Dog

Template:Taxobox begin
Conservation status: Secure Template:Taxobox image Template:Taxobox begin placement Template:Taxobox regnum entry Template:Taxobox phylum entry Template:Taxobox subphylum entry Template:Taxobox classis entry Template:Taxobox ordo entry Template:Taxobox familia entry Template:Taxobox genus entry Template:Taxobox species entry Template:Taxobox subspecies entry Template:Taxobox end placement Template:Taxobox section trinomial parens Template:Taxobox end

The dog is a canine mammal of the Order Carnivora that has been domesticated for at least 14,000 years and perhaps for as long as 150,000 years based on recent evidence. In this time, the dog has been developed into hundreds of breeds with a great degree of variation. For example, heights range from just a few inches (such as the Chihuahua) to nearly three feet (such as the Irish Wolfhound), and colors range from white to black with reds, grays, and browns also occurring in a tremendous variation of patterns. Dogs, like humans, are highly social animals and pack hunters; this similarity in their overall behavioral design accounts for their trainability, playfulness, and ability to fit into human households and social situations. Dogs fill a variety of roles in human society and are often trained as working dogs. For dogs that do not have traditional jobs, a wide range of dog sports provide the opportunity to exhibit their natural skills. In many countries, the most common and perhaps most important role of dogs is as companions. Dogs have lived with and worked with humans in so many roles that their loyalty has earned them the sobriquet "man's best friend." On the other hand, in some cultures they are considered to be unclean.

Terminology

Dog, in common usage, refers to 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 Institution 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.
Bitch is a female dog who is capable of breeding or has bred.
Pack is used to denote a group of dogs.
Puppy is a juvenile dog.
Pooch, Poochie, Dogay, Doggy or Doggie are all informal and affectionate terms for a dog often by used by children.

Classes of Dogs

According to the American Kennel Club, there are eight classes of dogs. These are recognized internationally. They are:

Sporting; Hunting Dogs including Pointers, Retrievers, Setters and Spaniels.
Hound; Dogs which follow prey by sight or scent including Beagles, Afghans and Dachshunds.
Terrier; Dogs originally bred to hunt or kill vermin whose size ranges from the tiny Cairn Terrier to the sizable Airedale Terrier.
Working; Dogs which work to guard property, perform rescues or pulling carts or sleds and include the Mastiff, Saint Bernard and Great Dane.
Herding; as the name implies, these dogs have all been bred to herd animals, from the small Corgi to the Old English Sheepdog.
Toy; Typically this is a class reserved for dogs of small stature who do not fall into the other categories including the Chihuahua and the Cavalier King Charles Spaniel.
Non-Sporting; Similar to toy breeds, these are larger dogs including Dalmations who do not fall into the other categories.
Miscellaneous; This is a unique class which is used to monitor new breeds and to ensure that healthy breeding practices are being used. After a period of time that ensures that good practices are in effect and that the gene pool for the breed is ample, the breed is moved to one of the seven traditional classes.

Many additional terms are used for dogs that are not purebred; see Terms for mixed-breed dogs.

Dog coats

Coat colors range from pure white to solid black and many other variations.

For a complete detailed list of dog colors and patterns, see Coat (dog).

Dogs exhibit a diverse array of coat textures, colors, and markings, and a specialized vocabulary has evolved to describe them.

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 and the English Bulldog.

Color

One often refers to a specific dog first by coat color rather than by breed; for example, "a blue merle Aussie" or "a chocolate Lab". Coat colors include:

Black: Usually pure black but sometimes grizzled.
Brown: From mahogany through very dark brown.
Red: Reminiscent of reddish woods such as cherry or mahogany; also tawny, chestnut, orange, rusty, liver, and red-gold.
Yellow: From pale cream to a deep yellowish-gold tan.
Gold: From pale apricot to rich reddish-yellow.
Gray: Pale to dark gray, including silver; can be mixed with other colors or various shades to create sandy pepper, pepper, grizzle, blue-black gray, or silver-fawn.
Blue: A dark metallic gray, often as a blue merle or speckled (with black).
Sable: Black-tipped hairs; the background color can be gold, silver, gray, or tan.
White: Distinct from albino dogs.

Pattern

Coat patterns include:

Two-color coats, such as Black and tan, red and white: Coat has both colors but in clearly defined and separated areas; usually the top and sides are darker and lower legs and underside are the lighter color.
Tricolor: Consisting of three colors; usually black, tan, and white or liver, tan, and white.
Brindle: A mixture of black with brown, tan, or gold; usually in a "tiger stripe" pattern.
Harlequin: "Torn" patches of black on white.
Merle: Marbled coat with darker patches and spots of the specified color.
Particolor: Two-colored coat with the colors appearing in patches in roughly equal quantiles.

