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Canine Aggression Part 4: Fear and Types


When a dog experiences fear, the sympathetic nervous system (one branch of the autonomic nervous system that controls all involuntary responses in the body) is activated as it is responsible for the fight or flight response. Survival mode is triggered, and fear responses begin automatically. Glucose is released into the bloodstream by the liver to provide the body with extra energy should the need to run arise. Adrenaline production increases and blood flow is redistributed throughout the body. The pupils of the eye will dilate and the bronchioles on the lungs will dilate in order to increase the capacity of the lungs. Fear aggressive behaviour if often a by-product of the fear response in the body and the dog is not under control of any of it. They are unable to take in new information when in this state and require help in returning to a calm state where training and management of behaviour can be more effective.

If we know what normal behaviour looks like in our dogs when they are calm and happy, and are aware of common behaviours that are shown in times of stress, then we can be better equipped to help them in situations where they become uncomfortable and work to prevent an escalated response. When a dog is stressed, they may shed excessively due to an increase of cortisol (the stress hormone) in the blood. They may lick their lips or nose, pant or pace/change positions frequently. A dog may yawn (a wide/open yawn) to release tension in the facial muscles, or do a quick, full body shake. Displacement behaviours such as sniffing, scratching in place of a requested behaviour may also be something that a dog experience stress will resort to. An often overlooked and misinterpreted sign of stress is the dog who is laying down quietly, not responding. Rather than a good behaviour, this can be a sign of total overwhelm and mental shut down. It is important to consider the context in which these behaviours may be being seen…hot dogs will pant, wet dogs will shake and a dog who just ate peanut butter will probably lick it’s lips.

Frightened dogs will do their best to communicate how they are feeling in sometimes very subtle ways before it appears that a behaviour has gotten out of hand. Yawning and shaking are ways that a scared dog may try to relieve stress if they are not in any immediate danger. If a perceived threat is approaching, a scared dog may exhibit appeasement gestures such as lip licking, avoiding eye contact and lowering their head to try to indicate that they are not a threat. Sometimes seeking guidance from their human by engaging in height seeking behaviour is a way that scared dogs close to their threshold try to get away from a fearful situation. These dogs are often stiff and tense in their posture. Barking, growling, lunging are often a last resort for scared dogs, and they will employ these behaviours if none of the others have worked to get rid of the threat. Should a bite occur as a result of a build up of fear, the bite is often shallow and quick and not intended to do any major harm. The dog simply wants the threat to go away.

The Canine Ladder of Aggression

The canine ladder of aggression was developed by Dr. Kendall Shepherd and explains the progression of signs that we may see a dog go through leading up to bite due to fear. The bottom of the ladder begins with the smallest signs of displayed aggression that are often missed by unobservant or uneducated owners. These include yawning, blinking, lip-licking, turning head away, turning body away, sitting and pawing. As a dog’s fear increases, the signs become more overt: walking away, creeping with ears back, standing crunched up, tail tucked under, lying down with legs up, stiffening, staring, growling. If nothing is done to intervene at any of these stages, the result will be a snap and then bite. Even though it sometimes seems that a dog’s behaviour ‘comes out of nowhere’, there are often many subtle signs that came before and if we can recognize them early enough and know how to help a dog calm down, we can prevent them reaching the top of the ladder of aggression (which is important as we do not want them to rehearse inappropriate behaviour). Dogs can progress up the ladder within seconds if their anxiety level is high enough, if the trigger is severe and sudden and/or if they feel trapped.

They can also skip over some of the lower level stages if they have learned that their appeasement behaviours given at those levels did not work in the past. Owners of dogs with anxiety need to be vigilant and present when with their dogs so that they can intervene at the earliest signs in order to prevent behaviours from getting worse. If the dog finds themselves in a position where they are unable to run away from the threat (or perceived threat) due to being on a lead, or being confined in some way, they may also skip that step and progress to a higher level one. Punishing a dog for exhibiting behaviours on the lower ladder rungs will lead to them learning that there is no use in trying that behaviour as the outcome is negative. There may also be issues relating to breeding or cosmetic alterations that prevent a dog from physically being able to display some of the appeasement behaviours at the lower rungs, and so they would therefor choose a different behaviour.

A growl is a dog’s way of communicating that it is uncomfortable in a situation, and it is likely happening because all the other behaviours below it on the ladder of aggression have failed to get the point across. Owner’s who hear a growl, think their dog is misbehaving and then reprimand them risk pushing their dog to choose higher level behaviours, such as snapping and biting, the next time they are in a similar situation. A verbal reprimand may stop a dog from growling in the current situation, but it will not do anything to make the dog feel better about the same situation in the future.

