DogHealth
Etymology and related terminology
The English word dog can be traced back to the Old English docga, a "powerful breed of canine".[5] The term may derive from Proto-Germanic *dukkon,
represented in Old English finger-docce ("finger-muscle").[6] Due to the linguistically archaic structure of the word, the term dog may ultimately derive
from the earliest layer of Proto-Indo-European vocabulary, reflecting the role of the dog as the earliest domesticated animal.[7]
The English word hound is cognate to other Germanic terms, including German Hund, Dutch hond, common Scandinavian hund, Icelandic hundur which,
though referring to a specific breed group in English, means "dog" in general in the other Germanic languages. Hound itself is derived from the Proto-Indo
-European *kwon-, which is also the direct root of the Greek ???? (kuon) and the indirect root of the Latin canis through the variant form *kani-.[8]
In breeding circles, a male canine is referred to as a dog, while a female canine is called a bitch. The father of a litter is called the sire, and the mother of
a litter is called the dam. 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.[9]
Taxonomy
The English word dog, in common usage, refers to the domestic pet dog, Canis lupus familiaris. The species was originally classified as Canis familiaris
and Canis familiarus domesticus by Linnaeus in 1758.[10][11] 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
Raccoon Dog and the African Wild Dog. A few animals have "dog" in their common names but are not canids, such as the prairie dog and the dog fish.
Origin and evolution
Origins
Main article: Origin of the domestic dog
Based on DNA evidence, the wolf ancestors of modern dogs diverged from other wolves about 100,000 years ago,[12][13] and dogs were
domesticated from those wolf ancestors about 15,000 years ago.[14] This date would make dogs the first species to be domesticated by humans.
Evidence suggests that dogs were first domesticated in East Asia,[15] and some of the peoples who entered North America took dogs with them
from Asia.[15]
As humans migrated around the planet, a variety of dog forms migrated with them. The agricultural revolution and subsequent urban revolution
led to an increase in the dog population and a demand for specialization. These circumstances would provide the opportunity for selective breeding
to create specialized working dogs and pets.
Ancestry and history of domestication
Main article: Origin of the domestic dog
This ancient mosaic, likely Roman, shows a large dog with a collar hunting a lion.
In Jan van Eyck's famous Arnolfini Portrait (1434). Care was taken to include the couple's little pet dog.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. 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 (a process known in genetics as 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.
Dogs on the Coat of Arms of the Canary Islands, which in ancient times had a dense population of an endemic breed of large and fierce dogs.
Genetic analyses have so far yielded divergent results. Vilà, Savolainen, and colleagues (1997) concluded that the ancestors of dogs split off
from other 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),[16] 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.[17]
The Soviets have attempted to domesticate the fox, mentioned in the article Tame Silver Fox, and were able to do so in just nine generations, or
less than a human lifetime. This also resulted in other changes, including color, which became black, white, or black and white. They also developed
year-round breeding ability, curled-up tails, and droopy ears.
The rapidity of this change has suggested to researchers a scenario of the origin of the domestic dog. Primitive people lived on the edge of survival
which involved occasional food shortages, and would not have taken wolf pups and made pets of them. However, wolves would raid garbage dumps
near human habitations. Wolves have a flight distance which they keep between themselves and a threatening creature. When a dump was
approached by humans, some wolves would run a greater distance from the dump than others. Those that ran the shortest distance would return
first, and obtain the greatest amount of food.
This set up a selective breeding situation that resulted in a strain of wolves having shorter and shorter flight distances, until they were eventually
comfortable near humans, having domesticated themselves, so to speak. At that point, they were tolerated by humans, so long as they were also
useful, in such ways as catching rats or driving away other predators. In time, other uses, such as hunting, were found for them. The Farm Fox
Experiment Evolution of Dogs
Development of dog breeds
Main article: Dog breeds
Dogs have been bred into a variety of shapes, colors and sizes. Variation can be wide even within a breed, as with these Cavalier King Charles
Spaniels.There are numerous dog breeds, with over 800 being recognized by various kennel clubs worldwide. Many dogs, especially outside the
United States of America and Western Europe, belong to no recognized breed. A few basic breed types have evolved gradually during the
domesticated dog's relationship with humans over the last 10,000 or more years, but all modern breeds are of relatively recent derivation. Many
of these are the product of a deliberate process of artificial selection. Because of this, some breeds are highly specialized, and there is
extraordinary morphological diversity across different breeds. Despite these differences, dogs are able to distinguish dogs from other kinds of animal.