Texture

Coat textures vary tremendously, so that some coats make the dogs more cuddly and others make them impervious to cold water. Densely furred breeds such as most sled dogs and Spitz types can have up to 600 hairs per inch, while fine-haired breeds such as the Yorkshire Terrier can have as few as 100, and the "hairless" breeds such as the Mexican Hairless have none on parts of their bodies. The texture of the coat often depends on the distribution and the length of the two parts of a dog's coat, its thick, warm undercoat (or down) and its rougher, somewhat weather-resistant outer coat (topcoat), also referred to as guard hairs. Breeds with soft coats often have more or longer undercoat hairs than guard hairs; rough-textured coats often have more or longer guard hairs. Textures include:

Double-coated: Having a thick, warm, short undercoat (or down) that is usually dense enough to resist penetration by water and a stronger, rougher weather-resistant outer coat (topcoat), also referred to as guard hairs. Most other coat types are also double coated.
Single-coated: Lacking an undercoat.

Smooth-coated: "Smooth" to the eye and touch.
Wire-haired: Also called broken-coated. The harsh outer guard hairs are prominent, providing excellent weather protection for hunting dogs such as the Border Terrier or Wirehaired Pointing Griffon.

Long-haired: Hair longer than an inch or so.
Short-haired: Hair around an inch or so long.

Corded coat: for example, see Puli

Anatomy

A special vocabulary has also been developed to describe the shapes of various body parts including the ears and tail.

Ears

Dogs ears come in a variety of sizes, shapes, lengths, position on the head, and amount and type of droop. Every variation has a term, including:

Bat ear: Erect, broad next to the head and rounded at the tip.
Button ear: A smaller ear where the tip folds forward nearly to the skull, forming a V, such as the Jack Russell Terrier.
Cropped ear: Shaped by cutting; see docking.
Drop ear: An ear that folds and droops close to the head, such as most scent hounds'. Also called a pendant ear.
Natural: Like a wolf's.
Prick ear: Erect and pointed; also called pricked or erect.
Rose ear: A very small drop ear that folds back; typical of many sight hounds and the English Bulldog.
Semiprick ear: A prick ear where the tip just begins to fold forward, such as with the Rough Collie.

Tails

As with ears, tails come in a tremendous variety of shapes, lengths, amount of fur, and tailset (positions). Among them:

Corkscrew: Short and twisted, such as a Pug
Docked: Shortened by surgery or other method, usually two or three days after birth; see docking
Odd: Twisted, but not short. Uncommon. Tibetan Terriers have odd tails.
Saber: Carried in a slight curve like that of a saber
Sickle: Carried out and up in a semicircle like a sickle
Squirrel: Carried high and towards the head, often with the tip curving even further towards the head.
Wheel: Carried up and over the back in a broad curve, resembling a wheel.

Physical Characteristics

Like most predatory mammals, the dog has powerful muscles, a cardiovascular system that supports both sprinting and endurance, and teeth for catching, holding, and tearing.

The dog's ancestral skeleton provided the ability to run and leap. Their legs are designed to propel them forward rapidly, leaping as necessary, to chase and overcome prey. Consequently, they have small, tight feet, walking on their front toes; their rear legs are fairly rigid and sturdy; the front legs are loose and flexible, with only muscle attaching them to the torso.

Although selective breeding has changed the appearance of many breeds, all dogs retain the basic ingredients from their distant ancestors. Dogs have disconnected shoulder bones (absent the collar bone of the human skeleton) that allow a greater stride length for running and leaping. They walk on four toes, front and back, and have vestigial dewclaws (dog thumbs) on their front and rear legs just like monkeys thumbs, in some cases these claws are missing due to surgery. The rear dewclaws are often removed for some obscure reason though in most civil countries this is illegal and thought of as cruel.

The dog's ancestor was about the size of a Dingo, and its skeleton took about 10 months to mature. Today's toy breeds have skeletons that mature in only a few months, while giant breeds such as the Mastiffs take 16 to 18 months for the skeleton to mature. Dwarfism has affected the proportions of some breeds' skeleton, as in the Basset Hound.

Diet

File:Tessaenjoyingbone.JPG

This English Springer Spaniel is enjoying a bone.

Presently, there is academic discussion as to whether domestic dogs are omnivores or carnivores. The classification in the Order Carnivora does not necessarily mean that a dog's diet must be restricted to meat. Unlike an obligate carnivore, such as a cat, a dog is not dependent on meat protein in order to fulfill its dietary requirements. Dogs are able to healthily digest a variety of foods including vegetables and grains, and in fact can consume a large proportion of these in its diet. Wild canines not only eat available plants to obtain key amino acids, but may also obtain nutrients from vegetable matter from the stomach contents of their herbivorous prey. Domestic dogs can survive healthily on a reasonable and carefully designed vegetarian diet, particularly if eggs and milk products are included. In the wild these diets are typically pursued in the absence of available meat. It has also been noted that extremely stressful conditions, such as the Iditarod race and scientific studies of similar conditions, suggest that high-protein diets including meat help prevent damage to muscle tissue. This research is also true of other mammals.

