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Status: Secure canine carnivorous mammal that has been domesticated for somewhere between 14,000 and 150,000 years. In those millenia, the dog has developed into hundreds of breeds of almost unimaginable variation, for example, with heights ranging from just a few inches (centimeters)—such as the Chihuahua—to nearly three feet (1 meter)—such as the Irish Wolfhound; and colors ranging from white to black with reds, grays, and browns also occurring, all in a tremendous variation of patterns. The dog is known for its trainability and for its ability to fit into human households and social situations. Today, dogs are most often kept as pets, although a wide range of dog sports provides opportunities for dogs to exhibit their natural skills, and working dogs of all kinds still fill traditional dog roles such as herding sheep while moving into new jobs such as drug detection. It has lived with and worked with humans in so many roles that it has earned the sobriquet Man's best friend.
Dog in common usage usually means the domestic dog, Canis lupus familiaris (originally classified as Canis familiaris by Linnaeus in 1758, but reclassified as a subspecies of the wolf, Canis lupus, by the Smithsonian Institute and the American Society of Mammalogists in 1993). The word is sometimes used to refer collectively to any mammal belonging to the family Canidae (as in "the dog family"), such as wolves, foxes and coyotes.
Dog is also a term used by breeders to specifically denote a male domestic dog. The female is known as a bitch. A young dog is called a puppy. The words pooch and poochie are generic, generally affectionate terms for a dog.
Many additional terms are used for dogs that are not purebred; see Terms for mixed-breed dogs.
Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Within that range of extremes, however, dogs generally share attributes with their wild cousins, the wolves. Dogs are predators and scavengers; as such, they have sharp teeth and strong jaws for attacking, holding, and tearing their food. Their legs are designed to propel them forward rapidly, leaping as necessary, to chase and overcome prey; hence, they have small, tight feet, walking on their front toes; their rear legs are fairly rigid and sturdy; while the front legs are loose and flexible, with only muscle attaching them to the torso.
All dogs have excellent scenting ability and hearing, although some breeds have been selectively bred by humans for excellence even among their canine brethren. All dogs have a tremendous capacity to learn complex social behavior and to interpret varied body language and sounds, and, like many predators, can react to and learn from unusual situations. Originally, dogs all had dense fur with an undercoat and long muzzles and heads, although both of these features have been altered in some of the more extremely modified breeds, such as the Mexican Hairless Dog and the English Bulldog.
Molecular systematics indicate that the domestic dog is descended from a wolf-like ancestor, and dogs and wolves can still interbreed. The domestication of the dog probably occurred at least 14,000 years ago, and perhaps long before that. There is archaeological evidence of dog remains, showing the characteristic morphological differences from wolves, from at least 14,000 years ago, while wolf remains have been found in association with hominid remains that are at least 400,000 years old. The molecular genetic data suggest that the domestic lineage separated from modern wolves around 150,000 years ago (Vilà et al, 1997). In the early 2000s, indicated that domestication in fact had already begun to occur as early as 100,000 years ago.
Dogs are valued for their aid in hunting. Dog burials at the Mesolithic cemetery of Svaerdborg in Denmark show that in ancient Europe, dogs were valued companions.
Some evidence suggests that several varieties of ancient wolves contributed to the domestic dog, with deliberate or unintentional interbreeding taking traits from one or more of the ancestral wolf lines. Although all wolves belong to the species canis lupus, there are (or were) many subspecies that had evolved somewhat distinctive appearance, social structure, and other traits. For example, the Japanese wolf, which became extinct in the early 20th century, was much smaller than most wolves, generally had a gray coat with reddish underbelly, and possibly had a more solitary hunting habit; the North American wolf, which still exists in limited ranges, is much larger than many wolf subspecies, displays many coat colors from nearly white through solid black, and exhibits a complex social structure involving highly formulaic dominance and submission rituals.
