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The dog is a mammal in the order Carnivora. Dogs were domesticated from wolves as recently as 15,000 years, ago Over time, the dog has developed into hundreds of breeds with a great degree of variation. For example, heights at the withers range from just a few inches (such as the Chihuahua) to roughly three feet (such as the Irish Wolfhound), and colors range from white to black, with reds, grays (usually called blue), and browns occurring in a tremendous variation of patterns. Dogs, like humans, are highly social animals and this similarity in their overall behavioral pattern accounts for their trainability, playfulness, and ability to fit into human households and social situations. This similarity has earned dogs a unique position in the realm of interspecies relationships. The loyalty and devotion that dogs demonstrate as part of their natural instincts as pack animals closely mimics the human idea of love and friendship, leading many dog owners to view their pets as full-fledged family members. Conversely, dogs seem to view their human companions as members of their pack, and make few, if any, distinctions between their owners and fellow dogs. 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 unique sobriquet "man's best friend" Conversely, some cultures consider dogs to be unclean. In some parts of the world, dogs are raised as livestock to produce dog meat for human consumption. In many places, consumption of dog meat is discouraged by social convention or cultural taboo. Terminology The English word dog, in common usage, refers to the domestic pet dog, Canis lupus familiaris. The species was originally classified as Canis familiaris by Linnaeus in 1758. In 1993, dogs were reclassified as a subspecies of the gray wolf, Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists. "Dog" 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. Some members of the family have "dog" in their common names, such as the African Wild Dog. The constellations Canes Venatici, Canis Major and Canis Minor are named from the Latin word for "dog," for their perceived resemblance to dogs. An alternative designation has also been presented, which is to name dogs either Canis lupus f. familiaris or Canis familiaris L.. This terminology has been considered accurate by geologists and zooarcheologists for a while, since dogs would not be a subspecies of wolf if the above designation should be considered correct, but 450 subspieces of wolf. The designation was presented by a group of scientists in the article "The naming of Wild Animals and their Domestic Deriatives" in the Journal of Archeological Science The English word dog might derive from the Old English docga, a "powerful breed of canine". The French dogue and Spanish dogo as in dogo Argentino are borrowings from English. The English word hound is a cognate of the German Hund and Dutch hond which, though referring to a specific breed in English, means "dog" in general in German and Dutch. Hound itself derives from the Proto-Indo-European In breeding circles, a male canine is referred to as a dog, while a female canine is called a bitch. Offspring are generally called pups or puppies until they are about a year old. A group of offspring is a litter. The process of birth is whelping. Many terms are used for dogs that are not purebred. Intelligence Among dog lovers, dogs are generally valued for their intelligence, and both anecdotal evidence and scientific research suggest that dogs have a reasonably high intelligence. This intelligence is expressed differently with different breeds and individuals, however. For example, Border Collies are noted for their ability to learn commands, while other breeds may not be so motivated towards obedience, but instead show their cleverness in devising ways to steal food or escape from a yard. Dogs are descended from wolves, and are also pack animals, making them easier than other animals to train because dogs' instincts are to obey. But most dogs rarely have to deal with complex tasks and are unlikely to learn relatively complicated activities (such as opening doors) unaided. Some dogs (such as guide dogs for the visually impared) are specially trained to recognize and avoid dangerous situations. Physical characteristics
Sight Dogs were thought to be dichromats and thus, by human standards, color blind.A&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).Alderton, David (1984). The Dog, Chartwell Books. ISBN 0-89009-786-0. New research is now being explored that suggests that dogs may actually see some color, but not to the extent that humans do; color may serve as a subliminal signal helping to distinguish overlapping objects from each other, rather than a distinct feature that the dog can directly determine. It has also been suggested that dogs see in varieties of purple/violet and yellow shades. 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 180° for humans), although broad-headed breeds with their eyes set forward have a much narrower field of vision, as low as 180°. Hearing
Smell 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. What information a dog actually detects when he is scenting is not perfectly 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 the dog must be motivated to continue this hard work for a long period of time. Diet At present, there is some debate as to whether domestic dogs should be classified as omnivores or carnivores, by diet. 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 the cat family with its shorter small intestine, a dog is dependent on neither meat-specific protein nor a very high level of protein in order to fulfill its basic 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 their diet. Wild canines not only eat available plants to obtain essential amino acids, but also obtain nutrients from vegetable matter from the stomach and intestinal contents of their herbivorous prey, which they usually consume. Domestic dogs can survive healthily on a reasonable and carefully designed vegetarian diet, particularly if eggs and milk products are included. Some sources suggest that a dog fed on a strict vegetarian diet may develop dilated cardiomyopathy since it lacks L-carnitine, however, maintaining a balanced diet is also a factor since L-carnitine is found naturally in many nuts, seeds, beans, vegetables, fruits and whole grains. In the wild, dogs can survive on a vegetarian diet when animal prey is not available. However it has been noted, both by observation of