What To Do When Your Dog Is Aggressive, Growls Or Bites

Ron Hines DVM PhD

Read an article when children are involved  

My life revolves around dogs. This article discusses approaches that have worked for me and my clients over the years. That does not mean that they will work for you. I do not know you. I do not know your dog. But I do know that aggressive dogs can be quite dangerous. You are always the safest getting your advice from a canine expert living near you rather than from a distant veterinarian like me who knows neither you, your dog nor your situation.

One of the most common nonmedical problem that dog owners ask their veterinarians about is aggressive behavior toward other people and other dogs. There is enormous variation in aggressiveness and assertiveness among dogs. Certain breeds are renowned for their aggressive qualities – but there is wide variation within each specific breed.

Experiences in puppyhood do influence aggressiveness and fear when a dog matures and owner temperament is also an important factor. But to a much greater extent, aggressive tendencies are hardwired in your dog’s individual, inherited genetics from birth. Genes alone are sufficient to convert foxes from wild to puppy-like-friendly. (read here)

The size of the dog involved determines much of the seriousness of the problem. Toy dogs can be almost cute when they growl and posture, but aggressive larger dogs are quite dangerous. (e.g. The Progressive Insurance Company, among others, factors your dog’s breed genetics into your homeowner’s insurance policy price. Currently, akitas, American bulldogs, Staffordshire terriers, malinois, mastiffs, chows, dalmatians, dobermans, German shepherds, great Danes, Rhodesian ridgebacks, rottweilers and wolf hybrids will up your premium.)

The importance of genetics and the dynamics of dog bites are not well understood by the public. Cartoons, the popular press and the humane movement concentrate on a dog’s experiences as crucial to molding its underlying personality (“any dog, given the proper home, will be a joy”) It would be nice if that were true. Unfortunately, it is not.

Few people realize that the dogs involved in biting incidents tend to be family pets – not strays. Also, more than two-thirds of dog bites happen to people who are acquainted with the dog. More than half the dog bites occur to the very young and the very old and almost half of all bites to children are on areas of the face. Almost half of the claims made against homeowner’s insurance policies are due to dog bites.

Healthy mature dogs do not suddenly become aggressive – although aggressiveness tends to increase with maturity. Veterinarians and dog trainers can detect a predisposition to aggressiveness in puppies as early as seven weeks of age. When they do detect signs that a pup will likely be an aggressive biter or a fear biter as an adult, I believe that cautioning the new owner or potential breeder that this particular puppy will need special care and training and is not a good candidate for breeding is incumbent upon them. I have, on occasion, refused to issue a health certificate for a problematic puppy or dog that was destined to be purchased as a pet by a typical family. That is because I believe that a dog’s mental attitude is as much a part of its general health as is its physical body. But I have had other clients who sought out large dogs with aggressive tendencies for their personal protection. Many of the breeds that Progressive shies away from insuring under homeowner policies were bred for just that.

That does not mean that you cannot improve things.

The Early Window Of Socialization

To understand canine dysfunctional aggression, you need to understand factors in play when your dog was a puppy. Beginning at three weeks of age, when their eyes opened, and lasting until about fourteen weeks of age, puppies develop bonds and sensitivity to the people and animals in their life. If a puppy is not exposed to positive interaction with dogs and humans during this period it may grow up without the skills need to deal with other dogs. If puppies are not exposed to people in a positive way during this period they may never be comfortable with people. The middle of this learning window (~8 weeks) is the best time to purchase a puppy. If only because of time allotment and environment, most dog breeders and shelters just do not have the time to socialize puppies as well as you do. If you do not have that free time right now, postpone purchasing or adopting a puppy. Shelter employees can tell you little about what an adopted puppy will mature into. If you accept a mature dog, what you see is what you get.

Puppies brought to their new home at twelve to sixteen weeks of age may be more fearful and slower to bond with their new family than younger puppies. If the socialization process is delayed until the puppy is twelve to sixteen weeks old or older, the dog may never be as relaxed or interactive with people or other dogs.

This is particularly true if the puppy has a genetic predisposition to shyness, fearfulness or aggression. If you do accept an older fearful puppy, be sure that you and your children handle it frequently and gently and not scold or speak harshly to it. Holding the puppy firmly but gently and resisting the temptation to let go of it when it squirms to be released sometimes minimizes later aggression and dominant behavior.

A puppy’s teenage years begin when it is about sixteen weeks of age and end when the pup is eight to sixteen-month-old. Near the end of this period a sex hormonal surge causes dogs to become more protective and territorial. Males begin to lift their leg to urinate and females enter their first heat period (some earlier). This will be the time that a normal dog begins to bark at strangers and guard the family and what they perceive as your property. This is also the time that some dogs begin to show objectionable aggressive behavior. It is also the time that dogs look to you to tell them what is acceptable and what is not. They read your emotions and desires like an open book. If you give them no feedback or are passive, they will make their own decisions.

