Saturday 14 July 2012

dog is good pet.


Dog (disambiguation).

The domestic dog (Canis lupus familiaris),[2][3] is a subspecies of the gray wolf (Canis lupus), a member of the Canidae family of the mammilian order Carnivora. The term "domestic dog" is generally used for both domesticated and feral varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in human history. The word "dog" may also mean the male of a canine species,[4] as opposed to the word "bitch" for the female of the species.
The present lineage of dogs was domesticated from gray wolves about 15,000 years ago.[5] Though remains of domesticated dogs have been found in Siberia and Belgium from about 33,000 years ago, none of those lineages seem to have survived the Last Glacial Maximum. Although mDNA testing suggests a split between dogs and wolves around 100,000 years ago, no specimens prior to 33,000 years ago are clearly morphologically domesticated dog.[6][7][8]
Dogs' value to early human hunter-gatherers led to them quickly becoming ubiquitous across world cultures. 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 impact on human society has given them the nickname "Man's Best Friend" in the Western world. In some cultures, dogs are also source of meat.[9][10] In 2001, there were estimated to be 400 million dogs in the world.[11]
Most breeds of dogs are at most a few hundred years old, having been artificially selected for particular morphologies and behaviors by people for specific functional roles. Through this selective breeding, the dog has developed into hundreds of varied breeds, and shows more behavioral and morphological variation than any other land mammal.[12] For example, height measured to the withers ranges from 6 inches (150 mm) in theChihuahua to about 2.5 feet (0.76 m) in the Irish Wolfhound; color varies from white through grays (usually called "blue") to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patterns; coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth.[13] It is common for most breeds to shed this coat.

Etymology and related terminology

"Dog" is the common use term that refers to members of the subspecies Canis lupus familiaris (canis, "dog"; lupus, "wolf"; familiaris, "of a household" or "domestic"). The term can also be used to refer to a wider range of related species, such as the members of the genus Canis, or "true dogs", including the wolf, coyote, and jackals, or it can refer to the members of the tribe Canini, which would also include the African wild dog, or it can be used to refer to any member of the family Canidae, which would also include the foxes, bush dog, raccoon dog, and others.[14] 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 theprairie dog.
The English word "dog" comes from Middle English dogge, from Old English docga, a "powerful dog breed".[15] The term may derive from Proto-Germanic *dukkōn, represented in Old Englishfinger-docce ("finger-muscle").[16] The word also shows the familiar petname diminutive -ga also seen in frogga "frog", picga "pig", stagga "stag", wicga "beetle, worm", among others.[17] Due to the 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.[18]
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 of "hound" was so common, it eventually became the prototype of the category “hound”.[19] By the 16th century, dog had become the general word, and hound had begun to refer only to types used for hunting.[20] Hound, cognate to German Hund, Dutch hond, common Scandinavian hund, and Icelandic hundur, is ultimately derived from the Proto-Indo-European *kwon- "dog", found in Welsh ci (plural cwn), Latin canis, Greek kýōn, and Lithuanian šuõ.[21]
In breeding circles, a male canine is referred to as a dog, while a female is called a bitch (Middle English bicche, from Old English bicce, ultimately from Old Norse bikkja). A group of offspring is a litter. The father of a litter is called the sire, and the mother is called the dam. Offspring are, in general, called pups or puppies, from French poupée, until they are about a year old. The process of birth is whelping, from the Old English word hwelp (cf. German Welpe, Dutch welp, Swedish valpa, Icelandic hvelpur).[22]

