The domestic dog is the first species, and the only large carnivore, known to have been domesticated. Especially over the past 200 years, dogs have undergone rapid phenotypic change and were formed into today's modern dog breeds due to artificial selection by humans. These breeds can vary in size and weight from a 0.46 kg (1.0 lb) teacup poodle to a 90 kg (200 lb) giant mastiff. Phenotypic variation can include height measured to the withers ranging from 15.2 centimetres (6.0 in) in the Chihuahua to 76 cm (30 in) 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. The skull, body, and limb proportions vary significantly between breeds, with dogs displaying more phenotypic diversity than can be found within the entire order of carnivores. Some breeds demonstrate outstanding skills in herding, retrieving, scent detection, and guarding, which demonstrates the functional and behavioral diversity of dogs. The first dogs were domesticated from shared ancestors of modern wolves, however the phenotypic changes that coincided with the dog–wolf genetic divergence are not known.
Typically, you should tip your dog groomer 15 to 20 percent of the service total to show your appreciation for a good job. Tips should be whatever you can afford and are a token of you gratefulness. It's quite common for your groomer to give you extra services at no charge, such as teeth brushing or nail trimming. Keep all this in mind when considering how much to tip. Additionally, there are certain circumstances when you should the tip the groomer a bit more.
It has been suggested that the most significant benefit would have been the use of dogs' robust sense of smell to assist with the hunt. The relationship between the presence of a dog and success in the hunt is often mentioned as a primary reason for the domestication of the wolf, and a 2004 study of hunter groups with and without a dog gives quantitative support to the hypothesis that the benefits of cooperative hunting was an important factor in wolf domestication.
In 2013, an estimate of the global dog population was 987 million. Although it is said that the "dog is man's best friend", this refers largely to the ~20% of dogs that live in developed countries. In the developing world, dogs are more commonly feral or communally owned, with pet dogs uncommon. Most of these dogs live their lives as scavengers and have never been owned by humans, with one study showing their most common response when approached by strangers is to run away (52%) or respond aggressively (11%). Little is known about these dogs, or the dogs in developed countries that are feral, stray or are in shelters, because the great majority of modern research on dog cognition has focused on pet dogs living in human homes.
Neutering reduces problems caused by hypersexuality, especially in male dogs. Spayed female dogs are less likely to develop some forms of cancer, affecting mammary glands, ovaries, and other reproductive organs. However, neutering increases the risk of urinary incontinence in female dogs, and prostate cancer in males, as well as osteosarcoma, hemangiosarcoma, cruciate ligament rupture, obesity, and diabetes mellitus in either sex.
Amongst apprenticeship programs and other hands-on training activities, Petco pet stylists who are trained from within the company are required to attend and pass Petco's comprehensive 12-week Pet Stylist Apprentice & Certification academy program. In addition to hands-on grooming training with a Petco-certified pet stylist mentor or instructor, all participants receive instruction in health, safety protocols and grooming salon operations. At the end of the program, candidates must pass a technical skills assessment in order to become a Petco Certified Pet Stylist.