extremely stressful conditions such as the Iditarod race and by scientific studies of similar conditions, that high-protein (approximately 40%) diets including meat help prevent damage to muscle tissue. (This research is also true for some other mammals.) This level of protein corresponds to the percentage of protein found in the wild dog's diet when prey is abundant; higher levels of protein seem to confer no added benefit. Dogs frequently avidly eat grass, a harmless activity. Explanations abound, but rationales such as that it neutralizes acid, or that eating grass might make the dog vomit, so dogs eat grass to remove unwanted substances from their stomachs, are at best educated guesses. Dogs do vomit more readily than humans, as part of their typical feeding behavior of gulping down food then regurgitating indigestible bones, fur, etc. This behavior is typical of pack feeding in the wild, where the most important thing is to get as much of the kill as possible before others consume it all. Individual domestic dogs, however, may be very "picky" eaters, in the absence of this evolutionary pressure. Dangerous substances Some foods commonly enjoyed by humans are dangerous to dogs, including chocolate (Theobromine poisoning), onions, grapes and raisins •, some types of gum, certain sweeteners• and Macadamia nuts. Now that it is thought that the only dangerous substance in chocolate is the cocoa, this means that white chocolate can be used as a rare treat. The acute danger from grapes and raisins has been uncovered only since about 2000, and made public slowly since then. At present the cause is not known, but one veterinarian • believes it may be an acute auto-immune response to plant-borne viruses • in the same manner as FIP in cats. Whatever the reason, since only small quantities are necessary to induce acute renal failure, dogs should not be fed grapes or raisins, and sultanas and currants should likely be withheld as well. Cooked bones should never be given to dogs, as the heat changes the chemical and physical properties so that they cannot be chewed properly, splintering into jagged shards, and resist digestion. Human medications should not be given to a dog as a substitute for their regular medication as some can be especially toxic, especially paracetamol/acetaminophen (Tylenol). Alcoholic beverages pose much of the same hazards to dogs as they do to humans. Dogs may also find some poisons attractive, including antifreeze, snail bait, insect bait, and rodent poisons. Antifreeze may be one of the most insidious of poisons to dogs because of its sweet taste and because a dog may walk upon or lie down upon a spill of it or its residue and then lick it off. Dogs must be kept strictly away from antifreeze and not allowed access to any place that has had a spill of it that has not been completely removed. Plants such as caladium, dieffenbachia and philodendron will cause throat irritations that will burn the throat going down as well as coming up. Hops are particularly dangerous and even small quantities can lead to malignant hyperthermia. • Amaryllis, daffodil, english ivy, iris, and tulip (especially the bulbs) cause gastric irritation and sometimes central nervous system excitement followed by coma, and, in severe cases, even death. Ingesting foxglove, lily of the valley, larkspur and oleander can be life threatening because the cardiovascular system is affected. Equally life threatening is the yew which affects the nervous system. If any of these plants are ingested, get the dog to a veterinarian immediately. Many household cleaners such as ammonia, bleach, disinfectants, drain cleaner, soaps, detergents, and other cleaners, mothballs and matches are dangerous to dogs, as are cosmetics such as deodorants, hair coloring, nail polish and remover, home permanent lotion, and suntan lotion. Overpopulation According to the Humane Society of the United States, 3-4 million dogs and cats are euthanized each year in the United States and many more are confined to cages in shelters because there are many more animals than there are homes. Spaying or neutering dogs helps keep overpopulation down. Local humane societies, SPCA's and other animal protection organizations urge people to spay or neuter their pets and to adopt animals from shelters instead of purchasing them. Several notable public figures have spoken out against animal over population, including Bob Barker. On his game show, The Price is Right, Barker stressed the issue every episode by stating: "Help control the pet population. Have your pets spayed or neutered." Dog health 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. Dogs, like all mammals, are also susceptible to heat exhaustion when dealing with high levels of humidity and/or extreme temperatures.• Diseases Infectious diseases commonly associated with dogs include rabies (hydrophobia), canine parvovirus, and canine distemper. Congenital diseases of dogs can include a wide range from hip dysplasia and medial patellar luxation to epilepsy and pulmonic stenosis. Canines can get just about anything a human can get (excluding many infections which are species specific) like hypothyroidism, cancer, dental disease, heart disease, etc. 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. Lifespan The typical lifespan of dogs varies considerably by breed. For example, many giant dog breeds average only 7 or 8 years, while some small terrier breeds might live as long as 20 years.The average lifespan for mixed-breed and midsize dogs is about 13 to 14 years. The longest-lived dog with reliable documentation died at 29 in 1939. Although the lifespans of all living species are mostly uncontrollable, one can significantly extend a dog's life by feeding it the right kinds of foods, giving it exercise, visiting the vet frequently, caring for its special needs, and loving it. Behavior For details, see . Dogs are very social animals, but their personality and behavior vary with breed as well as how they are treated by their owners and others who come in contact with them. Physical abuse and starvation can produce very neurotic, dangerous dogs, and even simply failing to socialize them properly may entail maladaptive behaviors. It is not uncommon for dogs to attack humans and other animals; however, this is usually because of lack of care or improper upbringing by its owner. Ancestry and history of domestication Molecular systematics indicate that the domestic dog (Canis lupus familiaris) descends from one or more populations of wild wolves (Canis