Dogs are highly social animals and are well adapted to living in groups. Recent studies have also shown that they are very good at interpreting human gestures and behavior.
In nature or under free-ranging conditions, dogs live in groups that include both males and females of a variety of ages. Relative social ranking or hierarchy (also referred to as dominance) is determined by age, although sex may play a role. Females appear to be responsible for guiding most group activities. Social hierarchies are maintained primarily by lower-ranking dogs giving way to higher-ranking ones and not, as commonly believed, by fighting. Sexual maturity in domestic dogs occurs between 6 to 9 months of age (later for giant breeds), while social maturity develops at 12 to 36 months of age. In free-ranging groups, dogs that challenge the established social hierarchy may leave and form their own groups if they do not succeed in gaining a high rank. This situation may be similar to one form of inter-dog aggression that occurs in multiple-dog households (see Behavior of Dogs: Behavior Problems Associated with Aggression). Social maturity is also the time when problems with aggression and anxiety develop. Roaming, mounting, urine marking, and fighting are stimulated by sex hormones, particularly testosterone. These problems are often greatly reduced in males by neutering.
Between 3 to 8 weeks of age, dogs tend to focus on other dogs (if available) for social interaction, and between 5 to 12 weeks of age they shift their focus to people. Dogs are most receptive to learning how to deal with new situations until about 16 to 20 weeks of age. After this age, dogs do not stop learning from exposure; they just do so at a much slower rate and perhaps in a different way. It is not critical to change the focus of exposure at one specific period, because given adequate opportunities, puppies will learn about the social and physical environments when they are ready. Dogs that are kept exclusively kenneled or not exposed to people by 14 weeks of age may have severely undeveloped social skills. The best age to adopt a puppy is at about 8 weeks of age. Unless there is no other choice, puppies should not be adopted until at least 7½ weeks of age.
Most domestic dogs, except for Basenjis, have 2 heat (estrous) cycles per year. All members of the group may assist in puppy care. In multiple-dog groups, the highest-ranking dogs may be the only ones to breed.
Last full review/revision July 2011 by Karen L. Overall, MA, VMD, PhD, DACVB, ABS Certified Applied Animal Behaviorist