Taxonomy

In 1753, the father of modern biological taxonomy, Carl Linnaeus, listed among the types of quadrupeds familiar to him, the Latin word for dog, canis. Among the species within this genus, Linnaeus listed the fox, as Canis vulpes, wolves (Canis lupus), and the domestic dog, (Canis canis; see File:Linnaeus - Regnum Animale (1735).png).
In later editions, Linnaeus dropped Canis canis and greatly expanded his list of the Canis genus of quadrupeds, and by 1758 included alongside the foxes, wolves, and jackels and many more terms that are now listed as synonyms for domestic dog, including aegyptius (hairless dog), aquaticus, (water dog), and mustelinus (literally “badger dog)”. Among these were two that later experts have been widely used for domestic dogs as a species: Canis domesticus and, most predominantly, Canis familiaris, the “common” or “familiar” dog.[23]
The domestic dog was accepted as a species in its own right until overwhelming evidence from behavior, vocalizations, morphology, and molecular biology led to the contemporary scientific understanding that a single species, the gray wolf, is the common ancestor for all breeds of domestic dogs.[24][25][26] In recognition of this fact, the domestic dog was reclassified in 1993 as Canis lupus familiaris, a subspecies of the gray wolf Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists. C. l. familiaris is listed as the name for the taxon that is broadly used in the scientific community and recommended by ITIS, although Canis familiaris is a recognised synonym.[27]
Since that time, C. domesticus and all taxa referring to domestic dogs or subspecies of dog listed by Linnaeus, Johann Friedrich Gmelin in 1792, and Christian Smith in 1839, lost their subspecies status and have been listed as taxonomic synonyms for Canis lupus familiaris [28]
Main articles: Origin of the domestic dog and Gray wolf
Ancient Greek rhyton in the shape of a dog's head, made by Brygos, early 5th century BC. Jérôme Carcopino Museum, Department of Archaeology, Aleria
Domestic dogs inherited complex behaviors from their wolf ancestors, which would have been pack hunters with complex body language. These sophisticated forms of social cognition and communication may account for their trainability, playfulness, and ability to fit into human households and social situations, and these attributes have given dogs a relationship with humans that has enabled them to become one of the most successful species on the planet today.[24]
Although experts largely disagree over the details of dog domestication, it is agreed that human interaction played a significant role in shaping the subspecies.[29] Domestication may have occurred initially in separate areas particularly Siberia and Europe. Currently it is thought domestication of our current lineage of dog occurred sometime as early as 15,000 years ago and arguably as late as 8500 years ago. Shortly after the latest domestication, dogs became ubiquitous in human populations, and spread throughout the world.
Emigrants from Siberia likely crossed the Bering Strait with dogs in their company, and some experts[who?] suggest the use of sled dogs may have been critical to the success of the waves that entered North America roughly 12,000 years ago,[citation needed] although the earliest archaeological evidence of dog-like canids in North America dates from about 9,000 years ago.[30] Dogs were an important part of life for the Athabascan population in North America, and were their only domesticated animal. Dogs also carried much of the load in the migration of the Apache and Navajotribes 1,400 years ago. Use of dogs as pack animals in these cultures often persisted after the introduction of the horse to North America.[31][page needed]
The current consensus among biologists and archaeologists is that the dating of first domestication is indeterminate,[29][31] although more recent evidence shows isolated domestication events as early as 33,000 years ago.[32][33] There is conclusive evidence the present lineage of dogs genetically diverged from their wolf ancestors at least 15,000 years ago,[5][34][35] but some believe domestication to have occurred earlier.[29] Evidence is accruing that there were previous domestication events, but that those lineages died out.[7]
It is not known whether humans domesticated the wolf as such to initiate dog's divergence from its ancestors, or whether dog's evolutionary path had already taken a different course prior to domestication. For example, it is hypothesized that some wolves gathered around the campsites of paleolithic camps to scavenge refuse, and associated evolutionary pressure developed that favored those who were less frightened by, and keener in approaching, humans.
Tesem, an old Egyptian sighthound-like dog.
The bulk of the scientific evidence for the evolution of the domestic dog stems from morphological studies of archaeological findings and mitochondrial DNA studies. The divergence date of roughly 15,000 years ago is based in part on archaeological evidence that demonstrates the domestication of dogs occurred more than 15,000 years ago,[24][31] and some genetic evidence indicates the domestication of dogs from their wolf ancestors began in the lateUpper Paleolithic close to the Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago.[36] But there is a wide range of other, contradictory findings that make this issue controversial.[citation needed] There are findings beginning currently at 33,000 years ago distinctly placing them as domesticated dogs evidenced not only by shortening of the muzzle but widening as well as crowding of teeth.
Archaeological evidence suggests the latest dogs could have diverged from wolves was roughly 15,000 years ago, although it is possible they diverged much earlier.[24] In 2008, a team of international scientists released findings from an excavation at Goyet Cave in Belgium declaring a large, toothy canine existed 31,700 years ago and ate a diet of horse, musk ox and reindeer.[37]
Prior to this Belgian discovery, the earliest dog fossils were two large skulls from Russia and a mandible from Germany dated from roughly 14,000 years ago.[5][24] Remains of smaller dogs from Natufian cave deposits in the Middle East, including the earliest burial of a human being with a domestic dog, have been dated to around 10,000 to 12,000 years ago.[5][38] There is a great deal of archaeological evidence for dogs throughout Europe and Asia around this period and through the next two thousand years (roughly 8,000 to 10,000 years ago), with fossils uncovered in Germany, the French Alps, and Iraq, and cave paintings in Turkey.[24]The oldest remains of a domesticated dog in the Americas were found in Texas and have been dated to about 9,400 years ago.[39]

