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Encyclopedia > Domestic dog
For other members of the dog family, see Canidae.
Domestic Dog
Conservation status: Secure

Norwegian Elkhound
A breed of domestic dog.
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Genus: Canis
Species: C. lupus
Subspecies: C. l. familiaris
Trinomial name
Canis lupus familiaris

The dog is a canine omnivorous mammal that has been domesticated for somewhere between 14,000 and 150,000 years. In this time, the dog has developed into hundreds of breeds with a great degree of variation. For example, heights ranging from just a few inches (such as the Chihuahua) to nearly three feet (such as the Irish Wolfhound), and colors ranging from white to black with reds, grays, and browns also occurring in a tremendous variation of patterns. The dog is known for its trainability, its playfulness, and for its ability to fit into human households and social situations. See dog training for details.

Dogs fill a variety of roles in human society. Working dogs of all kinds do traditional jobs such as herding and new jobs such as detecting contraband. For dogs that do not do their 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 they have earned the sobriquet Man's best friend.


Terminology for dogs

Puppies engage in teething on almost anything.

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. 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.


Dogs are predators suited to chasing after, leaping at, and killing prey.

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.

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.

Dogs have a form of colorblindness that affects how they see red (same as yellow), green, and blue (both appear white)1, 2. 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

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.

Dogs have about 220 million smell-sensitive cells (compared to 5 million for humans). Some breeds have been selectively bred for excellence in detecting scents, even compared to 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 novel situations.

Dog coats, colors, and markings

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

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.

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:

  • 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, often as a blue merle or speckled (with black). Kerry Blue Terriers, Australian Silky Terriers, Bearded Collies, 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.
  • 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.
  • 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.
  • Lemon: A very pale yellow or wheaten color which is not present at birth (the puppies are born white) but gradually becomes apparent, usually during the first six months of life.
  • 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.
  • Red: Reminiscent of reddish woods such as cherry or mahogany; also tawny, chestnut, orange, rusty, and red-gold.
  • Sable: Black-tipped hairs; the background color can be gold, silver, gray, or tan.
  • 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
  • White: Distinct from albino dogs.
  • Yellow: Yellowish-gold tan, as in a yellow Labrador Retriever.
The Dalmatian's coat is one of the more widely recognized markings.

Coat patterns include:

  • Brindle: A mixture of black with brown, tan, or gold; usually in a "tiger stripe" pattern
  • Harlequin: "Torn" patches of black on white; only the Great Dane exhibits this 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.
  • Particolor: Two-colored coat with the colors appearing in patches in roughly equal quantiles (in breeds where this is an allowed coat color; in breeds where patches of white are considered undesirable, a dog showing even a small patch of white might be classified as a particolor).

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:

The German Wirehaired Pointer's coat demonstrates a rough texture.
  • 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.


The Basset Hound's ears are extremely long drop 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.

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.


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


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. 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 most have vestigial dewclaws on their front legs.

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.

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 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.

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, are descended 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 hypotheses that the dog, like humans, had evolved originally in Africa. The Asian wolf also likely interbred 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 probable 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. Additionally, accidental crossbreeding occurs simply because dogs and wolves live in the same environment.

Current research indicates 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 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 master 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.

Ideally, the dominant/submissive social structure of dogs avoids conflict and enforces social stability. Poorly socialized dogs who are inept at establishing dominance hierarchy may become involved in excess conflicts, especially from a human viewpoint. People who misunderstand dog behavior or who have inadvertently placed themselves in a disadvantageous position within the dominance submissive hierarchy can find themselves participants in similar conflicts with the animal(s).

It is problematic to anthropomorphize the dominance/submission behavior of a pet or to mistake it for characteristics more appropriately applied to humans. It can be dangerous for a dog to be dominant relative to its master or mistress. By rewarding "bravery" or "boldness", there is a risk that in fulfilling a dog's wants it begins to feel it is the dominant pack member. Likewise, it can be dangerous for a dog to consider itself "the equal of any dog", because unnecessary and destructive conflict can result; rewarding a dog's aggressive behavior may eventually backfire. Likewise, submission in a dog is not necessarily an indication of a problem dog. Continuing to discipline a dog after it has adopted a submissive posture is contrary to a goal of obedience. From the dog's viewpoint, it has conceded the point and is communicating its acceptance of the owner's 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 are barking, howling, digging, and chewing. These activities may distress humans when they need to leave dogs alone for a period of time. However, this behavior, called separation anxiety, can be overcome with training, or at least decreased to the point where it becomes manageable. If young puppies are habituated to periods alone from an early age, this can normally be prevented entirely.

