It is the number one concern of dog guardians. Around 90% of the home visits that I do involve some form of aggression. A lack of understanding and knowledge on the subject can increase the risk of escalation. I believe many incidents could be prevented with the right type of education. I am hoping this article offers some valuable insights.

Aggressive behavior is not only an emotional expression, it is also an important form of communication, usually directed at a ‘trigger’. It can serve many functions, i.e. trying to keep a threat at a distance, trying to keep access to important resources, trying to stop interactions or trying to catch and kill prey.

When aggression is involved, I strongly advise dog guardians to consult a certified professional who can make a reliable behavioral analysis in order to find out what is causing the behavior (what is the function, which emotions are driving the behavior).

A professional will not only focus on the context and the behavior in itself, but also dig deep into the background of the dog (physical health, medical history, genetics, breed, learning history, living environment, daily routines, etc..).

Dogs never behave aggressively ‘out of the blue’. There is always an underlying cause that needs to be carefully assessed in order to minimize risks and work on prevention and behavior change.

The ladder of aggression

In 2001 Dr. Kendal Shepherd (a certified veterinary surgeon and animal behaviorist from the UK who is an expert on aggression) created a depiction of the gestures and body language dogs can show in response to escalating stress and threat. From mild stress/discomfort signals to severe aggression (biting). An illustrated version was first published in the BSAVA Manual of Canine and Feline behavior in 2002.

This is an extremely valuable and important guide (click here to visit her website) which can help many dog guardians and professionals to recognize and minimize the risk of further escalation by responding to these signals appropriately: stop the interaction, increase distance. 

By showing these signals the dog is trying to de-escalate the interaction.

It is important to note that each dog is a unique individual and many factors including breed and learning history can influence the signals that dogs give before escalation occurs. In example, a dog who has previously been punished for growling or barking, may skip this form of communication and attack without such clear noticeable warning signals. Another thing to note, is that not all signals that are related to stress or discomfort are a predecessor to aggression. The ladder of aggression is a valuable guideline, but it is not a formula set in stone.

The influence of stress

Stress, be it positive (sometimes called ‘arousal’) or negative (distress), can have a strong influence on the risk of occurrence and the intensity of aggressive responses. A high stress level, causes the dog’s nervous system to become more sensitive and to respond faster and, in many cases, more intense/severe. Stress can increase the risk for emotionally ‘explosive’ behavior such as aggression. During a stress response, hormones are released into the blood stream and it can take hours for them to be broken down by the body in order to restore it’s normal balance (homeostasis). If dogs are not given enough time to recover from stressful experiences, stress can build up inside the body, keeping the nervous system on ‘high alert’. This can not only impact the health of the dog (i.e. damage the immune system), but also the sensitivity (and reactivity levels) of the dog.

This is why, when aggression is involved, it is helpful to try to reduce stress in the dog body by changing daily routines/exposures/activities, by offering a healthy amount of rest and by stimulating activities that can have a calming effect (like sniffing, seeking and finding scattered treats, chewing or food puzzles that suit the individual needs).

Pain driven aggression

The physical health of a dog needs to be checked, because physical discomfort and pain can drive aggressive behavior with a clear function: stopping (further) discomfort/damage to the body. Discomfort also increases stress levels in the body, increasing the risk for 'outbursts'.

Good to know: pain driven aggression does not always have to be caused by medical conditions. The anticipation of pain or discomfort can also 'trigger' healthy dogs to respond aggressively. In example, if a dog guardian is using a tool that causes physical discomfort, such as a pinch collar or a choke chain, dogs can develop aggressive responses when they anticipate pain (i.e. barking and lunging while on leash when these tools are being used).

Dog guardians who physically hurt dogs by grabbing a dog’s scruff, poking, kicking or slapping can develop strong dog-to-human aggression cases, as harsh physical approaches can teach dogs that humans (and movement of hands or legs) can cause physical discomfort.

Fear driven aggression

In my experience this is by far the most common underlying cause for aggression in dogs. The function of fear driven aggression is to make threats increase distance for self protection.

A lack of socialization or a negative learning history can increase the risk for fear driven aggression in dogs.

A very common example is fear driven aggression during vet visits which may have involved negative learning experiences in the past. Dogs can quickly adapt their behavior and learn that aggression can stop interactions which they find threatening.