Dangerous Substances

Some foods commonly enjoyed by humans are dangerous to dogs, including chocolate, grapes and raisins, onions, Macadamia nuts, and hops.

Dogs also may find some poisons attractive, including antifreeze and snail bait.

Temperature Regulation

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, its mouth will be seen wide open with the tongue hanging out. This is a very efficient form of cooling in terms of maximizing heat lost while conserving moisture, because it carries heat from the hottest part of the body, the interior core of the thorax, compared to sweating, which cools the already coolest part of the body, the skin. Besides being intuitively correct, this higher efficiency of thermal loss in terms of moisture conservation stems from heat flow being proportional to temperature gradient in a given system. In addition, dogs effectively sweat through the pads of their feet, since they are not furred. Again, on a warm day and after exercise, a dog's naturally wet footprints might be visible on a smooth floor.

Dogs possess a rete mirabile in the carotid sinus at the base of their neck, a complex of intermingled small arteries and veins which acts as a heat exchanger to thermally isolate the head, containing the brain, the most temperature sensitive organ, from the body, containing the muscles, where most of the heat is generated. The net result is that dogs can sustain a high degree of physical exertion over a prolonged time in a hot environment, compared to animals which lack this apparatus; thus, a dog chasing a jackrabbit through the desert may not be able to outrun the rabbit, but it can continue the chase until the rabbit literally drops dead from overheating.

Reproduction

As with most domesticated species, one of the first and strongest effects seen from selective breeding is, logically enough, selection for cooperation with the breeding process as directed by humans. In dogs, this takes the form of abolition of the pair bonding seen in wild canines, as well as the ability of female domestic dogs to come into estrus (also called in season or in heat) at any time of the year and usually twice a year; unlike undomesticated canine species where the females typically come into once season a year, usually in late winter, and bear one litter of young. Most bitches come into season for the first time between 6 and 12 months, although some larger breeds delay until as late as 2 years. Like most mammals, the age that a bitch first comes into season is mostly a function of her current body weight as a proportion of her body weight when fully mature, rather than age, with the different maturation rates of the various sizes of dogs accounting for this variation in age of first season. 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 cesarean 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 black 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; in cases where they fail to straighten on their own, owners sometimes opt for surgical intervention.

Dog experts advise that dogs not intended for further breeding should be spayed or neutered so that they do not have undesired puppies, which are often abandoned. Abandoned dogs who go feral are particularly dangerous; they lack the skills of wild canines at survival in the wild, as well as the genetic and learned fear of humans that keeps wild canines away from humans and their possessions, so they form predatory packs that attack livestock and occasionally also prove dangerous to humans. The overpopulation of unwanted dogs is so great that almost all dogs who end up in animal shelters are euthanized due to lack of space and resources. Spaying and neutering can also help prevent hormone-driven diseases such as breast cancer and prostate cancer, as well as undesired hormone-driven behaviors. Contrary to myth, it is not required for a female dog to either experience a heat cycle or have puppies before spaying, and likewise, a male dog does not need the experience of mating before neutering; these myths are responsible for numerous unnecessary health problems and unwanted puppies. Attempts by owners to carry on some particular admirable qualities of their dogs by breeding them usually fail. Dogs of mixed breed do not "breed true"; i.e., with a mixed breed dog the offspring may not carry characteristics found in a parent, or even shared by both parents. Similarly, but to a lesser extent, even with purebreed dogs sold as pets the offspring may not have the subtle best qualities of the parents; it may be necessary to go back to the high quality breeding stock and reproduce the original mating as closely as possible to reproduce the desired characteristics very closely. Of course, most owners who let their dogs reproduce will feel the offspring are superior; however, realistically speaking, the natural sentimental bias makes it just as likely that they would feel the same way about any dog they acquired, from the pound or elsewhere.

Intelligence

Among dog lovers, 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.

Attributes

Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Within the range of extremes, dogs generally share attributes with their wild ancestors, the wolves. Dogs are predators and scavengers, possessing sharp teeth and strong jaws for attacking, holding, and tearing their food.

Sight

Dogs were thought to be dichromats and thus, by human standards, color blind.^{1, 2} New research is now being explored that suggests that dogs may actually see some colour, but not to the extent that humans do. Because the lenses of dogs' eyes are flatter than humans', they cannot see as much detail; on the other hand, their eyes are more sensitive to light and motion than humans' eyes. Some breeds, particularly the best sighthounds, have a field of vision up to 270° (compared to 100° to 120° for humans), although broad-headed breeds with their eyes set forward have a much narrower field of vision, as low as 180°.^{1, 2}

Hearing

Dogs detect sounds as low as the 20 to 70 Hz frequency range (compared to 16 to 20 Hz for humans) and as high as 70,000 to 100,000 Hz (compared to 20,000 Hz for humans)², and in addition have a degree of ear mobility that helps them to rapidly pinpoint the exact location of a sound. They can identify a sound's location much faster than can a human, and they can hear sounds up to four times the distance that humans can.

