the most common of which was helping with the washing-up by licking the plates in the dishwasher, and bringing in the newspaper from the lawn. Increasingly, human family members are engaging in activities centred on the perceived needs and interests of the dog, or in which the dog is an integral partner, such as Dog Dancing
Musical Canine Freestyle
Musical canine freestyle, also known as musical freestyle, freestyle dance, and canine freestyle, is a modern dog sport that is a mixture of obedience training, tricks, and dance that allows for creative interaction between dogs and their owners...

 and Doga
Doga (Dog Yoga)
Doga is the practice of yoga with pet dogs.Through acts of meditation, gentle massage, and stretching, doga practitioners seek to achieve a greater harmony with their dogs...

.

According to the statistics published by the American Pet Products Manufacturers Association
American Pet Products Manufacturers Association
The American Pet Products Association ' was founded in 1958 and was incorporated as a not for profit corporation in Greenwich . APPMA is a not-for-profit trade association made up of over 1000 pet product manufacturers, their representatives, importers and livestock suppliers...

 in the National Pet Owner Survey in 2009–2010, it is estimated there are 77.5 million dog owners in the United States. The same survey shows nearly 40% of American households own at least one dog, of which 67% own just one dog, 25% two dogs and nearly 9% more than two dogs. There does not seem to be any gender
Gender
Gender is a range of characteristics used to distinguish between males and females, particularly in the cases of men and women and the masculine and feminine attributes assigned to them. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity...

 preference among dogs as pets, as the statistical data reveal an equal number of female and male dog pets. Yet, although several programs are undergoing to promote pet adoption
Pet adoption
Pet adoption usually refers to the process of taking guardianship of and responsibility for a pet that a previous owner has abandoned or released to a shelter or rescue organization...

, less than a fifth of the owned dogs come from a shelter.

Work


Dogs have lived and worked with humans in so many roles that they have earned the unique nickname, "man's best friend", a phrase used in other languages as well. They have been bred for herding livestock, hunting (e.g. pointers and hounds), rodent control, guarding, helping fishermen with nets, detection dogs
Detection dog
A detection dog or sniffer dog is a dog that is trained to and works at using its senses to detect substances such as explosives, illegal drugs, or blood. Hunting dogs that search for game and search dogs that search for missing humans are generally not considered detection dogs...

, and pulling loads, in addition to their roles as companions.

Service dog
Service dog
A service dog is a type of assistance dog specifically trained to help people who have disabilities including visual or hearing impairment, and also to help people with mental disabilities including Post Traumatic Stress Disorder and severe depression...

s such as guide dog
Guide dog
Guide dogs are assistance dogs trained to lead blind and visually impaired people around obstacles.Although the dogs can be trained to navigate various obstacles, they are partially color blind and are not capable of interpreting street signs...

s, utility dogs, assistance dogs, hearing dogs, and psychological therapy dogs provide assistance to individuals with physical or mental disabilities. Some dogs owned by epileptics have been shown to alert their handler when the handler shows signs of an impending seizure, sometimes well in advance of onset, allowing the owner to seek safety, medication, or medical care.

Dogs included in human activities in terms of helping out humans are usually called working dogs. Dogs of several breeds are considered working dogs. Some working dog breeds include Akita
American Akita
The Akita is a large spitz breed of dog originating from the mountainous northern regions of Japan. There are now two separate strains: American, a/k/a "Akita" or "American Akita"; and Japanese, aka "Akita Inu" or "Japanese Akita"...

, Alaskan Malamute
Alaskan Malamute
The Alaskan Malamute is a generally large breed of domestic dog originally bred for use as a utilitarian dog and later an Alaskan sled dog. They are sometimes mistaken for a Siberian Husky, but in fact are quite different in many ways...

, Anatolian Shepherd Dog
Anatolian Shepherd Dog
The Anatolian Shepherd Dog also known as Karabash is a breed of dog which originated in Anatolia and was further developed as a breed in America....

, Bernese Mountain Dog
Bernese Mountain Dog
The Bernese Mountain Dog, called in German the Berner Sennenhund, is a large breed of dog, one of the four breeds of Sennenhund-type dogs from the Swiss Alps. The name Sennenhund is derived from the German "Senne" and "hund" , as they accompanied the alpine herders and dairymen called Senn...

, Black Russian Terrier
Black Russian Terrier
The Black Russian Terrier , abbreviated as BRT, or Stalin's dog is a breed of dog, developed to serve as guard dog and police dog...

, Boxer
Boxer (dog)
Developed in Germany, the Boxer is a breed of stocky, medium-sized, short-haired dog. The coat is smooth and fawn or brindled, with or without white markings. Boxers are brachycephalic , and have a square muzzle, mandibular prognathism , very strong jaws and a powerful bite ideal for hanging on to...

, Bullmastiff
Bullmastiff
The Bullmastiff is a large breed of domestic dog. It has a solid build and a short muzzle. The Bullmastiff shares the characteristics of Molosser dogs, and was originally developed by 19th-century gamekeepers in England to guard estates and immobilize poachers. The breed's bloodlines are drawn from...

, Doberman Pinscher, Dogue de Bordeaux
Dogue de Bordeaux
The Dogue de Bordeaux, Bordeaux Mastiff or French Mastiff or Bordeauxdog is a breed of dog that is strong, powerful, and imposing. The Dogue de Bordeaux is one of the most ancient French breeds. They are a typical brachycephalic molossoid type. Bordeaux are very powerful dogs, with a very muscular...

, German Pinscher
German Pinscher
The German Pinscher is a medium-sized, breed of dog, a Pinscher type that originated in Germany. The breed is included in the origins of the Dobermann, the Miniature Pinscher, the Affenpinscher, the Standard Schnauzer...

, German Shepherd, Giant Schnauzer
Giant Schnauzer
The Giant Schnauzer is a large, powerful, and compact breed of dog. It is one of the three Schnauzer breeds. Like most large breeds, the Giant Schnauzer needs a fair amount of exercise.-Appearance:...

, Great Dane
Great Dane
The Great Dane , also known as German Mastiff or Danish Hound , is a breed of domestic dog known for its giant size...

, Great Pyrenees, Great Swiss Mountain Dog, Komondor
Komondor
The Komondor is a large, white-colored Hungarian breed of livestock guardian dog with a long, corded coat....

, Kuvasz
Kuvasz
The Kuvasz is a dog breed of ancient Hungarian origin. Mention of the breed can be found in old Hungarian texts. It has historically been used to guard livestock, but has been increasingly found in homes as a pet over the last seventy years....

, Mastiff
English Mastiff
The English Mastiff, referred to by virtually all Kennel Clubs simply as the Mastiff, is a breed of large dog perhaps descended from the ancient Alaunt through the Pugnaces Britanniae. Distinguishable by enormous size, massive head, and a limited range of colors, but always displaying a black mask,...

, Neapolitan Mastiff
Neapolitan Mastiff
The Neapolitan Mastiff, Italian Mastiff, is a large, ancient dog breed. This massive breed is often used as a guard and defender of family and property due to their protective instincts and their fearsome appearance....

, Newfoundland
Newfoundland (dog)
The Newfoundland is a breed of large dog. Newfoundlands can be black, brown, gray, or black and white. They were originally bred and used as a working dog for fishermen in the Dominion of Newfoundland, now part of Canada. They are known for their giant size, tremendous strength, calm dispositions,...

, Portuguese Water Dog
Portuguese Water Dog
The Portuguese Water Dog is a breed of working dog as classified by the American Kennel Club. Portuguese Water Dogs are originally from the Portuguese region of the Algarve, from where the breed expanded to all around Portugal's coast, where they were taught to herd fish into fishermen's nets, to...

, Rottweiler
Rottweiler
The Rottweiler is a medium to large size breed of domestic dog that originated in Rottweil, Germany. The dogs were known as "Rottweil butchers' dogs" because they were used to herd livestock and pull carts laden with butchered meat and other products to market...

, Saint Bernard
St. Bernard (dog)
The St. Bernard is a breed of very large working dog from the Italian and Swiss Alps, originally bred for rescue. The breed has become famous through tales of alpine rescues, as well as for its large size.-Appearance:The St. Bernard is a large dog...

