Dogs have been bred for desired behaviors, sensory capabilities, and physical attributes.Dog breeds vary widely in shape, size, and color. They have the same number of bones (with the exception of the tail), powerful jaws that house around 42 teeth, and well-developedsenses of smell, hearing, and sight. Compared to humans, dogs possess a superior sense of smell and hearing, but inferiorvisual acuity. Dogs perform many roles for humans, such ashunting,herding,pulling loads,protection,companionship,therapy,aiding disabled people, andassisting police and themilitary.
Communication in dogs includes eye gaze, facial expression, vocalization, body posture (including movements of bodies and limbs), and gustatory communication (scents, pheromones, and taste). They mark their territories by urinating on them, which is more likely when entering a new environment. Over the millennia, dogs have uniquely adapted to human behavior; this adaptation includes being able to understand and communicate with humans. As such, thehuman–canine bond has been a topic of frequent study, and dogs' influence on human society has given them thesobriquet of "man's best friend".
The global dog population is estimated at 700 million to 1 billion,distributed around the world. The dog is the most popular pet in the United States, present in 34–40% of households. Developed countries make up approximately 20% of the global dog population, while around 75% of dogs are estimated to be from developing countries, mainly in the form of feral and community dogs.
Cladogram and divergence of the gray wolf (including the domestic dog) among its closest extant relatives[4]
Dogs are domesticated members of the familyCanidae. They are classified as asubspecies ofCanis lupus, along withwolves anddingoes.[5][6] Dogs were domesticated from wolves over 14,000 years ago byhunter-gatherers, before the development of agriculture.[7][8] The remains of theBonn–Oberkassel dog, buried alongside humans between 14,000 and 15,000 years ago, are the earliest to be conclusively identified as a domesticated dog.[9][7] Genetic studies show that dogs likely diverged from wolves between 27,000 and 40,000 years ago.[10] The dingo and the relatedNew Guinea singing dog resulted from thegeographic isolation and feralization of dogs inOceania over 8,000 years ago.[11][12]
Dogs, wolves, anddingoes have sometimes been classified as separate species.[6] In 1758, the Swedish botanist and zoologistCarl Linnaeus assigned thegenus nameCanis (which is theLatin word for "dog")[13] to the domestic dog, thewolf, and thegolden jackal in his book,Systema Naturae. He classified the domestic dog asCanis familiaris and, on the next page, classified the grey wolf asCanis lupus.[2] Linnaeus considered the dog to be a separate species from the wolf because of its upturning tail (cauda recurvata inLatin term), which is not found in any othercanid.[14] In the 2005 edition ofMammal Species of the World,mammalogistW. Christopher Wozencraft listed the wolf as a wild subspecies ofCanis lupus and proposed two additional subspecies:familiaris, as named by Linnaeus in 1758, anddingo, named by Meyer in 1793. Wozencraft includedhallstromi (the New Guinea singing dog) as another name (junior synonym) for the dingo. This classification was informed by a 1999mitochondrial DNA study.[3]
The classification of dingoes is disputed and a political issue in Australia. Classifying dingoes as wild dogs simplifies reducing or controlling dingo populations that threaten livestock. Treating dingoes as a separate species allows conservation programs to protect the dingo population.[15] Dingo classification affects wildlife management policies, legislation, and societal attitudes.[16] In 2019, a workshop hosted by theIUCN/Species Survival Commission's Canid Specialist Group considered the dingo and the New Guinea singing dog to beferalCanis familiaris. Therefore, it did not assess them for theIUCN Red List ofthreatened species.[17]
Wolves (left) were domesticated by humans into dogs (right)
The earliest remains generally accepted to be those of a domesticated dog were discovered inBonn-Oberkassel, Germany.Contextual,isotopic,genetic, andmorphological evidence shows that this dog was not a local wolf.[18] The dog was dated to 14,223 years ago and was found buried along with a man and a woman, all three having been sprayed with redhematite powder and buried under large, thick basalt blocks. The dog had died ofcanine distemper.[19] This timing indicates that the dog was thefirst species to be domesticated[20][21] in the time ofhunter-gatherers,[22] which predates agriculture.[1] Earlier remains dating back to 30,000 years ago have been described asPaleolithic dogs, but their status as dogs or wolves remains debated[23] because considerable morphological diversity existed among wolves during theLate Pleistocene.[1]
