27 August 2011

Fighting talk

Fighting between dogs who share the same household isn’t a behaviour problem that I help dog owners with on a daily basis, but it is an issue that I receive many calls about that do not result in bookings for 1-2-1 behaviour consultations.  I suspect that this is because when I tell people how much effort may be involved in resolving the problem, they have second thoughts.  More often than not, the response is "we’ll think about it" – and then I never hear from them again. 

I’m not sure what people expect me to tell them when they call – maybe that I have a magic wand that I can wave about and make the problem go away, or that I can show them one simple technique to stop the aggression and prevent it from ever coming back.  The truth is that resident dog-dog aggression is often a serious and complex behaviour issue, which requires a dedicated and concerted effort from owners in order to resolve the problem, often requiring changes to be made to the home environment, daily routines and personal habits.  I think that the route to resolution is just too much work for some people to want to take on.

Aggression between dogs who share the same household frequently results in more serious injuries than does aggression between dogs who do not live together.  Research shows that the on the whole, aggressive outbursts between resident dogs are usually the result of a progression of events and are initiated by the youngest and most recently obtained member of the group.   This is particularly so when the dogs are of the same sex, and statistically, the incidence of fighting between resident females is higher than between resident males, with fighting between spayed females being more common and injurious than between entire females.  This may be due to the effect that the removal of the female reproductive hormones has on the activity and production of other hormones such as arginine vasopressin (AVP), serotonin and thyroxin, whose levels in the brain can directly influence aggressive arousal in response to competition or threat.  Fighting between entire females is commonly due to fluctuating hormone levels during the few weeks of the reproductively receptive time of a bitch’s season or ‘heat’, when resident bitches may compete for breeding rights.  When the bitches are not in season, there is often no tension between them at all.  With male dogs who share the same household, hormone activity may play a part too, with the production and activity of testosterone, AVP, serotonin and thyroxin being possible contributors to aggressive arousal under the influence of threat or competition for resources.  Stress, and in particular circulating levels of the hormone, cortisol, also plays a big part in the regulation of emotional thresholds and tolerance towards social competition. 

Hormonal influences aside, there are three basic forms of aggressive interaction between dogs who share the same living space:
  1. Aggressive play.  Includes many of the behavioural components observed in actual fighting, but without the intention to subdue or injure.
  2. Actual dominance fighting.   Intended to subordinate an opponent but without injury.
  3. Overt and damaging fighting.  Intended both to subdue and injure an opponent.
All three forms of fighting are involved in the establishment and maintenance of relative social dominance between dogs who share the same living space.  Free-roaming feral and semi-feral dogs on the other hand do not form hierarchical relations with one another.  The establishment of dominance hierarchies only occurs between captive dogs who are forced to share the same home territory with one another and when space and other resources are limited and controlled, but that said, most dogs who live together establish remarkably stable relationships, and the majority test and maintain the status quo through play.

The two dogs in the above-left picture look like they are about to kill one another, but when looked at again in context (below-right), you can see that there is much more going on than at first glance, and that this frightening display of ‘weaponry’ is actually a mix of play aggression and friendly competition for a ‘resource’ (i.e. the ball) …

The dogs’ body language and facial expressions say it all.  The dog on the left is leaning his body backwards – if he were more serious about his intentions, he would be leaning forward.  The dog on the right seems relaxed about his brother's ‘threat’ and remains lying down.  Note that both dogs are avoiding direct eye contact too. 

Although playful competition around resources may always exist between these two boys, because both naturally tend towards ‘bluffing’, it is highly unlikely that this kind of behaviour will escalate into a problem.  It's important though to be able to recognise the difference between what is normal and harmless play behaviour, and aggressive behaviour that could develop into a problem. 

The causes for frequent or injurious aggression between resident dogs are complicated and varied, and to a certain degree, speculative.  Sometimes it is difficult to make a clear distinction between offensive fighting and other forms of aggression such as the dog who tends towards self-protective, defensive aggression when in a tight spot.  Sometimes the fights are clearly one-sided, with one dog being the instigator and attacker, and the other, the unfortunate ‘victim’.  Access points such as doorways and stairwells, and sudden changes in social dynamic such as the moment a person enters or leaves a room, are common triggers for fights because these relate directly to the control of movement, space and the enforcement of social dominance. 

