There are many reasons why a dog may act aggressively, but it is so important that any owner with such a dog should make an appointment with their vet to have the dog's health checked, before looking for any behavioural answers.  Just simple things, like toothache or an ear infection can make us all grumpy, so rule out these possibilities quickly, it could save you much hard work and money in the long run. If a behaviourist is recommended then once again your vet will be able to refer you to such.

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Fear aggression is one of the most commonest reasons people seek advice for their dogs.  It is usually caused because either:

1.The dog has not had enough positive social interactions with other dogs and learnt canine communication properly.
 

2. and/or has been attacked by another dog(s) and therefore may show aggression to only certain types of dogs, such as a certain size, colour or breed.
 

The problem is often made worse if the dog is being restrained on the lead or cornered in a small space with no means of escape.  The dog will often go through the Fight, Flight, Freeze responses to the fear, but if on a leash the dog soon realises that Freeze does not work. The owner is unlikely to have recognised the Freeze and continues walking pulling the dog out of Freeze.  

Flight is not an option on a leash, although in the initial stages some dogs may try to get away or hide behind the owners legs.  The dog is normally pulled out from behind the legs and told not to be so daft or worse still reassured, which further exasperates the problem.  

Fight is often used when the other options have not worked. The dog may go towards the end of the lead and bark, growl or even snap.  The owner will instinctively tighten or even shorten the lead bringing the dog AWAY from it's fear and towards them. This action will have confirmed to the dog that aggression can work when scared as you are pulled away from the fear.  The object that the dog was afraid of may now cross the road or detour round you. This moving away is another reinforcer for the scared dog to use aggression.  Lastly, the owner may try to reassure the dog or even scold him for the aggression, thus giving attention to the whole scenario which will make matters even worse.

When this has happened on more than one occasion it will become Classically Conditioned, which makes it automatic and more entrenched – the dog has learnt how to avoid getting close to what it fears by using an aggressive outburst, and dealing with its fear in the only way it knows how.  This does not make it a naughty dog and any form of punishment is strongly ill advised. After all, we would not punish a child for being frightened of something and expect the child to become better and overcome the fear, would we?

Your Vet should recommend an experienced behaviourist to advise you  how to teach your dog an alternative to aggression in a positive manner, without using force and if necessary to habituate to the dogs fears in a relaxed, non-confrontational manner at a level it can cope with.

Chase or Predatory aggression
This one is usually worse when the dog is exercised off the lead rather than on it.  

It will chase another dog that can by quite some distance away, ignoring any attempts by the owner to stop.  Typically the dog is usually quite well trained and responsive when other dogs are not around. The behaviour of the chased dog will often determine the outcome.  

Often the dog will also  be badly behaved in the car when travelling, particularly when it sees other dogs through the window. 

This type of dog behaves exactly the same no matter who takes it out for the walk.  It enjoys chase and the owner may report it chases anything that moves, from cats to joggers.  Often the owner will try to satisfy their dogs chase instinct by encouraging chase games using toys, but unfortunately due to the physiology of such problems, it can only make matters worse, especially if you could not stop your dog in the middle of it running after something.  Do not switch the “on” button if you do not have an “off” button!

Please remember, if your dog is acting aggressively:

1. There is no "Magic Wand" cure so looking for such is a waste of valuable time

2. A visit to your vet should always be the first step in helping both you and your dog overcome this problem before it gets worse.  If being referred to a behaviourist, it should always be through your vet.

3. Unfortunately they do not just grow out of it - you need good positive experience help to overcome such difficulties and move forward to a good conclusion.

4. There is a lot of involvement, both behaviourally and in the dog’s physiology, which has to be considered any aggression problem. 

(Updated April 2004)