Types of Aggression

Aggression in dogs can be one of a variety of different types, and each may be grouped into the categories of intraspecies, interspecies, instigated and responsive. What is important to remember is that even though as humans we love to label problems and having a name for something helps us to understand it better, all of these 'types of aggression' are painful emotionally for the dog and many (but not all) are based in fear. Fear of losing something, fear of pain, fear of the unknown/novelty. It doesn't actually matter what the name is for the behaviour that our dogs display, what matters is that we try to understand the driving emotions behind it.

Some dogs display aggressive behaviours only towards other dogs (intraspecies aggression). This may or may not include all dogs. There are some dogs who live happily in a household with another dog, but who bark, growl and lunge at any other dog when out and about and who would not take kindly to another of its species entering its home. Also, some dogs seem to only have an issue with certain types of other dogs – based on colour, size or breed. People may note that their dog seems to only react aggressively to large, white dogs but is fine with every other type. Or a dog may only react aggressively to Labradors because it had a bad interaction with one in the past.

Interspecies aggression is when a dog displays aggressive behaviour towards humans and any other species. Like intraspecies aggression, this behaviour could be generalised across a species or be directed towards only particular types with that species. Dogs who have been mistreated in their past by a male may be gentle in their interactions with women but lunge at and attempt to bite any male who comes close. Cats are a species that often trigger the predatory instinct in some dogs and so can also be a target of aggression.

When a dog is the one initiating the aggression, either towards a dog, human or other species it can be classified as instigated aggression. For this to occur a dog must perceive that there is enough threat and be fearful enough of what is going on in the situation that it decides to react pre-emptively in an attempt to make the threat go away. For example, a dog who struggles with resource guarding may lunge at a person in the house simply walking by who happened to get a little to close for the dog’s liking. Responsive aggression occurs as a reaction to something that has been done. For example, if a dog has been hit during a training session for failing to perform a behaviour it may turn and bite at the handler in an attempt to prevent further pain.

  • Fear Aggression

Fear aggression results when a dog is afraid in a situation and has not been able to escape it, or finds that its earlier communication attempts have not worked, have been punished or have been ignored. For example, a dog may snap at approaching children not because the child has done something to the dog, but simply because the dog views them as something to be worried about. This often happens when a dog is unable to escape, whether that is due to being leashed or enclosed in a crate. They look away, lick their lips, may sit and start scratching...but the child continues to approach. Over time, the dog may learn that only the behaviours at the higher rungs of the ladder work to make the ‘threat’ go away and so choose that behaviour more, thus strengthening the neural pathway associated with it, making it more likely to happen again in the future. In order to prevent this, owners must learn to notice and deal appropriately (help the dog learn new behaviour patterns and create better associations) with early signs of fear and anxiety. Dogs who are afraid may initially cower, have ears flattened to their heads, tuck their tail under their body, lick their lips and yawn and have raised hair on their hackles. You can tell the fear is escalating when you start to see whining, submissive urination, growling, pacing, biting, destructive behaviour, clinging to the owner and barking. Extreme fear is exhibited by drooling, panting, trembling, dilated pupils and/or whale eye and the loss of control of the bladder /bowels.

  • Territorial Aggression

Dogs may show territorial aggression towards anything that enters their perceived territory. This could be the home, the backyard, the space around them or spaces they see as valuable. Rooted in fear, and in the natural inclination to protect the den and alert adult dogs of possible intruders, territorial aggression will have similar signs as fear aggression – growling, barking and charging – all with the hope of making the ‘intruder’ go away. When inside a house or a backyard and displaying these behaviours, the dog’s wishes almost always come true…the person or animal invading their space goes away. This reinforces the behaviour in future situations.

  • Resource Guarding

Resource guarding develops from an instinct to survive – access to resources is important to dogs in the wild, and there is fear, anxiety and insecurity associated with losing valuable ones. Dogs who resource guard may be controlling access to food, toys, people and/or special locations. There are many contributing factors such as genetics, past trauma and competition. Rescue dogs in particular can be prone to resource guard as they are more likely to have had to fight for resources and to lack proper social skills due to poor socialisation. Dogs can progress through ten ‘warning levels’ rather quickly if feeling threatened. Early signs might be a dog who continues chewing their bone, but who keeps a close eye on you at the same time, becomes a little tense and starts to wag their tail more as you get closer. From there, freezing may occur and the dog may stare at the approaching threat, following up with a guarding posture and lip-lift while beginning to eat faster. If theses signs are not heeded a dog may growl, carry the item away quickly and then snarl. At the most escalated levels, resource guarders will snap at the air and then progress to contact bites.