Fighting between resident dogs rarely occurs when the owner is absent, which suggests that the presence of the owner is a primary trigger for resident dog-dog aggression.  Owner ‘interference’ in the form of favouring the ‘underdog’ appears to play a huge part in de-stabilising dominance relations.  There are several theoretical reasons as to why this should happen but none make total sense to me, so in my opinion, allowing fights to occur but then breaking them up before they are allowed to run their natural course in combination with favouring either dog simply increases the competition between the dogs for owner attention and affection.  Increasing competition narrows the relative social status between the dogs, which in turn drives the need to establish social dominance, causing aggression to escalate and hostilities to remain at the ready, with the potential for a fight breaking out at any time.  With all this in mind, the resolution lies directly with the owner – not as a dominator, side-taker, referee, or a resource to be competed for, but as the driving force behind a fundamental shift in the relationship between the dogs, and each dog's relationship with the owner.    


Trying to break up a fight by grabbing dogs with your hands or getting between them is a dangerous activity and runs a very real risk of getting bitten by accident or by redirection.  Your close proximity may even cause the dogs to increase their efforts to overthrow one another.  Similarly, hitting, kicking or causing pain to the dogs in other ways will likely sustain or increase aggressive arousal, not diminish it.

Preventing fights is always preferable to breaking them up and with spot on management this is 100% doable, but in case a fight does break out and needs to be stopped, there are a number of ways to prepare for and go about it:

  • A water-filled soda siphon in every room.  If a fight breaks out, a few rapid squirts INTO the attacker’s mouth can be enough to cause it to let go.  Never use the siphon to ‘prevent’ a fight from occurring.
  • A bath towel or blanket in every room.  If a fight breaks out, take the towel or blanket and throw it over the dogs’ heads before separating them.
  • Blasting an air-horn or safety whistle, or banging a saucepan or metal tea-tray close to the dogs’ heads can be enough to startle the dogs and cause them to let go of one another.  Only use this method if both dogs do not normally show fear of loud or sudden noises – the idea is to invoke the startle reflex and to interrupt the dogs, not to terrify them.
  • Lifting the hind legs/rear end of the attacker until it lets go of the other dog, who will then usually crawl away. 
  • Both dogs wear a trailing lead at all times.  This is by far the easiest way to separate two dogs, particularly if you are on your own.  If there are two people, each lead can be taken up by hand.  If you are on your own, take up the end of one lead and move/pull the dogs until you can tie-off the lead to something secure and solid.  Take up the end of the other lead and pull steadily – no jerking – until the dogs release their hold on one another.
  • If one dog is holding the other in a suffocation bite (around the throat) or by the back of the neck, slide a sturdy pole (e.g. a walking cane or broom handle) between the collar of the biting dog and the back of its neck and with the collar resting at the centre of the pole, use the pole as a two-ended handle to twist the collar until it tightens sufficiently to cause the dog to pass out and so release its jaws.

I recently read an article on how to solve resident dog-dog aggression that recommended the use of Gentle Leader headcollars to control the dogs.  PLEASE DO NOT DO THIS!  The Gentle Leader is a muzzle-clamping headcollar that when pulled (or when the dog pulls) clamps the dog’s jaws shut.  If either dog is already biting the other, any attempt to pull the biting dog away will result in him being unable to release his hold on the other dog.   If you absolutely have to use a headcollar to control either dog (i.e. if they are large, powerful dogs), you must ensure that it is a fixed-action, non-muzzle-clamping type, e.g. the noseband DOES NOT TIGHTEN around the dogs muzzle when the headcollar is used to turn the dog’s head towards you, and provides plenty of room for the dog to freely open its jaws.  I do not recommend or advocate the use of muzzle-clamping headcollars such as Gentle Leader, Halti, Gencon, Canny Collar at any time or for any purpose.  There simply is no need, when non-muzzle-clamping headcollars are readily available, e.g. Dogmatic, or the Pets at Home own brand (see below ...)

In the above picture, Beau is wearing the Pets at Home 'control headcollar'.  As you can see, the noseband provides plenty of room for him to open his mouth, and there are no moving parts to the headcollar. 