, Samoyed
Samoyed (dog)
The Samoyed dog takes its name from the Samoyedic peoples of Siberia. An alternate name for the breed, especially in Europe, is Bjelkier...

, Siberian Husky
Siberian Husky
The Siberian Husky is a medium-size, dense-coat working dog breed that originated in north-eastern Siberia. The breed belongs to the Spitz genetic family...

, Standard Schnauzer
Standard Schnauzer
The Standard Schnauzer is the original breed of the three breeds of Schnauzer, and despite its wiry coat and general appearance, is not related to the British terriers. Rather, its origins are in old herding and guard breeds of Europe. Generally classified as a working or utility dog, this...

, and Tibetan Mastiff
Tibetan Mastiff
The Tibetan Mastiff is an ancient breed and type of domestic dog originating with nomadic cultures of Central Asia.-Names and etymology:...

.

Sports and shows



Owners of dogs often enter them in competitions such as breed conformation shows or sports, including racing and sledding.

In conformation shows, also referred to as breed shows, a judge familiar with the specific dog breed evaluates individual purebred dogs for conformity with their established breed type as described in the breed standard. As the breed standard only deals with the externally observable qualities of the dog (such as appearance, movement, and temperament), separately tested qualities (such as ability or health) are not part of the judging in conformation shows.

As a food source



Dog meat is consumed in some East Asian countries, including Korea, China, and Vietnam, a practice that dates back to antiquity. It is estimated that 13–16 million dogs are killed and consumed in Asia every year. The BBC claims that, in 1999, more than 6,000 restaurants served soups made from dog meat in South Korea. In Korea, the primary dog breed raised for meat, the nureongi
Nureongi
The Nureongi also spelled Noo-rung-yee is a yellowish dog landrace from Korea. It is most often used as a livestock dog, raised for its meat and not commonly kept as a pet.-Terminology:This dog has no formal name...

(누렁이), differs from those breeds raised for pets that Koreans may keep in their homes. The most popular Korean dog dish is gaejang-guk
Bosintang
Boshintang , or Gaejangguk is a Korean soup that includes dog meat as its primary ingredient. The soup has been claimed to provide increased virility. The meat is boiled with vegetables such as green onions, perilla leaves, and dandelions, and spices such as Doenjang , Gochujang , and perilla...

(also called bosintang), a spicy stew meant to balance the body's heat during the summer months; followers of the custom claim this is done to ensure good health by balancing one's gi
Qi
In traditional Chinese culture, qì is an active principle forming part of any living thing. Qi is frequently translated as life energy, lifeforce, or energy flow. Qi is the central underlying principle in traditional Chinese medicine and martial arts...

, or vital energy of the body. A 19th century version of gaejang-guk explains that the dish is prepared by boiling dog meat with scallion
Scallion
Scallions , are the edible plants of various Allium species, all of which are "onion-like", having hollow green leaves and lacking a fully developed root bulb.-Etymology:The words...

s and chili powder. Variations of the dish contain chicken and bamboo shoots. While the dishes are still popular in Korea with a segment of the population, dog is not as widely consumed as beef, chicken, and pork.

Other cultures, such as Polynesia
Polynesia
Polynesia is a subregion of Oceania, made up of over 1,000 islands scattered over the central and southern Pacific Ocean. The indigenous people who inhabit the islands of Polynesia are termed Polynesians and they share many similar traits including language, culture and beliefs...

 and pre-Columbian Mexico
Pre-Columbian Mexico
The pre-Columbian history of the territory now within the contemporary nation of Mexico is known through the work of archaeologists and epigraphers, and through the accounts of the conquistadors, clergymen, and indigenous chroniclers of the immediate post-conquest period...

, also consumed dog meat in their history. However, Western, South Asian, African, and Middle Eastern cultures, in general, regard consumption of dog meat as taboo
Taboo food and drink
Taboo food and drink are food and beverages which people abstain from consuming for religious, cultural or hygienic reasons. Many food taboos forbid the meat of a particular animal, including mammals, rodents, reptiles, amphibians, bony fish, and crustaceans...

. In some places, however, such as in rural areas of Poland, dog fat is believed to have medicinal properties—being good for the lungs for instance.

A CNN report in China dated March 2010 interviews a dog meat vendor who states that most of the dogs that are available for selling to restaurant
Restaurant
A restaurant is an establishment which prepares and serves food and drink to customers in return for money. Meals are generally served and eaten on premises, but many restaurants also offer take-out and food delivery services...

 are raised in special farms but that there is always a chance that a sold dog is someone's lost pet, although dog pet breeds are not considered edible.

Health risks to humans


In the USA, cat
Cat
The cat , also known as the domestic cat or housecat to distinguish it from other felids and felines, is a small, usually furry, domesticated, carnivorous mammal that is valued by humans for its companionship and for its ability to hunt vermin and household pests...

s and dogs are a factor in more than 86,000 falls each year. It has been estimated around 2% of dog-related injuries treated in UK hospitals are domestic accidents. The same study found that while dog involvement in road traffic accidents was difficult to quantify, dog-associated road accidents involving injury more commonly involved two-wheeled vehicles.

Toxocara canis
Toxocara canis
Toxocara canis is worldwide distributed helminth parasite of dogs and other canids. T. canis are gonochorists, adult worms measure from 9 to 18 cm, are yellow-white in color, and occur in the intestine of the definitive host. In adult dogs, the infection is usually asymptomatic. By the...

(dog roundworm) eggs in dog feces can cause toxocariasis
Toxocariasis
-History of discovery:Werner described a parasitic nematode in dogs in 1782 which he named Ascaris canis. Johnston determined that what Werner had described was actually a member of the genus Toxocara established by Stiles in 1905. Fữlleborn speculated that T canis larvae might cause granulomatous...

. In the United States, about 10,000 cases of Toxocara infection are reported in humans each year, and almost 14% of the US population is infected. In Great Britain, 24% of soil samples taken from public parks contained T. canis eggs. Untreated toxocariasis can cause retinal damage and decreased vision. Dog feces can also contain hookworm
Hookworm
The hookworm is a parasitic nematode that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. A. duodenale predominates in the Middle East, North Africa, India...

s that cause cutaneous larva migrans
Cutaneous larva migrans
Cutaneous larva migrans is a skin disease in humans, caused by the larvae of various nematode parasites of the hookworm family...

 in humans.

The incidence of dog bites, and especially fatal dog bites, is extremely rare in America considering the number of pet dogs in the country. Fatalities from dog bites occur in America at the rate of one per four million dogs. A Colorado study found bites in children were less severe than bites in adults. The incidence of dog bites in the US is 12.9 per 10,000 inhabitants, but for boys aged 5 to 9, the incidence rate is 60.7 per 10,000. Moreover, children have a much higher chance to be bitten in the face or neck.
Sharp claws with powerful muscles behind them can lacerate flesh in a scratch that can lead to serious infections.

In the UK between 2003 and 2004, there were 5,868 dog attack
Dog attack
Dog attacks are attacks on humans by feral or domestic dogs. With the close association of dogs and humans in daily life , dog attacks—with injuries from very minor to significant, and severe to fatal—are not uncommon. Attacks on the serious end of the spectrum have become the focus of increasing...

s on humans, resulting in 5,770 working days lost in sick leave.

Health benefits for humans



A growing body of research indicates the companionship of a dog can enhance human physical health and psychological wellbeing. Dog and cat owners have been shown to have better mental and physical health than nonowners, making fewer visits to the doctor and being less likely to be on medication than nonowners. In one study, new pet owners reported a highly significant reduction in minor health problems during the first month following pet acquisition, and this effect was sustained in dog owners through to the end of the study. In addition, dog owners took considerably more physical exercise than cat owners and people without pets. The group without pets exhibited no statistically significant changes in health or behaviour. The results provide evidence that pet acquisition may have positive effects on human health and behaviour, and that for dog owners these effects are relatively long term. Pet ownership has also been associated with increased coronary artery disease survival, with dog owners being significantly less likely to die within one year of an acute myocardial infarction than those who did not own dogs.

