Aggression in dogs

Shelter dog

Types of aggression

Aggression in dogs is cause for concern in many dog owners. Aggression is defined as the threat of harm to another individual involving snarling, growling, snapping, biting, barking or lunging.

Understanding the contributing factors in aggression can often help in the treatment of aggression.

Changes in aggression

Your dog’s way of relating to other dogs will change as he goes through adolescence and even adulthood. How much it changes will depend on his early socialization, his genetic makeup, and the training and supervision he receives.

Managing aggressive behavior

Leash aggression

If your dog lunges, pulls toward or barks at other dogs on walks, you know how stressful and embarrassing it can be. Leash-reactive behavior has many components that must be considered.

Causes of leash aggression

  • Greeting on leash is unnatural. When off-leash and in their own environment, dogs naturally greet from the side. They don’t approach head-on and make hard eye contact unless a fight is about to start. When dogs meet on leash, they are typically forced to approach head-on and can't turn their bodies. Most dogs don’t want to fight, so they display a number of behaviors designed to prevent this: barking, lunging, growling, anything to make the threat go away.
  • Dogs feel trapped. If the owners let their dogs say hi, the problems can increase. Both dogs are trapped on leash and unable to increase the distance between each other. Owners often have their dogs on tight leashes in case anything happens, but tight leashes communicate tension to the dogs and further increase their stress. What happens is an explosion of barking as both dogs go from flight to fight. If this doesn’t happen, owners might assume the dogs are fine because neither is barking or growling, but don't recognize signs of stress like pacing, panting, scratching, flattened ears, and low tails.
  • Improper greeting. Letting your dog charge up to another dog, get in his face, bump him, and jump on him is extremely rude behavior among dogs, and is sometimes the result of insufficient dog-dog socialization past the young puppy stage. Adult dogs, while patient with puppy antics, will discipline the pup once he reaches five or six months old. The discipline is non-violent and usually takes the form of barks and growls. If a puppy never experiences these corrections, he may carry his inappropriate greetings right into adulthood. When an adult dog inappropriately greets another dog, the other dog will react, and the owner of the first is likely to criticize the other for his dog’s aggression, unaware that his own dog was the aggressor.
  • Improper correction. Many people correct their dog for any perceived display of aggression. Forcing your dog to sit or lie down in the approaching dog’s path can be very dangerous for several reasons. First, your dog learns that other dogs (and potentially other people) make bad things happen. He is feeling stressed, can't escape because of the leash, and is then punished. Punishment (yelling, jerking the leash, grabbing the dog, saying "no") increases your dog's anxiety level and will make him try even harder to keep other dogs away. Correcting him for growling or barking at another dog can also punish the warning out of him and cause him to go from seeing a dog to biting with no warning (barking, growling) in between. When you correct your highly aroused dog it can also cause him to redirect his aggression onto you.

