• Display of Aggression

  • Act of Aggression

  • Motivation / Context

  • Personality

  • Health Considerations

  • Spay or Neuter?

  • Drugs?

  • Probiotics for Behavior

  • Diet and Protein?

  • Guidance

All aggressive behavior is caused by the need to establish control. Occasional aggression toward others in a group of social animals is normal, although most acts of aggression are unacceptable when we are talking about dogs that are members of our household. Aggression can be directed at immediate family members, children, people outside the family, dogs, or other animals. Conflict and aggression is often confused with dominance. Conflict is not necessarily dominance based. People as well as other creatures have conflicts as a normal part of life. Everyone has disagreements… including your dog. People often classify dogs with training or behavior problems as being dominant or having dominant tendencies, when in fact most dogs referred to as dominant often are either confused, fearful, lack etiquette, or simply lack proper training.

  • Displays of Aggression

  • Acts of Aggression

With aggression displays (Reactive) it is often for the purpose of increasing the distance between them and the target. Acts of aggression (Intent to do harm) are for the purpose of gaining control of territory, resources, protection of others, protection of position, or protection of self. 

Most fearful dogs that I have encountered I would classify as “reactive” and not “aggressive”.  I consider “aggressive” as the intent to do harm. Most fear based dogs default to being reactive in order to accomplish what they need; time and distance. If we overwhelm a dog by backing them into a corner or applying to much pressure they may act out of self-defense.


Dogs can show aggression for many reasons. Aggression can be motivated out of:

  • Fear

    • Defense of self

  • Pain

    • Self-Protection from pain

  • Territorial

    • Defense of territory

  • Protection

    • Defense of others

  • Resource Guarding

    • Defense of things, places, or persons the dog does not want to share

  • Dominance

    • Defense of position

  • Dog Aggression

Successfully changing a dog's behavior depends upon accurately identifying the reason for the behavior. Most of what people focus on when assessing a dog′s behavior, is the dog, and its background. But before any approach can be taken to modify the dog′s behavior, you must determine what function the dog′s behavior serves. Start by looking at the behavior patterns exhibited in a specific circumstance, and look for things which may contribute to that behavior within that environment.  

motivation For Acts Of Aggression

Fear-related aggression

  • Lack of proper socialization

  • Unpleasant experiences in the past

  • Learned behavior from the mother

  • Learned behavior from the owners

  • Use of aggression displays to keep people away

Pain-related aggression

  • Dogs that are in pain can act irritable and aggressive when handled.

  • Dogs with confident assertive owners may suppress aggressive tendencies toward owners, but may act aggressively toward others when handled. .

  • Irritability and aggression can continue even after the injury has been healed or when the pain is no longer present due to the dog becoming sensitized to being handled by previously learning that handling was painful.

Territorial aggression

  • Natural tendency to protect the territory of the pack

  • Act ferociously aggressive toward people when they are in or near its territory

  • The territory defended may be the home, car, and common places the dog walks or other locations the dog frequently visits

  • Can be fear-aggression and/ or both territorial and fear aggression

  • Can be breed specific

  • Lack of becoming accustomed to visitors

  • No supervision and training / lack of control by owner

  • Not to be confused with watchdog alert barking

Resource Guarding Aggression

  • Defense of things, places, or persons the dog does not want to share. e.g. food, toys, bed, etc...

Dominance Aggression / Dominance-Related Aggression / Status-Related Aggression

  • Dominance aggression is frequently directed at immediate family members and/or anyone from the dog′s perspective that represents a threat of control over them or their place in the social hierarchy.

  • These dogs are easy to identify by the amount of control they have over their owner, and the owners inability to control their dog.

  • These dogs show an unwillingness to accept the owner′s authority, in at least some circumstances that are important to the dog.

Aggression toward young children

  • Dogs can show aggression tendencies toward children for many reasons.

  • Children are unpredictable; they move, sound and act differently than adults.

  • Motivated by fear due to the lack of proper socialization as a young puppy.

  • Unpleasant experience with children in the past.