The health benefits of dogs can result from contact with dogs, not just from dog ownership. For example, when in the presence of a pet dog, people show reductions in cardiovascular, behavioral, and psychological indicators of anxiety. The benefits of contact with a dog also include social support, as dogs are able to not only provide companionship and social support themselves, but also to act as facilitators of social interactions between humans. One study indicated that wheelchair users experience more positive social interactions with strangers when they are accompanied by a dog than when they are not.

The practice of using dogs and other animals as a part of therapy dates back to the late 18th century, when animals were introduced into mental institutions to help socialize patients with mental disorders. Animal-assisted intervention research has shown that animal-assisted therapy with a dog can increase a person with Alzheimer’s disease’s social behaviours, such as smiling and laughing. One study demonstrated that children with ADHD and conduct disorders who participated in an education program with dogs and other animals showed increased attendance, increased knowledge and skill objectives, and decreased antisocial and violent behavior compared to those who were not in an animal-assisted program.

Shelters



Every year, between 6 and 8 million dogs and cats enter US animal shelter
Animal shelter
An animal shelter is a facility that houses homeless, lost, or abandoned animals; primarily a large variety of dogs and cats.Parrots, for example, are the third most common pet owned by people...

s. The Humane Society of the United States
Humane Society of the United States
The Humane Society of the United States , based in Washington, D.C., is the largest animal advocacy organization in the world. In 2009, HSUS reported assets of over US$160 million....

 (HSUS) estimates that approximately 3 to 4 million dogs and cats are euthanized
Animal euthanasia
Animal euthanasia is the act of putting to death painlessly or allowing to die, as by withholding extreme medical measures, an animal suffering from an incurable, especially a painful, disease or condition. Euthanasia methods are designed to cause minimal pain and distress...

 yearly in shelters across the United States. However, the percentage of dogs in US animal shelters that are eventually adopted and removed from the shelters by their new owners has increased since the mid 1990s from around 25% up to around 60–75% in the mid first decade of the 21st century.

Pets entering the shelters are euthanized in countries all over the world because of the lack of financial provisions to take care of these animals. Most shelters complain of not having enough resources to feed the pets and by being constrained to kill them, as the likelihood for all of them to find an owner is very small. In poor countries, euthanasia
Euthanasia
Euthanasia refers to the practice of intentionally ending a life in order to relieve pain and suffering....

 is usually violent.

Biology



Domestic dogs have been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes. Modern dog breed
Dog breed
Dog breeds are groups of closely related and visibly similar domestic dogs, which are all of the subspecies Canis lupus familiaris, having characteristic traits that are selected and maintained by humans, bred from a known foundation stock....

s show more variation in size, appearance, and behavior than any other domestic animal. Nevertheless, their morphology is based on that of their wild ancestors, gray wolves.
Dogs are predators
Predation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...

 and scavenger
Scavenger
Scavenging is both a carnivorous and herbivorous feeding behavior in which individual scavengers search out dead animal and dead plant biomass on which to feed. The eating of carrion from the same species is referred to as cannibalism. Scavengers play an important role in the ecosystem by...

s, and like many other predatory mammals, the dog has powerful muscles, fused wrist bones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.
Dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier
Yorkshire Terrier
The Yorkshire Terrier is a small dog breed of terrier type, developed in the 19th century in the county of Yorkshire, England to catch rats in clothing mills. The defining features of the breed are its size, to , and its silky blue and tan coat...

, that stood only 6.3 centimetres (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4 oz). The largest known dog was an English Mastiff
English Mastiff
The English Mastiff, referred to by virtually all Kennel Clubs simply as the Mastiff, is a breed of large dog perhaps descended from the ancient Alaunt through the Pugnaces Britanniae. Distinguishable by enormous size, massive head, and a limited range of colors, but always displaying a black mask,...

 which weighed 155.6 kilograms (343 lb) and was 250 cm (98.4 in) from the snout to the tail. The tallest dog is a Great Dane
Great Dane
The Great Dane , also known as German Mastiff or Danish Hound , is a breed of domestic dog known for its giant size...

 that stands 106.7 cm (42 in) at the shoulder.

Vision


Like most mammals, dogs are dichromats and have color vision equivalent to red-green color blindness
Color blindness
Color blindness or color vision deficiency is the inability or decreased ability to see color, or perceive color differences, under lighting conditions when color vision is not normally impaired...

 in humans (deuteranopia). Dogs are less sensitive to differences in grey shades than humans and also can detect brightness at about half the accuracy of humans.

The dog's visual system has evolved to aid proficient hunting. While a dog's visual acuity
Visual acuity
Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....

 is poor (that of a poodle
Poodle
The Poodle is a breed of dog. The poodle breed is found officially in toy, miniature, and standard sizes, with many coat colors. Originally bred as a type of water dog, the poodle is highly intelligent and skillful in many dog sports, including agility, obedience, tracking, and even herding...

's has been estimated to translate to a Snellen
Snellen chart
A Snellen chart is an eye chart used by eye care professionals and others to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart during 1862...

 rating of 20/75), their visual discrimination for moving objects is very high; dogs have been shown to be able to discriminate between humans (e.g., identifying their owner) at a range of between 800 and 900 m, however this range decreases to 500–600 m if the object is stationary. Dogs have a temporal resolution
Temporal resolution
Temporal resolution refers to the precision of a measurement with respect to time. Often there is a tradeoff between temporal resolution of a measurement and its spatial resolution. This trade-off can be attributed to the finite speed of light and the fact that it takes a certain period of time...

 of between 60 and 70 Hz, which explains why many dogs struggle to watch television, as most such modern screens are optimized for humans at 50–60 Hz. Dogs can detect a change in movement that exists in a single diopter
Dioptre
A dioptre, or diopter, is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal length measured in metres . It is thus a unit of reciprocal length. For example, a 3-dioptre lens brings parallel rays of light to focus at metre...

 of space within their eye. Humans, by comparison, require a change of between 10 and 20 diopters to detect movement.

As crepuscular
Crepuscular
Crepuscular animals are those that are active primarily during twilight, that is during dawn and dusk. The word is derived from the Latin word crepusculum, meaning "twilight." Crepuscular is, thus, in contrast with diurnal and nocturnal behavior. Crepuscular animals may also be active on a bright...

 hunters, dogs often rely on their vision in low light situations: They have very large pupils, a high density of rods
Rod cell
Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in less intense light than can the other type of visual photoreceptor, cone cells. Named for their cylindrical shape, rods are concentrated at the outer edges of the retina and are used in peripheral vision. On...

 in the fovea
Fovea
The fovea centralis, also generally known as the fovea , is a part of the eye, located in the center of the macula region of the retina....

, an increased flicker rate, and a tapetum lucidum
Tapetum lucidum
The tapetum lucidum is a layer of tissue in the eye of many vertebrate animals....

. The tapetum is a reflective surface behind the retina that reflects light to give the photoreceptors a second chance to catch the photons. There is also a relationship between body size and overall diameter of the eye. A range of 9.5 and 11.6 mm can be found between various breeds of dogs. This 20% variance can be substantial and is associated as an adaptation toward superior night vision.

The eyes of different breeds of dogs have different shapes, dimensions, and retina configurations. Many long-nosed breeds have a "visual streak" – a wide foveal region that runs across the width of the retina and gives them a very wide field of excellent vision. Some long-muzzled breeds, in particular, the sighthound
Sighthound
Sighthounds, also called gazehounds, are hounds that primarily hunt by speed and sight, instead of by scent and endurance as scent hounds do.-Appearance:...

s, have a field of vision up to 270° (compared to 180° for humans). Short-nosed breeds, on the other hand, have an "area centralis": a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed sight much more like a human's. Some broad-headed breeds with short noses have a field of vision similar to that of humans. Most breeds have good vision, but some show a genetic predisposition
Genetic predisposition
A genetic predisposition is a genetic affectation which influences the phenotype of an individual organism within a species or population but by definition that phenotype can also be modified by the environmental conditions. In the rest of the population, conditions cannot have that effect...

 for myopia
Myopia
Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...

 – such as Rottweiler
Rottweiler
The Rottweiler is a medium to large size breed of domestic dog that originated in Rottweil, Germany. The dogs were known as "Rottweil butchers' dogs" because they were used to herd livestock and pull carts laden with butchered meat and other products to market...

s, with which one out of every two has been found to be myopic. Dogs also have a greater divergence of the eye axis than humans, enabling them to rotate their pupils farther in any direction. The divergence of the eye axis of dogs ranges from 12-25° depending on the breed.

