Socialization, personality, obedience training, genetics and home environment can affect and determine a dog's behavior, but all dogs have a natural instinct to show aggression under the right circumstances. Dogs display physical, verbal and behavioral aggressive signals before making a move against the object of their aggression.
Factors That Cause Aggression
Lack of socialization can cause a dog to feel intimidated and fearful around strangers and in unfamiliar places, provoking aggressive behavior. Aggressive behavior toward family members or fellow pets can occur when a dog feels that his boundaries are being overstepped or his security is in jeopardy. At times, the home environment itself can result in dog aggression. Some breeds are more aggressive than others, but a well-trained dog who has aggressive tendencies has another issue causing the behavior. Pain and mental can cause aggression, as can genetic disposition and bad breeding practices. If health problems are ruled out, consulting a behaviorist is in order.
Prolonged Eye Contact
Aggressive dogs will exhibit intense and prolonged staring toward the potential victim of a dog bite. This behavior is meant to alert the victim that his behavior or action towards the dog is seen as threatening. A dog staring you down is a signal he finds the current situation threatening. Prolonged eye contact is frequently accompanied with raised hackles.
Verbal and Mouth Signals
Growling is a common signal displayed by dogs showing aggressive behavior. Growling may occur if a dog senses a potential threat around them. Dogs who are protective of their food bowls, bedding, toys and other items will growl frequently when they feel these items will be taken from them. In addition to growling, aggressive dogs will show their teeth. These two signals commonly happen simultaneously.
Changes in Body Language
An aggressive dog wants everyone around him to know he is serious; for this reason he will demonstrate obvious body language. Arching of the body, where his back is raised and curved, is a noticeable sign of aggressive behavior. Also walking stiffly toward or backward from the potential victim is common. Be aware of ear positioning. Dogs who have their ears positioned to the side, resembling a bird's wings when in flight, are showing a sign meant to deter the victim from furthering the action that is aggravating the dog -- such ear signs are noticeable only by dogs with pricked ears: Dogs with floppy ears may hold their ears in a certain position, but it is barely noticeable to the observer.
Tail Position Signals
A fluffy tail that is held high over the dog's back is an aggressive tail positioning signal. The tail will exhibit a tense appearance and will lack momentum. A tail curled between the dog's two hind legs is another frequent aggressive dog signal. The curling of the tail means the dog feels anxious, vulnerable, defensive and insecure of the surrounding environment. He feels threatened and scared, causing him to show aggressive behavior. If a dog is exhibiting the tail between the legs signal and backing himself into a corner, he is showing weakness and submissive behavior. Aggressive behavior and dog bites can still occur, especially if the dog is approached while in the corner or area he has found for protection from potential danger.