The Indian or Asian wolf probably led to the development of more breeds of dogs than other subspecies. Many of today's wild dogs, such as the dingo and pariah dogs, came from this wolf, along with sighthounds such as the Greyhound. shows that most modern dog breeds are related to Asian canines, contradicting earlier hypothoses that the dog, like humans, had evolved originally in Africa. The Asian wolf also probably combined with descendants of the European wolf to create the Mastiffs—the Tibetan Mastiff being an example of a very ancient breed—leading eventually to the development of such diverse breeds as the Pug, the Saint Bernard, and the Bloodhound.
The European wolf, in turn, may have contributed many of its attributes to the Spitz dog types, most terriers, and many of today's sheepdogs. The Chinese wolf is a probably ancestor to the Pekingese and toy spaniels, although it is also likely that descendants of the Chinese and European wolves encountered each other over the millenia, contributing to many of the oriental toy breeds.
The North American wolf is a direct ancestor to most, if not all, of the North American northern sled dog types; this mixing and crossing still goes on today with dogs living in the Arctic where the attributes of the wolf that enable it to survive in a hostile environment are still valued—or accidental crossbreeding occurs simply because dogs and wolves live in the same environment.
Today we know that domestication, or the attributes of a domesticated animal, than previously believed, even within a human generation or two with determined selective breeding. It is also now generally believed that initial domestication was not attained deliberately by human intervention but through natural selection: wild canines who scavenged around human habitation received more food than their more skittish counterparts; those who attacked people or their children were probably killed or driven away, while those more tolerant animals survived; and so on.
Dogs thrive in small social groups or packs which from their cynomorphic (dog) viewpoint includes humans. Dog packs are characterized by companionate hierarchy, in which each individual has a rank, and in which there is intense loyalty within the group. Dogs thrive in human society because their relationships with humans mimic their natural social patterns. The dog is always aware of its rank relative to other individuals in the group. An assertive dog may consider itself the alpha animal, considering its human owner to be subordinate.
Dogs, like wolves, establish a hierarchy through aggressive play and roughhousing along a continuum of dominance and submission. When kept as pets, dogs include humans in this hierarchy. It is important for successful socialization that puppies participate with their littermates in learning to relate to other dogs. Dogs learn to successfully relate to other dogs by keeping the peace rather than constantly fighting to reestablish this hierarchy.
Dominant dogs generally take the initiative and are more active than less dominant dogs. Displays of dominance include standing above or over other dogs, placing a paw on other dogs, holding the tail and ears erect, looking directly at other dogs, circling and sniffing other dogs, growling if the other dog moves, and aggressive marking of territory with urine. Submissive displays mirror dominant displays and include adopting a posture that is lower than other dogs, such as crouching, rolling over on the back and exposing the abdomen, lowering the tail—even tucking it beneath the legs, flattening of the ears, averting the gaze, nervously licking or swallowing, dribbling of urine, and freezing or fleeing when other dogs are encountered.
If things go well, the dominant/submissive social structure of dogs avoids conflict and enforces social stability. Poorly socialized dogs who are inept at establishing dominance hierarchy may find themselves involved in unwanted conflicts, especially from the viewpoint of their human companions; as may people who misunderstand dog behavior or who have inadvertently placed themselves in a disadvantageous position within the dominance submissive hierarchy. Such situations may require expert help from professionals skilled in canine psychology.
It is a mistake to anthropomorphize the dominance submission behavior of a pet or to mistake it for characteristics more appropriately applied to humans. It is undesirable for a dog to be dominant relative to its master or mistress. One should not go so far in rewarding "bravery" or "boldness" that in fulfilling a dog's wants it begins to feel it is the boss. Likewise, it is generally unwise that a dog consider him or herself "the equal of any dog", because unnecessary and destructive conflict can result; rewarding a dog's aggressive behavior may eventually backfire. Likewise, viewing a submissive dog, who is simply displaying common sense, as being a low-quality dog or a cowardly dog is inappropriate. Never continue to discipline a dog after it has adopted a submissive posture; from the dog's viewpoint, it has conceded the point and is at a loss as to what more it might do to communicate its acceptance of your dominance.
