Dog

This article discusses the domestic dog. For other members of the dog family, see Canidae.

Conservation status: Secure

Terminology for dogs

Puppies enjoy teething on almost anything.

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 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. 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.

Attributes

Dogs are predators built for chasing, leaping at, and killing prey.

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.

Their senses are in some ways far superior to humans. Vision is a mixed bag; dogs are believed to be red-green colorblind and, because the lenses of their 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 have a field of vision up to 280° (compared to 180° for humans), although broad-headed breeds with their eyes set forward have a much narrower field of vision than, for example, sight hounds. They detect sounds in the 70-100,000 kHz frequency range (compared to 16-20,000 kHz for humans), and in addition have movable ears that help them to pinpoint the exact location of a sound and do it quickly. Dogs have about 220 million smell-sensitive cells (compared to 5 million for humans). 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 and the English Bulldog.

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

Dog coats, colors, and markings

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

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

• Blenheim: A combination of chestnut and white; for example, the Cavalier King Charles Spaniel.
• Black: Usually pure black but sometimes grizzled, particularly as dogs age and develop white hairs, usually around the muzzle.
• Black and tan: Coat has both colors but in clearly defined and separated areas; usually the top and sides are black and lower legs and underside are tan, reddish, or chestnut.
• Blue: A dark metallic gray, almost always as a blue merle or speckled (with black). Kerry Blue Terriers and Australian Shepherds are among many breeds that come in blue.
• Brown: Includes dark mahogany, midtone brown, gray-brown, and very dark brown.
• Cream: Depending on the breed and individual, ranges from white through ivory and blond, often occurring with or beneath lemon, yellow, and sable.
• 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.
• Red: Reminiscent of reddish woods such as cherry or mahogany; also tawny, chestnut, orange, rusty, and red-gold.
• Liver: A reddish brown somewhat the color of cinnamon or bronze; the breed often determines whether "liver", "chocolate", "brown", or "red" is used to describe the color, as in a liver German Shorthaired Pointer or a chocolate Labrador Retriever.
• Sable: Black-tipped hairs; the background color can be gold, silver, gray, or tan

Dogs' coats come in a wide variety of colors and markings, among which the Dalmatian's coat is one of the most striking.

• White
• Tricolor: Consisting of three colors; usually black, tan, and white or liver, tan, and white; for example, the Smooth Collie or the Sheltie.
• Wheaten: Pale yellow or fawn, like the color of ripe wheat
• Yellow: Yellowish-gold tan, as in a yellow Labrador Retriever
• Gold: Rich reddish-yellow, as in a Golden Retriever; often includes colors such as yellow-gold, lion-colored, fawn, apricot, wheaten, tawny, yellow-red, straw, mustard, and sandy.

Coat patterns include:

• Brindle: A mixture of black with brown, tan, or gold; usually in a somewhat striped pattern
• Merle: Marbled coat with darker patches and spots of the specified color; for example, a blue merle is marbled gray and blue with black and sometimes white patches; a red (or liver) merle has deep red or brown on lighter red, often with white or black mixed in.
• Harlequin: "Torn" patches of black on white; only the Great Dane exhibits this pattern
• Particolor: Two-colored coat with the colors appearing in patches in roughly equal quanties

The German Wirehaired Pointer's coat demonstrates a rough 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-resistent 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:

• Smooth-coated:
• 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:
• 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-resistent outer coat (topcoat), also referred to as guard hairs. Most other coat types can also be double coated.
• Short-haired:
• Corded coat: for example, see Puli

The Basset Hound's ears are extremely long drop ears.

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.

The Basenji's tail is tightly curled.

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
• Saber: Carried in a slight curve like that of a saber
• Sickle: Carried out and up in a semicircle like a sickle
• Odd: Twisted, but not short. Uncommon. Tibetan Terriers have odd tails.

Reference

• The New Encyclopedia of the Dog, Bruce Fogle DVM, 2000

Ancestry and history of domestication

This ancient mosaic shows a large dog with a collar hunting a lion.