Experimentation has proven that dogs can distinguish between complex visual images such as that of a cube or a prism. Dogs also show attraction to static visual images such as the silhouette of a dog on a screen, their own reflections, or videos of dogs; however, their interest declines sharply once they are unable to make social contact with the image.

Hearing


The frequency range of dog hearing is approximately 40 Hz to 60,000 Hz, which means that dogs can detect sounds far beyond the upper limit of the human auditory spectrum. In addition, dogs have ear mobility, which allows them to rapidly pinpoint the exact location of a sound. Eighteen or more muscles can tilt, rotate, raise, or lower a dog's ear. A dog can identify a sound's location much faster than a human can, as well as hear sounds at four times the distance.

Smell


While the human brain is dominated by a large visual cortex
Visual cortex
The visual cortex of the brain is the part of the cerebral cortex responsible for processing visual information. It is located in the occipital lobe, in the back of the brain....

, the dog brain is dominated by an olfactory cortex
Olfactory system
The olfactory system is the sensory system used for olfaction, or the sense of smell. Most mammals and reptiles have two distinct parts to their olfactory system: a main olfactory system and an accessory olfactory system. The main olfactory system detects volatile, airborne substances, while the...

. The olfactory bulb
Olfactory bulb
The olfactory bulb is a structure of the vertebrate forebrain involved in olfaction, the perception of odors.-Anatomy:In most vertebrates, the olfactory bulb is the most rostral part of the brain. In humans, however, the olfactory bulb is on the inferior side of the brain...

 in dogs is roughly forty times bigger than the olfactory bulb in humans, relative to total brain size, with 125 to 220 million smell-sensitive receptors. The bloodhound
Bloodhound
The Bloodhound is a large breed of dog which, while originally bred to hunt deer and wild boar, was later bred specifically to track human beings. It is a scenthound, tracking by smell, as opposed to a sighthound, which tracks using vision. It is famed for its ability to discern human odors even...

 exceeds this standard with nearly 300 million receptors. Subsequently, it has been estimated that dogs, in general, have an olfactory sense ranging from one hundred thousand to one million times more sensitive than a human's. In some dog breeds, such as bloodhounds, the olfactory sense may be up to 100 million times greater than a human's. The wet nose is essential for determining the direction of the air current containing the smell. Cold receptors in the skin are sensitive to the cooling of the skin by evaporation of the moisture by air currents.

Coat


The coats of domestic dogs are of two varieties: "double" being common with dogs (as well as wolves) originating from colder climates, made up of a coarse guard hair
Guard hair
Guard hairs are the longest, coarsest hairs in a mammal's coat, forming the topcoat . They taper to a point and protect the undercoat from the elements. They are often water repellent and stick out above the rest of the coat...

 and a soft down hair
Down hair
Down hairs, also called the ground hairs, are the very fine, fluffy hairs closest to the skin on some mammals. The hairs are short and crimped, which makes them highly efficient for trapping air and insulating the animal....

, or "single", with the topcoat only.

Domestic dogs often display the remnants of countershading
Countershading
Countershading, or Thayer's Law, is a form of camouflage. Countershading, in which an animal’s pigmentation is darker dorsally, is often thought to have an adaptive effect of reducing conspicuous shadows cast on the ventral region of an animal’s body...

, a common natural camouflage pattern. A countershaded animal will have dark coloring on its upper surfaces and light coloring below, which reduces its general visibility. Thus, many breeds will have an occasional "blaze", stripe, or "star" of white fur on their chest or underside.

Tail



There are many different shapes for dog tail
Tail
The tail is the section at the rear end of an animal's body; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, and birds...

s: straight, straight up, sickle, curled, or cork-screw. As with many canids, one of the primary functions of a dog's tail is to communicate their emotional state, which can be important in getting along with others. In some hunting dogs, however, the tail is traditionally docked to avoid injuries. In some breeds, puppies can be born with a short tail or no tail at all.

Types and breeds



While all dogs are genetically very similar, natural selection
Natural selection
Natural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....

 and selective breeding have reinforced certain characteristics in certain populations of dogs, giving rise to dog types and dog breeds. Dog types are broad categories based on function, genetics, or characteristics.

Dog breeds are groups of animals that possess a set of inherited characteristics that distinguishes them from other animals within the same species. Modern dog breeds are non-scientific classifications of dogs kept by modern kennel club
Kennel club
A kennel club is an organization for canine affairs that concerns itself with the breeding, showing and promotion of more than one breed of dog...

s. Purebred dogs of one breed are genetically distinguishable from purebred
Purebred (dog)
Purebred dog refers to a dog of a modern dog breed that closely resembles other dogs of the same breed, with ancestry documented in a stud book and registered with one of the major dog registries...

 dogs of other breeds, but the means by which kennel clubs classify dogs is unsystematic. Systematic analyses of the dog genome has revealed only four major types of dogs that can be said to be statistically distinct. These include the "old world dogs" (e.g., Malamute
Alaskan Malamute
The Alaskan Malamute is a generally large breed of domestic dog originally bred for use as a utilitarian dog and later an Alaskan sled dog. They are sometimes mistaken for a Siberian Husky, but in fact are quite different in many ways...

 and Shar Pei
Shar Pei
The Shar Pei, or Chinese Shar-Pei, is a breed of dog known for its distinctive features of deep wrinkles and a blue-black tongue. The breed comes from China. The name translates to "sand skin" and refers to the texture of its short, rough coat...

), "Mastiff"-type (e.g., English Mastiff
English Mastiff
The English Mastiff, referred to by virtually all Kennel Clubs simply as the Mastiff, is a breed of large dog perhaps descended from the ancient Alaunt through the Pugnaces Britanniae. Distinguishable by enormous size, massive head, and a limited range of colors, but always displaying a black mask,...

), "herding"-type (e.g., Border Collie
Border Collie
The Border Collie is a herding dog breed developed in the Anglo-Scottish border region for herding livestock, especially sheep. It is the most widespread of the collie breeds....

), and "all others" (also called "modern"- or "hunting"-type).

Health


Dogs are susceptible to various diseases, ailments, and poisons, some of which can affect humans
Zoonosis
A zoonosis or zoonoseis any infectious disease that can be transmitted from non-human animals to humans or from humans to non-human animals . In a study of 1415 pathogens known to affect humans, 61% were zoonotic...

. To defend against many common diseases, dogs are often vaccinated.


Some breeds of dogs are prone to certain genetic ailments such as elbow
Elbow dysplasia
Elbow dysplasia is a condition involving multiple developmental abnormalities of the elbow-joint in the dog, specifically the growth of cartilage or the structures surrounding it. These abnormalities, known as 'primary lesions', give rise to osteoarthritic processes...

 or hip dysplasia, blindness
Blindness
Blindness is the condition of lacking visual perception due to physiological or neurological factors.Various scales have been developed to describe the extent of vision loss and define blindness...

, deafness, pulmonic stenosis
Pulmonary valve stenosis
Pulmonary valve stenosis is a heart valve disorder in which outflow of blood from the right ventricle of the heart is obstructed at the level of the pulmonic valve. This results in the reduction of flow of blood to the lungs. Valvular pulmonic stenosis accounts for 80% of right ventricular outflow...

, cleft palate, and trick knees
Luxating patella
Luxating patella is a condition in which the patella, or kneecap, dislocates or moves out of its normal location....

. Two serious medical conditions particularly affecting dogs are pyometra
Pyometra
Pyometra is a disease of the uterus most commonly seen in female dogs, but also seen in female cats , rabbits, ferrets, rats and guinea pigs. Pyometra is an important disease to be aware of for any dog owner because of the sudden nature of the disease and the deadly consequences if left untreated...

, affecting unspayed
Neutering
Neutering, from the Latin neuter , is the removal of an animal's reproductive organ, either all of it or a considerably large part. The process is often used in reference to males whereas spaying is often reserved for females. Colloquially, both terms are often referred to as fixing...

 females of all types and ages, and bloat
Bloat
Bloat is a medical condition in which the stomach becomes overstretched by excessive gas content. It is also commonly referred to as torsion, gastric torsion, and gastric dilatation-volvulus when the stomach is also twisted. The word bloat is often used as a general term to cover gas distension...