What If I Just Spay Or Neuter My Dog Young?

Puberty is not just an ovarian and testicle (testicular) hormonal event. Your dog’s pituitary and adrenal glands play a crucial role in it as well. (read here) No one I know of has studies this in dogs. But it has been studied in detail in people. (read here) Neutered or un-neutered, these brain and thought changes will occur in any case as your dog matures. Besides, neutering dogs when they are very young is deleterious to their long-term health. (read here)

Factors Influencing Aggression

I mentioned earlier that besides age at socialization, individual breed genetics are critical factors in determining aggressiveness, trusting or a fearful nature. Guard dog breeds were bred to be naturally more aggressive and suspicious than the hunting and companion breeds. Aggressiveness, fearfulness and suspicion were seen as undesirable traits in hunting dogs. Over the centuries that hunting dogs were developed, those that displayed those tendencies were never bred. That is why Labrador and golden retrievers, setters and spaniels from hunting stock make such good family pets. Terriers were bred to be alert ratters and some still retain their natural vigilance and urge to snap.

Excessive punishment, teasing, chaining in the yard or long periods alone, can all contribute to neurotic and problem behaviors.

Types Of Aggression

There are a number of types of aggression. The most common forms are dominant and territorial aggression. Some dogs show fearful, possessive or intra-sexual (male to male and female to female) aggression while others have a predatory form of this trait. Some dogs share more than one type of aggression.

Dominance Aggression

Dominant aggressive dogs are overly protective of their possessions and status. This is probably the most common form of aggression. These dogs tend to snarl and growl or snap when a family member approaches them near their food bowl. They are prone to attack other dogs as well as cats and farmyard animals. They might attempt to sexually mount people’s legs – although there are other causes of that behavior. When petted, groomed or detained in any way they can growl and snap. They often chase cars and bicycles. They love to wander and escape and will ignore commands that they return or heel.

The first warning you will have that you have a dog prone to dominant aggression is when, as a small puppy, it growls when you approach it at its food dish or attempt to take away its toy. This is the earliest sign of dominance. As this personality type of dog grows, it will attempt to take charge of the household and the decision-making process. Dogs that have dominant type aggression are very confident in new situations. Dominant aggressive dogs have a very distinctive body language. They stand with their heads erect and their ears bent forward. They carry their tails proudly and stare intently at strange people and pets. They stand still facing the new individual and might even emit a low steady growl while they curl their lips and expose their teeth. These dogs will mount other dogs until the second dog assumes a submissive posture. They demand to be the center of attention in all situations, and must make the decision as to who does what and when. They are oblivious to commands from their owner and never heal or look to their owner for advice or reassurance. They often urine mark new areas such as my veterinary office walls. Most of these dogs are unneutered males.

Dogs as part of the family see humans as members of their pack and attempt to establish their place in the social hierarchy by challenging more submissive family members, especially children. When dogs show dominant gestures like growling while guarding their food dish, and they aren’t scolded for that behavior, they inch up in dominance eventually surpassing certain family members. Subtle signs of dominance can go unnoticed. Because we love our pets so, we explained away these faults and give excuses until the dog finally bites a person who infringed on its alpha position. Owners often do not realize what occurred and think their dog bit “for no reason”. Those dogs are often surrendered to animal shelters and are put down because their owners did not understand how aggressive behaviors comes about and the part they played in permitting it.

Reaching Out For A Solution:

Passive, submissive family members are going to have problems correcting aggressive dogs that can be very difficult or impossible to surmount. Obedience school support can be very helpful with this form of aggression – but the dog owner must be willing (and capable) of being assertive with an aggressive pet. The first thing to do when trying to resolve this problem is to change the peck order of the “pack” – in this case the hierarchy within your family. Most dogs, like most children are much happier not to have to be the pack leader. Your dog needs to be at the bottom of the pack, not the top. You need to become the pack leader. In my veterinary practice in Texas, husbands often appear more assertive than their wives. I noticed that many of these dogs obeyed the husband but not the wife. That puts the wife in a very difficult situation. I suppose that if roles within a family partnership were reversed, it would be no different. To gain control of your dog you need to dominate all aspects of that dog’s life. To minimize dominance, when you play tug of war with a pup or dog; do not let it end up with the ball or rope when you are finished. When you feed the dog, do not let it eat until you command it to come. When you take a walk, keep the dog on a standard length leash. Do not allow the dog to decide where you are going – have it look to you for guidance. Do not let dominant-prone dogs to sleep in your bed or in the bedroom. Reserve that space for your human family.

