Aggression is the most common and most serious behavior problem in dogs. It’s also the number-one reason why pet parents seek professional help from behaviorists, trainers and veterinarians.
What Is Aggression?
The term “aggression” refers to a wide variety of behaviors that occur for a multitude of reasons in various circumstances. Virtually all wild animals are aggressive when guarding their territories, defending their offspring and protecting themselves. Species that live in groups, including people and dogs, also use aggression and the threat of aggression to keep the peace and to negotiate social interactions.
To say that a dog is “aggressive” can mean a whole host of things. Aggression encompasses a range of behaviors that usually begins with warnings and can culminate in an attack. Dogs may abort their efforts at any point during an aggressive encounter. A dog that shows aggression to people usually exhibits some part of the following sequence of increasingly intense behaviors:
Becoming very still and rigid
Guttural bark that sounds threatening
Lunging forward or charging at the person with no contact
Mouthing, as though to move or control the person, without applying significant pressure
“Muzzle punch” (the dog literally punches the person with her nose)
Snarl (a combination of growling and showing teeth)
Quick nip that leaves no mark
Quick bite that tears the skin
Bite with enough pressure to cause a bruise
Bite that causes puncture wounds
Repeated bites in rapid succession
Bite and shake
Dogs don’t always follow this sequence, and they often do several of the behaviors above simultaneously. Many times, pet parents don’t recognize the warning signs before a bite, so they perceive their dogs as suddenly flying off the handle. However, that’s rarely the case. It can be just milliseconds between a warning and a bite, but dogs rarely bite without giving some type of warning beforehand.
Classification of Aggressive Behavior
If your dog has been aggressive in the past or you suspect she could become aggressive, take time to evaluate the situations that have upset her. Who bore the brunt of her aggression? When and where did it happen? What else was going on at the time? What had just happened or was about to happen to your dog? What seemed to stop her aggression? Learning the answers to these questions can clarify the circumstances that trigger your dog’s aggressive reaction and provide insight into the reasons for her behavior. You need an accurate diagnosis before you can hope to help your dog.
Aggressive behavior problems in dogs can be classified in different ways. A beneficial scheme for understanding why your dog is aggressive is based on the function or purpose of the aggression. If you think of aggression this way, you can determine what motivates your dog to behave aggressively and identify what she hopes to gain from her behavior.
Some dogs will attack and bite an intruder, whether the intruder is friend or foe.
Dogs may show aggressive behavior when they think that one of their family members or friends is in peril.
Many dogs show the tendency to guard their possessions from others, whether they need to or not.
A fearful dog may become aggressive if cornered or trapped.
Motivated by fear, defensively aggressive dogs decide that the best defense is a good offense.
A dog who perceives herself as high in status may show aggression toward family members.
A dog who’s excited or aroused by something but is held back from approaching it can become aggressive.
Redirected aggression occurs when a dog is aroused by or displays aggression toward a person or animal, and someone else interferes.
An otherwise gentle, friendly dog can behave aggressively when in pain.
Intact male dogs will still vie for the attention of females in heat, and females will still compete for access to a male.
Some pet dogs show classic canine predatory behaviors, including chasing and grabbing fast-moving things.
Family Members, Strangers or Other Animals
Determining whom your dog is aggressive toward is essential to understanding her behavior. It’s common for dogs to behave aggressively toward unfamiliar people. Some studies report that as many as 60 to 70% of all pet dogs bark threateningly at strangers and act unfriendly when around them. Aggression toward unfamiliar dogs is also widespread. It’s less common for dogs to direct aggression toward family members or other pets in the home. Most problematic are dogs who are aggressive toward children, especially children in the family. Not only is aggression toward children exceedingly difficult to treat because of safety concerns, the likelihood that a dog with this problem will ever become trustworthy is slim.
Some dogs are aggressive only to a certain category of people. A dog might be aggressive only with the veterinarian or groomer, or with the postal carrier, or with people in wheelchairs or individuals using canes and walkers. In some cases, it’s easy to limit a dog’s access to the people that upset her. For instance, if your short-haired dog dislikes the groomer, you can just groom her yourself at home. But in other cases, the targeted people are impossible to avoid. For example, if you have a dog who dislikes children and you live in a densely populated urban apartment building next to a preschool, it will be difficult to avoid exposing your dog to children.
Aggression toward people, aggression toward dogs and aggression toward other animals are relatively independent patterns of behavior. If your dog is aggressive toward other dogs, for example, that doesn’t mean she’s any more or less likely to be aggressive toward people.
If you’re deciding whether to live with and treat your aggressive dog, there are several factors to consider because you, as the pet parent, are ultimately responsible for your dog’s behavior. These factors involve the level of risk in living with your dog and the likelihood of changing her behavior:
Size. Regardless of other factors, large dogs are more frightening and can inflict more damage than small dogs.
Age. Young dogs with an aggression problem are believed to be more malleable and easier to treat than older dogs.
Bite history. Dogs who have already bitten are a known risk and an insurance liability.
Severity. Dogs who stop their aggression at showing teeth, growling or snapping are significantly safer to live and work with than dogs who bite. Likewise, dogs who have delivered minor bruises, scratches and small punctures are less risky than dogs who have inflicted serious wounds.