DNA studies

DNA studies have provided a wide range of possible divergence dates, from 15,000 to 40,000 years ago,[5] to as much as 100,000 to 140,000 years ago.[40] These results depend on a number of assumptions.[24] Genetic studies are based on comparisons of genetic diversity between species, and depend on a calibration date. Some estimates of divergence dates from DNA evidence use an estimated wolf-coyote divergence date of roughly 700,000 years ago as a calibration.[41] If this estimate is incorrect, and the actual wolf-coyote divergence is closer to one or two million years ago, or more,[42] then the DNA evidence that supports specific dog-wolf divergence dates would be interpreted very differently.
Furthermore, it is believed the genetic diversity of wolves has been in decline for the last 200 years, and that the genetic diversity of dogs has been reduced by selective breeding. This could significantly bias DNA analyses to support an earlier divergence date. The genetic evidence for the domestication event occurring in East Asia is also subject to violations of assumptions. These conclusions are based on the location of maximal genetic divergence, and assume hybridization does not occur, and that breeds remain geographically localized. Although these assumptions hold for many species, there is good reason to believe that they do not hold for canines.[24]
Genetic analyses indicate all dogs are likely descended from a handful of domestication events with a small number of founding females,[24][36] although there is evidence domesticated dogsinterbred with local populations of wild wolves on several occasions.[5] Data suggest dogs first diverged from wolves in East Asia, and these domesticated dogs then quickly migrated throughout the world, reaching the North American continent around 8000 BC.[5] The oldest groups of dogs, which show the greatest genetic variability and are the most similar to their wolf ancestors, are primarily Asian and African breeds, including the Basenji, Lhasa Apso, and Siberian Husky.[43] Some breeds thought to be very old, such as the Pharaoh Hound, Ibizan Hound, and Norwegian Elkhound, are now known to have been created more recently.[43]
A great deal of controversy surrounds the evolutionary framework for the domestication of dogs.[24] Although it is widely claimed that "man domesticated the wolf,"[44] man may not have taken such a proactive role in the process.[24] The nature of the interaction between man and wolf that led to domestication is unknown and controversial. At least three early species of the Homo genus began spreading out of Africa roughly 400,000 years ago, and thus lived for a considerable time in contact with canine species.[24]
Despite this, there is no evidence of any adaptation of canine species to the presence of the close relatives of modern man. If dogs were domesticated, as believed, roughly 15,000 years ago, the event (or events) would have coincided with a large expansion in human territory and the development of agriculture. This has led some biologists to suggest one of the forces that led to the domestication of dogs was a shift in human lifestyle in the form of established human settlements. Permanent settlements would have coincided with a greater amount of disposable food and would have created a barrier between wild and anthropogenic canine populations.[24]

Work

Dogs have lived and worked with humans in so many roles that they have earned the unique nickname, "man's best friend",[60] a phrase used in other languages as well. They have been bred for herding livestock,[61] hunting (e.g. pointers and hounds),[62] rodent control,[3] guarding, helping fishermen with nets, detection dogs, and pulling loads, in addition to their roles as companions.[3]
Book of the Hunt, Gaston III, Count of Foix, 1387–88.
Service dogs such as guide dogs, utility dogs, assistance dogs, hearing dogs, and psychological therapy dogs provide assistance to individuals with physical or mental disabilities.[63][64] Some dogs owned by epileptics have been shown to alert their handler when the handler shows signs of an impending seizure, sometimes well in advance of onset, allowing the owner to seek safety, medication, or medical care.[65]
good bye...