DNA sequences show that all ancient and modern dogs share a common ancestry and descended from an ancient, extinct wolf population that was distinct from anymodern wolf lineage. Some studies have posited that all living wolves are more closely related to each other than to dogs,[24][22] while others have suggested that dogs are more closely related to modern Eurasian wolves than to American wolves.[25]
The dog is a domestic animal that likely travelled acommensal pathway into domestication (i.e. humans initially neither benefitted nor were harmed by wild dogs eating refuse from their camps).[23][26] The questions of when and where dogs were first domesticated remains uncertain.[20] Genetic studies suggest a domestication process commencing over 25,000 years ago, in one or several wolf populations in either Europe, the high Arctic, or eastern Asia.[27] In 2021, aliterature review of the current evidenceinfers that the dog was domesticated inSiberia 23,000 years ago byancient North Siberians, then later dispersed eastward into the Americas and westward across Eurasia,[18] with dogs likely accompanying the first humans to inhabit the Americas.[18] Some studies have suggested that the extinctJapanese wolf is closely related to the ancestor of domestic dogs.[25]
In 2018, a study identified 429 genes that differed between modern dogs and modern wolves. As the differences in these genes could also be found in ancient dog fossils, these were regarded as being the result of the initial domestication and not from recent breed formation. These genes are linked toneural crest andcentral nervous system development. These genes affectembryogenesis and can confer tameness, smaller jaws, floppy ears, and diminished craniofacial development, which distinguish domesticated dogs from wolves and are considered to reflect domestication syndrome. The study concluded that during early dog domestication, the initial selection was for behavior. This trait is influenced by those genes which act in the neural crest, which led to the phenotypes observed in modern dogs.[28]
There are around 450 officialdog breeds, the most of any mammal.[27][29] Dogs began diversifying in theVictorian era, when humans took control of their natural selection.[21] Most breeds were derived from small numbers of founders within the last 200 years.[21][27] Since then, dogs have undergone rapidphenotypic change and have been subjected toartificial selection by humans. The skull, body, and limb proportions between breeds display more phenotypic diversity than can be found within the entire order ofcarnivores. These breeds possess distinct traits related to morphology, which include body size, skull shape, tail phenotype, fur type, and colour.[21] As such, humans have long used dogs for their desirable traits to complete or fulfill a certain work or role. Their behavioural traits include guarding, herding, hunting,[21] retrieving, and scent detection. Their personality traits include hypersocial behavior, boldness, and aggression.[21] Present-day dogs are dispersed around the world.[27] An example of this dispersal is the numerous modern breeds of European lineage during the Victorian era.[22]
Dogs are extremely variable in size, ranging from one of the largest breeds, theGreat Dane, at 50 to 79 kg (110 to 174 lb) and 71 to 81 cm (28 to 32 in), to one of the smallest, theChihuahua, at 0.5 to 3 kg (1.1 to 6.6 lb) and 13 to 20 cm (5.1 to 7.9 in).[30][31] All healthy dogs, regardless of their size and type, have the same amount of bones (with the exception of the tail), although there is significant skeletal variation between dogs of different types.[32][33] The dog's skeleton is well adapted for running; thevertebrae on the neck and back have extensions for back muscles, consisting ofepaxial muscles and hypaxial muscles, to connect to; the long ribs provide room for theheart andlungs; and the shoulders are unattached to the skeleton, allowing for flexibility.[32][33][34]
Compared to the dog's wolf-like ancestors, selective breeding since domestication has seen the dog's skeleton increase in size for larger types such asmastiffs and miniaturised for smaller types such asterriers;dwarfism has been selectively bred for some types where short legs are preferred, such asdachshunds andcorgis.[33] Most dogs naturally have 26 vertebrae in their tails, but some withnaturally short tails have as few as three.[32]
Skulls of different breeds, from left to right: Pug; Boxer; Rottweiler; Wolf; Collie; Standard Poodle.
The dog's skull has identical components regardless of breed type, but there is significantdivergence in terms of skull shape between types.[33][35] The three basic skull shapes are the elongated dolichocephalic type as seen insighthounds, the intermediate mesocephalic or mesaticephalic type, and the very short and broad brachycephalic type exemplified by mastiff type skulls.[33][35] The jaw contains around 42 teeth, and it has evolved for the consumption of flesh. Dogs use theircarnassial teeth to cut food into bite-sized chunks, more especially meat.[36]
The left half of the image shows the estimated difference in a dog's vision.
