Free-ranging dogs live in groups that include males and females of varying ages. Social rank is determined by age and to some extent by sex, size, and temperament. The dog's social structure has been previously referred to as a pack hierarchy but this does not properly explain the relationship of dogs with other dogs or with humans.

Scientific studies into the behavior of wild wolves have established that the wolf pack is a family, with the adult parents guiding the activities of the group. Canine domestication for over 15,000 yr and selective breeding have led to extensive variation in morphology. With domestication, dogs have lost elements of wolf “body language,” and retain juvenile characteristics (neotinization, paedomorphosis). Breeding for traits such as herding, hunting, retrieving, pointing, guarding, and companionship have also led to widespread behavioral differences between breeds. Thus it may be difficult for dogs to read and interpret the signals of other dogs, especially those of different breeds. Early socialization with a wide variety of dogs is therefore an important component of intraspecific communication.

The term dominance (see Behavioral Medicine Introduction: Dominance) does not describe a relationship between two individuals; it is a relative term that is established by the value of the resource to each individual (resource-holding potential) and the cumulative effects of learning. Hierarchy in dogs is neither static nor linear, because the motivation to obtain and retain a specific resource, as well as previous learning, defines the relationship between two individuals for each encounter. Stability is maintained by deference and not by agonistic behaviors between dogs.

Dogs use visual signaling (including body postures, facial expressions, tail and ear carriage, and piloerection), vocalization, pheromones, and scents to communicate with other dogs; however, human-dog relationships are a function of genetics, early handling, and socialization, and are shaped by learning and consequences and not by dominance or hierarchal relationships.

Canine Development

The first important period of development is the neonatal period, which extends into the third week of life. Puppies are born with closed eyes and limited motor ability. In the first few weeks, maternal care is critical. Grooming by the mother arouses the puppy to eat, stimulates elimination, and helps to keep the puppies in the nest. Good maternal care results in an increased ability to handle stress and increased maturation of the nervous system. Similarly, mild stress in the form of gentle human handling during the first 2 wk of life can improve cardiovascular performance and resistance to disease. Puppies that are handled also mature faster, perform better in problem-solving tasks, and are better able to withstand stress as adults. Feeding the bitch a diet enhanced with docosahexaenoic acid during the neonatal and prenatal periods has been shown to improve the puppy's brain and retinal development and trainability.

Between the neonatal and socialization period is a transition period, during which the eyes open and puppies begin to develop motor skills. At this time interactions with littermates are important for development of social skills.

The next period of development (socialization or sensitive period) extends from 3 wk to ~12–14 wk of age. During this period the puppy is most sociable and will most readily habituate to dogs, people, other animals, and the environment (sights, sounds, odor, touch, taste). Between 3 and 8 wk of age puppies start exploring their environment and continue to refine social skills with their littermates and other dogs. Weaning is normally completed at 7 wk of age, and at ~8 wk of age puppies start developing a preference for elimination locations.

As the socialization period winds down, puppies make attachments less easily. Therefore, a lack of adequate socialization and enrichment during the sensitive period can contribute to excessive responses to stimuli, including fear and aggression. Spending the first 7–8 wk with the mother and littermates plays an important role in the development of social skills with other dogs. However if exposure to people, other pets, and new environments does not begin before the end of the socialization period, the dog may become socially maladjusted and unable to cope. This can be accomplished in part by enrolling in puppy socialization classes prior to 12 wk of age, so that the puppy can be exposed to a range of dogs, humans, and other stimuli (eg, novel surfaces, noises, odors, moving objects, uniforms, and handling) in a controlled, instructional, and positive environment. Similarly, visits to the veterinarian or groomer, car rides, visitors to the home, and the use of sound desensitization recordings provide additional opportunities for exposure. If there are any signs of fear, every effort should be made to overcome the fear by proceeding more slowly and using favored treats or toys to try to ensure a positive outcome. Continued exposure to a wide variety of stimuli with positive outcomes should be continued to adulthood. If fears begin to arise, immediate assistance should be sought.

The third (juvenile) period extends from ~3 mo to 1 yr of age. Domestic dogs reach sexual maturity at 6–9 mo (later in some giant breeds) and social maturity at 12–36 mo of age. Social relationships are established to minimize conflicts within the group. Although heredity and previous socialization play important roles in the behavior of an individual, positive exposure to a wide range of animate and inanimate stimuli during this period should minimize the development of fear and anxiety.

Domestic dogs are nonseasonal breeders and have on average 2 heat cycles/yr (range 1–4). If the female does not get pregnant, she will go through hormonal changes as if she were pregnant, known as false pregnancy or pseudocyesis, which can be associated with overt physiologic and behavioral changes including lactation, nesting, and protective aggression of objects such as toys.

Canine Preventive Counseling

Veterinarians and staff should work with breeders, trainers, pet stores, and shelters to ensure that the newly adopted dog gets off to the right start. For puppies, this includes advice on socialization, normal canine behaviors and how they can be managed (eg, chewing, jumping up, play biting, elimination), as well as guidance on reinforcement-based training. The goal should be to reinforce desirable behaviors and to ignore or prevent undesirable behaviors. Oral behaviors are a common problem because puppies have normal behavioral needs for exploration and play. Therefore, providing constructive social activities that do not include mouthing or biting of humans, such as tug games, retrieving, walking and running, chasing, hide and seek, playing with other dogs, and training for rewards gives the dog something positive on which to focus. A head halter is also an option for better control of the head and muzzle. Another way to manage oral stimulation and exploration is to provide chew toys, food-stuffed toys, and food-dispensing toys. When the puppy cannot be effectively supervised, the household should be set up to ensure success (and avoid failure). A daily routine can be established that provides stability and predictability for the dog, beginning with meeting the social and physical needs, followed by sessions of inattention during which the dog is given the opportunity to nap and rest or to engage in exploratory play with its food and chew toys. By confining the dog to a crate, pen, or room during these “inattention” times, the dog learns to spend time on its own; this also may prevent damage to property, housesoiling, and even separation anxiety. Undesirable behavior might alternatively be prevented through environmental management (eg, child gate, shutting doors, tie downs, deterrent devices). Neutering males may also help to prevent testosterone-influenced behaviors such as urine marking, mounting, and roaming.

Last full review/revision April 2012 by Gary Landsberg, BSc, DVM, MRCVS, DACVB, DECVBM-CA; Sagi Denenberg, DVM