, which affects the larger breeds or deep-chested dogs. Both of these are acute conditions, and can kill rapidly. Dogs are also susceptible to parasites such as flea
Flea
Flea is the common name for insects of the order Siphonaptera which are wingless insects with mouthparts adapted for piercing skin and sucking blood...

s, tick
Tick
Ticks are small arachnids in the order Ixodida, along with mites, constitute the subclass Acarina. Ticks are ectoparasites , living by hematophagy on the blood of mammals, birds, and sometimes reptiles and amphibians...

s, and mite
Mite
Mites, along with ticks, are small arthropods belonging to the subclass Acari and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology.-Diversity and systematics:...

s, as well as hookworm
Hookworm
The hookworm is a parasitic nematode that lives in the small intestine of its host, which may be a mammal such as a dog, cat, or human. Two species of hookworms commonly infect humans, Ancylostoma duodenale and Necator americanus. A. duodenale predominates in the Middle East, North Africa, India...

, tapeworm
Cestoda
This article describes the flatworm. For the medical condition, see Tapeworm infection.Cestoda is the name given to a class of parasitic flatworms, commonly called tapeworms, of the phylum Platyhelminthes. Its members live in the digestive tract of vertebrates as adults, and often in the bodies...

, roundworm
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...

, and heartworm.

Dogs are highly susceptible to theobromine poisoning
Theobromine poisoning
Theobromine poisoning or chocolate poisoning is an adverse reaction to the alkaloid theobromine, found in chocolate, tea, cola beverages, açaí berries, and some other foods. Cacao beans contain about 1.2% theobromine by weight, while processed chocolate, in general, has smaller amounts...

, typically from ingestion of chocolate
Chocolate
Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. Cacao has been cultivated for at least three millennia in Mexico, Central and South America. Its earliest documented use is around 1100 BC...

. Theobromine is toxic to dogs because, although the dog's metabolism is capable of breaking down the chemical, the process is so slow that even small amounts of chocolate can be fatal, especially dark chocolate.

Dogs are also vulnerable to some of the same health conditions as humans, including diabetes
Diabetes in dogs
Diabetes mellitus is a disease in which the beta cells of the endocrine pancreas either stop producing insulin or can no longer produce it in enough quantity for the body's needs. The condition is commonly divided into two types, depending on the origin of the condition: Type 1 diabetes, sometimes...

, dental and heart disease, epilepsy, cancer, hypothyroidism, and arthritis.

Mortality


The typical lifespan of dogs varies widely among breeds, but for most the median longevity, the age at which half the dogs in a population have died and half are still alive, ranges from 10 to 13 years. Individual dogs may live well beyond the median of their breed.

The breed with the shortest lifespan (among breeds for which there is a questionnaire survey with a reasonable sample size) is the Dogue de Bordeaux
Dogue de Bordeaux
The Dogue de Bordeaux, Bordeaux Mastiff or French Mastiff or Bordeauxdog is a breed of dog that is strong, powerful, and imposing. The Dogue de Bordeaux is one of the most ancient French breeds. They are a typical brachycephalic molossoid type. Bordeaux are very powerful dogs, with a very muscular...

, with a median longevity of about 5.2 years, but several breeds, including Miniature Bull Terriers
Bull Terrier (Miniature)
The Bull Terrier is a breed with origins in the English White Terrier, the Dalmatian and the Bulldog. The first existence is documented 1872 in The Dogs of British Island.-Appearance:...

, Bloodhound
Bloodhound
The Bloodhound is a large breed of dog which, while originally bred to hunt deer and wild boar, was later bred specifically to track human beings. It is a scenthound, tracking by smell, as opposed to a sighthound, which tracks using vision. It is famed for its ability to discern human odors even...

s, and Irish Wolfhound
Irish Wolfhound
The Irish wolfhound is a breed of domestic dog , specifically a sighthound. The name originates from its purpose rather than from its appearance...

s are nearly as short-lived, with median longevities of 6 to 7 years.

The longest-lived breeds, including Toy Poodles, Japanese Spitz
Japanese Spitz
The is a small to medium breed of dog of the Spitz type. The Japanese Spitz is a companion dog and pet. There are varying standards around the world as to the ideal size of the breed, but they are always larger than their smaller cousins, the Pomeranian. They were developed in Japan in the 1920s...

, Border Terrier
Border Terrier
The Border Terrier is a small, rough-coated breed of dog of the terrier group. Originally bred as fox and vermin hunters, Border Terriers share ancestry with Dandie Dinmont Terriers and Bedlington Terriers....

s, and Tibetan Spaniel
Tibetan Spaniel
The Tibetan Spaniel is a breed of assertive, small, intelligent dogs originating in the Himalayan mountains of Tibet. They share ancestry with the Pekingese, Japanese Chin, Shih Tzu, Lhasa Apso, and Pug...

s, have median longevities of 14 to 15 years. The median longevity of mixed-breed dog
Mixed-breed dog
A mixed-breed dog, also known as a mutt or mongrel, is a dog whose ancestry is generally unknown and that has characteristics of two or more types of breeds. A mixed-breed may be a cross-breed dog, a random-bred dog, or a descendant of feral or pariah dog populations...

s, taken as an average of all sizes, is one or more years longer than that of purebred dogs when all breeds are averaged. The dog widely reported to be the longest-lived is "Bluey," who died in 1939 and was claimed to be 29.5 years old at the time of his death; however, the Bluey record is anecdotal and unverified. The longest verified records are of dogs living for 24 years.

Predation


Although wild dogs, like wolves, are apex predator
Apex predator
Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...

s, they can be killed in territory disputes with wild animals. Furthermore, in areas where both dogs and other large predators live, dogs can be a major food source for big cats or canines. Reports from Croatia indicate wolves kill more dogs more frequently than they kill sheep. Wolves in Russia apparently limit feral dog populations. In Wisconsin, more compensation has been paid for dog losses than livestock. Some wolf pairs have been reported to prey on dogs by having one wolf lure the dog out into heavy brush where the second animal waits in ambush. In some instances, wolves have displayed an uncharacteristic fearlessness of humans and buildings when attacking dogs, to the extent that they have to be beaten off or killed. Coyotes and big cats have also been known to attack dogs. Leopards in particular are known to have a predilection for dogs, and have been recorded to kill and consume them regardless of the dog's size or ferocity. Tigers in Manchuria, Indochina, Indonesia, and Malaysia, are reputed to kill dogs with the same vigor as leopards. Striped Hyenas are major predators of village dogs in Turkmenistan, India, and the Caucasus. Reptiles such as alligators and pythons have been known to kill and eat dogs.

Diet




Despite their descent from wolves and classification as Carnivora
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...

, dogs are variously described in scholarly and other writings as carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...

s or omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...

s. Unlike obligate carnivores, such as the cat family
Felidae
Felidae is the biological family of the cats; a member of this family is called a felid. Felids are the strictest carnivores of the thirteen terrestrial families in the order Carnivora, although the three families of marine mammals comprising the superfamily pinnipedia are as carnivorous as the...

 with its shorter small intestine
Small intestine
The small intestine is the part of the gastrointestinal tract following the stomach and followed by the large intestine, and is where much of the digestion and absorption of food takes place. In invertebrates such as worms, the terms "gastrointestinal tract" and "large intestine" are often used to...

, dogs can adapt to a wide-ranging diet, and are not dependent on meat-specific protein nor a very high level of protein in order to fulfill their basic dietary requirements. Dogs will healthily digest a variety of foods, including vegetables and grains, and can consume a large proportion of these in their diet.

A number of common human foods and household ingestibles are toxic to dogs, including chocolate solids
Chocolate
Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. Cacao has been cultivated for at least three millennia in Mexico, Central and South America. Its earliest documented use is around 1100 BC...

 (theobromine poisoning
Theobromine poisoning
Theobromine poisoning or chocolate poisoning is an adverse reaction to the alkaloid theobromine, found in chocolate, tea, cola beverages, açaí berries, and some other foods. Cacao beans contain about 1.2% theobromine by weight, while processed chocolate, in general, has smaller amounts...

