The most common causes include conflict aggression, fear-based, defensive aggression, status related aggression, possessive aggression, food guarding aggression and redirected aggression.
Dog aggression can be related to fear, prey drive, socialization issues, and guarding territory, among other things. Most aggressive behavior in dogs stems from fear and anxiety, rather than the desire to hurt others. A certified animal behaviorist can help you safely deal with your dog's aggressive behavior.
Most scientific studies indicate that it is very possible to rehabilitate a dog after they bite another dog or person.
However, sudden behavior changes in dogs are more likely due to trauma, severe pain, or possibly even a neurological issue.
Most cases however, are simply overly energetic dogs that may not be getting sufficient exercise and routine to their day, or who are being accidentally rewarded when they act excitedly (see Play and Exercise and Using Enrichment, Predictability, and Scheduling to Train Your Dog).
Stop it or remove your dog from the situation before it escalates. Do not discipline your dog with physical, violent, or aggressive punishments. Opt for positive reinforcement before resorting to the use of aversives. Remember to reward your dog for good behavior.
Ignore him for 30 to 60 seconds. If your dog follows you or continues to bite and nip at you, leave the room for 30 to 60 seconds. (Be sure that the room is “dog-proofed” before you leave your dog alone in it. Don't leave him in an area with things he might destroy or things that might hurt him.)
If the broken skin is more of a scratch than a serious wound, you can usually just clean it with soap and warm water, apply an antiseptic cream, and cover it with a bandage. But obviously, seek medical assistance if any bite wound doesn't heal quickly or it starts to look red, inflamed, or infected.
Straight off the bat you should be correcting your dog's growling and/or snapping with a firm “no” at the onset of the behavior. When he stops growling, reward him with a “good boy”, or in the beginning, a treat if it's handy at the exact moment of training so that he knows what he is being rewarded for.
The safest and most effective way to treat an aggression problem is to implement behavior modification under the guidance of a qualified professional. Modifying a dog's behavior involves rewarding her for good behavior—so you'll likely be more successful if your dog enjoys praise, treats and toys.
Many dogs simply tolerate patting but don't enjoy it, and many dogs find human touch to be scary or awful. And when something is scary or awful, the polite canine way for a dog to make this clear to the world is by a growl, a snarl, a snap, or an inhibited bite. Yes, you read that right.
If the aggression is motivated by fear, punishment will only make the dog more fearful, and therefore more aggressive. Attempting to punish a pushy or controlling dog is likely to make his behavior even worse. In either case, the dog and owner end up in a vicious cycle of escalating aggression.
Don't Punish Growling
If you punish your dog for growling, you will only inhibit growling. You won't have done anything to address the underlying issue. For example, punishing your dog for growling in the presence of other dogs will stop the growling. However, your dog will still feel uncomfortable around other dogs.
While it may sound obvious, growling at your dog is not likely to improve its aggressive behavioral problems, a new study suggests. Hitting it is probably worse. Researchers say dog owners who kick, hit or otherwise confront aggressive dogs with punitive training methods are doomed to have, well, aggressive pets.
When Lunging and Biting is a Sign of Resource Guarding. If your puppy is lunging or biting when you reach for a toy, their food, or another type of resource (such as where they are resting on the couch or in a dog bed), this might be a sign of resource guarding.
"The motivation for lots of dog bites is fear," he says. "Others are territorial - if they're guarding something that they highly value, or defending their favourite resting place, their bed... Or if they've learned to defend, say, a dog bowl - that can result in aggression."
Rather than reprimanding, removing, or restraining your pup, it is usually more effective to let them immediately know they have hurt you by giving a voluble yelp or cry “OUCH.” Usually, they will back off. Next, give your pup a minute or two to process what has just happened. Then call the dog back to you.
Level 3: One-four shallow punctures from a single bite and potentially small lacerations from pulling the biting dog or victim body part away. Level 4: One-four deep punctures from a single bite and lacerations or bruising from the dog holding on or shaking.
Here are some behaviors to avoid when your puppy starts biting: Don't hold your puppy's mouth closed when they nip at you. This method can send the wrong message to some developing pups.
The behavior is being reinforced.
As puppies, biting was a way for them to try to instigate play and attention, explore the world, and burn off some teething frustration. Which of those three still serves a functional purpose in an older dog? Instigating play and attention.
They bite out of aggression or fear: It's not always easy to know the difference between play biting and an aggressive bite, but body language can help indicate which is which. If your dog bites out of aggression, they may wrinkle their muzzle, seem tense or nervous, expose their teeth or curl back their lips.
A confident dog wanting you to move away will often deliver a low-pitched warning growl. His body will stiffen and the loose circular wag may become a stiff side-to-side motion. 2. A scared dog who really doesn't want to defend himself may make a high-pitched growl-bark to get you to move away from him.
Teach “Gentle” to a Dog
Commit to the idea that your dog needs to take the treats gently or they don't get them at all. In other words, don't allow the snapping behavior to be rewarded. To teach your dog what “Gentle” means, hold a treat in your hand, close your fist around it and offer it to your dog.