Dog

The dog (Canis familiaris when considered a distinct species or Canis lupus familiaris when considered a of the ) (canines), which forms part of the ,. are , which implies that the direct ancestor of the dog is . to be domesticated, and has been over millennia for various behaviors, sensory capabilities, and physical attributes.[17]

Their has led dogs to be uniquely attuned to human behavior Dogs vary widely in shape, size and colors., , , , and , and, more recently, and roles. This influence on human society has given them the of "".

• The term dog typically is applied both to the species (or subspecies) as a whole, and any adult male member of the same.


• An adult female is a bitch.


• An adult male capable of reproduction is a stud.


• An adult female capable of reproduction is a brood bitch, or brood mother.


• Immature males or females (that is, animals that are incapable of reproduction) are pups or puppies.


• A group of pups from the same is called a .


• The father of a litter is a sire. It is possible for one litter to have multiple sires.


• The mother of a litter is a dam.


• A group of any three or more adults is a pack.

In 1758, the Swedish botanist and zoologist published in his the – or the two-word naming – of . is the Latin word meaning "dog", 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..[22]

In 1999, a study of indicated that the domestic dog may have originated from multiple grey populations, with the and "breeds" having developed at a time when human populations were more isolated from each other. published in 2005, the mammalogist listed under the wolf Canis lupus its wild subspecies, and proposed two additional subspecies: "familiaris Linneaus, 1758 [domestic dog]" and "dingo Meyer, 1793 [domestic dog]". Wozencraft included hallstromi – the – as a for the dingo. Wozencraft referred to the mDNA study as one of the guides in forming his decision. This classification by Wozencraft is debated among zoologists.[25]

In 2019, a workshop hosted by the /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 .[26]

The origin of the domestic dog includes the dog's from the wolf, its , and its development into and . The dog is a member of the , which forms part of the , and was the first species and the only large to have been domesticated. The dog and the extant gray wolf are , as modern wolves are not closely related to the population of wolves that was first .[14]

The between dogs and wolves occurred between 40,000–20,000 years ago, just before or during the . 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. The commenced over 15,000 years ago, beginning with the (Canis lupus) by nomadic . buried beside humans 14,200 years ago to be the first undisputed dog, with disputed remains occurring 36,000 years ago. The domestication of the dog predates agriculture. entered into relationships with wild populations of , boar, sheep, and goats.[28]

Where the domestication of the dog took place remains debated, with the most plausible proposals spanning , and . This has been made more complicated by the recent proposal that an initial wolf population split into East and West groups. These two groups, before going , were domesticated independently into two distinct dog populations between 14,000 and 6,400 years ago. The Western Eurasian dog population was gradually and partially replaced by East Asian dogs introduced by humans at least 6,400 years ago. This proposal is also debated.[2]

In 2020, a 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.[32]

Anatomy

Domestic dogs have been selectively bred for millennia for various behaviors, sensory capabilities, and physical attributes. show more variation in size, appearance, and behavior than any other domestic animal. 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 , 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 a which weighed 167.6 kg (369 lb) and was 250 cm (98 in) from the snout to the tail. that stands 106.7 cm (42.0 in) at the shoulder.[34]

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.[37]

Coat

The 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 and a soft , or "single", with the topcoat only. Breeds may have an occasional "blaze", stripe, or "star" of white fur on their chest or underside.[38]

Regarding coat appearance or health, the coat can be maintained or affected by multiple nutrients present in the diet, see 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 , , fear of noise, and fear of unfamiliar people or animals.[39]

Tail

There are many different shapes for : 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 to avoid injuries., puppies can be born with a short tail or no tail at all.[41]

Differences from wolves

Despite their close genetic relationship and the ability to inter-breed, there are a number of diagnostic features to distinguish the gray wolves from domestic dogs. Domesticated dogs are clearly distinguishable from wolves by starch gel of red blood cell acid . are large, convex and almost spherical in gray wolves, while the bullae of dogs are smaller, compressed and slightly crumpled.:35 The teeth of gray wolves are also proportionately larger than those of dogs. The that closes the jaws is more robust in wolves. on their back legs, unless there has been admixture with dogs that had them. and enter twice yearly, unlike gray wolves which only do so once a year. So-called primitive dogs such as and retain the yearly estrus cycle.[50]

Dogs generally have brown eyes and wolves almost always have amber or light colored eyes. tribes favoring the former for use as clothing due to its greater resistance to wear and tear in harsh weather. The dog has developed into hundreds of varied , and shows more behavioral and morphological variation than any other land mammal.[54]

Health

There are many household plants that are poisonous to dogs (and other mammals) including , and .[55]

Some breeds of dogs are prone to certain genetic ailments such as and , , , , , and . Two serious medical conditions particularly affecting dogs are , affecting 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 , , , , , , and ( species that lives in the heart of dogs).

A number of common human foods and household ingestibles are toxic to dogs, including (), onion and (, or poisoning), and , , , Dogs are susceptible to , typically from ingestion of . Theobromine is toxic to dogs because, although the dog's metabolism is capable of breaking down the chemical, the process is so slow that for some dogs 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 , dental and heart disease, epilepsy, cancer, hypothyroidism, and arthritis.[61]

Lifespan

In 2013, a study found that mixed breeds live on average 1.2 years longer than pure breeds, and that increasing body-weight was negatively correlated with longevity (i.e. the heavier the dog the shorter its lifespan).[62]

The typical lifespan of dogs varies widely among breeds, but for most the median longevity, the age at which half the dogs in a population have died and half are still alive, ranges from 10 to 13 years. Individual dogs may live well beyond the median of their breed.

The breed with the shortest lifespan (among breeds for which there is a questionnaire survey with a reasonable sample size) is the , with a median longevity of about 5.2 years, but several breeds, including , , and are nearly as short-lived, with median longevities of 6 to 7 years.[66]

The longest-lived breeds, including , , , and , have median longevities of 14 to 15 years., taken as an average of all sizes, is one or more years longer than that of purebred dogs when all breeds are averaged. The longest-lived dog was "", an who died in 1939 at 29.5 years of age.

Reproduction

In domestic dogs, happens around six to twelve months of age for both males and females, although this can be delayed until up to two years old for some large breeds. This is the time at which female dogs will have their first . They will experience subsequent estrous cycles semiannually, during which the body prepares for . At the peak of the cycle, females will come into estrus, being mentally and physically receptive to . survive and are capable of being fertilized for a week after ovulation, it is possible for more than one male to sire the same litter.[17]

Fertilization typically occurs 2–5 days after ovulation; 14–16 days after ovulation, the embryo attaches to the uterus, and after 7-8 more days the heart beat is detectable.

Dogs bear their litters roughly 58 to 68 days after , with an average of 63 days, although the length of gestation can vary. An average litter consists of about six , produce from one to four puppies in each litter, while much larger breeds may average as many as twelve.

Some dog breeds have acquired traits through selective breeding that interfere with reproduction. Male , for instance, are incapable of mounting the female. For many dogs of this breed, the female must be in order to reproduce.[75]

Neutering

refers to the sterilization of animals, usually by or the female's and , in order to eliminate the ability to procreate and reduce . Because of the in some countries, many animal control agencies, such as the (ASPCA), advise that dogs not intended for further breeding should be neutered, so that they do not have undesired puppies that may later be euthanized.[76]

According to the , 3–4 million dogs and cats are 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 castrating dogs helps keep overpopulation down. urge people to neuter their pets and to adopt animals from shelters instead of purchasing them.