), onion and garlic
Garlic
Allium sativum, commonly known as garlic, is a species in the onion genus, Allium. Its close relatives include the onion, shallot, leek, chive, and rakkyo. Dating back over 6,000 years, garlic is native to central Asia, and has long been a staple in the Mediterranean region, as well as a frequent...

 (thiosulphate, sulfoxide
Sulfoxide
A sulfoxide is a chemical compound containing a sulfinyl functional group attached to two carbon atoms. Sulfoxides can be considered as oxidized sulfides...

 or disulfide
Disulfide
In chemistry, a disulfide usually refers to the structural unit composed of a linked pair of sulfur atoms. Disulfide usually refer to a chemical compound that contains a disulfide bond, such as diphenyl disulfide, C6H5S-SC6H5....

 poisoning), grape
Grape
A grape is a non-climacteric fruit, specifically a berry, that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or they can be used for making jam, juice, jelly, vinegar, wine, grape seed extracts, raisins, molasses and grape seed oil. Grapes are also...

s and raisin
Raisin
Raisins are dried grapes. They are produced in many regions of the world. Raisins may be eaten raw or used in cooking, baking and brewing...

s, macadamia nuts, as well as various plants and other potentially ingested materials.

Reproduction




In domestic dogs, sexual maturity
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...

 begins to happen around age six to twelve months for both males and females, although this can be delayed until up to two years old for some large breeds. This is the time at which female dogs will have their first estrous cycle
Estrous cycle
The estrous cycle comprises the recurring physiologic changes that are induced by reproductive hormones in most mammalian placental females. Estrous cycles start after puberty in sexually mature females and are interrupted by anestrous phases or pregnancies...

. They will experience subsequent estrous cycles biannually, during which the body prepares for pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

. At the peak of the cycle, females will come into estrus, being mentally and physically receptive to copulation
Sexual intercourse
Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis enters a female's vagina for the purposes of sexual pleasure or reproduction. The entities may be of opposite sexes, or they may be hermaphroditic, as is the case with snails...

. Because the ova
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...

 survive and are capable of being fertilized for a week after ovulation, it is possible for a female to mate with more than one male.

Dogs bear their litters roughly 56 to 72 days after fertilization, with an average of 63 days, although the length of gestation can vary. An average litter consists of about six puppies
Puppy
A puppy is a juvenile dog. Some puppies may weigh , while larger ones can weigh up to . All healthy puppies grow quickly after birth. A puppy's coat color may change as the puppy grows older, as is commonly seen in breeds such as the Yorkshire Terrier...

, though this number may vary widely based on the breed of dog. In general, toy dog
Toy dog
Toy dog traditionally refers to a very small dog or a grouping of small and very small breeds of dog. A toy dog may be of any of various dog types. Types of dogs referred to as toy dogs may include Spaniels, Pinschers and Terriers that have been bred down in size. Not all toy dogs are lapdogs,...

s produce from one to four puppies in each litter, while much larger breeds may average as many as twelve.

Some dog breeds have acquired traits through selective breeding that interfere with reproduction. Male French Bulldog
French Bulldog
The French bulldog is a small breed of domestic dog, related to the English bulldog and American bulldog.-History:The origin of the modern French Bulldog breed descends directly from the dogs of the Molossians, an ancient Greek tribe. The dogs were spread throughout the ancient world by Phoenician...

s, for instance, are incapable of mounting the female. For many dogs of this breed, the female must be artificially inseminated
Artificial insemination
Artificial insemination, or AI, is the process by which sperm is placed into the reproductive tract of a female for the purpose of impregnating the female by using means other than sexual intercourse or natural insemination...

 in order to reproduce.

Neutering



Neutering
Neutering
Neutering, from the Latin neuter , is the removal of an animal's reproductive organ, either all of it or a considerably large part. The process is often used in reference to males whereas spaying is often reserved for females. Colloquially, both terms are often referred to as fixing...

 refers to the sterilization
Neutering
Neutering, from the Latin neuter , is the removal of an animal's reproductive organ, either all of it or a considerably large part. The process is often used in reference to males whereas spaying is often reserved for females. Colloquially, both terms are often referred to as fixing...

 of animals, usually by removal of the male's testicle
Testicle
The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...

s or the female's ovaries
Ovary
The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in anatomically female individuals are analogous to testes in anatomically male individuals, in that they are both gonads and endocrine glands.-Human anatomy:Ovaries...

 and uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...

, in order to eliminate the ability to procreate and reduce sex drive. Because of the overpopulation of dogs in some countries, many animal control agencies, such as the American Society for the Prevention of Cruelty to Animals
American Society for the Prevention of Cruelty to Animals
The American Society for the Prevention of Cruelty to Animals is a non-profit organization dedicated to preventing cruelty towards animals...

 (ASPCA), advise that dogs not intended for further breeding should be neutered, so that they do not have undesired puppies that may have to later be euthanized.

According to the Humane Society of the United States
Humane Society of the United States
The Humane Society of the United States , based in Washington, D.C., is the largest animal advocacy organization in the world. In 2009, HSUS reported assets of over US$160 million....

, 3–4 million dogs and cats are put down
Euthanasia
Euthanasia refers to the practice of intentionally ending a life in order to relieve pain and suffering....

 each year in the United States and many more are confined to cages in shelters because there are many more animals than there are homes. Spaying or castrating dogs helps keep overpopulation down. Local humane societies, SPCAs, and other animal protection organizations urge people to neuter their pets and to adopt animals from shelters instead of purchasing them.

Neutering reduces problems caused by hypersexuality, especially in male dogs. Spayed female dogs are less likely to develop some forms of cancer, affecting mammary glands, ovaries, and other reproductive organs. However, neutering increases the risk of urinary incontinence
Urinary incontinence
Urinary incontinence is any involuntary leakage of urine. It is a common and distressing problem, which may have a profound impact on quality of life. Urinary incontinence almost always results from an underlying treatable medical condition but is under-reported to medical practitioners...

 in female dogs, and prostate cancer
Prostate cancer
Prostate cancer is a form of cancer that develops in the prostate, a gland in the male reproductive system. Most prostate cancers are slow growing; however, there are cases of aggressive prostate cancers. The cancer cells may metastasize from the prostate to other parts of the body, particularly...

 in males, as well as osteosarcoma, hemangiosarcoma, cruciate ligament rupture, obesity, and diabetes mellitus in either gender.

Intelligence



The domestic dog has a predisposition to exhibit a social intelligence that is uncommon in the animal world. Dogs are capable of learning in a number of ways, such as through simple reinforcement
Reinforcement learning
Inspired by behaviorist psychology, reinforcement learning is an area of machine learning in computer science, concerned with how an agent ought to take actions in an environment so as to maximize some notion of cumulative reward...

 (e.g., classical
Classical conditioning
Classical conditioning is a form of conditioning that was first demonstrated by Ivan Pavlov...

 or operant conditioning
Operant conditioning
Operant conditioning is a form of psychological learning during which an individual modifies the occurrence and form of its own behavior due to the association of the behavior with a stimulus...

) and by observation.

Dogs go through a series of stages of cognitive development. As with human
Human
Humans are the only living species in the Homo genus...

s, the understanding that objects not being actively perceived still remain in existence (called object permanence
Object permanence
Object permanence is the understanding that objects continue to exist even when they cannot be seen, heard, or touched. It is acquired by human infants between 8 and 12 months of age via the process of logical induction to help them develop secondary schemes in their sensori-motor coordination...

) is not present at birth. It develops as the young dog learns to interact intentionally with objects around it, at roughly 8 weeks of age.

Puppies learn behaviors quickly by following examples set by experienced dogs. This form of intelligence is not peculiar to those tasks dogs have been bred to perform, but can be generalized to myriad abstract problems. For example, Dachshund puppies that watched an experienced dog pull a cart by tugging on an attached piece of ribbon in order to get a reward from inside the cart learned the task fifteen times faster than those left to solve the problem on their own. Dogs can also learn by mimicking human behaviors. In one study, puppies were presented with a box, and shown that, when a handler pressed a lever, a ball would roll out of the box. The handler then allowed the puppy to play with the ball, making it an intrinsic reward. The pups were then allowed to interact with the box. Roughly three-quarters of the puppies subsequently touched the lever, and over half successfully released the ball, compared to only 6% in a control group that did not watch the human manipulate the lever. Another study found that handing an object between experimenters who then used the object's name in a sentence successfully taught an observing dog each object's name, allowing the dog to subsequently retrieve the item.

