A dog breed is a particular strain of dog that was purposefully bred by humans to perform specific tasks, such as herding, hunting, and guarding.
Dogs are the most variable mammal on earth, with artificial selection producing around 450 globally recognized breeds. These breeds possess distinct traits related to morphology, which include body size, skull shape, tail phenotype, fur type, and coat colour.
Their behavioural traits include guarding, herding, and hunting, and personality traits such as hypersocial behavior, boldness, and aggression. Most breeds were derived from small numbers of founders within the last 200 years. As a result, today dogs are the most abundant carnivore species and are dispersed around the world.
The domestic dog is the first species, and the only large carnivore, to have been domesticated. The first dogs were certainly wolflike, but the phenotypic changes that coincided with the dog–wolf genetic divergence are not known.
In 2017, a study showed that 9,000 years ago the domestic dog was present at what is now Zhokhov Island, arctic north-eastern Siberia, which was connected to the mainland at that time. The dogs were selectively bred as either sled dogs or as hunting dogs, which implies that a sled dog standard and a hunting dog standard existed at that time.
As humans became more sophisticated, so did their dogs. Eventually, there emerged specific breeds of dogs, custom-bred to suit the breeders’ local needs and circumstances.
Between 3,000 and 4,000 years ago greyhound-type dogs were depicted on pottery and paintings in Egypt and Western Asia. Mastiff-type dogs were kept for guarding and hunting, and short-legged dogs were also bred.
Most modern dog breeds are the products of the controlled breeding practices of the Victorian era (1830-1900), and the accurate documenting of pedigrees with the establishment of the English Kennel Club in 1873 in imitation of other stud book registries for cattle and horses.
A purebred dog is considered to be one whose genealogy is traceable for three generations within the same breed.
National registries, such as the American Kennel Club (AKC) in the United States, the Canadian Kennel Club, the Kennel Club of England, and the Australian National Kennel Council, maintain pedigrees and stud books on every dog in every breed registered in their respective countries. The Foxhound Kennel Stud Book, published in England in 1844, was one of the earliest registries.
Other countries also have systems for registering purebred dogs. The AKC represents an enrollment of more than 36 million since its inception in 1884, and it registers approximately 1.25 million new dogs each year. The groups recognized by the AKC are identified below and in the Table.
Dogs bear their litters roughly 58 to 68 days after fertilization, with an average of 63 days, although the length of gestation can vary. An average litter consists of about six puppies, though this number may vary widely based on the breed of dog. Puppies grow to half their body weight in the first four to five months!
According to genetic studies, dogs originated in China, the Middle East and Eastern Europe. According to Greger Larson, an archeologist and geneticist, gray wolves were domesticated by humans somewhere in western Eurasia. He surmises people in the East were also domesticating wolves at the same time.
Partnership between dogs and humans was likely originally based on a human need for help with herding and hunting, for an early alarm system, and for a source of food in addition to the companionship many of us today know and love. In return, dogs received companionship, protection, shelter, and a reliable food source.
The greatest reliable age recorded for a dog is 29 years 5 months for an Australian cattle-dog named Bluey, owned by Les Hall of Rochester, Victoria, Australia.
The smallest known adult dog was a Yorkshire Terrier, that stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.7 in) in length along the head-and-body, and weighed only 113 grams (4.0 oz).
The tallest dog ever is ‘Zeus’ (USA) a Great Dane, who measured 1.118 m (44 in) tall on 4 October 2011 and is owned by Denise Doorlag and her family, of Otsego, Michigan, USA.
The heaviest dog ever reported by the Guinness Book of World Records was Zorba, an English Mastiff. He reached a weight of 155.6 kg (343 lb)!
When you think of fast dogs, the tall and lean Greyhound is the first breed that usually springs to mind. This long-legged, smooth-coated racing breed has been clocked at speeds up to 72 kilometers (45 miles) per hour.
In 2004, a Neapolitan mastiff named Abellatino Arabella (“Tia”) gave birth to an astounding 24 puppies on the same day—nine females and 15 males total. Tia, from Manea, Cambridgeshire, U.K., was owned by Damian Ward (U.K.) and Anne Kellegher (Ireland); the puppies’ father was named Caesar. All 24 puppies were born by Cesarean section; unfortunately, one was stillborn and three died within the first week.