Dogs' senses include vision, hearing, smell, taste, touch, andmagnetoreception. One study suggests that dogs can feel small variations inEarth's magnetic field.[37] Dogs prefer to defecate with their spines aligned in a north–south position in calmmagnetic field conditions.[38]
Dogs' vision isdichromatic; their visual world consists of yellows, blues, and grays.[39] They have difficulty differentiating between red and green,[40] and much like other mammals, the dog's eye is composed of two types of cone cells compared to the human's three. The divergence of the eye axis of dogs ranges from 12 to 25°, depending on the breed, which can have different retina configurations.[41][42] Thefovea centralis area of the eye is attached to anerve fiber, and is the most sensitive tophotons.[43] Additionally, a study found that dogs'visual acuity was up to eight times less effective than a human, and their ability to discriminate levels ofbrightness was about two times worse than a human.[44]
While the human brain is dominated by a largevisual cortex, the dog brain is dominated by a largeolfactory cortex. Dogs have roughly forty times moresmell-sensitive receptors than humans, ranging from about 125million to nearly 300million in some dog breeds, such asbloodhounds.[45] This sense of smell is the most prominent sense of the species; it detects chemical changes in the environment, allowing dogs to pinpoint the location of mating partners, potential stressors, resources, etc.[46] Dogs also have an acute sense of hearing up to four times greater than that of humans. They can pick up the slightest sounds from about 400 m (1,300 ft) compared to 90 m (300 ft) for humans.[47]
Dogs have stiff, deeply embedded hairs known aswhiskers that sense atmospheric changes, vibrations, and objects not visible in low light conditions. The lower most part of whiskers hold more receptor cells than other hair types, which help in alerting dogs of objects that could collide with the nose, ears, and jaw. Whiskers likely also facilitate the movement of food towards the mouth.[48]
Thecoats of domestic dogs are of two varieties: "double" being common in dogs (as well as wolves) originating from colder climates, made up of a coarseguard hair and a softdown hair, or "single", with the topcoat only. Breeds may have an occasional "blaze", stripe, or "star" of white fur on their chest or underside.[49] Premature graying can occur in dogs as early as one year of age; this is associated withimpulsive behaviors,anxiety behaviors, and fear of unfamiliar noise, people, or animals.[50] Some dog breeds are hairless, while others have a very thick corded coat. The coats of certain breeds are often groomed to a characteristic style, for example, theYorkshire Terrier's "show cut".[36]
Dewclaw
A dog'sdewclaw is the fifthdigit in its forelimb and hind legs. Dewclaws on the forelimbs are attached by bone and ligament, while the dewclaws on the hind legs are attached only by skin. Most dogs are not born with dewclaws in their hind legs, and some are without them in their forelimbs. Dogs' dewclaws consist of theproximal phalanges and distal phalanges. Some publications theorize that dewclaws in wolves, who usually do not have dewclaws, were a sign of hybridization with dogs.[51][52]
Tail
A dog's tail is the terminal appendage of thevertebral column, which is made up of a string of 5 to 23vertebrae enclosed in muscles and skin that support the dog's back extensor muscles. One of the primary functions of a dog's tail is to communicate their emotional state.[53] The tail also helps the dog maintain balance by putting its weight on the opposite side of the dog's tilt, and it can also help the dog spread itsanal gland's scent through the tail's position and movement.[54] Dogs can have aviolet gland (or supracaudal gland) characterized bysebaceous glands on the dorsal surface of their tails; in some breeds, it may be vestigial or absent. The enlargement of the violet gland in the tail, which can create abald spot from hair loss, can be caused byCushing's disease or an excess of sebum fromandrogens in the sebaceous glands.[55]
A study suggests that dogs show asymmetric tail-wagging responses to different emotive stimuli. "Stimuli that could be expected to elicit approach tendencies seem to be associated with [a] higher amplitude of tail-wagging movements to the right side".[56][57] Dogs can injure themselves by wagging their tails forcefully; this condition is calledkennel tail,happy tail,bleeding tail, orsplitting tail.[58] In somehunting dogs, the tail is traditionallydocked to avoid injuries. Some dogs can be born without tails because of a DNA variant in theT gene, which can also result in a congenitally short (bobtail) tail.[59] Tail docking is opposed by many veterinary and animal welfare organisations such as theAmerican Veterinary Medical Association[60] and theBritish Veterinary Association.[61] Evidence from veterinary practices andquestionnaires showed that around 500 dogs would need to have their tail docked to prevent one injury.[62]
