The Domestic Dog
The domestic dog (Canis lupus familiaris or Canis familiaris) is a domesticated canid which has been selectively bred over millennia for various behaviours, sensory capabilities, and physical attributes.
Dogs perform many roles for people, such as hunting, herding, pulling loads, protection, assisting police and military, companionship and, more recently, aiding handicapped individuals. This influence on human society has given them the sobriquet, "man's best friend".Although initially thought to have originated as an artificial variant of an extant canid species (variously supposed as being the dhole, golden jackal, or gray wolf , extensive genetic studies undertaken during the 2010s indicate that dogs diverged from an extinct wolf-like canid in Eurasia 40,000 years ago.
Their long association with humans has led to dogs being uniquely attuned to human behavior and are able to thrive on a starch-rich diet which would be inadequate for other canid species. Dogs are also the oldest domesticated animal. Dog vary widely in shape, size and colours.
A male canine is referred to as a dog, while a female is called a bitch. The father of a litter is called the sire, and the mother is called the dam. (Middle English bicche, from Old English bicce, ultimately from Old Norse bikkja) The process of birth is whelping, from the Old English word hwelp; the modern English word "whelp" is an alternate term for puppy. A litter refers to the multiple offspring at one birth which are called puppies or pups from the French poupée, "doll", which has mostly replaced the older term "whelp".In 14th-century England, hound (from Old English: hund) was the general word for all domestic canines, and dog referred to a subtype of hound, a group including the mastiff.
It is believed this "dog" type was so common, it eventually became the prototype of the category "hound". By the 16th century, dog had become the general word, and hound had begun to refer only to types used for hunting. The word "hound" is ultimately derived from the Proto-Indo-European word *kwon-, "dog". This semantic shift may be compared to in German, where the corresponding words Dogge and Hund kept their original meanings.The term "domestic dog" is generally used for both domesticated and feral varieties. The English word dog comes from Middle English dogge, from Old English docga, a "powerful dog breed". The term may possibly derive from Proto-Germanic *dukkōn, represented in Old English finger-docce ("finger-muscle"). The word also shows the familiar petname diminutive -ga also seen in frogga "frog", picga "pig", stagga "stag", wicga "beetle, worm", among others. The term dog may ultimately derive from the earliest layer of Proto-Indo-European vocabulary.
The dog is classified as Canis lupus familiaris under the Biological Species Concept and Canis familiaris under the Evolutionary Species Concept.
In 1758, the taxonomist Linnaeus published in Systema Naturae a categorization of species which included the Canis species. Canis is a Latin word meaning dog, and the list included the dog-like carnivores: the domestic dog, wolves, foxes and jackals. The dog was classified as Canis familiaris, which means "Dog-family" or the family dog. On the next page he recorded the wolf as Canis lupus, which means "Dog-wolf". In 1978, a review aimed at reducing the number of recognized Canis species proposed that "Canis dingo is now generally regarded as a distinctive feral domestic dog. Canis familiaris is used for domestic dogs, although taxonomically it should probably be synonymous with Canis lupus."
In 1982, the first edition of Mammal Species of the World listed Canis familiaris under Canis lupus with the comment: "Probably ancestor of and conspecific with the domestic dog, familiaris. Canis familiaris has page priority over Canis lupus, but both were published simultaneously in Linnaeus (1758), and Canis lupus has been universally used for this species", which avoided classifying the wolf as the family dog. The dog is now listed among the many other Latin-named subspecies of Canis lupus as Canis lupus familiaris.
In 2003, the ICZN ruled in its Opinion 2027 that if wild animals and their domesticated derivatives are regarded as one species, then the scientific name of that species is the scientific name of the wild animal. In 2005, the third edition of Mammal Species of the World upheld Opinion 2027 with the name Lupus and the note: "Includes the domestic dog as a subspecies, with the dingo provisionally separate - artificial variants created by domestication and selective breeding".