If paying close attention, it is possible to notice early signs of resource guarding behaviour and work with your dog to diminish them. Dr. Tom Mitchell, of Absolute Dogs, says that dogs who resource guard need help disengaging from objects and benefit from confidence building games, as well as toy and food switching games in order to learn that giving up a resource is not a bad thing. Another approach is to slowly work on conditioning the approach of people to equal a good thing by tossing treats towards a dog who is resource guarding and slowly decrease the distance over time.

  • Dog-Dog Aggression and Predatory Drift

Dog to dog aggression can stem from improper socialisation or specific traumatic events in the dog’s past. Overall, dogs who display aggressive behaviours towards other dogs lack confidence and may not be able to correctly interpret the behaviours of other dogs. An attack can result in a dog developing a fear towards dogs in general, or specific dogs that match the characteristics of the dog that attacked them. Owners can inadvertently contribute to dog-dog aggression when they tense up on the lead as other dog’s approach. This communicates to their own dog that something is wrong, and often restricts natural behaviours, such as trying to lower the head to show submission and approaching on a curve rather than straight line. This can lead to leash/barrier frustration and result in worse behaviours from the dog.

Predatory drift differs from dog to dog aggression in that it is not based in fear but is a hardwired and instinctual behaviour that is often tripped when large and small dogs are playing together, and excitement/arousal levels get too high. The natural predatory sequence of search, eye-stalk, chase, grab-bite and kill-bite is triggered and a dog who may normally be able to stop themselves at the chase section follows through to the end. As a result, it is important to carefully monitor dogs of different sizes playing together and play close attention to the individual stress levels of the dogs in the group. One anxious or stressed dog can add to the anxiety and stress levels of the other dogs and before you know it, things can get out of hand.

Most dogs are still driven to engage in some of the levels involved in the natural predatory sequence, even though many no longer need to hunt for and obtain their own food. For example, searching, eye-stalking and chasing are common characteristics of sight-hounds and other working dogs. Some breeds have had parts of the sequence bred out of them (or at least they have been bred in order to diminish stages as much as possible) …for example, the border collie. Not many people who rely on their border collie for working purposes want one who cannot stop themselves from grabbing and biting the sheep. People also tend to selectively breed dogs meant to become family pets and over time the last few stages of the predatory sequence have been not breed characteristics than most people want in their pets.

That said, predatory drift is based on an instinctual drive to chase down and kill another animal for food, and it can be almost impossible to breed out an instinctual drive. Knowing what appropriate play looks like between dogs is vital in helping to identify when a dog may be at risk of going a bit too far along the predatory sequence. Highly aroused dogs, mis-matched in size and comfort level with the play is a recipe for disaster. Often times the smaller of the two will do things that make itself resemble prey – running away, squealing, acting submissively. This can also apply to young children who to a larger dog, may appear to be acting like a prey animal. In addition, allowing a dog who lacks socialization skills and who may not read the body language of their playmate to continue with escalating arousal levels during play can be enough to trigger the sequence as they may not understand signals that they other dog is giving off indicating that it needs a break. Dopamine is released during play, which just strengthens the behaviours and makes them more likely to continue once they have started.

  • Pharmacological (Medicinal Side-Effects)

Dogs being treated for pain and other illnesses may be given medication that could result in an increase in aggressive behaviour if the dosage of the medication is too high. Prednisone (an anti-inflammatory that is used to treat Addison’s Disease and other Nervous System disorders), Phenobarbital (used to help with seizures) and various corticosteroids that might be used to help dogs with arthritis, can all have negative influences on behaviour if given in too high a dose, or if not weaned off properly. It is important to note a dog’s natural behaviour before administering medication so that you have a baseline to refer to if needing to administer something new that could have these adverse side-effects.

  • Alliance Aggression

Dogs form close bonds, both with their human and with other dogs living in the household. Alliance aggression occurs for some dogs when they are in the presence of either a close human caregiver or another dog they consider to be a part of their family group. Alone, or under the care of another person the aggressive behaviour may not be displayed. An example of this type of aggression can be seen when a dog walked primarily by one person in the household barks and lunges at other dogs while out on lead with them, but when walked by a dog walker who visits once a week (or even another person in the household who walks them less frequently) displays none of these behaviours. Why does this happen? If a dog has a negative experience, such as being attacked by another dog, a ‘trigger picture’ can be formed in that dog’s mind that includes some, or all, of the sights, sounds and smells that were in the environment at the time of the incident. They associate all those individual items with the negative event that happened and when present together at any time they become a predictor of that same negative experience. A dog who was attacked on a sunny day while walking with another dog in the household by the female caregiver may become reactive whenever these individual triggers occur together. Walk them on a sunny day with the same female caregiver but leave the other dog at home and there may not be an issue at all.