Dogs are the companion animal most frequently reported for exposure totoxins. Most poisonings are accidental and over 80% of reports of exposure to theASPCA animal poisoning hotline are due to oral exposure. The most common substances people report exposure to are: pharmaceuticals, toxic foods, androdenticides.[67] Data from the Pet Poison Helpline shows that human drugs are the most frequent cause of toxicosis death. The most common household products ingested are cleaning products. Most food related poisonings involvedtheobromine poisoning (chocolate). Other common food poisonings includexylitol,Vitis (grapes, raisins, etc.), andAllium (garlic, onions, etc.).Pyrethrin insecticides were the most common cause of pesticide poisoning.Metaldehyde, a common pesticide for snails and slugs, typically causes severe outcomes when ingested by dogs.[68]
Neoplasia is the most common cause of death for dogs.[69][70][71] Other common causes of death areheart andrenal failure.[71] Theirpathology is similar to that of humans, as is theirresponse to treatment and their outcomes. Genes found in humans to be responsible for disorders are investigated in dogs as being the cause and vice versa.[27][72]
The typical lifespan of dogs varies widely among breeds, but the median longevity (the age at which half the dogs in a population have died and half are still alive) is approximately 12.7 years.[73][74] Obesity correlates negatively with longevity with one study finding obese dogs to have a life expectancy approximately a year and a half less than dogs with a healthy weight.[73]
In a 2024 UK study analyzing 584,734 dogs, it was concluded that purebred dogs lived longer than crossbred dogs, challenging the previous notion of the latter having the higher life expectancies. The authors noted that their study included "designer dogs" as crossbred and that purebred dogs were typically given better care than their crossbred counterparts, which likely influenced the outcome of the study.[75] Other studies also show that fully mongrel dogs live about a year longer on average than dogs with pedigrees.[76] Furthermore, small dogs with longer muzzles have been shown to have higher lifespans than larger medium-sized dogs with much more depressed muzzles.[77] For free-ranging dogs, less than 1 in 5 reach sexual maturity,[78] and the median life expectancy for feral dogs is less than half of dogs living with humans.[79]
In domestic dogs,sexual maturity happens around six months to one year for both males and females, although this can be delayed until up to two years of age for some large breeds. This is the time at which female dogs will have their firstestrous cycle, characterized by theirvulvas swelling and producingdischarges, usually lasting between 4 and 20 days.[80][81] They will experience subsequent estrous cycles semiannually, during which the body prepares forpregnancy. At the peak of the cycle, females will become estrous, mentally and physically receptive tocopulation. Because theova survive and can be fertilized for a week after ovulation, more than one male can sire the same litter.[82] Fertilization typically occurs two to five days after ovulation. Afterejaculation, the dogs arecoitally tied for around 5–30 minutes because of the male'sbulbus glandis swelling and the female'sconstrictor vestibuli contracting; the male will continue ejaculating until they untie naturally due tomuscle relaxation.[83] 14–16 days after ovulation, the embryo attaches to theuterus, and after seven to eight more days, a heartbeat is detectable.[84][85] Dogs bear their litters roughly 58 to 68 days afterfertilization,[82][86] with an average of 63 days, although the length ofgestation can vary. An average litter consists of about sixpuppies.[87]
Neutering is the most common surgical procedure in dogs less than a year old in the US and is seen as a control method for overpopulation. Neutering often occurs as early as 6–14 weeks in shelters in the US.[93] TheAmerican Society for the Prevention of Cruelty to Animals (ASPCA) advises that dogs not intended for further breeding should be neutered so that they do not have undesired puppies that may later be euthanized.[94][95] However, the Society for Theriogenology and the American College of Theriogenologists made a joint statement that opposes mandatory neutering; they said that the cause of overpopulation in the US is cultural.[93]