Dog body language is only ONE piece of a puzzle

It is important to be aware that dog body language is only one piece of the puzzle when assessing a dog’s emotional state. A dog with a high posture (ears forward, tail upward) can be experiencing fear and a dog in a low posture (ears backwards, tail tucked) can be experiencing pleasure. It is VERY valuable to understand this, as this is still a greatly misunderstood subject in the dog world.

The posture and body language of a dog can give hints about the intention of a dog. A forward/upward based posture shows a willingness to interact (active aggression). A backward/downward based posture shows a willingness to avoid interaction (ritualised aggression).

Frustration driven aggression

The goal and function of frustration driven aggression can be to keep or gain access to resources that are of value to the dog or to enforce a dog's expectations. Frustration can arise when a dog wants to achieve something that is not possible due to restricted movement (i.e. being on leash or tied) or by barriers.  A lack of predictability or circumstances in which the expectations of a dog are not being met (i.e. during training with poor timing, lack of reinforcement or unclear instructions) can also result in frustration.

It can be valuable to understand that not all forms of aggression that occur around resources are caused by frustration. In my experience, when humans are involved, the chances are higher that it's fear driven aggression, where the dog feels threatened around resources after negative learning experiences (i.e. dog guardians who have physically held down and opened the mouth of a young puppy who had something in it’s mouth). These dogs are not protecting their resource, but themselves, which is a big difference.

If the social bond has not been damaged in any way, then frustration may very well be driving aggression around resources.

The term ‘resource guarding’ says something about the behavior and the context, but the underlying emotions can differ per dog and per situation.

Prey aggression - driven by pleasure/seeking

Prey aggression is a very concentrated, quiet and extremely intense form of instinctive (high intrinsic motivation) aggression aimed at catching and killing prey to consume. Some argue that this is a behavior sequence/pattern which has been so strongly stored in the brain, that the emotional component is low or may even be lacking. They prefer to call it prey behavior instead of aggression and there may be good sense in this. Through selective breeding, humans have influenced the prey drive and prey behavior sequence of dogs, resulting in differences within many dog breeds (i.e. border collies have been bred not to catch and kill, but only to stalk and influence the movements of prey).

Because this type of aggression often involves moving triggers, many people misuse this term when dogs chase cars or bikes while barking loudly. In most cases, these dogs are not hunting. If they were, they would be quiet and concentrated. When dogs chase bikes while barking loudly, it is more likely they are doing so out of fear or frustration, than out of seeking prey.

Redirected aggression

This is a form of aggression that can occur when a dog redirects it’s aggression onto something or someone that is closer to it while the aggression was actually triggered and directed at something further away. In example, a dog who explodes when seeing a trigger pass by at a distance, suddenly turns around and bites the leash, it’s owner or another dog family member who happens to be close. In these cases, the aggression is not triggered by the 'receiver', but by something that was out of reach. An example: two dogs are in a fenced yard. A trigger passes by outside the fence and one of the dogs suddenly attacks the other dog in the yard. Family members may report that these two dogs seem to be fighting over something in the yard when it is actually a form of redirected aggression of one of the dogs, triggered by something outside the yard.

Pathological aggression (disease)/impulsive aggression

This is a rare type of aggression which is highly unpredictable and extremely impulsive, occurring completely at random (there are no clear triggers or context). A dysfunctional balance of hormones and/or neurotransmitters could be a cause, amongst other medical issues. For proper treatment, veterinary behaviorists are a necessity, as in most cases behavioral medication will be needed.

Consulting a veterinary behaviorists may always be a wise choice when it comes to aggression cases, as their expertise may offer forms of help, insights and medication options which could be of great benefit to a dog’s welfare.

© LotsDogs | Written by Liselot Boersma, dog welfare & behavior consultant (PgDip CABW) and owner of LotsDogs, september 2018; translated in 2020. Copy paste of images or text is forbidden. Sharing the URL of this website is very much appreciated. Many thanks in advance.


  • K. L. C. Sueda, R. Malamed, Canine Aggression Toward People: A Guide For Practitioners. Veterinary Clinics of North America: Small Animal Practice, 2014
  • K. Shepherd, Ladder of aggression. Horowitz D, Mills D.S., BSAVA Manual of Canine and Feline Behavioural Medicine, 2009
  • Mills, D., Braem Dube, M., Zulch, H. (2013). Stress and Pheromonatherapy in Small Animal Clinical Behaviour.

Based in the Netherlands, Westbeemster 


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Liselot Boersma


Dog Welfare & Behaviour consultant



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