The definition of a dog breed is a matter of some controversy. Depending on the size of the original founding population, closed gene pool breeds
can have problems with inbreeding, specifically due to the founder effect. Dog breeders are increasingly aware of the importance of population
genetics and of maintaining diverse gene pools. Health testing and new DNA tests can help avoid problems, by providing a replacement for
natural selection. Without selection, inbreeding and closed gene pools can increase the risk of severe health or behavioral problems. Some
organizations define a breed more loosely, such that an individual may be considered of one breed as long as 75% of its parentage is of that
breed. These considerations affect both pets and the show dogs entered in dog shows. Even prize-winning purebred dogs sometimes possess
crippling genetic defects due to founder effect or inbreeding.[18] These problems are not limited to purebred dogs and can affect cross-breed
populations.[19] The behavior and appearance of a dog of a particular breed can be predicted to a degree, while mixed-breed dogs show a
broader range of innovative appearance and behavior.
This puppy is a mix of many breeds.Mixed-breed dogs or Mongrels (also called "mutts") are dogs that do not belong to specific breeds, being
mixtures more than two in variant percentages. Mixed breed dogs and purebred dogs are both suitable as companions, pets, working dogs,
or competitors in dog sports. Sometimes different breed dogs are deliberately bred, to create cross-breeds such as the Cockapoo, a mixture
of Cocker Spaniel and Miniature Poodle. Such deliberate crosses may display some degree of hybrid vigor and other desirable traits, but may
or may not inherit any of the desired traits of their parents, such as temperament or a particular color or coat. Without genetic testing of the
parents, the crosses can end up inheriting genetic defects that occur in both parental breeds.
A breed is a group of animals that possesses a set of inherited characteristics that distinguishes it from other animals within the same species.
Deliberately crossing two or more breeds is also a manner of establishing new breeds, but it is only a breed when offspring will reliably
demonstrate that particular set of characteristics and qualities.
The Bulldog is well known for its short muzzle and saggy skin on its face
Breed popularity
Breed popularity varies widely over time[20] 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.[21] 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 while the Yorkshire Terrier was
the second-most-registered breed in Houston.[22] 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.[23] Two decades ago, in 1983, the AKC's top two registered breeds were the American
Cocker Spaniel and the Poodle.[24]
In the United Kingdom, 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 US, and the English Cocker Spaniel[25] ,
which is no longer in the top ten in the US. In the UK, a national dog adoption and rescue service indicates that the most common breed
appearing in shelters is the Greyhound followed by the Staffordshire Bull Terrier.[26]
Differences from wolves
Physical characteristics
Compared to equally sized wolves, dogs tend to have 20% smaller skulls and 10% smaller brains, as well as proportionately smaller teeth
than other canid species.[3] Dogs require fewer calories to function than wolves. Their diet of human refuse in antiquity made the large brains and
jaw muscles needed for hunting unnecessary. It is thought by certain experts that the dog's limp ears are a result of atrophy of the jaw muscles.[3]
The skin of domestic dogs tends to be thicker than that of wolves, with some Inuit tribes favouring the former for use as clothing due to its greater
resistance to wear and tear in harsh weather.[3] Unlike wolves, but like coyotes, domestic dogs have sweat glands on their paw pads.[3] The paws
of a dog are half the size of those of a wolf, and their tails tend to curl upwards, another trait not found in wolves.[27]
Behaviour
Dogs tend to be poorer than wolves and coyotes at observational learning, being more responsive to instrumental conditioning.[3] Feral dogs show
little of the complex social structure or dominance hierarchy present in wolf packs. For dogs, other members of their kind are of no help in locating
food items, and are more like competitors.[3] Feral dogs are primarily scavengers, with studies showing that unlike their wild cousins, they are poor
ungulate hunters, having little impact on wildlife populations where they are sympatric. Free ranging pet dogs however are more prone to predatory
behaviour toward wild animals. Feral dogs have been reported to be effective hunters of reptiles in the Galapagos islands.[28] Despite common belief,