The goal of behaviour therapy should be to take control and prevent fights, not to referee or direct the ongoing drama and tension between the dogs – the idea being to end conflict, not to explore dominance and pack theories!  The focus therefore for resolving resident dog-dog aggression should not be about reinforcing relative dominant/subordinate status between the dogs or refereeing the dogs’ social interactions, but on conflict-prevention, reward-based impulse control and social tolerance training, and the dogs’ owner becoming a source of social control and order.  The human influence over each dog's behaviour must be stronger than the dogs’ influence over one another's behaviour, and this can be achieved by way of instigating and reinforcing positive, non-competitive social interactions.  By changing the relationship dynamic, strong leader-follower relationship pairs are encouraged between each dog and the owner, as opposed to the reactive dog-dog dynamic where the owner, access points, mealtimes, resting areas, visitors, etc, are primary sources for conflict and competitive arousal.

General stress reduction is also important.  Correct diet and exercise, mental stimulation, massage, quality rest and sleep, and complimentary therapies such as flower essences, herbal remedies and acupuncture, are all areas that can bring overall benefit to the dogs' well-being and so help to lower tension in the home.


All triggers must be identified and steps taken to ensure that the dogs are unable to make threatening or aggressive contact with one another in the presence of those triggers:

  • If you coming home is a trigger, ensure that the dogs are separated either in crates or different rooms before you leave them alone.  Upon your return, greet each dog separately before bringing the dogs together (trailing leads for safety if necessary) for a few minutes of impulse control and social tolerance training to reinforce your position as the source of social order.
  • If the arrival of visitors is a trigger, change the dogs’ focus to something else, e.g. the expectation of a food tit-bit, in order to prevent them from becoming excited and emotional, and to create an alternative and positive/rewarding association with the change in social dynamic.  Maintain social order and keep the dogs apart with basic obedience commands such as ‘back’ and ‘wait’.
  • If doorways are a trigger, allowing one dog access (on a first come, first serve basis, you do not decide who goes first) whilst requiring the other dog to ‘wait’ (in return for a food tit-bit if necessary) will help to prevent conflict and competitive arousal.
  • If mealtimes are a trigger, separate the dogs while their food is being prepared and when feeding them but do not exclude either or both of them – use child/stair gates, leash and tether the dogs away from one another, or put the dogs in crates to keep them apart.
  • If beds, sofas/chairs or other favoured resting places are a trigger, if one in particular, either remove it or block the dogs’ access to it.  Ensure that both/all dogs have somewhere comfortable to rest and that there is plenty of space between resting areas.  Do not place resting areas near other potential triggers for conflict/competition, e.g. next to water bowls, doorways/stairwells, kitchen food preparation area, ‘your’ chair, etc.
  • If other resources such as chews, bones and toys are a trigger, remove them and only give them to the dogs under close supervision – with both dogs leashed and tethered away from one another if necessary, but in the same room, and with you present.  Alternatively, if you cannot supervise the dogs, separate them into different rooms if they are to have chews, bones or toys.

Creating physical barriers throughout the home territory to keep the dogs apart when owner attention and supervision cannot be fully engaged is an important aspect of fight prevention.  Doors, gates and crates can all be utilised when needed. 

Muzzle-training both dogs and having one or both muzzled when they are together is an often over-looked management tool – it won’t necessarily prevent a fight from breaking out, but if you cannot be certain of the dogs’ behaviour in any given trigger situation, it will at least prevent bite injuries.  Muzzling the dogs is not a substitute for training, and training must take place alongside muzzling.  Even though the dogs cannot bite one another whilst wearing muzzles, the emphasis should still remain on conflict prevention.  The muzzle is merely a safeguard against injuries – and if your management is spot on, injuries shouldn’t have the potential to occur. 

I prefer fabric muzzles as these are more comfortable for the dog to wear than are basket-type muzzles.  The nylon Mikki muzzle (pictured right) is a good choice as it allows the dog just enough room to pant and drink (and to be fed treats during training) and comes in a range of sizes to fit long and short-nosed breeds.

If you are thinking about muzzling you dog for any reason, you must desensitise him to the muzzle before making him wear it in a potentially stressful situation.  As all dogs have the potential to bite, training any dog to wear a muzzle is good practice.      