Dogs value the companionship of the others in their "pack" and are sometimes distressed if they are separated from it. Typical reactions when a dog is separated from the pack or from his human companions are barking, howling, digging, and chewing. These activities may distress their human companions, who may need to leave dogs alone for a period of time.
Nothing is more pleasurable to dogs than spending time with and interacting with other dogs. Roughhousing and chasing one another are favorite activities. When quiet, dogs especially love lying about with their companions, favoring spots with a good view.
There are numerous dog breeds, over 800 being recognised by various kennel clubs worldwide. However, many dogs, especially outside the United States and Western Europe, belong to no recognized breed. A few basic breed types have evolved gradually during the domesticated dog's relationship with man over the last 10,000 or more years, but most modern breeds are of relatively recent derivation. Many of these are the product of a deliberate process of artificial selection. Because of this, some breeds are highly specialized, and there is extraordinary morphological diversity across different breeds. Despite these differences, dogs are able to distinguish dogs from other kinds of animal.
The definition of a dog breed is a matter of some controversy. Some groups use a definition that ultimately requires extreme in-breeding to qualify. Dogs that are bred in this manner often end up with severe health problems. Other organizations define a breed more loosely, such that an individual may be considered of one breed as long as, say, three of its grandparents were of that breed. These considerations come into play among breeders who enter their dogs in dog show competitions. According to Larry Shook, the author of The Puppy Report: How to Select a Healthy, Happy Dog, purebred dogs frequently suffer from serious health and behavioral problams. Even prize winning purebred dogs are sometimes the victim of crippling genetic defects due to inbreeding.
In February 2004, the Canine Studies Institute in Aurora, Ohio, managed to arrange all breeds of dog into ten categories, according to Darwinian Evolutionary principles.
Mixed-breed dogs are dogs that do not belong to specific breeds, being mixtures of two or more. Mixed breeds or dogs with no purebred ancestry are in general terms no better or worse than purebred dogs as companions, pets, working dogs, or competitors in dog sports. Sometimes mixed-breed dogs are deliberately bred, for example, the Cockapoo, a mixture of Cocker Spaniel and Minature Poodle. Such deliberate crosses may display hybrid vigor and other desirable traits, but can also lack one or more of the desired traits of their parents, such as temperament or a particular colour or coat.
The relationship between dogs and humans is ancient. Dogs serve humans in many ways.
There are guard dogs, hunting dogs, and herding dogs. Dogs have served as guides for the blind, as commandos, have flown into outer space (see Laika), and a dog (P.H. Vazak) was even credited as author of an Oscar-nominated screenplay.
Many people compete with their dogs in a variety of dog sports, including agility, flyball, and many others. This often strengthens the bond between human and dog, since they must trust one another in a variety of environments and must learn how the other works and thinks.
Relationships between humans and dogs are often characterized by strong emotional bonds, earning the dog the title of "Man's best friend". Consequently, dogs are popular as pets and companions, independent of any utilitarian considerations. Many dog owners consider having unconditional acceptance from a friend who is always happy to see them to be quite utilitarian, particularly if the dog also leads them to regular exercise. Dogs are quite dependent on human companionship and may suffer poor health without it.
Some research has shown that dogs are able to convey a depth of emotion not seen to the same extent in any other animal - this is purportedly due to their closely-knit development with modern man, and the survival-benefits of such communication as dogs became more dependent on humans for sustenance.
However, one must be cautious not to anthropomorphize the responses of dogs. Despite understandably positive interpretations by dog owners, it is questionable whether these animals are truly capable of feeling emotions on a human level. More research is needed to determine the intelligence level of dogs, and the motivations behind their responses to their masters.
In certain cultures, dogs are raised on farms and slaughtered as a source of meat. Consequently, the conflicts between dog lovers and dog eaters occasionally appear as headline news. In other cultures, dogs have served as a standby source of food. One example is in China where Chow Chows were often posted to guard family storehouses. During a hard season when the food store was depleted, the dog would be then slaughtered as an emergency ration.