For highly aggressive dogs my first recommendation is to surrender them. I worry about your safety. If that is not an option, purchase a muzzle. Put it on just after you feed the dog and take it off when you give treats. Do not feed these dogs from the table. Instead, crate them during meals and feed them last. If the dog has already begun to bite owners, hiring a professional dog trainer is a very good idea. But you need to realize that not all dogs can be cured of their aggressiveness and that a “trained” dog often revert to its previous bad habits once the trainer has left. I have seen that happen time and again.

Some General Rules For Curbing Aggression:


The first step goes back to before you purchased or accepted a puppy. What people tell you about the personality of a dog they want you to buy or accept is not nearly as important as what the dog tells you about its personality. People often lie or bend the truth. Dogs never do.

All puppies are cute and endearing. But be sure that the breed and the individual puppy that you choose are right for your family. If it’s a puppy, sit alone in a quiet room with the entire litter and observe all of them for a while. The more dominant pups will soon take charge of play activities and seek out strangers in the room. If it’s an older dog, spend time with it alone too.The fearful pups will be the ones that sit by themselves in the corner looking downcast. If you want a well-behaved pet, do not choose the most dominant or the most fearful puppy. Assertive breeds are never good breeds for timid owners, the handicapped or the elderly. They need a family in which all members are willing and capable of exerting their authority. If you choose a shy puppy you must be willing to spend extra time coaxing its courage in new situations. Realize that it will never become a confident dog. Lapdogs are wonderful pets, but shyer ones do not like rowdy, active children. The popular press encourages the fantasy of changing animal personalities into what we want them to be: Molding the savage wolf into a loving domestic dog through love and patience, taming the wild lion and bear with affection. It is an endearing story, but it exists only in Hollywood and in our dreams.

All puppies need to be handled gently, firmly and frequently between the ages of six and eighteen weeks. They should be hand-fed by all members of the family and taught to accept food slowly and daintily without snapping or lunging. They should be verbally scolded or affection denied when they jump up on people, chase running joggers and children, ride legs or growl for any reason. Aggression-prone dogs should not be rough housed with, wrestled with or engaged in tug of war. Instead of physically punishing them one should speak to with a sharp “No” when they break the rules and then deny them affection and interaction for ten minutes or so. When they begin to understand what you consider objectionable actions reward them with a food treat and a pat.

Puppies learn good behavior from other dogs too. Once they have had their puppy vaccinations (read here) It is good to expose them to well-trained, people-friendly, non-aggressive dogs as playmates. It is amazing how quickly good behavior rubs off on misbehaving pets. They learn from the pack.

Adult Dogs:

Once a dog has assumed a dominance aggressive temperament it can be very difficult and sometimes impossible to change its outlook on life. Through fear, he may allow one or two members of the family to dominate him, but he may never be fully trustworthy around lower ranking members of the family and children. I personally think these dogs are unhappy in their roles and long to have more assertive owners. If you are not that person, consider rehoming the pet. That is not something you should feel guilty about or let others criticize. Some things just were not meant to be.

Adult dogs should always receive rewards for good behavior and be denied rewards for bad behavior. Normal dogs love to be petted and have their heads patted. If you have a dog that is prone to aggression or bad behavior of any kind always have your dog sit and heel before petting, going outside, or entering and exiting the car. Dogs should be taught to sit calmly when you snap on their leash. These may not seem like important things, but they help your dog define the rules that apply to all activities that you and the pet will share. They also teach the dog that you, not it, set the rules. You need to be consistent in your praise or criticisms. The dog will quickly learn that a given behavior always elicit a given positive or negative response from you. If you are inconsistent, it will be confused. Never let a pet win a showdown or take charge. If you give an inch they will take a mile. What appears to you to be a trivial disagreement may not be so trivial to your dog. The dog coming out on top elevates its social status and can eventually lead to dominance aggression. It is much better for the pet to understand that you won the disagreement and then have him/her shake hands, sit or fetch and then give him all the praise you want.

You can try to alter triggers in your home that lead to outbursts of dominance aggression. For instance, if a dog growls when you approach it as it lies on the sofa, make the sofa off limits to the dog. Rather than limiting the amount of contact that the family member(s) who are having the biggest problem with the dog have, make that person(s) the primary caregiver for the dog. During this period have other family members ignore the dog. However, it is dangerous to do that in a dog that has already progressed to snarling, growling or biting.