Scent

Dogs have nearly 220 million smell-sensitive cells over an area about the size of a pocket handkerchief (compared to 5 million over an area the size of a postage stamp for humans). Some breeds have been selectively bred for excellence in detecting scents, even compared to their canine brethren. Other than the oversimplified obvious, i.e. chemical compounds that affect chemical sensors in the nose, what a dog actually detects when he is scenting is not really understood; although once a matter of debate, it now seems to be well established that dogs can distinguish two different types of scents when trailing, an air scent from some person or thing that has recently passed by, as well as a ground scent that remains detectable for a much longer period. The characteristics and behavior of these two types of scent trail would seem, after some thought, to be quite different, the air scent being intermittent but perhaps less obscured by competing scents, whereas the ground scent would be relatively permanent with respect to careful and repetitive search by the dog, but would seem to be much more contaminated with other scents. In any event, it is established by those who train tracking dogs that it is impossible to teach the dog how to track any better than it does naturally; the object instead is to motivate it properly, and teach it to maintain focus on a single track and ignore any others that might otherwise seem of greater interest to an untrained dog. An intensive search for a scent, for instance searching a ship for contraband, can actually be very fatiguing for a dog, and it must be motivated to continue this hard work for a long period of time.

Direction and Spatial Sense

It has been observed that a lost dog can often find its way home, sometimes traveling over long distances.

Weather Detection

Dogs also have the ability to sense inclement weather (mainly thunderstorms) many miles away. This is due to their keen ability to detect fluctuations in barometric pressure and can explain a dog's anxiety before and during a storm. The evolutionary ability of sensing weather can be traced back to when wolves used it to move the pack into proper shelter before a dangerous storm.

Diseases and Ailments

Dogs are susceptible to various diseases, ailments, and poisons, some of which affect humans in the same way, others of which are unique to dogs.

Diseases

Diseases commonly associated with dogs include rabies (hydrophobia), canine parvovirus, and canine distemper, although there are many others.

Parasites

Common external parasites are various species of fleas, ticks, and mites. Internal parasites include hookworms, tapeworms, roundworms, and heartworms.

Common Physical Disorders

Some breeds of dogs are also prone to certain genetic ailments, such as hip dysplasia, luxating patellas, cleft palate, blindness, or deafness. Dogs are also susceptible to the same ailments that humans are, including diabetes, epilepsy, cancer, and arthritis. Gastric torsion and bloat is a dangerous problem in some large-chested breeds.

For additional information on these and other related topics, see dog health and Category:Dog health.

Behaviour

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 novel situations. The requirements of coordinating complex social behavior requires that canines have the ability to sense and deliver a wide variety of cues via body language, more so than for even humans, who can use language for the same purpose. Physiologically, this correlates with such features as a large number of nerves innervating the facial muscles of dogs, allowing subtle control of a wide variety of facial expressions; in contrast to cats, for instance, who have many fewer nerves governing their facial muscles, resulting in a smaller repertoire or "vocabulary" of expressions. This ability to read and deliver nonverbal cues makes dogs expert at reading human beings, as well, often even more so than other humans are, who rely on language. Most dog owners have a large collection of stories about their dogs recognizing individuals by their footsteps outside the door, and so on.

Interactions between Dogs and Humans

Main article: Dog society

The relationship between dogs and humans is rooted in history and coexist with humans in a variety of ways. Dogs thrive in small social groups or packs which, from their viewpoint, can include humans. Dog society can be thought of as dog packs characterized by a 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 master to be subordinate.

Treats

Many dogs consider anything given them directly by hand to be a treat, even the food they are accustomed to at meal time. Special dog treats are not necessary for such animals. Care should also be taken to avoid dropping small but inedible objects (such as marbles, coins, rings, etc.) around such dogs.

If a dog has something valuable (rings, money, irreplaceable items), a treat should be used to "barter" with the dog to retrieve the stolen item. Chasing a dog will encourage play behavior, which may cause the item to be swallowed or destroyed.

Dogs as working partners

German Shepherd dogs are commonly used as working dogs. There are service dogs, guard dogs, hunting dogs, and herding dogs. Dogs have served as guides for the blind, as commandos, and have flown into outer space (see Laika and other Russian space dogs). Most modern working dogs are put in positions which capitalize on their sensory or strength and endurance advantages over normal humans.

Dogs as hunting and sporting partners

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.

Setters in particular have a long history as upland gun dogs. They have a native ability to discover and "hold" upland game birds; to freeze them momentarily on the ground with their silent, elongated pointing stance. Once the hunter approaches, at his command they will flush the birds to fly and for the hunter to shoot at.

As water dogs, the retrievers are unsurpassed. They can spend long hours in a duck blind and, after the hunter has fired at multiple ducks or geese, they can visually spot and remember the location of downed birds. At command, they dive into the icy water, swim out and retrieve the birds one by one. They can follow hand, verbal, and whistle commands at great distance as the hunter directs them to the downed bird. They typically have large, gentle muzzles to mitigate any potential damage to the game.