Neutering is less common in most European countries, especially inNordic countries—except for the UK, where it is common. In Norway, neutering is illegal unless for the benefit of the animal's health (e.g., ovariohysterectomy in case of ovarian or uterine neoplasia). Some European countries have similar laws to Norway, but their wording either explicitly allows for neutering for controlling reproduction or it is allowed in practice or by contradiction through other laws. Italy and Portugal have passed recent laws that promote it. Germany forbids early age neutering, but neutering is still allowed at the usual age. In Romania, neutering is mandatory except for when a pedigree to select breeds can be shown.[93][96]
A common breeding practice for pet dogs is tomate them between close relatives (e.g., between half- and full-siblings).[97] In a study of seven dog breeds (theBernese Mountain Dog,Basset Hound,Cairn Terrier,Brittany,German Shepherd Dog,Leonberger, andWest Highland White Terrier), it was found that inbreeding decreases litter size and survival.[98] Another analysis of data on 42,855Dachshund litters found that as theinbreeding coefficient increased, litter size decreased and the percentage of stillborn puppies increased, thus indicating inbreeding depression.[99] In a study ofBoxer litters, 22% of puppies died before reaching 7 weeks of age. Stillbirth was the most frequent cause of death, followed by infection. Mortality due to infection increased significantly with increases in inbreeding.[100]
Dog behavior has been shaped by millennia of contact with humans. They have acquired the ability to understand and communicate with humans and are uniquely attuned to human behaviors.[101][102] Behavioral scientists suggest that a set of social-cognitive abilities in domestic dogs that are not possessed by the dog's canine relatives or other highly intelligent mammals, such asgreat apes, are parallel to children's social-cognitive skills.[103] Dogs have about twice the number of neurons in their cerebral cortexes than what cats have, which suggests they could be about twice as intelligent.[104]
Most domestic animals were initially bred for the production of goods. Dogs, on the other hand, were selectively bred for desirable behavioral traits.[105][106] In 2016, a study found that only 11 fixed genes showed variation between wolves and dogs.[107] These gene variations indicate the occurrence ofartificial selection and the subsequent divergence of behavior and anatomical features. These genes have been shown to affect thecatecholamine synthesis pathway, with the majority of the genes affecting thefight-or-flight response[106][108] (i.e., selection fortameness) and emotional processing.[106] Compared to their wolf counterparts, dogs tend to be less timid and less aggressive, though some of these genes have been associated with aggression in certain dog breeds.[109][106] Traits of high sociability and lack of fear in dogs may include genetic modifications related toWilliams-Beuren syndrome in humans, which causehypersociability at the expense ofproblem-solving ability.[110] In a 2023 study of 58 dogs, some dogs classified asattention deficit hyperactivity disorder-like showed lowerserotonin anddopamine concentrations.[111] A similar study claims that hyperactivity is more common in male and young dogs.[112] A dog can become aggressive because of trauma or abuse, fear or anxiety, territorial protection, or protecting an item it considers valuable.[113]Acute stress reactions frompost-traumatic stress disorder (PTSD) seen in dogs can evolve intochronic stress.[114] Police dogs with PTSD can often refuse to work.[115]
Dog swimming over to catch a ball
Dogs have a natural instinct calledprey drive (the term is chiefly used to describetraining dogs' habits) which can be influenced by breeding. These instincts can drive dogs to consider objects or other animals to be prey or drive possessive behavior. These traits have been enhanced in some breeds so that they may be used to hunt and killvermin or other pests.[116] Puppies or dogs sometimesbury food underground. One study found that wolves outperformed dogs in finding food caches, likely due to a "difference in motivation" between wolves and dogs.[117] Some puppies and dogs engage incoprophagy out of habit, stress, for attention, or boredom; most of them will not do it later in life. A study hypothesizes that the behavior was inherited from wolves, a behavior likely evolved to lessen the presence ofintestinal parasites in dens.[118] Most dogs can swim. In a study of 412 dogs, around 36.5% of the dogs could not swim; the other 63.5% were able to swim without a trainer in aswimming pool.[119] A study of 55 dogs found a correlation between swimming and 'improvement' of the hiposteoarthritis joint.[120]
Nursing
A female dog nursing her newborn puppies.
