Aggressive dogs exhibit a few tell-tale signs of defensive behavior, such as growling, snarling, staring, an immobile stance, holding a tail up or down and snapping. A dog displays these characteristics when it feels provoked, threatened or cornered.
Aggressive behavior in dogs is attributed to many factors, such as inbreeding, abuse, poor living conditions, lack of early socialization, sexual maturation, genetic factors and pack order behavior. Dogs raised in isolation from human or animal contact or dogs that have been beaten or roughly handled may exhibit signs of aggression.
The critical period for preventing aggression in a dog is between 3 and 14 weeks of age, when socialization of puppies becomes crucial for behavior development. The puppy must be introduced to children, adults and other dogs in the home. Harsh punishment is to be avoided, as puppies this age are especially fearful and hypersensitive. At 14 weeks, adolescence begins, and the dog starts to become more protective and mistrusting of strangers. If a dog has not been properly socialized by this age, it can become more difficult to train and control.
As of 2014, there is no medication prescribed to treat canine aggression. The only recourse is to manage the dog's aggression through behavioral modification training.