When trained, beagles are particularly adept at chasing through thick briars and brush to chase rabbits. Many hound breeds are excellent at treeing raccoons during hunting season.

Hunters with dogs report the satisfaction that the dogs seem to exhibit. Excitement is evident as they see the hunters load weapons, take to the field, and begin the hunt.

Dogs as pets

Relationships between humans and dogs are often characterized by strong emotional bonds. 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. Empirically, dogs are quite dependent on human companionship and may suffer poor health in its absence. Many dogs are reported to have separation anxiety if its owner is away for an extended period of time.

Some research demonstrates 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.

Nevertheless, it is often unwise 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.

Dogs as food

Main article: Taboo food and drink

In some places, dogs are raised for their meat, causing friction with people who keep dogs as pets. In times of great stress, such as when the Vikings of Greenland starved to death at the start of the Little Ice Age (14th century - 19th century), humans have been known to eat their pets.

In some small Chinese provincial towns, there is a special breed of dog (called "Black Dogs" in Chinese language) mainly used for cuisine. However, dog meat is banned in several major cities such as Hong Kong, Peking and Shanghai and will lead to a serious prosecution if caught by authorities. Although dog meat is still served in some restaurants, Chinese people generally regard it as a rather "low status" food, and it would be an insult if served to an important person. Also, dog meat tends to be poisonous to certain people if not eaten carefully.

The people of South Korea have been known to eat dogs as well. Recently, this lead to some of racial abuse during the 2002 Football World Cup when Korea was hosting the game.

Dangers of Domestication

This Labrador Retriever could pose a threat to this groundhog, however the breed is not known for its aggressiveness.

The most dangerous thing that can be done as humans is to anthropomorphize an animal. Animals are often given attributes such as "loyal", "cute", and "guardian", but these all have the potential to lure people into a false sense of security.

As evidenced by their attacks on other creatures, both wild and domestic dogs are superpredators. Their sharp teeth and powerful jaws can inflict serious injuries; their sharp claws have powerful muscles behind them. Scratches from dogs are easily infected. Even a boisterous dog of adequate size can knock down a person and possibly cause serious injury although there was no intent on the part of the animal. A single large dog, or a group of medium-sized dogs are capable of seriously injuring or killing an adult human.

Education for adults and children, animal training, selective breeding for temperament, and society's intolerance for dangerous animals combine to reduce the incidence of attacks and accidents involving humans and dogs. However, improperly managed confrontations can lead to severe injury from even the most well-tempered dog, much like most humans can be incited to violence given sufficient provocation.

Ignoring a dog's warning bark can be very dangerous. A wagging tail indicates an attempt to communicate excitement, but a territorial dog may wag its tail at a chance to defend its home. A highly disturbed dog may sometimes emit confusing or misleading signals, much like humans can be difficult to read or misleading.

Human behavior as provocation

Some human behavior (especially by people unfamiliar with dogs) can potentially evoke a predatory or aggressive response from a dog. These include:

Attacking a dog or its companions, or acting in a manner that the dog perceives as an attack (for example, a sudden enthusiastic hug or inadvertently stepping on any portion of the dog's anatomy, such as a paw or tail).
Attempting to take food away from a dog, or moving towards a dog's food or between a dog and its food, even inadvertently.
Threatening a puppy in the presence of an adult dog, especially its mother.
Looking a dog directly in the eyes. This is an act of aggression to dogs. This is more dangerous when on the same visual level as the dog (such as small children), or when the human is unfamiliar to the dog.
Approaching a sick or injured dog. Note that older dogs, like people, often become "cranky" and develop a tendency to become "snappish"
Related to the previous point, failure to recognize a dog showing signs of insecurity or fear and continuing whatever behavior is causing the dog's anxiety to increase, until "fear biting" occurs. Again, an older or chronically infirm dog is liable to develop feelings of vulnerability and anxiety, and therefore become less tolerant and more aggressive
Running away from a dog: the chase-and-catch instinct inherited from wolves is not fully lost, and most dogs can outrun and overtake the average human.
Similarly, the natural instinct to jerk one's hands upwards away from an inquisitive dog often elicits in the dog a strong impulse to grab and hold, or at least to investigate, resulting in the dog jumping on the person and thrusting its head towards the raised hands
Ignoring "Beware of Dog" signs: trained attack dogs, unlike most dogs, may attack an intruder without warning
Startling a resting or sleeping dog
Entering a dog's "territory" and behaving in an unfamiliar pattern or being unfamiliar to the dog. The dog's territorialism, powerful senses, and latent ferocity makes almost any dog, irrespective of size, a powerful deterrent to burglars.

Many adoption agencies test for certain aggressive behaviours in dogs, and destroy any animal that shows certain types of aggression.