The female dog may producecolostrum, a type of milk high in nutrients and antibodies, 1–7 days before giving birth. Milk production lasts for around three months,[121][122] and increases with litter size.[122] The dog can sometimes vomit and refuse food duringchild contractions.[123] In the later stages of the dog's pregnancy,nesting behaviour may occur.[124] Puppies are born with aprotective fetal membrane that the mother usually removes shortly after birth. Dogs can have the maternal instincts to start grooming their puppies, consume their puppies' feces, and protect their puppies, likely due to their hormonal state.[125][126] While male-parent dogs can show more disinterested behaviour toward their own puppies,[127] most can play with the young pups as they would with other dogs or humans.[128] A female dog may abandon or attack her puppies or her male partner dog if she is stressed or in pain.[129]
Researchers have tested dogs' ability to perceive information, retain it as knowledge, and apply it to solve problems. Studies of two dogs suggest that dogs can learn byinference. A study withRico, aBorder Collie, showed that he knew the labels of over 200 different items. He inferred the names of novel things by exclusion learning and correctly retrieved those new items after four weeks of the initial exposure. A study of another Border Collie, Chaser, documented that he had learned the names and could associate them by verbal command with over 1,000 words.[130]
One study of canine cognitive abilities found that dogs' capabilities are similar to those ofhorses,chimpanzees, orcats.[131] One study of 18 household dogs found that the dogs could not distinguish food bowls at specific locations without distinguishing cues; the study stated that this indicates a lack ofspatial memory.[132] A study stated that dogs have avisual sense for number. The dogs showed a ratio-dependentactivation both for numerical values from 1–3 to larger than four.[133]
Dogs demonstrate atheory of mind by engaging in deception.[134] Another experimental study showed evidence that Australiandingos can outperform domestic dogs in non-social problem-solving, indicating that domestic dogs may have lost much of their original problem-solving abilities once they joined humans.[135] Another study showed that dogs stared at humans after failing to complete an impossible version of the same task they had been trained to solve. Wolves, under the same situation, avoided staring at humans altogether.[136]
Dog communication is the transfer of information between dogs, as well as between dogs and humans.[137] Communication behaviors of dogs include eye gaze, facial expression,[138][139] vocalization, body posture (including movements of bodies and limbs), and gustatory communication (scents, pheromones, and taste). Dogs mark theirterritories by urinating on them, which is more likely when entering a new environment.[140][141] Both sexes of dogs may also urinate to communicate anxiety or frustration, submissiveness, or when in exciting or relaxing situations.[142] Aroused dogs can be a result of the dogs' highercortisol levels.[143] Dogs begin socializing with other dogs by the time they reach the ages of 3 to 8 weeks, and at about 5 to 12 weeks of age, they alter their focus from dogs to humans.[144] Belly exposure in dogs can be a defensive behavior that can lead to a bite or to seek comfort.[145]
Humans communicate with dogs by using vocalization, hand signals, and body posture. With their acute sense of hearing, dogs rely on the auditory aspect of communication for understanding and responding to various cues, including the distinctivebarking patterns that convey different messages. A study usingfunctional magnetic resonance imaging (fMRI) has shown that dogs respond to both vocal and nonvocal voices using the brain's region towards thetemporal pole, similar to that of humans' brains. Most dogs also looked significantly longer at the face whose expression matched thevalence of vocalization.[146][147][148] A study ofcaudate responses shows that dogs tend to respond more positively to social rewards than to food rewards.[149]
Ecology
Population
The dog is the most widely abundant largecarnivoran living in the human environment.[150][151] In 2020, the estimated global dog population was between 700 million and 1 billion.[152] In the same year, a study found the dog to be the most popular pet in the United States, as they were present in 34 out of every 100 homes.[5] About 20% of the dog population live indeveloped countries.[153] In thedeveloping world, it is estimated that three-quarters of the world's dog population lives in the developing world asferal,village, or community dogs.[154] Most of these dogs live asscavengers and have never been owned by humans, with one study showing that village dogs' most common response when approached by strangers is to run away (52%) or respond aggressively (11%).[155]
Competitors
Feral andfree-ranging dogs' potential to compete with other large carnivores is limited by their strong association with humans.[150] Although wolves are known to kill dogs, wolves tend to live in pairs in areas where they are highly persecuted, giving them a disadvantage when facing large dog groups.[156][157] 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.[158] Although the numbers of dogs killed each year are relatively low, there is still a fear among humans of wolves entering villages and farmyards to take dogs, and losses of dogs to wolves have led to demands for more liberal wolf hunting regulations.[156]