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, some research (http://www.amonline.net.au/archive.cfm?id=716) 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. Recent genetic evidence (http://www.abc.net.au/rn/science/ss/stories/s728909.htm) 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 millennia, 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, can occur much more quickly (http://www.amsci.org/amsci/articles/99articles/Trut.html#26879) 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.

Dog society

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.

Properly socialized dogs can interact with unfamiliar dogs of any size and shape and understand how to communicate.

Dominance and submission

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.

Dominance behavior

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.

Dog language can generally be learned by humans; this dog is inviting play.

Behavior when isolated

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.

Favorite activities

Nothing is more pleasurable to dogs than spending time with and interacting with other dogs. Roughhousing and chasing one another are favorite activities. Off-leash dog parks can be good places for dogs to exercise and interact with other dogs when all owners take responsibility for their dogs' behavior. When quiet, dogs especially love lying about with their companions, favoring spots with a good view.

Dog breeds

There are numerous dog breeds, over 800 being recognised by various kennel clubs worldwide. No dog breed is truly purebred. All dog breeds have been derived from mixed-breed dog populations. Moreover, 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. Purebred dogs frequently suffer from serious inherited health and behavioral problems, although by no means a majority of purebred dogs. 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. [1] (http://news.independent.co.uk/world/science_medical/story.jsp?story=491197)

The behavior and appearance of a dog of a particular breed can be predicted fairly accurately, while mixed-breed dogs show a broad range of innovative appearance and behavior.

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.

Most dogs are capable of and enjoy swimming, but they should be tested in shallow water first to make sure that they do not panic.

Interactions between dogs and humans

The relationship between dogs and humans is ancient. Dogs serve humans in many ways.

Dogs as working partners

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. Most modern working dogs are put in positions which capitalize on their sensory or strength advantages over normal humans.

For example, a new and particularly effective breed of working dog is the drug- or bomb-sniffing dog. All canines have olfactory sensitivity thousands or millions of times more sensitive than humans. This allows them to pick up on the subtle smells of distinctive chemicals, such as cannabis or plastic explosive. Airport security frequently tours concourses and baggage areas with a dog trained to respond to detect such chemicals, allowing their owners to be apprehended.

K-9 police units typically feature a long-term human-canine team, in which the dog is trained to home in on the scents of particular people, and to facilitate their arrest once located. Most criminals find that being wrestled to the ground by an aggressive dog is much more frightening then being tackled by a human. Such dogs are also frequently used to find missing persons, especially in the wilderness where visual clues may go unnoticed by humans.

Several cities in Italy are experimenting with a new use for working dogs: rescue swimmers. In this situation, a strong and well-trained dog is equipped with flotation devices and dropped in the water near a floundering swimmer. The swimmer then grabs onto the dog, and the animal tows the swimmer to shore.

Dogs as 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 unexcelled. They can spend long hours in a duck blind and, after the party 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.

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. Their energy level is at full tilt as they see the hunters load weapons, take to the field, and begin the hunt. The contentment at the end of the day is felt by man and dog.

Dogs as pets

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.

A portrait of an adult female cockapoo.

Dogs as food

In certain cultures, dogs are raised on farms and slaughtered as a source of meat. In Korea for example, dog meat is the basis for winter soups and stews in some segments of the population(see Gaegogi). The source of the meat and the alleged methods of slaughter has generated friction between dog lovers and dog eaters, that occasionally breaks out as headline news.

In other cultures, dogs have served as a standby source of food. One example is in China where in times past Chow Chows were often posted to guard family storehouses. During a hard season when the food store was depleted, the dog would be slaughtered as an emergency ration.

Traditionally, Eskimo and non-native sled dog teams would feed a dog who expired during a grueling run to the remaining dogs.

Dog reproduction

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.

Catahoula Leopard Dog nursing litter of puppies

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. Spaying and neutering can also help prevent diseases such as breast cancer and prostate cancer that occur as the unneutered animal ages. Also, it is not required for a female dog to either experience a heat cycle or have puppies before spaying; likewise, a male dog does not need the experience of mating before neutering. These myths account for numerous health problems and unwanted puppies.