Favorite activities

Dogs enjoy 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 seeking relaxation, dogs enjoy lying about with their companions, favoring spots with a good view of their surroundings.

Dog breeds

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. 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 reorganizations 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 shows. Purebred dogs frequently suffer from serious inherited health and/or behavioral problems. This is by no means true of the majority of purebred dogs, and the same problems can occur in populations of mixed breed dogs. Even prize-winning purebred dogs are sometimes possessed 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 broader 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 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.

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, and have flown into outer space (see Laika). Most modern working dogs are put in positions which capitalize on their sensory or strength and endurance advantages over normal humans.

For example, a new and particularly effective role of working dogs is that of 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 such chemicals.

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 being wrestled to the ground by an aggressive dog much more frightening than being tackled by a human. Such dogs are also frequently used to find missing persons, especially in the wilderness.

Several cities in Italy are experimenting with working dogs as 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. The Newfoundland has long been used for water rescue, not only on shore, but from fishing boats as well.

Dogs are commonly used as search and rescue workers in cases of disasters. The St. Bernard has been historically used for such purposes in Europe in the case of avalanche. In the aftermath of the 9-11 attacks in New York, rescue dogs were brought in to search for survivors in the rubble. Some of the dogs became so disturbed at being unable to find any survivors that people had to be "planted" for the dogs to find so that they did not become depressed at their failure.

Dogs as hunting/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. 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.

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.

A portrait of an adult female cockapoo.

Dogs as food

Main article: Taboo meat

In some places (such as parts of East Asia) 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 in the "little iceage", humans have been known to eat their pets.

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 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.

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 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.

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 or are euthanized due to lack of space and resources in shelters. 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 (due to hormonal changes). 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.


As evidenced by their attacks on other creatures, both wild and domestic, dogs can be voracious, aggressive, predators. Their sharp teeth and powerful jaws can inflict serious injuries; 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, human ignorance or 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 indicates an excited state, which is not always a result of "happy" excitation; a wagging dog is not equivalent to a purring cat.

Some behaviors that people (especially people unfamiliar with dogs) might display could potentially evoke a predatory or aggressive response from a dog. These include (but are not limited to):

  • Attacking a dog
  • Attempting to take food away from a dog
  • Threatening a puppy in the presence of an adult dog, especially its mother
  • Looking a dog directly in the eyes, especially when on the same level of the dog (such as small children)
  • Approaching a sick or injured dog
  • Running away from a dog: the chase-and-catch instinct in wolves is not fully lost, and most dogs can outrun and overtake the average human
  • Ignoring "Beware of Dog" signs: trained attack dogs, unlike most dogs, may attack an intruder without warning

Although most dogs are not inherently aggressive (unless they are feral, trained to attack intruders, threatened or provoked), it is important to remember that they are predatory by nature and instinct is something that never disappears. This is not to say that all of the above behaviors will always result in injury. In fact, some dog experts advocate acclimating a puppy to a removal of its food in order that its handler can, later in life, do so if needed (the dog is eating something dangerous, for example) without as high a degree of danger.

Small children are especially prone to provoking dogs, in part because their pre-ambulatory movements suggest similarities to prey that dogs instinctively attack. Also, young children may well unintentionally provoke the dog (pulling on ears or tails is common) because they do not know any better. Because of a dog's pack instincts, they may also attempt to establish a dominant position over a child, this should not be allowed. To avoid potential conflicts, 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 and the child has shown an understanding of appropriate behavior.

Miscellaneous facts


Many dogs consider anything given them directly by hand to be a treat, even the food they are accustomed to

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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.
Dogs with strong chase instincts may also fixate on specific stimuli, such as a fast-moving, brightly colored running or cycling shoe, as a prey object, and not recognize the whole picture as a human being; this is probably operative in the majority of cases of otherwise nonaggressive dogs chasing cyclists and runners.
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