Coyotes andbig cats have also been known to attack dogs. In particular,leopards are known to have a preference for dogs and have been recorded to kill and consume them, no matter their size.[159]Siberian tigers in theAmur river region have killed dogs in the middle of villages. They will not tolerate wolves as competitors within their territories, and the tigers could be considering dogs in the same way.[160]Striped hyenas are known to kill dogs in their range.[161] Dogs as introduced predators have affected the ecology ofNew Zealand, which lacked indigenous land-based mammals before human settlement.[162] Dogs have made 11vertebrate species extinct and are identified as a 'potential threat' to at least 188 threatened species worldwide.[163] Dogs have also been linked to the extinction of 156 animal species.[164] Dogs have been documented to have killed a few birds of the endangered species, thekagu, inNew Caledonia.[165]
Dogs are typically described asomnivores.[82][166][167] Compared to wolves, dogs from agricultural societies haveextra copies of amylase and other genes involved in starch digestion that contribute to an increased ability to thrive on a starch-rich diet.[168] Similar to humans, some dog breeds produce amylase in theirsaliva and are classified as having a high-starch diet.[169] Despite being an omnivore, dogs are only able to conjugatebile acid withtaurine. They must getvitamin D from their diet.[170]
The keeping of dogs as companions, particularly by elites, has a long history.[195] Pet-dog populations grew significantly afterWorld War II assuburbanization increased.[195] In the 1980s, there have been changes in the pet dog's functions, such as the increased role of dogs in theemotional support of their human guardians.[196][197][198] Within the second half of the 20th century, more and more dog owners considered their animal to be a part of the family. This major social status shift allowed the dog to conform to social expectations of personality and behavior.[198] The second has been the broadening of the concepts of family and the home to include dogs-as-dogs within everyday routines and practices.[198]
Products such as dog-training books, classes, and television programs target dog owners.[199][200] Some dog-trainers have promoted adominance model of dog-human relationships. However, the idea of the"alpha dog" trying to be dominant is based on a controversial theory about wolf packs.[201][202] It has been disputed that "trying to achieve status" is characteristic of dog-human interactions.[203] Human family members have increased participation in activities in which the dog is an integral partner, such asdog dancing anddog yoga.[199]
According to statistics published by the American Pet Products Manufacturers Association in the National Pet Owner Survey in 2009–2010, an estimated 77.5 million people in the United States have pet dogs.[204] The source shows that nearly 40% of American households own at least one dog, of which 67% own just one dog, 25% own two dogs, and nearly 9% own more than two dogs. The data also shows an equal number of male and female pet dogs; less than one-fifth of the owned dogs come fromshelters.[205]
Dogs compete in breed-conformation shows anddog sports (includingracing,sledding, andagility competitions). In dog 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 abreed standard.[215]Weight pulling, a dog sport involving pulling weight, has been criticized for promotingdoping and for its risk of injury.[216]
Humans have consumed dog meat going back at least 14,000 years. It is unknown to what extent prehistoric dogs were consumed and bred for meat. For centuries, the practice was prevalent inSoutheast Asia,East Asia, Africa, andOceania before cultural changes triggered by the spread of religions resulted in dog meat consumption declining and becoming more taboo.[217]Switzerland,Polynesia, andpre-Columbian Mexico historically consumed dog meat.[218][219][220] SomeNative American dogs, like thePeruvian Hairless Dog andXoloitzcuintle, were raised to be sacrificed and eaten.[221][222]Han Chinese traditionally ate dogs.[223] Consumption of dog meat declined but did not end during theSui dynasty (581–618) andTang dynasty (618–907) due in part to the spread of Buddhism and the upper class rejecting the practice.[224][225] Dog consumption was rare in India, Iran, and Europe.[217]
Eating dog meat is asocial taboo in most parts of the world,[226] though some still consume it inmodern times.[227][228] It is still consumed in someEast Asian countries, includingChina,[193]Vietnam,[194]Korea,[229]Indonesia,[230] and thePhilippines.[231] An estimated 30 million dogs are killed and consumed in Asia every year.[223] China is the world's largest consumer of dogs, with an estimated 10 to 20 million dogs killed every year for human consumption.[232] In Vietnam, about 5 million dogs are slaughtered annually.[233] In 2024, China, Singapore, and Thailand placed a ban on the consumption of dogs within their borders.[234] In some parts ofPoland[235][236] andCentral Asia,[237][238] dog fat is reportedly believed to be beneficial for the lungs.[239] Proponents of eating dog meat have argued that placing a distinction between livestock and dogs is Western hypocrisy and that there is no difference in eating different animals' meat.[240][241][242][243]
There is a long history ofdog meat consumption in South Korea, but the practice has fallen out of favor.[244] A 2017 survey found that under 40% of participants supported a ban on the distribution and consumption of dog meat. This increased to over 50% in 2020, suggesting changing attitudes, particularly among younger individuals.[7] In 2018, theSouth Korean government passed a bill banning restaurants that sell dog meat from doing so during that year'sWinter Olympics.[245] On 9 January 2024, theSouth Korean parliament passed a law banning the distribution and sale of dog meat. It will take effect in 2027, with plans to assist dog farmers in transitioning to other products.[246] The primary type of dog raised for meat in South Korea has been theNureongi.[247] InNorth Korea where meat is scarce, eating dog is a common and accepted practice, officially promoted by the government.[248][249]