Dangers

As is proved by their attacks upon other creatures, wild and domestic, dogs can be voracious, aggressive, predators. Their sharp teeth and powerful jaws can inflict serious injuries requiring hospitalization; their sharp claws have powerful muscles behind them. Scratches from dogs are easily infected. Although confrontations between man and dog ordinarily stop well short of harm due to the mutual respect that man has for dogs, human stupidity can lead to severe injury from even the most well-tempered dog. Contrary to myth, barking dogs can bite a person who fails to recognize the warning. Likewise, a wagging tail does not necessarily mean the dog is happy or friendly.

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 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, and 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 bring to anger. Dogs are not inherently aggressive unless they are feral, trained to attack intruders, threatened, or provoked.

Small children are especially prone to provoking dogs, in part because their pre-ambulatory movements suggest similarities to prey that dogs instinctively attack. Children should be kept separate from any dog in the absence of adult supervision until the dog has shown its acceptance of the child in its midst.

Dogs should never be taught aggressive behavior toward humans, even as a 'game'.

Miscellaneous Facts

Dogs and the Zodiac

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.

Dogs and Perspiration

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.

A Fine Sense of Direction

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.

Diseases and Ailments

Most diseases that affect dogs or humans are not transferable between the two species. There are some exceptions:

• Rabies, or Hydrophobia, is an often fatal disease that can be transmitted to humans by dog bite. Areas that do not have the disease, such as Australia or the U.S. state of Hawaii, have strict quarantine laws to keep their territories rabies-free. Areas that do have the disease usually require that dogs be vaccinated against rabies.
• Parasites, particularly worms such as tapeworms and roundworms, can be transmitted in a dog's saliva or feces.

Genetic conditions are a problem in some dogs, particularly purebreeds:

• Hip dysplasia primarily affects larger breeds.
• Luxating patellas can be a problem for smaller breeds.
• Genes for blindness or deafness seem to be carried by some breeds.

Several types of parasites are commonly associated with dogs:

• Intestinal worms cause varying degrees of discomfort.
• Heartworm is a dog parasitoid. It is hard to eliminate and can be fatal; therefore, the best course is prevention.
• Fleas and ticks are common parasites for which there are effective preventive medications and ointments.
• Various mites cause skin problems such as mange.

Some foods commonly enjoyed by humans are dangerous to dogs:

• Dogs like the flavor of chocolate, but chocolate in sufficient doses is lethally toxic to dogs (and horses) and should never be fed to them. This is because chocolate contains theobromine, a chemical stimulant which, together with caffeine and theophylline, belongs to the group of methylxanthine alkaloids. Dogs are unable to metabolize theobromine effectively. If they eat chocolate, the theobromine can remain in their bloodstream for up to 20 hours, and these animals may experience racing heartbeats, hallucinations, severe diarrhea, epileptic seizures, heart attacks, internal bleeding, and eventually death. A chocolate candy bar can be sufficient to make a small dog extremely ill or even kill it. In case of accidental intake of chocolate by a dog, contact a veterinarian or animal poison control immediately; it is commonly recommended to induce vomiting within two hours of ingestion.

  Carob treats are often available as dog treats; these are unrelated to chocolate and are safe. Many dogs consider anything given them directly by hand to be a treat, even a piece of kibble plucked from the bag, or a crust of bread. Special dog treats are not necessary for such animals.

• Grapes and raisins can cause acute renal failure in dogs.

• Alcoholic beverages pose much the same temptation and hazard to dogs as to humans.

• Antifreeze, due to its sweet taste, poses an extreme danger of poisoning to a dog that either drinks from a spill or licks it off its fur. It can cause seizures and death. Dogs should not be allowed access to any place in which an antifreeze leak or spill has happened until the spill is completely cleaned out.

For additional information on dog health, see Category:Dog health.

Intelligence

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.