  • Dog must compete with new baby for attention

  • Dogs that silently stalk a moving child may be showing predatory behavior in order to control the child

Dog Aggression − Toward Strange Dogs

Aggression tendencies are stronger in some breeds of dogs

  • Lack of proper socialization

  • Fearful of strange dogs

  • Previous unpleasant experience

  • Never developed proper social etiquette with other dogs

  • Unable to read another dog′s social signals communication

  • Territorial aggression at locations the dog frequently visits

  • Protection of owner, or resource

  • Unwilling to show submissive gestures

Many dogs are out of control when they see another dog. They will whine, bark, lunge, etc… even when the dog is at a great distance. Dogs can act this way out of frustration, fear, excitement, and sometimes out of aggression. Most of these dogs can learn to be in the presence of other dogs without acting out. For some of these dogs the behavior can be greatly improved but they may always need to be supervised and managed.

Idiopathic Aggression / Episodic / Dysfunctional Rage

  • No explanation for behavior / Unknown cause

  • Rare type of aggressive behavior

  • Unpredictable and unprovoked attacks on people the dog knows well

  • Typically infrequent and spaced a month or more apart

  • Possibly a neurotransmitter disorder

  • Often confused with severe forms of dominance-related aggression


A dog’s personality is a combination of temperament and character.

  • Temperament = pre-disposition (heritable propensities)

  • Character = disposition, (learned style of coping or navigating the world)

    • Character develops through the interaction of temperament and environment

    • Character emerges as one matures and has more life experience

    • Patterns form habits

A dog’s behavior is influenced by four things: Genetics, early learning, the current environment, and the humans they live with. Genetics give the ability and environment provides the opportunity for these traits to develop to their full potential.

Dogs nor humans “just snap” or have sudden behavior changes unless there is a medical reason or impactful experience. Behavior does not change without a reason. Often times behavior changes gradually but people are not aware of the changes until it has moved further across the continuum. If there is a sudden change in behavior it is advisable that dogs be evaluated by a veterinarian.

Health Considerations

Diseases and physical issues can cause pain and irritability and contribute to reactive / aggressive behavior. A normal physical exam is a good place to start but it will not uncover more difficult to diagnose diseases or physical issues.

When evaluating dogs’ observe how the dog moves and uses its body to assess their physical abilities. When they sit are they slow, fast, tight, sloppy, rolled over on one hip, back onto pelvis, legs tucked or extended? How long before the dog changes positions? Do they prefer to lay down rather then sit? Does there appear to be any pain in the back, knees, hocks, or hips? Dogs like humans will move or shift weight to compensate for pain or discomfort.

Since food sensitivities and thyroid problems are common those are two things I would rule out as contributing to irritability or other behavior problems. For both tests I recommend: Hemopet (Dr. Dodds)

Probiotics for Behavior & Mood

Sample of rescued dogs shows link between gut microbiome, aggressiveness

Bifidobacterium longum BL999 has been reported to help with behavior and mood. You may need to inquire of the manufacturer to determine strain.

Microbiome Dog & Cat testing and Gut Restoration Supplement


Behavioral pharmacology with animals differs from other areas of pharmacology because animal behavior seems to be more prone to environmental influences, rather than pathophysiology. There is no reason to believe that a neurotransmitter imbalance is commonly the cause for most problem behaviors. Rather than seek out a drug for a quick fix, the owner should seek out a professional who understands dogs and has the skills to bring about positive results. Using psychotropic drugs to correct behavior should always be a last resort and always under the direct supervision of a veterinary behaviorist.

Since the majority of problem behaviors are not caused by a neurotransmitter imbalance, these problems can be resolved without the necessity for drug treatment. Problems behaviors such as, anxiety, barking, hyperactivity, separation anxiety, whining or any other behavior considered disruptive should first be addressed by a knowledgeable individual who understands a dog′s development and behavior. When drugs are used the common approaches are typically to assist a behavior modification program that theoretically could work alone, or to correct an existing physiological abnormality such as deficiency in a neurotransmitter system.