In 2018, theWorld Health Organization (WHO) reported that 59,000 people died globally fromrabies, with 59.6% of the deaths in Asia and 36.4% in Africa. Rabies is a disease for which dogs are the most significantvector.[250] Dog bites affect tens of millions of people globally each year.[251] The primary victims of dog bite incidents are children. They are more likely to sustain more serious injuries from bites, which can lead to death.[251] Sharp claws can lacerate flesh and cause serious infections.[252]In the United States, cats and dogs are a factor in more than 86,000 falls each year.[253] It has been estimated that around 2% of dog-related injuries treated in U.K. hospitals are domestic accidents. The same study concluded that dog-associatedroad accidents involving injuries more commonly involvetwo-wheeled vehicles.[254] Some countries and cities have also banned or restricted certain dog breeds, usually for safety concerns.[255]
Toxocara canis (dogroundworm) eggs in dog feces can causetoxocariasis. It is estimated that nearly 14% of people in the United States are infected withToxocara; about 10,000 cases are reported each year.[256] Untreated toxocariasis can cause retinal damage and decreased vision.[257] Dog feces can also containhookworms that causecutaneous larva migrans in humans.[258][259]
Health benefits
A woman walking a dog
The scientific evidence is mixed as to whether a dog's companionship can enhance human physical and psychological well-being.[260] Studies suggest that there are benefits to physical health and psychological well-being, but they have been criticized for being "poorly controlled".[261][262] One study states that "the health of elderly people is related to their health habits andsocial supports but not to their ownership of, or attachment to, a companion animal".[263] Earlier studies have shown that pet-dog or -cat guardians make fewer hospital visits and are less likely to be on medication for heart problems and sleeping difficulties than non-guardians.[263] People with pet dogs took considerably more physical exercise than those with cats or those without pets; these effects are relatively long-term.[264] Pet guardianship has also been associated with increased survival in cases ofcoronary artery disease. Human guardians are significantly less likely to die within one year of an acutemyocardial infarction than those who do not own dogs.[265] Studies have found a small to moderate correlation between dog-ownership and increased adult physical-activity levels.[266]
Recent research has failed to support earlier findings that pet ownership is associated with a reduced risk ofcardiovascular disease, a reduced use ofgeneral practitioner services, or any psychological or physical benefits on health for community dwelling older people. Research has, however, pointed to significantly lessabsenteeism from school through sickness among children who live with pets.
Health benefits of dogs can result from contact with dogs in general, not solely from having dogs as pets. For example, when in a pet dog's presence, people show reductions in cardiovascular, behavioral, and psychological indicators of anxiety[267] and are exposed toimmune-stimulating microorganisms, which can protect against allergies and autoimmune diseases (according to thehygiene hypothesis). Other benefits include dogs as social support.[268]
One study indicated that wheelchair-users experience more positive social interactions with strangers when accompanied by a dog than when they are not.[269] In a 2015 study, it was found that having a pet made people more inclined to foster positive relationships with their neighbors.[270] In one study, new guardians reported a significant reduction in minor health problems during the first month following pet acquisition, which was sustained through the 10-month study.[264]
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 withmental disorders.[271] Animal-assisted intervention research has shown that animal-assisted therapy with a dog can increase smiling and laughing among people withAlzheimer's disease.[272] One study demonstrated that children with ADHD andconduct disorders who participated in an education program with dogs and other animals showed increased attendance, knowledge, and skill-objectives and decreasedantisocial andviolent behavior compared with those not in an animal-assisted program.[273]
InChristianity, dogs represent faithfulness.[276] Within theRoman Catholic denomination specifically, the iconography ofSaint Dominic includes a dog after the saint's mother dreamt of a dog springing from her womb and became pregnant shortly after that.[282] As such, theDominican Order (Ecclesiastical Latin:Domini canis) means "dog of the Lord" or "hound of the Lord".[282] In Christian folklore, achurch grim often takes the form of a black dog to guard Christian churches and theirchurchyards fromsacrilege.[283]Jewish law does not prohibit keeping dogs and other pets but requires Jews to feed dogs (and other animals that they own) before themselves and to make arrangements for feeding them before obtaining them.[284][285] The view on dogs inIslam is mixed, with some schools of thought viewing them as unclean,[276] althoughKhaled Abou El Fadl states that this view is based on "pre-Islamic Arab mythology" and "a tradition [...] falsely attributed to the Prophet".[286] The SunniMaliki school jurists disagree with the idea that dogs are unclean.[287]
Terminology
Dog – the species (or subspecies) as a whole, also any male member of the same.[288]
Bitch – any female member of the species (or subspecies).[289]
Puppy orpup – a young member of the species (or subspecies) under 12 months old.[290]
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