There is a lot of misinformation around the reasons why dogs behave aggressively.  For example, there is a common expression that suggests that there are “no bad dogs, only bad owners”. In reality, even people who understand dogs and raise them kindly can have a dog who behaves aggressively.

Others think it has everything to do with being “too soft” or not being a leader or “alpha” of the pack.  Yet there are plenty of dog owners who have been the ultimate “alpha” and still end up with an aggressive dog.

Some think a dog’s behavior might be a result of the dog being previously abused.  But there are some dogs who were abused never become aggressive.  Some dogs will even behave more or less normally until the dog matures socially around 2 or 3 years of age.

Some think it’s the breed, or the way the dog was bred.  But what really causes dog aggression?

On This Page:

  • Causes of aggression
  • What we do to make aggression worse
  • Next steps for our aggressive dog

Aggression is a symptom

It is important to understand that aggression is a symptom of an underlying cause. In some cases the aggression could be categorized as a normal appropriate, if undesirable response. Other times aggression is not appropriate. But in all cases, aggression always stems from an underlying cause.

The underlying causes of dog aggression can be broadly categorized into three main areas

Aggression may be stem from one or a combination of reasons. For example, play can sometimes turn aggressive as well and maternal aggression may be hormonally modulated (we get into this further).


But to challenge the idea that dog aggression “just happens”  it may help to broadly categorize the most common reasons for aggression into three common areas: fear/anxiety, frustration and pain/discomfort. It may be one or a combination.

Fear and Anxiety

Fear and anxiety are common causes of aggression in dogs (2) (3) (5). In some cases the fear and anxiety is a normal response to a threat. In other cases, the fear or anxiety may be related to an issue that may need to be treated with medication. In just about all aggression cases, there is a learned component.

  • Fear
    • Specific and targeted.
    • Dogs might be afraid of dogs, bicycles, children, a specific child, men with hats, etc.
  • Anxiety
    • Generalized and vague.
    • Dogs may feel anxious about not knowing what is going to happen or how another might react. They may feel on edge or be too worried to fully let down their guard.
  • Fear/Anxiety about negative feelings
    • Not usually discussed in regards to dogs but should be addressed. The feeling of fear and anxiety is very negative feeling. Dogs may act out in order to avoid feeling anxious or fearful. For example, in the case of dogs who are worried about responses from others, may test them in order to get much needed information. They may also act out of jealousy.

Pain or Discomfort

It is well known that pain can elicit aggression in dogs (2) Pain is often a normal response to pain, however a learned component can develop. If dogs experience pain in certain situations, they may develop of a habit of responding aggressively even when the pain is no longer an issue.

Dogs frequently do not show pain and we may we unaware of how they are feeling until something becomes so obvious we can’t miss it. Whenever a dog becomes aggressive, medical issues should be explored.

  • Physical pain
  • Dental problems, arthritis, sore paws, backs, joints, sore paws, digestion problems, etc. Check out medical causes of dog aggression for more information.
  • Poor health
    • Fatigue, lethargy, depression, etc.
  • Negative feelings.
    • irritation, jealousy (7)


Frustration is an unmet need or desire and can contribute to aggression in dogs (8). In all likelihood there are varying degrees of frustration, and at some point there may be a tipping point. Some scenarios that may cause frustration in dogs.

  • Feeling trapped
  • Needs not being met adequately
  • Being forced or coerced into doing something again their will
  • Not having sufficient control over one’s environment
  • Personal space may not be respected
  • Confusion about expectations and or punishments
  • Being blocked from accessing a desirable thing
  • Redirected aggression, Leash aggression, Boundary or Fence aggression can all be example of aggression that may be frustration driven

The issue: Most canine behavioral problems either involve normal behaviors that people don’t like or understand or anxiety-related concerns that comprise true behavioral diagnoses. – Dr. Karen Overall, Dumbed down by dominance, 2012

Factors that contribute to the development of the underlying causes of aggression in dogs


Physical Aspects

From how we’re wired to the coping mechanisms we use, there are many things about aggression that go beyond what has happened before and what is happening at the moment. Here are just some of things about dogs as physical being that can influence aggression.