Health risks to humans

Main article: Dog attack
It is estimated that two percent of the US population, 4.7 million people, are bitten each year.[75] In the 1980s and 1990s the US averaged 17 fatalities per year, while in the 2000s this has increased to 26.[76] 77% of dog bites are from the pet of family or friends, and 50% of attacks occur on the dog owner's property.[76]
A Colorado study found bites in children were less severe than bites in adults.[77] The incidence of dog bites in the U.S. is 12.9 per 10,000 inhabitants, but for boys aged 5 to 9, the incidence rate is 60.7 per 10,000. Moreover, children have a much higher chance to be bitten in the face or neck.[78] Sharp claws with powerful muscles behind them can lacerate flesh in a scratch that can lead to serious infections.[79]
In the UK between 2003 and 2004, there were 5,868 dog attacks on humans, resulting in 5,770 working days lost in sick leave.[80]
In the United States, cats and dogs are a factor in more than 86,000 falls each year.[81] It has been estimated around 2% of dog-related injuries treated in UK hospitals are domestic accidents. The same study found that while dog involvement in road traffic accidents was difficult to quantify, dog-associated road accidents involving injury more commonly involved two-wheeled vehicles.[82]
Toxocara canis (dog roundworm) eggs in dog feces can cause toxocariasis. In the United States, about 10,000 cases of Toxocara infection are reported in humans each year, and almost 14% of the U.S. population is infected.[83] In Great Britain, 24% of soil samples taken from public parks contained T. canis eggs.[84] Untreated toxocariasis can cause retinal damage and decreased vision.[84] Dog feces can also contain hookworms that cause cutaneous larva migrans in humans.[85][86][87][88]

Health benefits for humans

Small dog laying between the hands
A human cuddles a Doberman puppy.
A growing body of research indicates the companionship of a dog can enhance human physical health and psychological wellbeing.[89] Dog and cat owners have been shown to have better mental and physical health than nonowners, making fewer visits to the doctor and being less likely to be on medication than nonowners.[90] In one study, new pet owners reported a highly significant reduction in minor health problems during the first month following pet acquisition, and this effect was sustained in dog owners through to the end of the study.[91]
In addition, dog owners took considerably more physical exercise than cat owners and people without pets. The group without pets exhibited no statistically significant changes in health or behaviour. The results provide evidence that pet acquisition may have positive effects on human health and behaviour, and that for dog owners these effects are relatively long term.[91] Pet ownership has also been associated with increased coronary artery disease survival, with dog owners being significantly less likely to die within one year of an acute myocardial infarction than those who did not own dogs.[92]
Gunnar Kaasen and Balto, the lead dog on the last relay team of the 1925 serum run to Nome.
The health benefits of dogs can result from contact with dogs, not just from dog ownership. For example, when in the presence of a pet dog, people show reductions in cardiovascular, behavioral, and psychological indicators of anxiety.[93] Other health benefits are gained from exposure to immune-stimulating microorganisms, which, according to the hygiene hypothesis, can protect against allergies and autoimmune diseases. The benefits of contact with a dog also include social support, as dogs are able to not only provide companionship and social support themselves, but also to act as facilitators of social interactions between humans.[94] One study indicated that wheelchair users experience more positive social interactions with strangers when they are accompanied by a dog than when they are not.[95]
The practice of using dogs and other animals as a part of therapy dates back to the late 18th century, when animals were introduced into mental institutions to help socialize patients with mental disorders.[96] Animal-assisted intervention research has shown that animal-assisted therapy with a dog can increase a person with Alzheimer’s disease’s social behaviours, such as smiling and laughing.[97] One study demonstrated that children with ADHD and conduct disorders who participated in an education program with dogs and other animals showed increased attendance, increased knowledge and skill objectives, and decreased antisocial and violent behavior compared to those who were not in an animal-assisted program.[98]

Shelters

Main article: Animal shelter
Every year, between 6 and 8 million dogs and cats enter US animal shelters.[99] The Humane Society of the United States (HSUS) estimates that approximately 3 to 4 million dogs and cats are euthanized yearly in shelters across the United States.[100] However, the percentage of dogs in US animal shelters that are eventually adopted and removed from the shelters by their new owners has increased since the mid 1990s from around 25% up to around 60–75% in the mid first decade of the 21st century.[101]
Pets entering the shelters are euthanized in countries all over the world because of the lack of financial provisions to take care of these animals. Most shelters complain of not having enough resources to feed the pets and by being constrained to kill them, as the likelihood for all of them to find an owner is very small. In poor countries, euthanasia is usually violent.




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