Aggressive behaviour

Aggressive behaviour expresses the individual’s feeling about the current situation they’re in. Discover more.

Trailhound dog running to camera with a toy in their mouth, in a field on a sunny day.

The term aggression is value-laden and inconsistently defined. It is generally used to describe a collection of behaviours in which there is a perceived risk of harm from one individual to another, such as lunging, growling, and biting.

However, aggressive behaviour has a potential biological cost to the aggressor as it risks potential injury and damage to relationships upon which the individual might depend.

Therefore, unless a dog has learned that aggressive behaviour is particularly successful within a specific context, they might initially attempt to diffuse a perceived threatening situation with avoidance, inhibition, or appeasement/affiliative behaviour.

Aggressive behaviour expresses the individual’s feeling about the current situation they’re in. It is usually, but not always, emotional for the signaller, as well as for the receiver or observer. Because behaviour is itself so individual-specific and influenced by so many factors, two dogs might respond very differently within the same situation.


Fear helpfully enables an individual to anticipate potentially hazardous and/or painful stimuli, motivating avoidance behaviour. Consequently, an individual can become sensitised to situations in which they have been overwhelmingly or repeatedly traumatised.

For example, a dog might develop sound sensitivity upon hearing unexpected and unexplained loud noises – such as fireworks – and might try to hide away to avoid them.

Where an individual is unable to avoid a stimulus perceived as fearful, however, they might try to repel the stimulus by behaving aggressively. The inability to avoid a fearful situation can be a reason for aggressive behaviour displayed within a veterinary context.


Can a dog be angry? They can certainly be frustrated, which is closely linked with anger.

Dogs have brain systems that generate highly irritated behaviours and negative emotional feelings which have been termed ‘rage’. However, exactly how dogs experience this feeling is still being explored.

Aggressive behaviour associated with frustration is commonly observed in individuals within a variety of contexts, including:

  • restriction of physical activity or ability to achieve their desired goal
  • irritation to the body (either internally or externally provoked/elicited)
  • sudden withdrawal of anticipated rewards 
  • the effect of physical and emotional needs – particularly where these are unmet, such as hunger arising from food deprivation, as well as thirst and sexual frustration.

Aggressive behaviour can provide immediate relief by effectively reducing distress and any associated pain. For example, an arthritic dog being held tightly or in an uncomfortable position for a blood sample might respond aggressively, perhaps growling or even snapping.

The pain associated with the restraint is alleviated when the person holding them lets go. This can lead to an individual viewing aggression as a successful behavioural strategy for times when they feel threatened.

Learned or unemotional aggressive behaviour

Aggressive behaviour is usually functional and serves a purpose for the individual. It is possible, however, for aggressive behaviour to become a habitual response to a stimulus if the response results in a predictable outcome for the dog.

The aggressive response may well have been emotionally driven initially, but over time the emotional component of the behaviour has reduced until what manifests is a learnt habitual response to the stimulus.

For example, a dog who initially lunged, growled, and then snapped when touched by a vet in the consult room, due to pain, might learn that this works well to keep vets safely at bay. The dog now has a behavioural strategy that can give them confidence when vets approach in the consult room.

The aggressive behaviour of lunging, growling, and snapping is performed without any emotional component, but instead as a learned and now habitual response within this setting.

Emotional conflict

It is important to remember that several emotions may be expressed, to varying degrees, at the same time. For example, a dog who is frightened about being in the consultation area might also be frustrated that they are contained, restrained on a lead, and unable to escape to a position of perceived safety.

Another common example is a dog who would really like to eat the treat offered to them but is at the same time worried about approaching the person who is offering it. Especially if it is someone unfamiliar and in an unusual or worrying place, such as the veterinary team in the clinic.

This might be described as an approach-avoidance conflict, with a dog hesitating over a choice that could have both positive and negative effects, or between two equally desirable options presented simultaneously.

The function of aggressive behaviour

Understanding a dog’s expectations from their aggressive behaviour can help one respond appropriately. Most aggressive behaviour aims to increase the distance between the dog and the stimulus they perceive as threatening or feel uncomfortable about. This happens particularly when other distance-increasing options, such as avoidance or escape, are limited.

Typical goals of aggressive behaviour include:

  • self-defence from an actual or perceived threat, or because of the presence of physical or emotional distress
  • protection of possession of anything that the individual values
  • to feel in control over a situation where there is competition or conflict.

However, an exception to this would be where aggressive behaviour is a result of a redirected act due to frustration, where the recipient of the action is not the trigger of the response.

For example, if a dog wishes to positively interact with another dog but is prevented from doing so by being on a lead, the frustration created by the barrier of the lead might manifest as aggressive behaviour and the dog might lunge, growl and bark towards the other dog.

They might even grab hold of the lead or their owner’s clothing and rag or bite at it repeatedly, redirecting their frustration in this way. Hence why it’s vital to always assess aggressive behaviour within the context in which it occurs.