  • Temperament
    • Reactivity can contribute to dog aggression (4)
    • Coping styles and tendencies (9)(10)
  • Genetic (6)
  • Congenital (present from birth) diseases, disorders or conditions
  • Hormonal (levels and receptor density) (4)
  • Neurophysiologic (6)
    • Science relating to physiology and how the brain works in conjunction with the nervous system


Past learning affects how dogs respond to occurences in the present. Fear, negative experiences, failures and successes greatly shape how a dog responds now.

  • Negative experiences
  • Associations linked to negative experiences
  • Generalizing experiences from negative experiences
  • Poor socialization

The Role Of Socialization

There is a critical period in a puppy’s development where they need to be exposed to a variety of different things they might encounter in life. Otherwise they can often develop of fear of those things later on. Some dog need to be continually exposed to a variety of things in a positive way to maintain this confidence.

Dogs with poor socialization histories during the critical phase or who have learned fear from a negative experience are not beyond help. Behaviour modification may take longer but it’s possible to make life better for these dogs (and for you!)



We primarily focus on the immediate circumstances of aggression as a way of understanding it. But stress can play a big factor in the development of aggression and we might not even be aware of what is contributing to it, or how we can alleviate it. In some cases basic – and simple – changes can make a big difference. Here are some factors that could be playing a role:

  • What occurs immediately prior to the aggression
  • Social interaction and mental stimulation
  • Stress in the environment (ie. noise, threats, frustrations)
  • Predictability (ie. routines and schedules)
  • Exercise needs
  • Nutrition needs and affects
  • Boredom

What we do to make dog aggression worse

Our intentions are usually good but there is a lot of things we can and often do that a make things worse.

Allowing the aggression to continue to occur

Dogs are not simply misbehaving. Aggression is not just “behavior”, it is a coping response. But each time the aggression occurs, the brain rewires itself to be a little better at making that process occur more efficiently and effectively.

Using training methods that make things worse

In many cases aggression can attract the kind of responses from humans that make the situation worse.  Either we become frustrated or we take on bad advice such as intimidating the dog as a way to try to deal with it. Unfortunately outdated methods that have been popularized by the media can make dogs who are predisposed to aggression worse (see 5 treatment methods to avoid and the world’s worse dog aggression advice).  Dogs don’t choose to be fearful or anxious or frustrated. Check out treatment methods that will help.

Ignoring signs of stress

We miss the signs that we could act on to help our dog avoid unnecessary stress. Behaviors such as turning the dog turning his or her head away, stiffening, licking of the lips, putting the ears back are just a few. These signals are important to learn if we have a reactive, fearful or aggressive dog.

Not meeting needs

These days most of us have a lot going on. Sometimes we don’t always meet the needs of dogs.  Dogs need stimulation, exercise, social experiences, proper diet, a certain amount of freedom in many conditions, routines.  A dog that is left along for long periods of time, is left outside all day on the end a leash, is ignored, is bored, frustrated, etc. is going to have more problems than one whose needs are met.

Not recognizing health concerns

Sudden aggression in dogs might be a result of medical issues that contribute to dog aggression or simple pain or discomfort of any sort.   It is very common for dogs that are seen by a veterinary behaviorist to also have medical conditions as well.  (1)

Your first step should be to see a vet.  However, even when the dog’s aggression is completely a result of pain, it is very likely that you will need to do behavior modification to changer the associations your dog developed while the situation developed.

Assuming that “That’s just the way the dog is”

You should talk to your vet about any unusual behavior, whether it’s repeated paw licking, excessive drinking, barking at nothing, chasing imaginary flies, lying with a head under a seat, etc. In particular, anxiety may manifest in unexpected ways and this may shed some light on your dg’s aggression issues.

In some cases, it may be that it’s just the way they are. Genetically your dog might be predisposed to overreacting or misinterpreting important communication signals.

This does not mean they are beyond help however. There are ways to humanely treat dog aggression just as we would try to help people with mood disorders or behavior challenges.

Next steps for your treating your aggressive dog


Dog aggession is stressful – for your dog and for those around them. To improve it, there are three main areas that dog owners should review to improve the lives of their dogs and those around them.