Canine and Feline Behavior Therapy Second Edition       Benjamin L. Hart, Lynette A. Hart, Melissa J. Bain

The Dog : Its Behavior, Nutrition, & Health  Second Edition     Linda P. Case

Drugs for Dogs

Spay or Neuter

For most behaviors, spaying/neutering was associated with worse behavior, contrary to conventional wisdom
— Effects on Behavior By Dr. Deborah Duffy

Effects on Behavior By Dr. Deborah Duffy

Effects of ovariohysterectomy on reactivity in German Shepherd dogs

Neutering: What’s Behaviour Got To Do With It?

Neutering Risks and benefits: Bitches

The timing of spaying may have an affect on aggression.

“The calming effect of the high level of progesterone is also the reason why it is best to avoid spaying bitches for two months after estrus. Spaying during this time can result in a precipitous drop in progesterone levels with possible accompanying emotional disturbances, irritability, aggression and depression.”   The Dog’s Mind  By Bruce Fogle, D.V.M., M.R.C.V.S.      

“Progesterone has calming influences, and because spaying removes the source of progesterone production, causing a precipitous fall in progesterone may increase irritable tendencies in young females. After a female has gone through some estrus cycles, and possibly been disciplined for aggressive behavior, the spaying may have less of an impact.”    Canine and Feline Behavior Therapy   Second Edition  By Benjamin L. Hart, Lynette A. Hart, Melissa J. Bain 

“Hart and Eckstein (1997) point out that female dogs are in a progestational state for 2 months following an estrus period and spaying them during that period creates a sudden removal of the source of progesterone (which tend to have a calming influence on animals). It is postulated that this removal of progesterone may promote irritability or aggression in some individuals.”    Aggressive Behavior In Dogs    By James O’Heare 

For more information on Spay or Neuter!

Probiotics for Behavior & Mood

Sample of rescued dogs shows link between gut microbiome, aggressiveness

Purchasing Probiotics for Dogs and Cats

Probiotics for Dogs and Cats: What Are They and How Do They Help?

Written by Dr. Karen Shaw Becker

“Probiotics are beneficial strains of live microorganisms that help maintain healthy levels of gut-friendly bacteria in your pet’s digestive tract”

Look for CFU (Colony Forming Units) which is a measure of viable microorganisms. The standard I use is a minimum of 1 billion for the primary microorganisms and a capsule or coated powder so the microorganisms are active in digestion. “Choose a probiotic with the highest CFU to make sure that you give your dog a diverse array of beneficial organisms in just one dose.”

Each microorganism has its own job to do so for specific purposes be sure to look for the correct strain.

Behavior & Mood

Bifidobacterium longum BL999 has been reported to help with behavior and mood. You may need to inquire of the manufacturer to determine strain.

Genus - Bifidobacterium

Species - longum

Strain - BL999

Stress-Related Gastrointestinal Upsets and Diarrhea in Dogs.

(Bifidobacterium animalis AHC7) may help to prevent stress-related gastrointestinal upsets and diarrhea in dogs.

Probiotics for Behavior / Mood

  • Bifidobacterium longum BL999

  • Lactobacillus acidophilus

  • Bifidobacterium bifidum  

  • Lactobacillus casei

  • Bifidobacterium lactis

  • Bifidobacterium animalis

How To Make Food Better!

Diet and Protein

There has been some concern that high protein diets are correlated with aggressive behavior. Dogs “do not have a requirement for protein per se but have an amino acid requirement.” [1] Proteins are made up of amino acids and dogs have a requirement for 10 of these essential amino acids in their diet and one of these 10 essential acids is tryptophan. So the issue is not with protein per se but with the tryptophan levels.  Tryptophan is found in just about every food that contains protein but in small amounts. (Turkey’s tryptophan context is similar to other meats) Tryptophan is the precursor to serotonin and is needed for the steady production of serotonin. Serotonin is responsible for controlling “mood,” and arousal levels, and is thought to be one of the key neurochemicals, modulating impulsivity, aggressive behavior, antisocial behavior, and others.

Tryptophan competes with other amino acids in high-protein foods to cross the blood-brain barrier. Increasing the ratio of tryptophan to amino acids can increase the amount of serotonin in the brain. Tyrosine is an amino acid like tryptophan. Tyrosine is also found in high-protein foods, but in higher concentrations. Both compete for entry into the brain, so consuming high-protein foods will typically raise brain concentrations of tyrosine but decrease levels of tryptophan because diets rich in protein tend to deplete brain tryptophan levels. Corn is high with the amino acid tyrosine and has a very low level of tryptophan so it has been advised to avoid corn for this reason.