Predictability. Dogs at the highest risk of being euthanized for aggression are those who give little or no warning before they bite and who are inconsistently, unpredictably aggressive. Dogs who give warning before they bite allow people and other animals time to retreat and avoid getting hurt. As counterintuitive as it might seem, it’s easier to live with a dog who always reacts aggressively when, for instance, every time you push him off the bed than a dog who does so only sporadically.
Targets. How often your dog is exposed to the targets of her aggression can affect how easy it is to manage and resolve her behavior. A dog who’s aggressive to strangers is relatively easy to control if you live in a rural environment with a securely fenced yard. A dog who’s aggressive to children can be managed if her pet parents are childless and have no friends or relatives with children. A dog who is aggressive to unfamiliar dogs poses little difficulty for pet parents who dislike dog parks and prefer to exercise their dog on isolated hiking trails. In contrast, living with a dog who has recurring ear infections and bites family members when they try to medicate her can be stressful and unpleasant.
Triggers. Are the circumstances that prompt your dog to behave aggressively easy or impossible to avoid? If your dog only guards her food while she’s eating, the solution is straightforward: Keep away from her while she’s eating. If no one can safely enter the kitchen when your dog’s there because she guards her empty food bowl in the cupboard, that’s another story. If your dog bites any stranger within reach, she’s a lot more dangerous than a dog who bites strangers only if they try to kiss her.
Ease of motivating your dog. The final consideration is how easy it is to motivate your dog during retraining. 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. Dogs who aren’t particularly motivated by the usual rewards can be especially challenging to work with, and the likelihood of such a dog getting better is small
Always Work with Your Veterinarian
Some aggressive dogs behave the way they do because of a medical condition or complication. In addition to acute painful conditions, dogs with orthopedic problems, thyroid abnormality, adrenal dysfunction, cognitive dysfunction, seizure disorders and sensory deficits can exhibit changes in irritability and aggression. Geriatric dogs can suffer confusion and insecurity, which may prompt aggressive behavior. Certain medications can alter mood and affect your dog’s susceptibility to aggression. Even diet has been implicated as a potential contributing factor. If your dog has an aggression problem, it’s crucial to take her to a veterinarian, before you do anything else, to rule out medical issues that could cause or worsen her behavior. If the veterinarian discovers a medical problem, you’ll need to work closely with her to give your dog the best chance at improving.
Always Work with a Professional Behavior Expert
Aggression can be a dangerous behavior problem. It’s complex to diagnose and can be tricky to treat. Many behavior modification techniques have detrimental effects if misapplied. Even highly experienced professionals get bitten from time to time, so living with and treating an aggressive dog is inherently risky. A qualified professional can develop a treatment plan customized to your dog’s temperament and your family’s unique situation, and she can coach you through its implementation. She can monitor your dog’s progress and make modifications to the plan as required. If appropriate, she can also help you decide when your dog’s quality of life is too poor or the risks of living with your dog are too high and euthanasia is warranted. Please see our article, Finding Professional Behavior Help, to learn how to find a Certified Applied Animal Behaviorist (CAAB or ACAAB), a veterinary behaviorist (Dip ACVB) or a Certified Professional Dog Trainer (CPDT) in your area. If you choose to employ a CPDT, be sure that the trainer is qualified to help you. Determine whether she has education and experience in treating canine aggression, as this expertise isn’t required for CPDT certification.
Can Aggression Be Cured?
Pet parents of aggressive dogs often ask whether they can ever be sure that their dog is “cured.” Taking into account the behavior modification techniques that affect aggression, our current understanding is that the incidence and frequency of some types of aggression can be reduced and sometimes eliminated. However, there’s no guarantee that an aggressive dog can be completely cured. In many cases, the only solution is to manage the problem by limiting a dog’s exposure to the situations, people or things that trigger her aggression. There’s always risk when dealing with an aggressive dog. Pet parents are responsible for their dogs’ behavior and must take precautions to ensure that no one’s harmed. Even if a dog has been well behaved for years, it’s not possible to predict when all the necessary circumstances might come together to create “the perfect storm” that triggers her aggression. Dogs who have a history of resorting to aggression as a way of dealing with stressful situations can fall back on that strategy. Pet parents of aggressive dogs should be prudent and always assume that their dog is NOT cured so that they never let down their guard.
Are Some Breeds More Aggressive Than Others?
It’s true that some breeds might be more likely to bite if we look at statistics gathered on biting and aggression. There are many reasons for this. One likely reason is that most dog breeds once served specific functions for humans. Some were highly prized for their guarding and protective tendencies, others for their hunting prowess, others for their fighting skills, and others for their “gameness” and tenacity. Even though pet dogs of these breeds rarely fulfill their original purposes these days, individuals still carry their ancestors’ DNA in their genes, which means that members of a particular breed might be predisposed to certain types of aggression. Despite this, it’s neither accurate nor wise to judge a dog by her breed. Far better predictors of aggressive behavior problems are a dog’s individual temperament and her history of interacting with people and other animals. You should always research breeds to be sure that the breed or breed mix you’re interested in is a good fit for you and your lifestyle. However, the best insurance policies against aggression problems are to select the best individual dog for you.