Avoiding aggression is essential in treating the underlying cause. Don’t get caught up into the trap of thinking that punishment will “change” the behavior. Aggression is at the tail end of the behavior sequence – not at the beginning. Each time the behavior sequence occurs, the brain rewires and it become more likely to be repeated, regardless of punishment.

  • Get further distance from the circumstances and situation that cause the anxiety and aggression – You might be interested in 6 Other ways to keep other away from your dog
  • Teach your dog a variety of commands and cues that can help you navigate situation where you can’t get eneough distance right away and your dog might start feeling anxious
  • Avoid the circumstances and situation that cause anxiety and aggression – see how anxiety is related to aggression. For example, if the dog reacts when pushed off the bed, stop pushing them off the bed for now

Meet Needs

Dogs have a variety of needs – from basic needs for exercise and social interaction to more complex needs for medication. Some needs are general to all dogs, and some very specific to the individual. Anxious dogs in particular are more vulnerable to stress.

Therefor a number of stress reducing strategies should be included to meet the needs of the dog. At a minimum:

  • Consult your veterinarian to rule out any medical causes of aggression.
  • Develop a safe and trusting relationship and environment
  • Ensure your dog’s basic needs are being met adequately. Going above and beyond may actually improve stress and passively improve aggression.

Behavior Modification

Behavior modification can be done both passively and actively. You can change behavior indirectly and/or target behavior modification to particular situation. Either way, the goal is to change behavior by targeting the underlying cause.

This means develop strategies to reduce anxiety, develop better tolerance and better coping skills and create new positive associations:

  • Teach your dog how to relax
  • Develop your dog’s ability to self-control
  • Treat the underlying causes
  • Learn about humane effective treatment methods for more information

You vet may be able to recommend you to a veterinary behaviorist or get a consultation on your behalf.  In less serious cases, a force-free trainer who uses positive methods only, and has a good background in successfully treating aggression may be able to help.

If you want to learn more about treating dog aggression, refer to the  The Dog Aggression System Every Dog Owner Needs e-book. It discusses management strategies, treatment methods, things you can do to modify the dog’s environment that will help, as well as the common traps and pitfalls to steer clear of.


(1) Ilana R Reisner, Frances S Shofer, and Michael L Nance, Behavioral assessment of child‐directed canine aggression, Inj Prev. 2007 Oct; 13(5): 348–351.

(2) Frank D., Aggressive dogs: What questions do we need to ask? Can Vet J. 2013 Jun; 54(6): 554–556.

(3) Overall KL, Clinical Behaviorial Medicine for Small Animals.

(4) Sayaka Arata, Yukari Takeuchi, Mai Inoue, and Yuji MoriReactivity to Stimuli” Is a Temperamental Factor Contributing to Canine Aggression, PLoS One. 2014; 9(6): e100767.

(5) Katriina Tiira and Hannes Lohi, Early Life Experiences and Exercise Associate with Canine Anxieties, PLoS One. 2015; 10(11): e0141907.

(6) Heidi G. Parker, Abigail L. Shearin, and Elaine A. Ostrander,  Man’s Best Friend Becomes Biology’s Best in Show: Genome Analyses in the Domestic DogAnnu Rev Genet. 2010; 44: 309–336.

(7) Christine R. Harris and Caroline Prouvost, Jealousy in Dogs, PLoS One. 2014; 9(7): e94597.

(8) Daniel Mills, Christos Karagiannis, Helen Zulch, Stress—Its Effects on Health and Behavior: A Guide for Practitioners, Vet Clin Small Anim 44 (2014) 525 541,

(9) J.M. Koolhaasa,*, S.M. Korteb , S.F. De Boera , B.J. Van Der Vegta , C.G. Van Reenenb , H. Hopsterb , I.C. De Jonga,b, M.A.W. Ruisb , H.J. Blokhuisb, Coping styles in animals: current status in behavior and stress-physiology, Neuroscience and Biobehavioral Reviews 23 (1999) 925–935, Retrieved Mar 1, 2023 from

(10) Alexa H. Veenema Inga D. Neumann, Neurobiological Mechanisms of Aggression and Stress Coping: A Comparative Study in Mouse and Rat Selection Lines, Brain Behav Evol 2007;70:274–285,


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