In 1999, a study of mitochondrial DNA indicated that the domestic dog may have originated from multiple grey wolf populations, with the dingo and New Guinea singing dog "breeds" having developed at a time when human populations were more isolated from each other.[23] In the third edition of Mammal Species of the World published in 2005, the mammalogist W. Christopher Wozencraft 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 New Guinea singing dog – as a taxonomic synonym for the dingo. Wozencraft referred to the mDNA study as one of the guides in forming his decision.[1] The inclusion of familiaris and dingo under a "domestic dog" clade has been noted by other mammalogists.[24] This classification by Wozencraft is debated among zoologists.[25]
Cut out mats that can't be brushed out. Severe matting can pull the skin every time the dog moves, making daily life painful for your pet. If you can't brush a mat out, you need to either cut or shave it off, depending on how close it is to the skin. Be extremely careful if you use scissors to avoid injuring yourself or your pet. Try to cut parallel to the growth of the hair to avoid a choppy look.
A Colorado study found bites in children were less severe than bites in adults.[179] The incidence of dog bites in the US 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.[180] Sharp claws with powerful muscles behind them can lacerate flesh in a scratch that can lead to serious infections.[181]
In addition, people with pet dogs took considerably more physical exercise than those with cats and those without pets. The results provide evidence that keeping pets may have positive effects on human health and behaviour, and that for guardians of dogs these effects are relatively long-term.[195] Pet guardianship has also been associated with increased coronary artery disease survival, with human guardians being significantly less likely to die within one year of an acute myocardial infarction than those who did not own dogs.[196]
Various kinds of service dogs and assistance dogs, including guide dogs, hearing dogs, mobility assistance dogs, and psychiatric service dogs provide assistance to individuals with disabilities.[160][161] 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 guardian to seek safety, medication, or medical care.[162]
Cultural depictions of dogs in art extend back thousands of years to when dogs were portrayed on the walls of caves. Representations of dogs became more elaborate as individual breeds evolved and the relationships between human and canine developed. Hunting scenes were popular in the Middle Ages and the Renaissance. Dogs were depicted to symbolize guidance, protection, loyalty, fidelity, faithfulness, watchfulness, and love.[219]

Wolves kill dogs wherever they are found together.[111] One study reported that in Wisconsin in 1999 more compensation had been paid for losses due to wolves taking dogs than for wolves taking livestock. In Wisconsin wolves will often kill hunting dogs, possibly because the dogs are in the wolf's territory.[111] A strategy has been reported in Russia where one wolf lures a dog into heavy brush where another wolf waits in ambush.[112] In some instances, wolves have displayed an uncharacteristic fearlessness of humans and buildings when attacking dogs, to the extent that they have to be beaten off or killed.[113] Although the numbers of dogs killed each year are relatively low, it induces a fear of wolves entering villages and farmyards to take dogs, and losses of dogs to wolves has led to demands for more liberal wolf hunting regulations.[108]
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