References and further reading

• 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. (http://www.mnh.si.edu/GeneticsLab/StaffPage/MaldonadoJ/PublicationsCV/Science_Dog_Paper.pdf) Science 276, pp. 1687-1689.
• Donaldson, Jean (1997). The Culture Clash (paperback), James & Kenneth Publishers. ISBN 1888047054.
• Thomas, Elizabeth Marshall (1993). The Hidden Life of Dogs (hardcover), A Peter Davison Book, Houghton Mifflin. ISBN 0395669588.
• Myrna M. Milani, 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, 1986, trade paperback, 283 pages, ISBN 0688128416
• Pages 13 to 34, Chapter Two, "Breeders Can Hazardous to Health",The Puppy Report: How to Select a Healthy, Happy Dog, Larry Shook, Ballantine, 1995, mass market paperback, 130 pages, ISBN 0345384393; hardcover, Globe Pequot, 1992, ISBN 1558211403 (hardcover is much cheaper should you buy)
• Pages 57 to 72, Chapter Four, "Hereditary Problems in Purebred Dogs",The Puppy Report: How to Select a Healthy, Happy Dog, Larry Shook, Ballantine, 1995, mass market paperback, 130 pages, ISBN 0345384393; hardcover, Globe Pequot, 1992, ISBN 1558211403 (hardcover is much cheaper should you buy)
• Clare Pfaffenberger, New Knowledge of Dog Behavior, Wiley, 1971, hardcover, ISBN 0876057040; paperback, Dogwise Publications, 2001, 208 pages, ISBN 1929242042
• Roger Abrantes, Dogs Home Alone, Wakan Tanka, 1999, paperback, 46 pages, ISBN 0966048423

Related topics

• List of dog topics
• How to choose your pet and take care of it
• List of historical dogs
• List of fictional dogs

Related topics in other Wiki media

Look up Dog in Wiktionary, the free dictionary.

• Dog Care

External links

• Dogpatch (http://www.dogpatch.org/dogs) Considerable info about breeds, training, sports, and all other things dog
• Dog Training (http://www.dogtraininghq.com) Resources for dog owners to train their dogs correctly.
• National Geographic News (http://news.nationalgeographic.com/news/2004/02/0209_040209_dogsdogsdogs.html) Many articles and photos about dogs
• Genetics and origins:
  • "Multiple and Ancient Origins of the Domestic Dog" (http://www.idir.net/~wolf2dog/wayne1.htm)
  • Canid Genetics (http://www.fiu.edu/~milesk/Genetics.htm)
  • "Dog Genome Assembled" (http://www.nhgri.nih.gov/12511476) - NHGRI
  • "World's dogs are descended from Asian wolves" (http://www.ananova.com/news/story/sm_713600.html)

• Health and medical:
  • Information about the third eyelid of dogs, and the problem of Kertao, or "dry eye". (http://www.petcat.us/questions.shtml)
  • How to keep a dog healthy (http://www.publicbookshelf.com/public_html/Boys_Own_Book_of_Outdoor_Sports/healthydo_g.html)
  • Why chocolate is poisonous to dogs (http://www.avma.org/careforanimals/animatedjourneys/livingwithpets/poisoninfo.asp) from the American Veterinarian Medical Association
  • Information about grapes and raisins (http://www.snopes.com/critters/crusader/raisins.asp)
  • Petalia: Human foods that poison pets (http://www.petalia.com.au/templates/storytemplate_process.cfm?story_no=257&specie=&url.section=answers)
  • Common household items that can poison pets (http://www.thepetcenter.com/wai/poi_PP.html)
  • Pros and Cons of Inbreeding (http://www.dogbreedinfo.com/inbreeding.htm)

• Breed listings from major kennel clubs:
  • American Kennel Club (http://www.akc.org/)
  • United Kennel Club (http://www.ukcdogs.com/breeds/) Breed lists for many breeds and types not recognized by the AKC--and for many that are (U.S.)
  • FCI (http://www.fci.be)Fédération Cynologique Internationale - FCI
  • FCI (http://www.dogdomain.com/fci-1.htm)International breed standards
  • Australian National Kennel Club (http://www.ankc.aust.com/breed_list.html)
  • The Kennel Club (UK) (http://www.the-kennel-club.org.uk)
  • New Zealand Kennel Club (http://www.nzkc.org.nz/dogselect.html)
• Your Dogs -- 1000s of public postings about dogs (http://www.yourdogs.net)

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