Preventing leash aggression

  • Work on getting your dog's attention before you go out. Say his name and reward him for looking at you. Start in a low-distraction environment (like your living room) and gradually move to busier areas, only continuing when you can get his attention no matter what. You are teaching him to look at you comfortably regardless of his environment.
  • Start walking at a distance from any dogs. Wait until your dog notices them, and immediately get his attention and reward him. Don't wait for him to react. This will teach him to associate the presence of other dogs with good things. When he looks up at you for more, go closer, and repeat. If your dog barks and lunges at another dog, your training went too far too fast. Add more distance and repeat the previous step. Don't punish your dog for barking or you will undo all of your work so far.
  • Manage your dog's environment. Keep him at a comfortable distance from other dogs and don’t allow others to greet him or invade his space. Every negative experience will set your dog’s progress back. If you live in a very busy walking area, consider taking your dog where less dogs are present.
  • Go around other dogs in an arc. If you find yourself approaching another dog head-on, go around him in an arc shape, rewarding your dog with treats. If the other dog starts to lunge and bark, keep your dog's attention and reward more often. Put away the treats as soon as the other dog has passed so that your dog will associate other dogs with good things.
  • If your dog has harmed another person or dog, we recommend acclimating him to a basket muzzle for walks. This will keep everyone safe while you are working on the behavior. We also recommend seeking professional assistance. Call our free Pet Helpline at 952-HELP-PET for additional information.
Other types of aggression
  • Social agression: In multi-dog households, there isn't usually a dominant dog or submissive dog. Instead, dogs' roles change depending on the context involved. For example, a dog that claims access to a favorite toy may let the other dog claim the couch. But if more than one dog wants to be the leader in a situation, fights can break out. Reward polite behavior and manage the environment to prevent conflicts from developing.
  • Pain-induced aggression: Animals attempt to protect themselves by responding aggressively when they feel pain in attempt to prevent future pain. Unfortunately, animals often attack the person or animal nearest to them rather than only the thing actually causing pain. Handle a dog in pain very cautiously. Many owners get bit while attempting to help their injured dog. Using training devices that inflict pain on animals, such as prong collars, choke chains, and e-collars, are not recommended because they can lead the animal to become more aggressive to stop the pain.
  • Resource guarding: Dogs often attempt to protect resources they control. A dog may guard valuable resources such as food, toys, and a bed, but they may also guard less valuable resources such as bits of trash. In guarding these resources, they can use techniques such as growling, snapping, and even biting to maintain the control over the resource.
  • Frustration aggression: When a dog is prevented from doing something they want or forced to do something they don't want to, they can become frustrated and direct aggression towards the nearest animal or person. In dogs, examples of frustration aggression include aggression resulting from being physically held back by their collar or forced into a kennel.
  • Learned aggression: Once a dog acts aggressively for any of the above reasons, but especially for fear-motivated aggression, they may learn the best way to get what they want is to repeat the aggression. If barking and lunging at the mailman gets him to leave then the dog will learn barking and lunging is effective. Similarly, if biting a hand reaching for them gets the hand to go away, they will quickly learn to bite to remove unwanted contact.
  • Redirected aggression: Another form of frustration aggression in which a dog becomes aroused by a stimulus (such as a doorbell or dog outside the window) and is prevented from directing aggression at the stimulus and instead turns and attacks another dog or their owner.

  • Fear-motivated aggression: Dogs fearing for their own safety are more likely than confident dogs to bite another human or dog. The perceived threat to the dog can be real or imagined. Remember the threat is from the dog’s perspective. For example, a person could be very innocently trying to reach over the dog to take a hold of their collar, but the dog may perceive the motion as intent to do harm, which leads the dog to react aggressively.
  • Genetic predisposition: Some dogs are genetically predisposed to aggression. Dogs of any breed can be selectively bred for aggression intentionally or unintentionally.
  • Protective aggression: Most often happens when a mother protects her young puppies.
  • Territorial aggression: Dogs may attempt to guard or defend their home or space. Territorial aggression includes barking and lunging at fences or from windows.
  • Predatory aggression: Motivated by an animal’s drive to hunt and consume food. Often, predatory behavior is seen in dogs chasing smaller dogs, cats or even young children.
Changes you might notice
  • High arousal: Working breeds, such as herding dogs or those traditionally bred for hunting or fighting, may exhibit high arousal in excitable environments like play groups, and arousal in any form can lead to aggressive behavior. Such dogs may tip from excited play to fighting, or team up with other dogs to torment a victim dog.
  • Irritability: Dogs who previously enjoyed rowdy play might begin to exhibit irritable behavior instead, snarking at dogs who attempt to engage them in play. They might also gravitate more toward human contact in a play setting rather than engaging other dogs. This is particularly common among mature females.
  • Reactivity in shy dogs: Timid dogs might develop reactive behavior, hiding from boisterous young dogs and snapping at them whenever they approach. In a playgroup setting, they may go from hiding under a chair to rushing other dogs, barking, and snapping, in an attempt to chase them away. If they learn this behavior is successful, it may become more entrenched as the dog ages further.
  • Bullying: Confident dogs with rough-and-tumble play styles might bully more timid dogs. They will continue playing despite cut-off signals from the victim dog (flattened ears and tail, lowered body, lip-licking, frightened yipping) and may appear to enjoy such interactions.
How to handle these changes
  • Avoid overly-aroused play situations. It is the rare adolescent dog who can remain calm and play appropriately when surrounded by other young, excited dogs. If your dog plays too roughly in these situations, remove him: choose quieter, less stressful venues for him. Visit the dog park when fewer dogs are present, making sure that at least some of them are mature adults. Well-socialized adult dogs are valuable park-mates for “teen” dogs, as they can teach them appropriate behavior without causing harm.
  • Reinforce calm behavior. If you and your dog are approaching a dog park or playgroup and your dog begins barking excitedly, turn around and walk him away. Leave the building or return to your car and wait until your dog is calm again. If he simply cannot calm down, take him home. This may seem mean, but allowing him to rehearse overexcited behavior will not do him any favors!
  • Continue introducing your adolescent to well-behaved adult dogs. “Well behaved” means the dog interacts well with young dogs but will interrupt inappropriate/rough behavior. Adult dogs typically use eye contact and tall, still postures to discourage unwanted contact. Interruptions normally consist of a quick, deep sound (sometimes called a “snark”), not a confrontation lasting several seconds. If the adult dog pursues the adolescent, this is inappropriate and must be interrupted.
  • Allow your dog to rehearse only desirable behavior. Remember that any behavior will strengthen with practice so don’t let them rehearse the wrong behavior. Are visits to the dog park teaching your dog to chase and bully every dog he sees? Is allowing your dog in the yard unsupervised allowing him to bark and lunge at dogs and people passing by? Don’t be afraid to choose new activities for your dog if his current ones are reinforcing bad habits.
  • Teach your dog to calm himself down. Put your dog on leash while you watch TV and ignore him. If he climbs in your lap, gently move him away from you with the leash. If he barks, ignore him. Wait until he settles quietly on the floor, then quietly praise him. If he jumps up again, start over. Practicing this “settle” exercise regularly will teach your dog that calm behavior is the way to get your attention.
Talk with your veterinarian