Responding to aggressive behaviour in the veterinary clinic

Aggressive behaviour such as displaying teeth or growling, even snapping – however low in frequency – must never be punished by telling a dog off, or by using physical force or interaction to try to prevent them aggressing.

It’s important to remember that aggressive behaviour generally signifies escalating nervousness and/or fear and punishing such behaviour will only add to those feelings.

Punishment is likely to make a dog feel confused about people who generally behave pleasantly around them and yet are suddenly behaving in an unpleasant, potentially physically or emotionally painful way.

It can damage the human-dog relationship and make a dog feel anxious about how people might behave in future, particularly in the context within which the punishment happened.

Punishment might also result in the individual suppressing those behaviours in the future as they were unsuccessful/inconsequential.

The dog is essentially learning that relatively low-level attempts to communicate discomfort, such as teeth-baring, will be ignored, which may encourage them to display more overtly aggressive behaviours in the future.

For example, a dog may learn that snapping is a much more immediately successful alternative. This illustrates the importance of remaining fully vigilant when handling patients, as it would be easy to overlook the more subtle warning signals put out by dogs with limited behavioural choice.

Signs of escalating aggressiveness must be taken extremely seriously, and you may need to reconsider the timing and urgency of the examination/medical procedure. The acute stress response is relatively short-lived, so simply stopping at that moment allows the dog to feel safer in the understanding that their communication has been successfully understood, with no need to escalate further.

Where it is not possible to complete your clinical examination or investigations due to risks to staff and/or owner and patient safety, there are several options for consideration depending on available resources, listed below.

  • Using trial therapies based on reported history – including analgesia trials
  • Chemical restraint and/or the use of ‘pre-event medication’ to facilitate clinical examination/diagnostic intervention/treatment
  • Commencing muzzle-training in conjunction with handling programmes to introduce them with a positive and enjoyable association. Once the dog learns to feel differently about the veterinary environment the appointment can be rescheduled
  • Asking owners for photos or video evidence – for example, of specific body parts or limb movements – to support history-taking (as long as the dog is comfortable being photographed by their owner at close range)
  • Considering a home visit to remove any anxiety arising from the veterinary environment itself.

The use of muzzles

A muzzle does not change a dog’s emotional experience, it merely protects the handler and facilitates a specific, required procedure such as venepuncture for blood sampling. Therefore, when choosing to use a muzzle, the consequences for the dog should always be considered.

If it is necessary to perform an examination and/or intervention with a dog muzzled, one should take steps to mitigate the risk of the dog forming a negative association with muzzling by undertaking the steps below.

  • Perform incremental handling as a standard approach even though the dog is muzzled. This provides the dog with breathing space and allows the clinician to observe their response
  • Recommend that the owner commences/continues muzzle training, with an alternative style of muzzle, within the home
  • Consider a referral to a behaviourist if the dog shows severe difficulty being muzzled – or at the owner’s request.

Recording aggressive behaviour

Creating a reliable account of a dog’s responses to handling and treatment interventions can be a helpful aid in planning their next visit to the clinic, for the benefit of the patient, their owner, and clinical staff. Where aggressive behaviour has been displayed, a standard approach to record-keeping can be implemented.

It would need to be applied consistently across the clinical team and would benefit from including the following elements:

Descriptions of observed behaviour without inference to motivation or underpinning emotion. For example:

  • stiffening up, staring
  • growing
  • snapping
  • biting
  • turning away
  • leaning away
  • lip-smacking.

Contextual descriptors to include:

  • physical location where the aggressive behaviour was displayed
  • what was happening at the time the aggressive behaviour was displayed
  • the response to the aggressive behaviour from those present
  • what worked well to help the patient and what didn’t
  • how the situation was resolved and/or the plan made to continue helping the patient.


  • Ferguson, C.J., & Beaver, K.M. (2009). Natural born killers: The genetic origins of extreme violence. Aggression and Violent Behaviour, 14(5), pp286-294
  • O’Neill, D.G., Church, D.B., McGreevy, P.D., Thomson, P.C., & Brodbelt, D.C. (2013). Longevity and mortality of owned dogs in England. The Veterinary Journal, 198(3), 638-643
  • Francis, D.D., Diorio, J., Plotsky, P.M., & Meaney, M.J. (2002). Environmental enrichment reverses the effects of maternal separation on stress reactivity. Journal of Neuroscience, 22: pp7840-7843
  • Kis, A., Szakadát, S., Gácsi, M. et al. The interrelated effect of sleep and learning in dogs (Canis familiaris); an EEG and behavioural study. Sci Rep 7, 41873 (2017).

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Disclaimer notice: The advice given on this website [in these materials] is intended for your general information only and should not be relied upon as specific advice for any veterinary practice or clinic. Each veterinary practice or clinic will be unique in its physical environment and each dog attending the veterinary practice or clinic will have specific needs and requirements, which the veterinary practice or clinic is solely responsible for. Unless prohibited by law, Dogs Trust and the British Veterinary Behaviour Association do not accept liability to any person veterinary practice or clinic relating to the use of this information.

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