However, Canis familiaris is sometimes used due to an ongoing nomenclature debate because wild and domestic animals are separately recognizable entities and that the ICZN allowed users a choice as to which name they could use, and a number of internationally recognized researchers prefer to use Canis familiaris.
Later genetic studies strongly supported dogs and gray wolves forming two sister monophyletic clades within the one species, and that the common ancestor of dogs and extant wolves is extinct.
Origin of the domestic dog
The origin of the domestic dog (Canis lupus familiaris or Canis familiaris) is not clear. Whole genome sequencing indicates that the dog, the gray wolf and the extinct Taymyr wolf diverged at around the same time 27,000–40,000 years ago. These dates imply that the earliest dogs arose in the time of human hunter-gatherers and not agriculturists. Modern dogs are more closely related to ancient wolf fossils that have been found in Europe than they are to modern gray wolves. Nearly all dog breeds' genetic closeness to the gray wolf are due to admixture, except several Arctic dog breeds are close to the Taimyr wolf of North Asia due to admixture.
A group of any three or more adults is a pack .
- The mother of a litter is a dam.
- The father of a litter is a sire.
- It is possible for one litter to have multiple sires.
- A group of pups from the same gestation period is a litter.
- Immature males or females (that is, animals that are incapable of reproduction) are pups or puppies.
- An adult female capable of reproduction is a brood bitch, or brood mother.
- An adult male capable of reproduction is a stud. An adult female is a bitch.
- In some countries, especially in North America, dog is used instead due to the vulgar connotation of bitch.
- The term dog typically is applied both to the species (or subspecies) as a whole, and any adult male member of the same.
Biology - Anatomy
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, and 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 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 largest known dog was an English Mastiff which weighed 155.6 kg (343 lb) and was 250 cm (98 in) from the snout to the tail. The tallest dog is a Great Dane that stands 106.7 cm (42.0 in) at the shoulder.
The dog's senses include vision, hearing, sense of smell, sense of taste, touch and sensitivity to the earth's magnetic field.
A heavy winter coat with countershading in a mixed-breed dog
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.
Domestic dogs often display the remnants of countershading, a common natural camouflage pattern. A countershaded animal will have dark coloring on its upper surfaces and light coloring below, which reduces its general visibility. Thus, many breeds will have an occasional "blaze", stripe, or "star" of white fur on their chest or underside.
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.
There are many household plants that are poisonous to dogs including begonia, Poinsettia and aloe vera.
Some breeds of dogs are prone to certain genetic ailments such as elbow and hip dysplasia, blindness, deafness, pulmonic stenosis, cleft palate, and trick knees. Two serious medical conditions particularly affecting dogs are pyometra, affecting unspayed females of all types and ages, and bloat, which affects the larger breeds or deep-chested dogs. Both of these are acute conditions, and can kill rapidly. Dogs are also susceptible to parasites such as fleas, ticks, and mites, as well as hookworms, tapeworms, roundworms, and heartworms.
A number of common human foods and household ingestibles are toxic to dogs, including chocolate solids (theobromine poisoning), onion and garlic (thiosulphate, sulfoxide or disulfide poisoning), grapes and raisins, macadamia nuts, xylitol, as well as various plants and other potentially ingested materials. The nicotine in tobacco can also be dangerous. Dogs can be exposed to the substance by scavenging garbage or ashtrays; eating cigars and cigarettes. Signs can be vomiting of large amounts (e.g., from eating cigar butts) or diarrhea. Some other signs are abdominal pain, loss of coordination, collapse, or death. Dogs are highly susceptible to theobromine poisoning, typically from ingestion of chocolate. Theobromine is toxic to dogs because, although the dog's metabolism is capable of breaking down the chemical, the process is so slow that even small amounts of chocolate can be fatal, especially dark chocolate.
Dogs are also vulnerable to some of the same health conditions as humans, including diabetes, dental and heart disease, epilepsy, cancer, hypothyroidism, and arthritis.