Talk with your vet about the possibility of a medical cause for the aggression, particularly if you notice other symptoms. Aggression accompanied by hair loss, increased bodyweight, and lethargy may be a sign of hypothyroidism. Aggression following convulsions, when the dog appears absent, or when rapid mood changes occur may be the result of full or partial seizures. Damage to certain areas of the brain through disease such as hydrocephalus, tumors, thyroid issues or trauma can also result in aggression problems. A consultation with your veterinarian can diagnose these conditions and offer medical treatment as necessary.

Seek professional help

If your dog has shown aggression toward people or other animals, it is critical to seek help from a qualified professional who can evaluate your dog and provide assistance with long-term behavior modification. Do not expect your dog to get better on their own or just grow out of it. Aggression is a very serious problem. Contact our behavior helpline at 763-489-2202 for more information and assistance.

If your dog has bitten a person or animal

Follow these steps until you can seek professional help:

  • No contact with visitors: If you know visitors are coming, take your pet to another room where he will be unable to come in contact with them. If children will be present, we recommend a crate behind a locked door. Don’t assume everything will be fine because “he’s OK most of the time.”
  • Institute a “no petting” rule: Do not allow others, especially children, to approach your pet at all. If this cannot be guaranteed, keep him in his “safe room” as described above. This same rule applies when walking your dog: do not let others approach or pet him, even if he appears relaxed. If others disregard your request, simply walk away from them. Acclimating your dog to a basket muzzle will keep everyone safe in the event your dog is suddenly frightened (by a loose dog, a small child, etc.).
  • No punishment: If your pet reacts aggressively (barks, growls, hisses, lunges or swats) simply remove him from the situation. Take him as far away as necessary for him to calm down. Remember that any punishment – whether verbal or physical – might make the behavior worse, and attempting to “show him who’s boss” could result in serious injury to you or others.
  • Keep him on leash: Keep your dog on-leash at all times while outside of the house or fenced yard. Dog parks, playgroups, and other off-leash activities are not appropriate for dogs with a bite history. It is impossible to predict the dog’s response to other dogs and humans, and thereby puts them at risk. Focus instead on providing plenty of exercise in the form of leash walks, ball/Frisbee-throwing and similar activities. Mental exercises such as obedience training and tricks can also burn excess energy.
  • Don't leave your dog outside unattended: Dogs who lunge and bark at passing people and dogs cannot be allowed to practice this behavior, or it will continue to escalate.  If a passerby sticks his hand through your fence and is bitten by your dog, you will be held liable for the injury.

Private training from Animal Humane Society

For dogs that are aggressive, reactive, fearful, or need more individualized training, AHS offers private on-site and virtual training solutions. Our expert trainers will work with you to create a customized training plan to bring out the best in your best friend.

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