domestic dogs can be monogamous.[29] Breeding in feral packs can be, but does not have to be restricted to a dominant alpha pair (despite common
belief, such things also occur in wolf packs).[30] Male dogs are unusual among canids by the fact that they mostly seem to play no role in raising their
puppies, and do not kill the young of other females to increase their own reproductive success.[28] Some sources say that dogs differ from wolves and
most other large canid species by the fact that they do not regurgitate food for their young, nor the young of other dogs in the same territory.[3] However,
this difference was not observed in all domestic dogs. Regurgitating of food by the females for the young as well as care for the young by the males
has been observed in domestic dogs, dingos as well as in other feral or semi-feral dogs. Regurgitating of food by the females and direct choosing of
only one mate has been observed even in those semi-feral dogs of direct domestic dog ancestry. Also regurgitating of food by males has been
observed in free-ranging domestic dogs.[29][31]
Trainibility
Dogs display much greater tractability than tame wolves, and are generally much more responsive to coercive techniques involving fear, aversive
stimuli and force than wolves, which are most responsive toward positive conditioning and rewards.[32] Unlike tame wolves, dogs tend to respond
more to voice than hand signals.[33] Although they are less difficult to control than wolves, they can be comparatively more difficult to teach than
a motivated wolf.[32]
Main article: Dog anatomy
See also: Dog health
Modern dog breeds show more variation in size, appearance, and behavior than any other domestic animal. Within the range of extremes,
dogs generally share attributes with their wild ancestors, the wolves. Dogs are predators and scavengers, possessing sharp teeth and strong
jaws for attacking, holding, and tearing their food. Although selective breeding has changed the appearance of many breeds, all dogs retain
basic traits from their distant ancestors. Like many other predatory mammals, the dog has powerful muscles, fused wristbones, a cardiovascular
system that supports both sprinting and endurance, and teeth for catching and tearing. Dogs are more variable in size than any other
domesticated animal. The smallest known dog was a Yorkshire Terrier, who stood only 6.3 cm (2.5 in) at the shoulder, 9.5 cm (3.75 in) along
the head-and-body length and weighed only 113 grams (4 ounces). The largest known dog was an English Mastiff which weighed 155.6 kg
(343 lbs) and was 250 cm (8.2 feet) from the snout to the tail. The tallest dog is a Great Dane that stands 106.7 cm (42.2 in) at the shoulder.[34]
Sight
A Greyhound, one of many breeds of sighthoundLike most mammals, dogs are dichromats and have color vision equivalent to red-green
color blindness in humans.[35][36][37] Different breeds of dogs have different eye shapes and dimensions, and they also have different retina
configurations.[38] Dogs with long noses have a "visual streak" which runs across the width of the retina and gives them a very wide field of
excellent vision, while those with short noses have an "area centralis" — a central patch with up to three times the density of nerve endings
as the visual streak — giving them detailed sight much more like a human's.
Some breeds, particularly the sighthounds, have a field of vision up to 270° (compared to 180° for humans), although broad-headed breeds
with short noses have a much narrower field of vision, as low as 180°.[35][36]
Hearing
According to hypertextbook.com, the frequency range of dog hearing is approximately 40 Hz to 60,000 Hz.[39] Dogs detect sounds as low as
the 16 to 20 Hz frequency range (compared to 20 to 70 Hz for humans) and above 45 kHz[40] (compared to 13 to 20 kHz for humans),[39][36]
and in addition have a degree of ear mobility that helps them to rapidly pinpoint the exact location of a sound.[41] Eighteen or more muscles
can tilt, rotate and raise or lower a dog's ear. Additionally, a dog can identify a sound's location much faster than a human can, as well as hear
sounds up to four times the distance that humans are able to.[41] Those with more natural ear shapes, like those of wild canids like the fox,
generally hear better than those with the floppier ears of many domesticated species.
Smell
Scent hounds, especially the Bloodhound, are bred for their keen sense of smell.[42]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).[43][44] According
to nhm.org, dogs can sense odors at concentrations nearly 100 million times lower than humans can.[45] According to Dummies.com, the
percentage of the dog's brain that is devoted to analyzing smells is actually 40 times larger than that of a human.[43] Some dog breeds have
been selectively bred for excellence in detecting scents, even compared to their canine brethren.
