Since the process of domestication first began, selective breeding over 4,000 generations or more has changed the physical appearance of some dogs almost beyond recognition. But even the tiny Chihuahua still displays many of the behavioural characteristics of its ancestor, the wolf. Like the wolf, the domestic dog communicates by means of calls and body language, its ears and tail being especially expressive, and it retains the same strong social instincts.
Dogs generally have a very acute sense of hearing, and are able to hear sounds that are too high-pitched for human beings. This greater hearing range assists dogs in tracking down their quarry, and in communicating with each other. Recently, dogs have been used to help deaf people, some being trained to indicate such sounds as a ringing telephone.
Wolves keep in touch with each other by howling, a means of communication well developed in northern spitz breeds which work in groups. Pack hounds tracking a scent may also bay, which is useful to the hunter when the dog is not visible.
The position of the eyes, towards the sides of the head, gives dogs a wider field of vision than human beings, making them more aware of their environment. Dogs also have better vision at dusk because the cells in the retina, where the image is focused, respond well to low light. However, colour vision is limited.
The keen sense of smell common to all dogs is most fully developed in breeds such as the Bloodhound, which uses it to track quarry. Dogs rely on the nose, as well as Jacobson’s Organ in the mouth, to detect scent particles.
Dog urine contains highly individual chemical scent markers, or phcromones. A male will convey the boundaries of his territory to other dogs by using urine as a marker. After puberty, male dogs spray urine by lifting their leg, rather than squatting like a bitch, in order to hit a target such as a tree or a post.
They may also scratch the ground, leaving a scent from the sweat glands between their toes. There is a distinct difference in scent marking between the sexes, and male dogs urinate perhaps three times more frequently than bitches.
Male dogs meeting in antagonistic situations carry out a well-defined series of gestures, indicating submission (below), or threatening aggression without actually attacking their opponent. The dog stands upright, tail erect, raising its hackles (the hairs along its back). The neck extends forwards and the mouth opens into a snarl.
If a dog wants to submit, it will probably crouch down, with its tail between its legs and its ears down. In some cases it may run off, with the dominant dog in pursuit. Alternatively, it may roll over on to its back, like a puppy, and may urinate a litde if it has no easy means of retreat A submissive dog is not likely to be attacked.
Despite their need to establish a “pocking order”, dogs are social by nature and generally get on well together. Dogs bred as companions tend to be less noisy than hounds, since barking is not considered a desirable trait where dogs arc living in close proximity to people. A companion dog will wag its tail and open its mouth slightly in greeting when a member of the family returns home.