Adult dogs that bite often do so because they need to lash out at whatever s causing them to feel anxious. Dogs with this problem have usually either been abused or are naturally very timid and shy dogs.
With care and patience, most adult dogs can be successfully trained not to bite. Punishing a dog that bites because of fear is not a good idea, as the punishment only increases his fear. This can create a vicious cycle where the dog becomes increasingly anxious and just lashes out more and more.
The bad news is that in the case of an abused dog, (and it is easy to adopt a dog with a history of being abused from a shelter) that it can take months or even years of rehabilitation for him not to lash out and bite at things that trigger his anxiety. In this case, all you can do is take note of what triggers the dog’s fear and what makes him anxious and try to steer him away from those situations. An example is the dog that was beaten with belt. The dog may freak out or lash and bite at people when he sees them reaching to undo their pants or clothing or when he sees them opening a closet as he is afraid he is going to be beaten.
If he has specific fears, then try gradually reintroducing the object or situation that brought on the fear. For example if he is scared of people then utilize some dog loving friends to approach your leashed dog without attempting to touch him. Once his confidence has built up you can increase the amount of time that he is exposed to different people and start physical contact. Using a muzzle is a good idea if you are unsure of how your dog might react in a certain situation and especially if that situation involves children.
Adult dogs have stronger jaws and stronger teeth, so biting and nipping is often a much more serious situation with them. Not only can an adult dog cause another creature or human a terrible injury, it is also harder for them to break the habit.
An adult dog that bites is usually an aggressive dog. An adult dog usually bites because they are displaying fear based, dominance, protective or territorial aggressive behavior.
The main causes of biting and nipping in adult dogs are fear, anxiety, memories of abuse, teasing from children, jealousy, possessiveness, pain and illness.
If your dog is a severe fear biter than you may need to take him to see a certified professional animal behaviorist to try and modify his behavior. He or she may be able to delve deeper into your dog’s individual psyche and help retrain your dog’s behavior. It is imperative that a biting problem is dealt with immediately as the consequences of having your dog, say, bite a child could well lead to a criminal conviction for you an euthanasia for your dog.