Child Safety

In 1999, more child maulings by dogs were as a result of a child being left alone with a Golden Retriever than with any other breed of dog. A parent would rarely leave a child alone with an unknown pitbull, but people forget that a even a cute dog is still a dog. Just because a dog typically has a good temperament, does not mean that it is safe to leave a child alone with it. Since children are most easily harmed by dogs, there are a few steps that can be taken to ensure no harm comes to a child, or the dog by extension.

Teach your child never to approach a dog they don't know.
Always ask the owner if you can pet their dog. Owners know the temperament of their dogs.
Approach dogs from the front. They could be startled if approached from behind and at the least may knock you over.
Refrain from making sudden jerky movements. This could make the dog think you are playing or being aggressive.
Never let a child play unsupervised with an adult dog or puppy, yours or a neighbours. An accident only takes a minute.
Intervene and stop play if it looks to rambunctious or boisterous. Children aren't as durable as puppies. Puppies regularly bite as a part of regular play with other puppies.

Training and Aggression

In a domestic situation, canine aggression is normally suppressed. Exceptions are if the the dog is feral, trained to attack intruders, threatened, or provoked. it is important to remember that dogs are predators by nature and instinct is something that never completely disappears. It is possible to acclimatize a dog to common human situations in order to avoid adverse reactions by a pet. Dog experts advocate removal of a dog's food, startling a dog, and performing sudden movements in a controlled setting to train out aggressive impulses in common situations. This also allows better animal care since owners may now remove an article directly from a dog's mouth, or transport a wounded pet to seek medical attention.

Small children are especially prone to provoking dogs, in part this is because their size and movements can be similar to prey. Also, young children may unintentionally provoke a dog (pulling on ears or tails is common, as is surprising a sleeping dog) because of their inexperience. Because of a dog's pack instincts, more dominant dogs may view children or even adults as rivals rather than as superiors, and attempt to establish dominance by physical means. Any attempt at dominance behavior, no matter how tentative, should be extremely firmly discouraged as early as possible, to affirm to the dog that all humans are pack superiors. To avoid potential conflicts, even reliably well-behaved children and dogs should not be allowed to interact in the absence of adult supervision until both human and animal have demonstrated the ability to always behave appropriately towards each other.

Dogs with strong chase instincts, especially shepherds, may fail to recognize a human being in its entirety. They may fixate on specific aspect of the person, such as a fast-moving, brightly colored shoe, as a prey object. This is probably the cause for the majority of non-aggressive dogs chasing cyclists and runners. In these cases, if the individual stops, it immediately loses interest since the prey has stopped. This is not always the case, and aggressive dogs might take the opportunity to attack.

Additionally, most dogs who bark aggressively at strangers, particularly when not on "their" territory, will flee if the stranger challenges it. Conversely, there is always the danger of the occasional dog who will stand its ground and escalate the situation.

Ancestry and history of domestication

Molecular systematics indicate that the domestic dog is descended from a wolf-like ancestor. As reflected in the nomenclature, dogs are a subspecies of wolf and are thus still able to interbreed.

The relationship between man and canine is a long-standing tradition. Wolf remains have been found in association with hominid remains dating from 400,000 years ago. Dogs were, and are, valued for their aid in hunting. Dog burials at the Mesolithic cemetery of Svaerdborg in Denmark indicate that in ancient Europe dogs were valued companions. The molecular genetic data suggests that the domestic lineage separated from modern wolves around 150,000 years ago (Vilà et al, 1997). Conservative estimates propose that the domestication of the dog probably occurred at least 14,000 years ago. There is archaeological evidence of dog remains that are morphologically different from wolves from that time frame. However, in the early 2000s some research indicated that domestication in fact had already begun to occur as early as 100,000 years ago.

Wolf Ancestors

Some evidence suggests that several varieties of ancient wolves contributed genetically to the domestic dog. These contributions may have been deliberate or unintentional interbreeding. The means that various traits from one or more of the ancestral wolf lines were preserved in the domestic dog.

Although all wolves belong to the species Canis lupus, there are (or were) many subspecies that had developed a distinctive appearance, social structure, and other traits. For example, the Japanese wolf and the Eastern Timber Wolf posses different distinctive colouration, hunting and social structures.

The Indian Wolf is thought to have contributed to the development of more breeds of dogs than other subspecies. Many of today's wild dogs, such as the dingo, the dhole and pariah dogs, are descended from this wolf. Domestic dogs like sight hounds are also thought to have descended from this wolf according to recent genetic evidence. This hypothesis that modern dog breeds originated from Asia contradicts an earlier theory that dogs had evolved in Africa, much like humans.

The Indian wolf is also thought to have bred with descendants of the European wolf to create the Mastiffs and eventually leading to the development of such diverse breeds as the Pug, the Saint Bernard, and the Bloodhound. The Tibetan Mastiff is an example of an ancient breed.

