You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Aggression is an antisocial behaviour trait which is very distressing for owners, friends and family. But why does a normally placid pet dog develop aggressive behaviour ?

There are several reasons why dogs show aggressive behaviour  :

• Dominance aggression within a family (or "pack") is an inherited trait - reflecting the evolution of the species - and this can be aggression towards members of the family, or towards other dogs in a household. Mounting* is a classic sign associated with this form of dominance behaviour. (*Note : Mounting can also be a sign of sexual behaviour - if the subject is an intact female, or if the animal is a puppy, or if the animal mounts "objects") With this form of aggression, dogs will sometimes shy away from owner attention - for example it won't let you pat it's head.
• Dog fights - are expressions of aggression due to territorial competition
• Guarding objects - this has been covered in another Provet Petfact (CLICK HERE for more information)
• Attacking strangers is territorial guarding behaviour which develops in dogs from sexual maturity at about 6 months of age through to 3 years of age. A dogs territory is its home, immediate environment and anywhere it associates with "family" or "pack". It can even include cars and friends and their houses. 
• Fear-induced aggression - loud noises and strange environments can make some dogs aggressive. This is usually the result of poor socialisation as a young puppy. Young animals should be exposed to as many people, sounds and other environmental situations as possible from 7 weeks of age onwards.
• Learned aggression - once an animal is "rewarded" for showing aggression the behaviour is reinforced and so it is more likely to be aggressive again. In a perverse way even scolding a dog for being aggressive  may in fact be interpreted as a positive reaction from you by your dog because you are giving it attention ! 
• Finally aggression can be associated with medical illness. Some clinical diseases - such as liver disease, and portocaval shunts increase ammonia concentrations in the blood which affect the brain and make an animal aggressive. Rabies of course can change an animals temperament making it aggressive, and so on. 
• Some animal behaviourists claim high protein rations induce aggression but there is no sound scientific evidence for this yet - although abnormally high brain concentrations of some amino acids (which are derived from protein) have been associated with aggression in humans.

If your dog is showing signs of aggression it is important to get the underlying cause accurately identified. This requires a detailed history and evaluation of numerous factors including environmental conditions, and a veterinary examination in case there is an underlying medical problem.

There are numerous treatment protocols that can be tried once the underlying cause of the aggression is understood. As with most problems - the earlier it is identified the sooner treatment can be started and the better the chances of a successful outcome.

Remember - if you have an aggressive dog YOU are legally, as well as morally, responsible for any injury it may cause to other people, other dogs or possessions  (CLICK HERE  for more information)

Last updated : September 2013