lupus). As reflected in the nomenclature, dogs are descended from the wolf and are able to interbreed with wolves. The relationship between human and canine has deep roots. Wolf remains have been found in association with hominid remains dating from 400,000 years ago. Converging archaeological and genetic evidence indicate a time of domestication in the late Upper Paleolithic close to the Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago. Fossil bone morphologies and genetic analysis of current and ancient dog and wolf populations have not yet been able to conclusively determine whether all dogs descend from a single domestication event, or whether dogs were domesticated independently in more than one location. Domesticated dogs may have interbred with local populations of wild wolves on several occasions (so-called introgression). The earliest dog fossils, two crania from Russia and a mandible from Germany, date from 13,000 to 17,000 years ago. Their likely ancestor is the large northern Holarctic wolf, Canis lupus lupus. Remains of smaller dogs from Mesolithic (Natufian) cave deposits in the Middle East, dated to around 12,000 years ago, have been interpreted as descendants of a lighter Southwest Asian wolf, Canis lupus arabs. Rock art and skeletal remains indicate that by 14,000 years ago, dogs were present from North Africa across Eurasia to North America. Dog burials at the Mesolithic cemetery of Svaerdborg in Denmark suggest that in ancient Europe dogs were valued companions. Genetic analyses have so far yielded divergent results. Vilà, Savolainen, and colleagues (1997) concluded that dogs split off from wolves between 75,000 and 135,000 years ago, while a subsequent analysis by Savolainen et al. (2002) indicated a "common origin from a single gene pool for all dog populations" between 40,000 and 15,000 years ago in East Asia. Verginelli et al. (2005), however, suggest both sets of dates must be reevaluated in light of recent findings showing that poorly calibrated molecular clocks have systematically overestimated the age of geologically recent events. On balance, and in agreement with the archaeological evidence, 15,000 years ago is the most likely time for the wolf-dog divergence. Verginelli examined ancient DNA evidence from five prehistoric Italian canids carbon-dated to between 15,000 and 3,000 years old, 341 wolves from several populations worldwide, and 547 purebred dogs. Their results indicate multiple independent origins of dogs and/or of frequent interbreeding between early proto-dogs and wolves throughout a vast geographic range. The detailed history remains unexplored and until further evidence is available, the following section on wolf ancestors must be considered purely speculative. Wolf ancestors 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 possess different distinctive coloration, hunting and social structures. The origin of the dog is so ancient and so worldwide that many varieties of wolf played a part in it. It is wrong to say that dogs descended from modern wolves. They descended from ancestral wolves, and this difference must always be kept in mind. Ancestral wolves of many varieties existed all over the world, as they do today. Humans are of a tropical origin, and it was there that the domestication of dogs from wolves first took place. It follows then, that the first wolves to be domesticated were the warm-climate, short-haired varieties that gave rise to many of our dog breeds, with the long-haired, northern wolves giving rise to our northern breeds when humans reached these lattitudes. 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 and the pariah dogs, are descended from this wolf. 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 Timber Wolf 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 characteristics that distinguish 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 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. With their sharp senses, they would also be valuable as an alarm against marauding predators. The relationship is theorized to have developed in this way. Dog meat for human consumption Main article: Dog meat In a number of countries around the world, apart from being kept as pets, certain breeds of dogs are slaughtered as a source of meat and specifically raised on farms for that purpose. In countries where dogs are particularly popular as household pets, the use of dogs as a source of food is often considered a taboo and abhorrent cultural practice, although there are exceptions such as Vietnam where dogs are popular as pets and as meat. Dog abuse Cruelty to dogs refers to treatment which causes unacceptable suffering or harm. What qualifies as unacceptable suffering varies depending on the country and its culture. Famous dogs The long shared history of dogs and humans has resulted in many individual dogs achieving fame or notoriety, and many fictional dogs have been created for literature, cinema, and elsewhere. Dog 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. 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. Breed popularity Breed popularity varies widely over time and in different parts of the world and different segments of the population. Counting by American Kennel Club (AKC) registration (not by licensing registration or by United Kennel Club (UKC) registration, which could present different statistics), the Labrador Retriever has been the United States's most commonly registered breed of dog since 1991. However, even within parts of the United States, popularity varies; for example, in 2005 the most-registered breed in New York City was the Poodle; the Yorkshire Terrier was the second-most-registered breed in Houston but didn't even make the top ten in Honolulu. However, animal shelters in many parts of the United States report that the most-commonly available dog for adoption is the American Pit Bull Terrier or pit bull-type mixes, making up as much as 20% of dogs available for adoption, none of which would be registered with the AKC. Two decades ago, in 1983, the AKC's top two registered breeds were the American Cocker Spaniel and the Poodle.• In Britain, The Kennel Club reports that the most-registered breed from at least 1999 to 2005 was the Labrador Retriever. It rounds out the top three for 1999 to 2005 with the German Shepherd Dog, also popular in the States, and the English Cocker Spaniel, which is no longer even in the top ten in the States. See also Further reading | |||||||||||||
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