Dogs also demonstrate sophisticated social cognition
Social cognition
Social cognition is the encoding, storage, retrieval, and processing, in the brain, of information relating to conspecifics, or members of the same species. At one time social cognition referred specifically to an approach to social psychology in which these processes were studied according to the...

 by associating behavioral cues with abstract meanings. One such class of social cognition involves the understanding that others are conscious agents. Research has shown that dogs are capable of interpreting subtle social cues, and appear to recognize when a human or dog's attention is focused on them. To test this, researchers devised a task in which a reward was hidden underneath one of two buckets. The experimenter then attempted to communicate with the dog to indicate the location of the reward by using a wide range of signals: tapping the bucket, pointing to the bucket, nodding to the bucket, or simply looking at the bucket. The results showed that domestic dogs were better than chimpanzee
Chimpanzee
Chimpanzee, sometimes colloquially chimp, is the common name for the two extant species of ape in the genus Pan. The Congo River forms the boundary between the native habitat of the two species:...

s, wolves, and human infants at this task, and even young puppies with limited exposure to humans performed well.

Psychology research has shown that human faces are asymmetrical
Facial symmetry
Facial symmetry, is one element of bodily symmetry, including fluctuating asymmetry. Along with traits such as averageness and youthfulness it influences judgements of aesthetic traits of physical attractiveness and beauty, and is associated with fitness-linked traits including health, It is also...

 with the gaze instinctively moving to the right side of a face upon encountering other humans to obtain information about their emotions and state. Research at the University of Lincoln
University of Lincoln
The University of Lincoln is an English university founded in 1992, with origins tracing back to the foundation and association with the Hull School of Art 1861....

 (2008) shows that dogs share this instinct when meeting a human being, and only when meeting a human being (i.e., not other animals or other dogs). As such they are the only non-primate
Primate
A primate is a mammal of the order Primates , which contains prosimians and simians. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment...

 species known to do so.

Stanley Coren
Stanley Coren
Stanley Coren is a psychology professor and neuropsychological researcher who has become best known to the general public for a series of books regarding the intelligence, mental abilities and history of dogs...

, an expert on dog psychology, states that these results demonstrated the social cognition of dogs can exceed that of even our closest genetic relatives, and that this capacity is a recent genetic acquisition that distinguishes the dog from its ancestor, the wolf. Studies have also investigated whether dogs engaged in partnered play change their behavior depending on the attention-state of their partner. Those studies showed that play signals were only sent when the dog was holding the attention of its partner. If the partner was distracted, the dog instead engaged in attention-getting behavior before sending a play signal.

Coren has also argued that dogs demonstrate a sophisticated theory of mind by engaging in deception, which he supports with a number of anecdotes, including one example wherein a dog hid a stolen treat by sitting on it until the rightful owner of the treat left the room. Although this could have been accidental, Coren suggests that the thief understood that the treat's owner would be unable to find the treat if it were out of view. Together, the empirical data and anecdotal evidence
Anecdotal evidence
The expression anecdotal evidence refers to evidence from anecdotes. Because of the small sample, there is a larger chance that it may be true but unreliable due to cherry-picked or otherwise unrepresentative of typical cases....

 points to dogs possessing at least a limited form of theory of mind
Theory of mind
Theory of mind is the ability to attribute mental states—beliefs, intents, desires, pretending, knowledge, etc.—to oneself and others and to understand that others have beliefs, desires and intentions that are different from one's own...

.

A study found a third of dogs suffered from anxiety when separated from others.

A Border Collie
Border Collie
The Border Collie is a herding dog breed developed in the Anglo-Scottish border region for herding livestock, especially sheep. It is the most widespread of the collie breeds....

 named Chaser has learned the names for 1,022 toys after three years of training, so many that her trainers have had to mark the names of the objects lest they forget themselves. This is higher than Rico
Rico (Border Collie)
Rico was a border collie dog who made the news after being studied by animal psychologist Juliane Kaminski from the Max Planck Institute for Evolutionary Anthropology in Leipzig after his owners reported that he understood more than 200 simple words...

, another border collie who could remember at least 200 objects.

Behavior


Although dogs have been the subject of a great deal of behaviorist psychology
Behaviorism
Behaviorism , also called the learning perspective , is a philosophy of psychology based on the proposition that all things that organisms do—including acting, thinking, and feeling—can and should be regarded as behaviors, and that psychological disorders are best treated by altering behavior...

 (e.g. Pavlov's dog
Classical conditioning
Classical conditioning is a form of conditioning that was first demonstrated by Ivan Pavlov...

), they do not enter the world with a psychological "blank slate". Rather, dog behavior is affected by genetic factors as well as environmental factors. Domestic dogs exhibit a number of behaviors and predispositions that were inherited from wolves. The Gray Wolf
Gray Wolf
The gray wolf , also known as the wolf, is the largest extant wild member of the Canidae family...

 is a social animal
Social animal
A social animal is a loosely defined term for an organism that is highly interactive with other members of its species to the point of having a recognizable and distinct society.All mammals are social to the extent that mothers and offspring bond...

 that has evolved a sophisticated means of communication and social structure
Social structure
Social structure is a term used in the social sciences to refer to patterned social arrangements in society that are both emergent from and determinant of the actions of the individuals. The usage of the term "social structure" has changed over time and may reflect the various levels of analysis...

. The domestic dog has inherited some of these predispositions, but many of the salient characteristics in dog behavior have been largely shaped by selective breeding by humans. Thus some of these characteristics, such as the dog's highly developed social cognition
Social cognition
Social cognition is the encoding, storage, retrieval, and processing, in the brain, of information relating to conspecifics, or members of the same species. At one time social cognition referred specifically to an approach to social psychology in which these processes were studied according to the...

, are found only in primitive forms in grey wolves.

The existence and nature of personality traits in dogs have been studied (15329 dogs of 164 different breeds) and five consistent and stable "narrow traits" identified, described as playfulness, curiosity/fearlessness, chase-proneness, sociability and aggressiveness. A further higher order axis for shyness–boldness was also identified.

Sleep



The average sleep time of a dog is said to be 10.1 hours per day. Like humans, dogs have two main types of sleep: Slow-wave sleep
Slow-wave sleep
Slow-wave sleep , often referred to as deep sleep, consists of stages 3 and 4 of non-rapid eye movement sleep, according to the Rechtschaffen & Kales standard of 1968. As of 2008, the American Academy of Sleep Medicine has discontinued the use of stage 4, such that the previous stages 3 and 4 now...

, then Rapid Eye Movement
Rapid eye movement
Rapid eye movement sleep is a normal stage of sleep characterized by the random movement of the eyes. REM sleep is classified into two categories: tonic and phasic. It was identified and defined by Nathaniel Kleitman, Eugene Aserinsky, and Jon Birtwell in the early 1950s...

 sleep, the state in which dreams occur.

Dog growl


A new study in Budapest, Hungary has found that dogs are able to tell how big another dog is just by listening to its growl. A specific growl is used by dogs to protect their food. The research also shows that dogs do not lie about their size, and this is the first time research has shown animals can determine another’s size by the sound it makes. The test used image of many kind of dogs and together showed a small and big dog and also a growl. The result, showed that 20 of the 24 test dogs looked at the image of the appropriate-sized dog first and looked at it longest.

Differences from wolves



Physical characteristics



Compared to equally sized wolves, dogs tend to have 20% smaller skulls, 30% smaller brains, as well as proportionately smaller teeth than other canid species. Dogs require fewer calories to function than wolves. It is thought by certain experts that the dog's limp ears are a result of atrophy
Atrophy
Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations , poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself...

 of the jaw muscles. The skin of domestic dogs tends to be thicker than that of wolves, with some Inuit
Inuit
The Inuit are a group of culturally similar indigenous peoples inhabiting the Arctic regions of Canada , Denmark , Russia and the United States . Inuit means “the people” in the Inuktitut language...

 tribes favoring the former for use as clothing due to its greater resistance to wear and tear in harsh weather.