Dr. Nicholas H. Dodman who was involved in two studies is a big believer in switching an aggressive dog’s diet to a low protein diet to see if there is any change. “high protein levels in the diet do not actually cause behavior problems, but they may exacerbate them” In Dr. Dodman’s research a low protein diet was 17%, moderate 25%, and high was 32% protein.

The results of the Dodman studies show that “dominance aggression” was the same on low-protein diets and high-protein diets supplemented with tryptophan. (there was no decrease) In Dr. Dodman’s studies territorial aggression did show a reduction. Their findings were that high protein diets are not the cause of aggression, but that they “may exacerbate them”. Dodman states that if the diet is going to help it will be quick and almost immediately result in a reduction in dominance and territorial aggression.

A much larger study then the Dodman studies completed in the Netherlands where dogs were feed diets supplemented with tryptophan showed no difference in behavior with anxiety-related behavior problems even though there was a significant increase of tryptophan levels in the blood.

Important note. Tryptophan should not be taken with SSRI medication (“Selective Serotonin Reuptake Inhibitors” e.g. Fluoxetine/Prozac, and others) without consultation with your vet. 

 I think it is always advised to consult with your vet before giving any supplements.

If I were interested in using tryptophan I would opt for the higher protein diet and supplement with tryptophan since the Dodman study found this was as effective as the low-protein diet. This is also what is recommended by Dr. Jean Dodds in her book “CANINE NUTRIGENOMICS”.

“keep your skeptic cap firmly in place when considering the effectiveness of supplemental L-tryptophan or a tryptophan-enriched food as a treatment for anxiety-related problems. The early study in 2000 reported a modest effect in dogs with dominance-related aggression or territorial behaviors but found no effect in treating hyperactivity. Subsequently, two placebo-controlled studies reported no effect at all and the single study that reported a small degree of behavior change could not discount the possibility of a placebo effect.” Case, Linda. Beware the Straw Man: The Science Dog Explores Dog Training Fact & Fiction. Autumn Gold Publishing

General Guidance:

The first rule is to only do what is safe and things you are completely comfortable doing. You are ultimately responsible for your own safety. Anytime there are behavioral issues it is always good to rule out any health issues that may be contributing to the problem which can result in irritability or anxiety.

The first place to start is to remove the opportunities for the dog to continue to practice the wrong behavior. Behavior that is practiced becomes stronger and opportunities/patterns create habits and expectations on how to act around others. When a negative behavior is predictable, prepare by limiting the chances of the behavior occurring. It all starts with management not confrontation. Attempting to use physical force on the dog can be seen as a confrontation and the dog may accept your challenge. The goal is to “take control” and not “fight for control”.  Taking control steers away from being confrontational but still places you in control.

If you are having challenges with any form of aggression, please consult a professional for assistance.

[1] Small Animal Clinical Nutrition, 5th Edition Hardcover – Michael S. Hand (Editor)


DeNapoli JS, Dodman NH, Shuster L, et al. Effect of dietary protein content and tryptophan supplementation on dominance aggression, territorial aggression, and hyperactivity in dogs. Journal of the American Veterinary Medical Association 2000; 217:504-508.

Bosch G, Beerda B, Beynen AC, et al. Dietary tryptophan supplementation in privately owned mildly anxious dogs. Applied Animal Behaviour

Case, Linda. Beware the Straw Man: The Science Dog Explores Dog Training Fact & Fiction (p. 87). AutumnGold Publishing. Kindle Edition.

Kaulfuss P, Hintze S, Wurbel H. Effect of tryptophan as a dietary supplement on dogs with abnormal-repetitive behaviours. Abstract. Journal of Veterinary Behavior 2009; 4:97.

Kato M, Miyaji K, Ohtani N, Ohta M. Effects of prescription diet on dealing with stressful situations and performance of anxiety-related behaviors in privately owned anxious dogs. Journal