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 probably ancestor to the Pekingese and toy spaniels, although it is also probable that descendants of the Chinese and European wolves encountered each other over the millennia, contributing to many of the oriental toy breeds.

The Eastern Timberwolf is a direct ancestor to most, if not all, of the North American northern sled dog types. This interbreeding still occurs with dogs living in the Arctic region, where the attributes of the wolf that enable survival in a hostile environment are valued by humans. Additionally, unintentional crossbreeding occurs simply because dogs and wolves live in the same environment. The general reproductive isolation which is required to define dogs and wolves as separate species is purely a result of lack of opportunity, stemming from a general mutual unfamiliarity, suspicion, mistrust, and fear.

The phenotypic characteristic that define a wolf from a dog are tenuous. Wolves typically have a "brush tail" and erect ears. While some dog breeds possess one of these characteristics, they rarely possess both.

Speed of domestication

Current research indicates that domestication, or the attributes of a domesticated animal, can occur much more quickly than previously believed. Domestication of a wild dog may occur within one or two human generations with deliberate selective breeding. It is also now generally believed that initial domestication was not attained solely by human desire intervention but through mutual desire. Wild canines who scavenged around human habitations received more food than their more skittish or fearful counterparts. Canines who attacked people or their children were likely killed or driven away, while those more friendly animals survived. Canines would have been beneficial by chasing away other vermin or scavengers. The relationship is theorized to have developed in this way.

Dog breeds

File:AdaRowlands.jpg

A brown short-haired mixed-breed dog.

There are numerous dog breeds, over 800 being recognized by various kennel clubs worldwide. As all dog breeds have been derived from mixed-breed dog populations, the term "purebred" has meaning only with respect to a certain number of generations. 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 due to the low gene pool. Dogs that are bred in this manner often end up with severe health or behavioural problems. Other organizations define a breed more loosely, such that an individual may be considered of one breed as long as 75% of its parentage is of that breed. These considerations come into play among breeders who enter their dogs in dog shows. Even prize-winning purebred dogs are sometimes possessed with crippling genetic defects due to inbreeding. These problems are not limited to purebred dogs and can affect mixed-breed populations. The behavior and appearance of a dog of a particular breed can be predicted fairly accurately, while mixed-breed dogs show a broader range of innovative appearance and behavior.

In February 2004, the Canine Studies Institute in Aurora, Ohio, arranged recognized breeds of dogs into ten categories.

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 not inherently "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 Miniature 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 color or coat. However, without genetic testing of the parents, the crosses can sometimes end up inheriting genetic defects that occur in both parental breeds. Deliberately crossing two or more breeds is also a manner of establishing new breeds.

Neoteny in the rapid evolution of diverse dog breeds

This rapid evolution of dogs from wolves is an example of neoteny or paedomorphism. As with many species, the young wolves are more social and less dominant than adults; therefore, the selection for these characteristics, whether deliberate or inadvertent, is more likely to result in a simple retention of juvenile characteristics into adulthood than to generate a complex of independent new changes in behavior. This is true of many domesticated animals, including human beings themselves, who have many characteristics similar to young bonobo. This paedomorphic selection naturally results in a retention of juvenile physical characteristics as well. Compared to wolves, many adult dog breeds retain such juvenile characteristics as soft fuzzy fur, round torsos, large heads and eyes, ears that hang down rather than stand erect, etc.; characteristics which are shared by most juvenile mammals, and therefore generally elicit some degree of protective and nurturing behavior cross-species from most adult mammals, including humans, who term such characteristics "cute" or "appealing".

The example of canine neoteny goes even further, in that the various breeds are differently neotenized according to the type of behavior that was selected.

Breeds that guard flocks, such as the various sheepdog breeds, retain the most juvenile characteristics: they stay close to home with their foster "litter" (which might include a flock of sheep), rather than going out hunting, they have almost no predatory behavior (which would be disastrous in the vicinity of such a natural prey stimulus as sheep), they respond to perceived threats with a lot of vocalization and attempts to alert and engage the dominant individuals in their "pack" (i.e. humans) whenever possible, engaging in actual combat only as a last resort. In addition, they retain very juvenile physical characteristics such as round bodies and heads, soft coats, ears that hang down, and so on, which do not elicit fear responses from the sheep in the way that an appearance similar to that of an adult wolf would. (Compare to the physical appearance of the border collie, a sheep herding dog, whose physical configuration is closer to that of an adult wild canine and who therefore has a greater capacity to frighten sheep into a desired pattern of movement, along with the more adult aggressive temperament to do so).
Breeds that are hunting dogs—that is, pointers, setters, spaniels, retrievers, etc.—have an intermediate degree of paedomorphism; they are at the point where they share in the pack's hunting behavior, but are still in a junior role, not participating in the actual attack. They identify potential prey and freeze into immobility, for instance, but refrain from then stalking the prey as an adult predator would do next; this results in the "pointing" behavior for which such dogs are bred. Similarly, they seize dead or wounded prey and bring it back to the "pack", even though they did not attack it themselves, that is, "retrieving" behavior. Their physical characteristics are closer to that of the mature wild canine than the sheepdog breeds, but they typically do not have erect ears, etc.
Scenthounds maintain an intermediate body type and behavior pattern that causes them to actually pursue prey by tracking their scent, but tend to refrain from actual individual attacks in favor of vocally summoning the pack leaders (in this case, humans) to do the job. This contrasts with sighthounds, who pursue and attack perceived prey on sight, and who maintain the mature canine body type with erect ears, lean bodies, and adult coats.
Terriers similarly have adult aggressive behavior, famously coupled with a lack of juvenile submission, and display correspondingly adult physical features such as erect ears, although many breeds have also been selected for size and sometimes dwarfed legs to enable them to pursue prey in their burrows.
The least paedomorphic behavior pattern may be that of the basenji, bred in Africa to hunt alongside humans almost on a peer basis; this breed is often described as highly independent, neither needing nor appreciating a great deal of human attention or nurturing, often described as "catlike" in its behavior. It too has the body plan of an adult canine predator.

