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.
Dog communication is how dogs convey information to other dogs, how they understand messages from humans, and how humans translate the information that dogs are transmitting.:xii Communication behaviors of dogs include eye gaze, facial expression, vocalization, body posture (including movements of bodies and limbs) and gustatory communication (scents, pheromones and taste). Humans communicate to dogs by using vocalization, hand signals and body posture.
Clip the dog's nails. If left untrimmed, a dog's nails can curl under into the paw pads or twist toes in a way that causes joint damage. To keep your dog's nails short, clip them regularly, depending on how fast his nails grow. If you can hear his nails on the ground when he walks, that means his nails are touching the ground, and are too long. 
Unlike other domestic species which were primarily selected for production-related traits, dogs were initially selected for their behaviors. In 2016, a study found that there were only 11 fixed genes that showed variation between wolves and dogs. These gene variations were unlikely to have been the result of natural evolution, and indicate selection on both morphology and behavior during dog domestication. These genes have been shown to affect the catecholamine synthesis pathway, with the majority of the genes affecting the fight-or-flight response (i.e. selection for tameness), and emotional processing. Dogs generally show reduced fear and aggression compared with wolves. Some of these genes have been associated with aggression in some dog breeds, indicating their importance in both the initial domestication and then later in breed formation. Traits of high sociability and lack of fear in dogs may include genetic modifications related to Williams-Beuren syndrome in humans, which cause hypersociability at the expense of problem solving ability.
Dogs have been described as carnivores or omnivores. Compared to wolves, dogs have genes involved in starch digestion that contribute to an increased ability to thrive on a starch-rich diet. Based on metabolism and nutrition, many consider the dog to be an omnivore. However, the dog is not simply an omnivore. More like the cat and less like other omnivores, the dog can only produce bile acid with taurine, and it cannot produce vitamin D, which it obtains from animal flesh. Also more like the cat, the dog requires arginine to maintain its nitrogen balance. These nutritional requirements place the dog part-way between carnivores and omnivores.
The genetic divergence between dogs and wolves occurred between 40,000–20,000 years ago, just before or during the Last Glacial Maximum. 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 domestication of animals commenced over 15,000 years ago, beginning with the grey wolf (Canis lupus) by nomadic hunter-gatherers. The archaeological record and genetic analysis show the remains of the Bonn–Oberkassel dog buried beside humans 14,200 years ago to be the first undisputed dog, with disputed remains occurring 36,000 years ago. It was not until 11,000 years ago that people living in the Near East entered into relationships with wild populations of aurochs, boar, sheep, and goats.
In Christianity, dogs represent faithfulness. Within the Roman Catholic denomination specifically, the iconography of Saint Dominic includes a dog, after the hallow's mother dreamt of a dog springing from her womb and becoming pregnant shortly thereafter. As such, the Dominican Order (Ecclesiastical Latin: Dominicanus) means "dogs of the Lord" or "hounds of the Lord" (Ecclesiastical Latin: domini canis). In Christian folklore, a church grim often takes the form of a black dog to guard Christian churches and their churchyards from sacrilege.
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. 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.
Clip the dog's fur after it's completely dried. If you plan to clip your dog's hair, make sure to read the directions that came with the clippers. Get an information book or video, or consult with a groomer about the proper use of your clippers. Make sure that the clipper blades are sharp and the clippers well lubricated. If the blades are not sharp, they can pull on the hair.
Dog behavior is the internally coordinated responses (actions or inactions) of the domestic dog (individuals or groups) to internal and/or external stimuli. As the oldest domesticated species, with estimates ranging from 9,000–30,000 years BCE, the minds of dogs inevitably have been shaped by millennia of contact with humans. As a result of this physical and social evolution, dogs, more than any other species, have acquired the ability to understand and communicate with humans, and they are uniquely attuned to human behaviors. Behavioral scientists have uncovered a surprising set of social-cognitive abilities in the domestic dog. These abilities are not possessed by the dog's closest canine relatives nor by other highly intelligent mammals such as great apes but rather parallel some of the social-cognitive skills of human children.
Certain Pacific islands whose maritime settlers did not bring dogs, or where dogs died out after original settlement, notably: the Mariana Islands, Palau, Marshall Islands, Gilbert Islands, New Caledonia, Vanuatu, Tonga, Marquesas, Mangaia in the Cook Islands, Rapa Iti in French Polynesia, Easter Island, Chatham Islands, and Pitcairn Island (settled by the Bounty mutineers, who killed off their dogs in order to escape discovery by passing ships).
Dogs bear their litters roughly 58 to 68 days after fertilization, with an average of 63 days, although the length of gestation can vary. An average litter consists of about six puppies, though this number may vary widely based on the breed of dog. In general, toy dogs produce from one to four puppies in each litter, while much larger breeds may average as many as twelve.
^ Bridgett M. von Holdt, Emily Shuldiner, Ilana Janowitz Koch, Rebecca Y. Kartzinel, Andrew Hogan, Lauren Brubaker, Shelby Wanser4, Daniel Stahler, Clive D.L. Wynne, Elaine A. Ostrander, Janet S. Sinsheimer and Monique A.R. Udell (19 July 2017). "Structural variants in genes associated with human Williams-Beuren syndrome underlie stereotypical hypersociability in domestic dogs". Science Advances. 3 (7): e1700398. Bibcode:2017SciA....3E0398V. doi:10.1126/sciadv.1700398. PMC 5517105. PMID 28776031.
There are a vast range of commodity forms available to transform a pet dog into an ideal companion. The list of goods, services and places available is enormous: from dog perfumes, couture, furniture and housing, to dog groomers, therapists, trainers and caretakers, dog cafes, spas, parks and beaches, and dog hotels, airlines and cemeteries. While dog training as an organized activity can be traced back to the 18th century, in the last decades of the 20th century it became a high-profile issue as many normal dog behaviors such as barking, jumping up, digging, rolling in dung, fighting, and urine marking (which dogs do to establish territory through scent), became increasingly incompatible with the new role of a pet dog. Dog training books, classes and television programs proliferated as the process of commodifying the pet dog continued.
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. 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.