Behavior


Dogs tend to be poorer than wolves at observational learning
Observational learning
Observational learning is a type of learning that occurs as a function of observing, retaining and replicating novel behavior executed by others...

, being more responsive to instrumental conditioning
Operant conditioning
Operant conditioning is a form of psychological learning during which an individual modifies the occurrence and form of its own behavior due to the association of the behavior with a stimulus...

. Feral dogs show little of the complex social structure or dominance hierarchy
Dominance hierarchy
A dominance hierarchy is the organization of individuals in a group that occurs when competition for resources leads to aggression...

 present in wolf packs. For example, unlike wolves, the dominant alpha pairs of a feral dog pack do not force the other members to wait for their turn on a meal when scavenging off a dead ungulate as the whole family is free to join in. For dogs, other members of their kind are of no help in locating food items, and are more like competitors. Feral dogs are primarily scavengers, with studies showing that unlike their wild cousins, they are poor ungulate
Ungulate
Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...

 hunters, having little impact on wildlife populations where they are sympatric
Sympatric speciation
Sympatric speciation is the process through which new species evolve from a single ancestral species while inhabiting the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap or are even identical, so that...

. However, feral dogs have been reported to be effective hunters of reptiles in the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...

, and free ranging pet dogs are more prone to predatory behavior toward wild animals.

Domestic dogs can be monogamous
Monogamy
Monogamy /Gr. μονός+γάμος - one+marriage/ a form of marriage in which an individual has only one spouse at any one time. In current usage monogamy often refers to having one sexual partner irrespective of marriage or reproduction...

. Breeding in feral packs can be, but does not have to be restricted to a dominant alpha pair (such things also occur in wolf packs). Male dogs are unusual among canids by the fact that they mostly seem to play no role in raising their puppies, and do not kill the young of other females to increase their own reproductive success. Some sources say that dogs differ from wolves and most other large canid species by the fact that they do not regurgitate food for their young, nor the young of other dogs in the same territory.
However, this difference was not observed in all domestic dogs. Regurgitating of food by the females for the young as well as care for the young by the males has been observed in domestic dogs, dingo
Dingo
The Australian Dingo or Warrigal is a free-roaming wild dog unique to the continent of Australia, mainly found in the outback. Its original ancestors are thought to have arrived with humans from southeast Asia thousands of years ago, when dogs were still relatively undomesticated and closer to...

s as well as in other feral or semi-feral dogs. Regurgitating of food by the females and direct choosing of only one mate has been observed even in those semi-feral dogs of direct domestic dog ancestry. Also regurgitating of food by males has been observed in free-ranging domestic dogs.

Trainability



Dogs display much greater tractability than tame wolves, and are, in general, much more responsive to coercive techniques involving fear, aversive stimuli, and force than wolves, which are most responsive toward positive conditioning and rewards. Unlike tame wolves, dogs tend to respond more to voice than hand signals.

Mythology


In mythology, dogs often serve as pets or as watchdogs.

In Greek mythology
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...

, Cerberus
Cerberus
Cerberus , or Kerberos, in Greek and Roman mythology, is a multi-headed hound which guards the gates of the Underworld, to prevent those who have crossed the river Styx from ever escaping...

 is a three-headed watchdog who guards the gates of Hades
Hades
Hades , Hadēs, originally , Haidēs or , Aidēs , meaning "the unseen") was the ancient Greek god of the underworld. The genitive , Haidou, was an elision to denote locality: "[the house/dominion] of Hades". Eventually, the nominative came to designate the abode of the dead.In Greek mythology, Hades...

. In Norse mythology
Norse mythology
Norse mythology, a subset of Germanic mythology, is the overall term for the myths, legends and beliefs about supernatural beings of Norse pagans. It flourished prior to the Christianization of Scandinavia, during the Early Middle Ages, and passed into Nordic folklore, with some aspects surviving...

, a bloody, four-eyed dog called Garmr guards Helheim
Helheim
-Biography:Helheim was founded in 1992 by V’gandr and H’grimnir , who added drummer Hrymr. The band began performing in local Bergen festivals, and in 1993, the band released their debut demo, Helheim, distributed only within Norway.Soon after the release of their first demo, the band began...

. In Persian mythology
Persian mythology
Persian mythology are traditional tales and stories of ancient origin, some involving extraordinary or supernatural beings. Drawn from the legendary past of the Iranian cultural continent which especially consists of the state of Iran, Afghanistan, Tajikistan and Central Asia, they reflect the...

, two four-eyed dogs guard the Chinvat Bridge
Chinvat bridge
The Chinvat Bridge in Zoroastrianism is the bridge which separates the world of the living from the world of the dead. All souls must cross the bridge upon death....

. In Philippine mythology
Philippine mythology
Philippine mythology include a collection of tales and superstitions about magical creatures and entities. Some Filipinos, even though heavily westernized and Christianized, still believe on these tales...

, Kimat who is the pet of Tadaklan, god of thunder, is responsible for lightning. In Welsh mythology
Welsh mythology
Welsh mythology, the remnants of the mythology of the pre-Christian Britons, has come down to us in much altered form in medieval Welsh manuscripts such as the Red Book of Hergest, the White Book of Rhydderch, the Book of Aneirin and the Book of Taliesin....

, Annwn
Annwn
Annwn or Annwfn was the Otherworld in Welsh mythology. Ruled by Arawn, or much later by Gwyn ap Nudd, it was essentially a world of delights and eternal youth where disease is absent and food is ever-abundant. It later became Christianised and identified with the land of souls that had departed...

 is guarded by Cŵn Annwn
Cwn Annwn
In Welsh mythology and folklore, Cŵn Annwn were the spectral hounds of Annwn, the otherworld of Welsh myth. They were associated with a form of the Wild Hunt, presided over by Gwynn ap Nudd...



In Judaism and Islam, dogs are viewed as unclean scavengers. In Christianity, dogs represent faithfulness. In Asian countries such as China, Korea, and Japan, dogs are viewed as kind protectors.

Gallery of dogs in art



See also


  • Argos (dog)
    Argos (dog)
    In Homer's the Odyssey, Argos is Odysseus' faithful dog. After twenty years struggling to get home to Ithaca, Odysseus finally arrives at his homeland. In his absence, reckless suitors have taken over his house in hopes of marrying his wife Penelope...

  • Dog odor
    Dog odor
    Dogs, as all mammals, have natural odors. Natural dog odor can be unpleasant to dog owners especially when dogs are kept inside the home, as some people are not used to being exposed to the natural odor of a non-human species living in close proximity to them...

  • Dog king – Scandinavian tradition
  • Dognapping
    Dognapping
    Dognapping is the crime of taking a dog from its owner with the intention of demanding a ransom. Historically in the United States, dogs had been stolen and sold on for medical research, but the introduction of the Animal Welfare Act of 1966 reduced these occurrences...

  • Ethnocynology
    Ethnocynology
    Ethnocynology, is a neologism coined by anthropologist Bryan Cummins in his book First Nations, First Dogs: Canadian Aboriginal Ethnocynology . It refers to the study of dogs within their cultural contexts. The term has not been generally accepted....

  • Hachikō
    Hachiko
    , known in Japanese as chūken Hachikō , was an Akita dog born on a farm near the city of Ōdate, Akita Prefecture, remembered for his remarkable loyalty to his owner, even many years after his owner's death.-Life:In 1924, Hidesaburō Ueno,...

     Dog loyalty
  • List of dog breeds
  • List of dogs
  • List of fictional dogs
  • List of most popular dog breeds
  • New Guinea Singing Dog
    New Guinea Singing Dog
    The New Guinea Singing Dog is a wild dog once found throughout New Guinea. New Guinea Singing Dogs are named for their unique howl....

  • Subspecies of Canis lupus
    Subspecies of Canis lupus
    Canis lupus has 39 subspecies currently described, including two subspecies of domestic dog, Canis lupus dingo and Canis lupus familiaris, and many subspecies of wolf throughout the Northern hemisphere...

  • Wolfdog
    Wolfdog
    A wolfdog is a canid hybrid resulting from the mating of a wolf and a dog . The term "wolfdog" is preferred by most of the animals' proponents and breeders because the domestic dog recently was taxonomically recategorized as a subspecies of wolf...



External links