See also Gaegogi.
Unlike undomesticated canine species, where the females typically come into estrus (also called in season or in heat) once a year, usually in late winter, and bear one litter of young, the female of the domestic dog can come into season at any time of the year and usually twice a year. Most dogs come into season for the first time between 6 and 12 months, although some larger breeds delay until as late as 2 years. The amount of time between cycles varies greatly among different dogs, but a given dog's cycle tends to be consistent through her life.
Dogs bear their litters roughly 9 weeks after insemination.
An average litter consists of about six puppies, especially for breeds that have not strayed too far from their wild ancestors. However, litters of many more or only one or two puppies are also common. Some breeds have a tendency to produce very large litters. Since a mother can provide milk for only a few of those puppies, humans must assist in the care and feeding when the litter exceeds eight or so.
Some breeds have been developed to emphasize certain physical traits beyond the point at which they can safely bear litters on their own. For example, the Bulldog often requires artificial insemination and almost always requires cesarian section for giving birth.
Puppies often have characteristics that do not last beyond early puppyhood. For example, eyes are often blue when they first open but change to other colors as the puppy matures. As another example, Kerry Blue Terrier puppies have light-colored coats when they are born and their distinctive "blue" color appears gradually as the puppy nears maturity. The ears of erect-eared breeds such as the German Shepherd Dog are softly folded at birth but straighten as the puppy grows.
Dogs not intended for further breeding should be spayed or neutered so that they do not have undesired puppies, which are too often abandoned to miserable lives. Abandoned dogs often go feral and form predatory packs that attack livestock and occasionally also prove dangerous to humans.
Dogs are voracious, territorial, aggressive, protective predators. They have sharp teeth in powerful jaws that can inflict serious injuries requiring hospitalization. Although confrontations between man and dog ordinarily stop well short of harm, certain actions lead to the possibility of severe injury. To avoid conflicts, never attack a dog; never try to take food away from a dog; never threaten a puppy in the presence of an adult dog, especially its mother; never approach a sick dog (rabies, worms) or injured dog unless aware of how to handle it appropriately. Never run from any dog: the chase-and-catch instinct in wolves is not fully lost. Most dogs can outrun and overtake the average human. Take all "Beware of Dog" signs seriously. The "trained attack dog", unlike most dogs, may attack an intruder without warning. Despite its reputation as "Man's Best Friend", it is one of the worst animals to anger. Dogs are not inherently aggressive unless they are feral, trained to attack intruders, threatened, or provoked.
The Dog is one of the 12-year cycle of animals which appear in the Chinese zodiac related to the Chinese calendar. It is thought that each animal is associated with certain personality traits. See: Dog (Zodiac).
Sirius, the Dog Star, is the brightest star in the night sky.
A common misconception is that dogs do not sweat. Primarily, dogs regulate their body temperature in a completely different way, through their tongue. That is why after a dog has been running or on a hot day you will see its mouth wide open and tongue hanging out. In addition, dogs effectively sweat through the pads of their feet. Again, on a warm day and after exercise, a dog's naturally wet footprints might be visible on a smooth floor.
It has been observed that a lost dog can often find its way home, sometimes travelling over long distances. It is believed that dogs and cats know the correct position of the sun at their homes. When lost, the animal notes the angle of the sun as it travels, and moves in the direction that indicates that the angle is becoming correct.
Most diseases that affect dogs or humans are not transferable between the two species. There are some exceptions:
Genetic conditions are a problem in some dogs, particularly purebreeds:
Several types of parasites are commonly associated with dogs:
Some foods commonly enjoyed by humans are dangerous to dogs:
For additional information on dog health, see Category:Dog health.
Dogs are generally valued for their intelligence. Anecdotal evidence suggests that dogs have a reasonably high intelligence. For a detailed discussion on what dog intelligence is, see dog intelligence.
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