The highly sensitive nose of a dog.
Coat color
Domestic dogs often display the remnants of counter-shading, a common natural camouflage pattern. The general theory of countershading
is that an animal that is lit from above will appear lighter on its upper half and darker on its lower half where it will usually be in its own shade.
[46][47] This is a pattern that predators can learn to watch for. A countershaded animal will have dark coloring on its upper surfaces and
light coloring below.[46] This reduces the general visibility of the animal. One reminder of this pattern is that many breeds will have the
occasional "blaze", stripe, or "star" of white fur on their chest or undersides.[47]
Tail
There are many different shapes for dog tails: straight, straight up, sickle, curled, cork-screw. In some breeds, the tail is traditionally docked
to avoid injuries (especially for hunting dogs).[48] It can happen that some puppies are born with a short tail or no tail in some breeds.[49]
Behavior and intelligence
Further information: Category:Dog training and behavior
Many dogs, such as this American Water Spaniel, have had their natural hunting instincts suppressed or altered to suit human needs.
Many dogs can be trained to skillfully perform tasks not natural to canines, such as in this dog agility competition.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. 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.
Intelligence
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this article by introducing more precise citations where appropriate. (August 2008)
Main article: Dog intelligence
Dogs are valued for their 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. Being highly adaptable animals themselves, dogs have learned
to do many jobs as required by humans over the generations. Dogs are employed in various roles across the globe, proving invaluable assets
in areas such as search-and-rescue; law enforcement (including attack dogs, sniffer dogs and tracking dogs); guards for livestock, people or
property; herding; Arctic exploration sled-pullers; guiding the blind and acting as a pair of ears for the deaf; assisting with hunting, and a great
many other roles which they may be trained to assume. 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 impaired) are specially trained to
recognize and avoid dangerous situations.
Evaluation of a dog's intelligence
The meaning of "intelligence" in general, not only in reference to dogs, is hard to define. Some tests measure problem-solving abilities and
others test the ability to learn in comparison to others of the same age. Defining it for dogs is just as difficult. It is likely that dogs do not have
the ability to premeditate an action to solve a problem.
A mirror test is one possible measure of self-awareness.For example, the ability to learn quickly could be a sign of intelligence. Conversely
it could be interpreted as a sign of a desire to please. In contrast, some dogs who do not learn very quickly may have other talents. An
example is breeds that are not particularly interested in pleasing their owners, such as Siberian Huskies. Huskies are often fascinated
with the myriad of possibilities for escaping from yards, catching small animals, and often figuring out on their own numerous inventive
ways of doing both.
Many owners of livestock guardian breeds believe that breeds like the Great Pyrenees or the Kuvasz are not easily trained because their
stubborn nature prevents them from seeing the point of such commands as “sit” or “down”. Hounds may also suffer from this type of ranking.
These dogs are bred to have more of a "pack" mentality with other dogs and less reliance on a master's direct commands. While they may
not have the same kind of intelligence as a Border Collie, they were not bred to learn and obey commands quickly, but to think for themselves
while trailing game.
Human relationships
A U.S. Army Staff Sgt. and his military working dog wait at a safe house before conducting an assault against insurgents in Buhriz, Iraq on April
10, 2007.Dogs are highly social animals. This can account for their trainability, playfulness, and ability to fit into human households and social
situations. These attributes have earned dogs a unique position in the realm of interspecies relationships despite being one of the most effective,
voracious, and potentially dangerous predators. Dogs and humans at times co-operate in some of the most effective hunting in the animal world;
n that context, dogs are superpredators.
Barking can be used as a form of communication amongst dogs.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 and worked with humans in so many roles that their loyalty has earned them the unique sobriquet "man's best friend",[50] a term
which is used in other languages as well as in Icelandic (“besti vinur mannsins”). However, 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.
Dog communication
Main article: Dog communication
Dog communication refers to body movements and sounds dogs use to send signals to other dogs, and other animals (usually humans). Dog
communication comes in a variety of forms. Dogs use certain movements of their bodies and body parts and different vocalizations to send signals.
There are a number of basic ways a dog can communicate. These are movements of the ears, eyes and eyebrows, mouth, head, tail, and entire
body, as well as barks, growls, whines and whimpers, and howls.