Of course, dogs in general possess a significant ability to modify their behavior according to experience, including adapting to the behavior of their "pack leaders"—again, humans. This allows them to be trained to behave in a way that is not specifically the most natural to their breed; nevertheless, the accumulated experience of thousands of years shows that some combinations of nature and nurture are quite daunting, for instance, training whippets to guard flocks of sheep.

References and further reading

References

Kennel Club Books Website 400 titles on dogs.
Abrantes, Roger (1999). Dogs Home Alone. Wakan Tanka, 46 pages. ISBN 0966048423 (paperback).
¹A&E Television Networks (1998). Big Dogs, Little Dogs: The companion volume to the A&E special presentation, A Lookout Book, GT Publishing. ISBN 1-57719-353-9 (hardcover).
²Alderton, David (1984). The Dog, Chartwell Books. ISBN 0-89009-786-0.
Brewer, Douglas J. (2002) Dogs in Antiquity: Anubis to Cerberus: The Origins of the Domestic Dog, Aris & Phillips ISBN 0856687049
Donaldson, Jean (1997). The Culture Clash. James & Kenneth Publishers. ISBN 1888047054 (paperback).
Fogle, Bruce DVM The New Encyclopedia of the Dog, 2000
Milani, Myrna M. (1986). The Body Language and Emotion of Dogs: A practical guide to the Physical and Behavioral Displays Owners and Dogs Exchange and How to Use Them to Create a Lasting Bond, William Morrow, 283 pages. ISBN 0688128416 (trade paperback).
Pfaffenberger, Clare (1971). New Knowledge of Dog Behavior. Wiley, ISBN 0876057040 (hardcover); Dogwise Publications, 2001, 208 pages, ISBN 1929242042 (paperback).
Shook, Larry (1995). "Breeders Can Hazardous to Health",The Puppy Report: How to Select a Healthy, Happy Dog, Chapter Two, pp. 13–34. Ballantine, 130 pages, ISBN 0345384393 (mass market paperback); Globe Pequot, 1992, ISBN 1558211403 (hardcover; this is much cheaper should you buy).
Shook, Larry (1995). The Puppy Report: How to Select a Healthy, Happy Dog, Chapter Four, "Hereditary Problems in Purebred Dogs", pp. 57–72. Ballantine, 130 pages, ISBN 0345384393 (mass market paperback); Globe Pequot, 1992, ISBN 1558211403 (hardcover; this is much cheaper should you buy).
Thomas, Elizabeth Marshall (1993). The Hidden Life of Dogs (hardcover), A Peter Davison Book, Houghton Mifflin. ISBN 0395669588.
Vilà, Caries; Savolainen, Peter; Maldonado, Jesus E.; Amorim, Isabel R.; Rice, John E.; Honeycutt, Rodney L.; Crandall, Keith A.; Lundeberg, Joakim; Wayne, Robert K. (1997). Multiple and ancient origins of the domestic dog. Science 276, pp. 1687–1689.

External links

General info

dog encyclopedia
The best dog breeds for families with little children
Dogpatch Considerable info about breeds, training, sports, and all other things dog
National Geographic News Many articles and photos about dogs
Global Paw Large dog community with considerable information.
Free Online Veterinarian Advice Free online veterinary advice and lots of dog health articles.
Pictures of dogs published on USENET stored with an search function.

Genetics and origins

Health and medical

Training and behavior

noncommercial site sponsored by the University of Wisconsin-Stevens Point

Breed listings from major kennel clubs

American Kennel Club
Canadian Kennel Club
United Kennel Club Breed lists for many breeds and types not recognized by the AKC--and for many that are (U.S.)
FCIFédération Cynologique Internationale - FCI
FCI International breed standards
Australian National Kennel Club
The Kennel Club (UK)
New Zealand Kennel Club