Encouraging impulse control and social tolerance through reward-based training is a pivotal part of behaviour therapy when treating any aggression problem.  Intensive ‘wait’ training and delaying of gratification builds a desire around waiting and taking turns to obtain attention, affection, and other rewards by way of following rules and owner direction.  Working both dogs together (under restraint or restricted movement if necessary and for safety) focusing on simple reward-based obedience training, for example, instructing one dog to wait/sit/down at a distance while the other dog receives friendly interaction (fuss, praise, play with a toy), and so long as the waiting dog controls the impulse to move, tossing it food tit-bits (eating allows for the release of oxytocin, the ‘bonding’ hormone) before swapping positions (owner moves, dogs stay in place) and repeating the activity with the other dog.  The focus of this area of training is to create impulse control (waiting and taking turns), social tolerance (of the other dog receiving owner attention), positive association with the other dog receiving owner attention (via food tit-bits), and to teach the dogs to yield to the owner’s control of space, movement and social interactions at all times.  The impulse control aspect of training also enforces strong dominant-subordinate relationships between each dog and the owner, which diminishes the dogs’ need to enforce social dominance over one another.


Recreational activities are also important in the creation and maintenance of harmonious relations between resident dogs.

Outside of the home and away from sources of competition and conflict, many resident aggressors get along without so much as a sideways snarl at one another.

 Non-competitive activities that both dogs can enjoy together in the presence of the owner should therefore be encouraged, for example, foraging for treats, walking or jogging with the owner, exploring a new piece of ground together, etc.


Allowing each dog to individually engage in activities that utilise their particular strengths and interests can also be helpful in reducing resident dog-dog aggression on a number of levels. 

Activities such as agility, working trials and canny-cross can provide valuable exercise, mental stimulation, beneficial neuro-hormone activity in the brain and purposeful focus, as well as relieving pent-up tension and energies, and utilising the leader-follower dimension of the human-canine bond.  Activities that utilise the prey sequence of behaviours such as herding and retrieval and scent work fulfil the dog on a fundamental and instinctive level.


Diet is also an important area to consider when treating any aggression issue.   Feeding a natural, species-appropriate raw diet is always preferable over feeding a processed diet, but if you choose to feed a processed diet, pick a non-cereal/grain based formula.  Avoid foods that contain artificial additives, in particular artificial colours (Bakers Complete and Pedigree Large Breed kibbles to name but two).  Including omega 3 every day, and if not feeding a lamb or turkey based raw food diet, the inclusion of a tryptophan supplement such as Canovel/Catovel Calmdown will boost serotonin levels in the brain, which makes for a calmer, less impulsive, more relaxed and tolerant dog.  For more information on how diet can be used to affect behaviour, see my Mood Food article.


My advice, if you have an existing resident dog-dog aggression issue, is to employ the help of a reputable dog behaviour psychologist.  He or she will likely refer you back to your vet in order for the dog to have an external physical examination to check for pain (eyes, ears, teeth, joints, etc) and to carry out a complete blood count, chemistry panels and urinalysis to check for possible medical causes and hormone/chemical imbalances for your dog’s aggressive behaviour.  Your dog behaviour psychologist should then visit you in your home to assess the dogs in their normal environment, and to discuss with you the problem in depth before advising you on the best way to control your dogs’ movement around the home and how to manage trigger situations, and demonstrating with your dogs the basics of reward-based impulse control and social tolerance training.  He or she should then provide you with a behaviour modification and training plan that is uniquely tailored to your individual situation and your dogs, and backed by ongoing support. 

Be prepared for the expense that may be involved if veterinary treatment is required, if repeat visits from your dog behaviour psychologist are needed and equipment needs to be bought, and if dietary changes are necessary.  Be prepared for the time that you will need to find for training.  Be prepared to make some simple modifications to your home by way of dog gates, crates and tie-out points.  Be prepared to change how you interact with your dogs – no taking sides, no favouritism when both are together.  Be prepared to put in whatever effort is needed to reach a resolution.  There is no magic wand.  No simple technique.  But there is a very important key – you. 


  1. I cannot even tell you how much I appreciate this article. It came at a perfect time because we are dealing with the damaging type of fighting between our two spayed females. I am going to follow all of your advice and work through this. Thank you!!!

  2. Wow, so pleased I wrote it, I deliberated whether or not to as it is such a difficult subject to write a 'general' article about. Wishing you every success with resolving your girls' fighting and please feel free to drop me a line if you feel that you could benefit from some extra guidance (click on the link below to my website and use the email address on the contact and service page). And do book your girls in for veterinary appointments to check that their physical and medical health is in good order - ensure that the blood work includes a full thyroid panel.

  3. Also writing a note of thanks. My neutered males had a damaging fight tonight. I will be changing my ways here on out. Just at the beginning of our "journey" for a safe and peaceful home enviroment.


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