Aggression in dogs is a very concerning problem for both dog owners and the general public. A dog that is aggressive can still be an excellent guard dog, family pet, or protection dog provided that he or she is obedient, well behaved, and controllable and is not dangerous to others. A dog that has problems with excessive aggression will behave in a way that makes the dog a problem to either people, including the owner and family, or towards other pets or animals.
There are four basic types of aggression that most dog breeds will exhibit to some degree. These include prey instinct, or the instinct to chase and hunt, territoriality, protection of owner, and self defense. Some breeds have been developed particularly to enhance their ability as hunters, called the prey instinct, but they are aggressive only towards specific targets, not to everything in their environment. Police dogs used for restraining and tracking fugitives are a good example of this instinct that is used in a productive and very controlled way.
Territoriality or guard instinct is important in many family dogs that are responsible for keeping strangers off of the property or away from the house or yard. These dogs will show aggression to protect their property, but are not aggressive unless they are placed in the position to guard the area.
Protection of the owner may be part of territoriality but it can also be used even when the dog is not on the property. Some breeds will protect the owner at all times, even when out for a walk or on neutral territory such as a park. Under control this is an important aspect to many breeds and can be very beneficial to the owner.
All dogs have a self-defense instinct that will work either in a fight or flight mechanism, just like we have as people. Some breeds will only become aggressive when they can't run away, while others are more likely to fight first and then run if they are unsuccessful in the aggression.
There are other types of aggression such as dominance, possessiveness of toys or food, fear, or aggression during mating, but these are all normal types of aggression that will usually be corrected with obedience training and socialization.
Excessive aggression is defined as inappropriate aggression that does not respond to traditional corrective methods of retraining or socialization. Sometimes excessive aggression can be neurologically based and caused by chemical imbalances in the brain or brain injury and trauma. Often excessive aggression can be a sign of trauma and abusive treatment of the dog throughout its life, with the dog's ability to trust completely destroyed through abusive treatment at the hands of previous owners.
Any breed of dog can become excessively aggressive in the case of neurological trauma, brain injury or disease, but some dogs have a higher rate of excessive aggression from non-disease related issues. Often it is not the breed itself but the irresponsible and inhuman actions of the owners and breeders that select for high levels of aggression that cause problems within certain breeding lines.
In some cases excessive aggression can be treated with drug therapies, intensive, positive training with a specialized dog behavioralist, and time and patience as well as safety measures taken on the part of the owner to keep the dog secured until fully trained. In most cases, however, an excessively aggressive dog will usually be destroyed as the risk of handling these dogs is simply too great for most people to take on.