Always reward these pets when they show signs of submission. These signs include laying their ears back on their heads, licking their lips, rolling over, sitting, and curling in their tails. Once a dog is displaying some of these activities begin slowly counter conditioning the dog to submission. This is done by getting the dog to allow you to handle its paws, hold it in a sitting or laying position and holding its head still. Make the dog lay down before it is allowed to fetch. Praise the pet and give him/her a food treat when it cooperates and gradually increase the length of its lessons.

Fear Biting Dogs

These dogs are very uncertain and tentative in their actions. They are sometimes called defensive-aggressive dogs. When faced with new situations with people or dogs, they avoid direct eye contact and assume a low submissive stance. They stand with their ears flat against their heads and their tails tucked between their legs. They bend their head and neck toward any individual who seeks their attention while they lick their lips. They will often roll on their backs exposing their belly. Their expression is one of profound worry. They are very fearful about being touched and shy away from being petted stroked or brushed. At any instant, they may snap and bite out of fear. They strike out silently like a snake, never locking their jaws on another person or pet. They will often urinate and defecate in fear.

Reaching Out For A Solution:

Most fear biting dogs were born shy. It is highly unusual for a shy puppy to be born from gregarious, confident parents. One needs to do everything possible to build up these dog’s sense of confidence. Do this with verbal praise, petting and treats. Enlist your friends in this activity. In order not to get bitten, begin this process with a muzzled dog. Just remove the muzzle for the dog to eat. Only feed the dog (cautiously) from your hands. You can crate the dog and let the neighbors assist you in feeding it when it gets very hungry. If a shy dog comes to you of its own free will, it is unlikely to bite unless a sudden movement or loud sound is made. Sometimes the pets are so shy that the food treat needs to be put on a long stick at first. With the dog muzzled gradually take it wherever you go to expose the pet to new people and situations. Begin slowly – no more than the mall parking lot. Try to calm and stroke the dog as you go. Take the dog wherever you go. Keep the leash short and taut. Calm and stroke the pet. Obedience training is very helpful for dogs that are not too shy to go to class.

I find that a small dose of acepromazine tranquilizer is quite helpful in starting these dogs in their education. Acepromazine has been found to vary in its effects depending on canine breed and genetic makeup (read here), but I have never run into problems dispensing it. Valium® (diazepam) seems to have minimal effects on dog behavior. Perhaps your veterinarian will dispense you some “ace” to give in a food treat thirty minutes or so before lessons. I have found that surgically neutering fear biting dogs is quite unlikely to be beneficial. 

Territorially Aggressive Dogs

Barking to guard their home and announce visitors is a common characteristic of dogs. When a dog is physically aggressive, that can be a problem. Dogs have an innate need to protect their own real estate. As a puppy grows into a dog, it begins to regard its yard, the home and even their car as family property. When I lived on Sarasota bay, dogs guard their owner’s sailboat homes and the dock it was anchored to just as fiercely.

Territorial aggression is a prized attribute in guard dog breeds such as German Shepherds, Rottweilers and Akitas. If you do not want an aggressive guard dog do not purchase these types of breeds. Some dogs readily learn to differentiate between welcome guests and intruders, but others do not. They are very good at sensing your attitude toward strangers. If you are fearful or apprehensive, these breeds of dog will know it and will become protective.

Reaching Out For A Solution:

You set the rules as to who is a friend and who is a foe. The meter reader and the UPS man should not be a foe. Introduce them. Give them snacks to feed the dog and encourage the dog to accept them. Your dog should look at you for advice when a stranger approaches. Enlist some friends to help you by approaching the house when the dog is hungry and have them cautiously offer your pet some treats. Let your friends take the dog on short walks on a leash. Fence your yard, so the limits of its territory is clear to the dog.

Predatory Aggression

Australian shepherds, healers, border collies and other herding dogs have an instinctive drive to chase, worry and nip. It takes a supreme effort on their part not to apply their herding talents to children of the family as well.

Reaching Out For A Solution:

Obedience training by every member of the family – especially the children – often helps resolve this problem. These dogs are basically loving. They just have a very strong natural urge to be bossy and herd. This can usually be overcome if you make the dog aware that it is a problem. A sharp non-physical reprimand and a “no” is usually sufficient. You have to occasionally remind them of the rules. Dogs are much less likely to express this behavior when they are on a short leash.

Might My Dog’s Diet Have Any Effect On Aggression?


I do not think you are likely to cure an aggressive dog by changing its diet. Talk about that is based on a 2000 study in dogs that seemed to indicated that high-protein diets tended to make aggression problems worse. (read here  & here) An earlier study in dogs was not as optimistic (read here) and none have shown that low protein diets lower aggression in humans. But you can give it a try and get back to me.

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