DOGS

The dog (Canis familiaris when considered a distinct species or Canis lupus familiaris when considered a subspecies of the wolf) is a domesticated carnivoran of the family Canidae. It is part of the wolf-like canids, and is the most widely abundant terrestrial carnivore. The dog and the extant gray wolf are sister taxa as modern wolves are not closely related to the wolves that were first domesticated, which implies that the direct ancestor of the dog is extinct. The dog was the first species to be domesticated, and has been selectively bred over millennia for various behaviors, sensory capabilities, and physical attributes.

Their long association with humans has led dogs to be uniquely attuned to human behavior and they are able to thrive on a starch-rich diet that would be inadequate for other canids. Dogs vary widely in shape, size and colors. They perform many roles for humans, such as hunting, herding, pulling loads, protection, assisting police and military, companionship and, more recently, aiding disabled people and therapeutic roles. This influence on human society has given them the sobriquet of "man's best friend".

Taxonomy

In 1758, the Swedish botanist and zoologist Carl Linnaeus published in his Systema Naturae the binomial nomenclature – or the two-word naming – of species. Canis is the Latin word meaning "dog", and under this genus he listed the dog-like carnivores including domestic dogs, wolves, and jackals. He classified the domestic dog as Canis familiaris, and on the next page he classified the wolf as Canis lupus. Linnaeus considered the dog to be a separate species from the wolf because of its cauda recurvata - its upturning tail which is not found in any other canid.

In 1758, the Swedish botanist and zoologist Carl Linnaeus published in his Systema Naturae the binomial nomenclature – or the two-word naming – of species. Canis is the Latin word meaning "dog", and under this genus he listed the dog-like carnivores including domestic dogs, wolves, and jackals. He classified the domestic dog as Canis familiaris, and on the next page he classified the wolf as Canis lupus. Linnaeus considered the dog to be a separate species from the wolf because of its cauda recurvata - its upturning tail which is not found in any other canid.

In 2019, a workshop hosted by the IUCN/Species Survival Commission's Canid Specialist Group considered the New Guinea singing dog and the dingo to be feral dogs Canis familiaris, and therefore should not be assessed for the IUCN Red List.

Origen

The origin of the domestic dog includes the dog's genetic divergence from the wolf, its domestication, and its development into dog types and dog breeds. The dog is a member of the genus Canis, which forms part of the wolf-like canids, and was the first species and the only large carnivore to have been domesticated. Genetic studies comparing dogs with modern wolves show reciprocal monophyly (separate groups), which implies that dogs are not genetically close to any living wolf and that their wild ancestor is extinct. An extinct Late Pleistocene wolf may have been the ancestor of the dog, with the dog's similarity to the extant grey wolf being the result of genetic admixture between the two. In 2020, a literature review of canid domestication stated that modern dogs were not descended from the same Canis lineage as modern wolves, and proposes that dogs may be descended from a Pleistocene wolf closer in size to a village dog.

The genetic divergence between dogs and wolves occurred between 20,000 and 40,000 years ago, just before or during the Last Glacial Maximum (20,000-27,000 years ago). This timespan represents the upper time-limit for the commencement of domestication because it is the time of divergence and not the time of domestication, which occurred later. One of the most important transitions in human history was the domestication of animals, which began with the long-term association between wolves and hunter–gatherers more than 15,000 years ago.[28] The archaeological record and genetic analysis show the remains of the Bonn–Oberkassel dog buried beside humans 14,200 years ago to be the first undisputed dog, with disputed remains occurring 36,000 years ago.

Anotomy

Domestic dogs have been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes. Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Dogs are predators and scavengers; like many other predatory mammals, the dog has powerful muscles, fused wrist bones, a cardiovascular system that supports both sprinting and endurance, and teeth for catching and tearing.

Size and Weight

Dogs are highly variable in height and weight. The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 centimetres (2 1⁄2 inches) at the shoulder, 9.5 cm (3 3⁄4 in) in length along the head-and-body, and weighed only 113 grams (4 ounces). The largest known dog was a Saint Bernard which weighed 167.6 kg (369 1⁄2 lb) and was 250 cm (8 ft 2 in) from the snout to the tail. The tallest dog is a Great Dane that stands 106.7 cm (3 ft 6 in) at the shoulder.

Senses

The dog's senses include vision, hearing, sense of smell, sense of taste, touch and sensitivity to the earth's magnetic field. Another study suggested that dogs can see the earth's magnetic field.

Coat

The coats of domestic dogs are of two varieties: "double" being common with dogs (as well as wolves) originating from colder climates, made up of a coarse guard hair and a soft down hair, or "single", with the topcoat only. Breeds may have an occasional "blaze", stripe, or "star" of white fur on their chest or underside.

Regarding coat appearance or health, the coat can be maintained or affected by multiple nutrients present in the diet, see Coat (dog) for more information.

Premature graying can occur in dogs from as early as one year of age. This has been shown to be associated with impulsive behaviors, anxiety behaviors, fear of noise, and fear of unfamiliar people or animals.

Tail

There are many different shapes for dog tails: straight, straight up, sickle, curled, or cork-screw. As with many canids, one of the primary functions of a dog's tail is to communicate their emotional state, which can be important in getting along with others. In some hunting dogs, however, the tail is traditionally docked to avoid injuries. In some breeds, such as the Braque du Bourbonnais, puppies can be born with a short tail or no tail at all.