  • Maternal / Protective Aggression

Dogs may show protective aggression if they feel one of their family members are in danger. The family member in question might be a human, a puppy or other animal that they share their home with. There are dogs who will not tolerate strangers approaching their primary care-giver to whom they are closely bonded, and while this may sound appealing for some people, it could quickly become a problem that leads to someone getting hurt. Some female dogs may begin to display protective aggression behaviours after having a littler of puppies, and others (male and female dogs) may find that a new baby at home stirs up this desire to protect.

  • Barrier Aggression

Barrier aggression has its roots in frustration. This type of aggression is seen when a dog sees something in its environment that it would like to get to, but it is restricted by some type of barrier. The barrier may be a leash, fence, window, or anything that prevents access. Dogs may show leash reactive behaviour while being walked and seeing another dog on the other side of the road. If pessimistic, they may feel the need to ‘check out’ the dog to make sure its safe and find themselves unable to do so due to the lead. The emotions of worry and fear can quickly turn into frustration and that is when we see the dog begin to lunge, growl and pull towards the other dog. Barrier aggression can also occur when two dogs are allowed to greet on lead and the communication/greeting skills of one or both dogs are weak. If one of the dogs feels the need to leave the situation and cannot, they may resort to a snap or bite to try to increase the distance between them and the other dog. This is one of the reasons why leash greetings with unfamiliar dogs is not recommended. Dogs who are unable to carry out the natural chain of interaction with each other (see, approach in a curve, sniff face, move to rear and sniff, then disengage and move on or stay and play) may have difficulty and experience frustration. Fence running and fighting is another example of barrier aggression in play. Dogs in a backyard that borders another yard also containing a dog may find themselves in a constant state of high arousal and excitement at the sight/smell of another dog so close, yet unreachable. They may charge the fence, barking and growling but be fine greeting the same dog off lead in a separate, safe area.

  • Physiological/Biological

Biological and chemical changes in the brain due to sickness and diseases can cause serious and seemingly ‘out of nowhere’ aggressive behaviours in dogs. Checking in with a veterinarian at the first sign of aggression in a dog may help to determine if there is a physiological reason for the behaviour and if so, treatment for the health condition will likely result in the aggression dissipating.

Thyroid disease in dogs is one health condition where behavioural changes can occur alongside the physical symptoms. Hypothyroidism can result in sudden onset aggression towards people and animals, a lack of focus, passivity and the development of phobias, lethargy, and an intolerance for the cold. Mood swings are not uncommon, and there may be signs of depression and anxiety along with mental dullness, an intolerance for exercises, body weakness and the dragging of feet. Hyperthyroidism can result in dogs showing an increase in the need to drink, eat and urinate, as well as hyper-excitability.

Canine cognitive dysfunction is an age-related syndrome in dogs that leads to a decline in cognitive function. It is a difficult condition to watch a dog suffer with as they can become depressed, wander aimlessly, lose control of their bowels, and become hyper-aggressive in some cases. They lose their ability to effectively communicate with other dogs and sometimes can neither give, nor understand appeasing signals. A dog who never displayed aggressive behaviours before in their life may begin to snap and growl in situations and at other dogs and people that in the past, they would have been able to tolerate just fine.

Encephalitis is an inflammation of the brain that can result in aggressive behaviour depending on the area of the brain that is affected. It can be caused by diseases such as distemper or rabies. Keeping a dog up to date on these vaccinations in parts of the world where they are still known to exist is one step we can take to minimize the likelihood of our dogs contracting them.

Snappy, anxious and fearful behaviour can be seen in dogs suffering from hypoglycemia (low blood sugar). Regular vet visits and blood work ups to check blood sugar levels in the body can help identify if this is a possible cause of behavioural changes.

Brain tumors and head injuries to specific parts of the brain interfere with normal brain functioning and may cause a dog to show symptoms such as irritability, barking incessantly, confusion, whining and aggressive outbursts.

  • Idiopathic Aggression

Dog owners often seek help for aggressive behaviour their dog begins to show by proclaiming that it, ‘came out of nowhere’. True idiopathic aggression, aggression that really occurs for no apparent reason, is extremely rare. Sometimes called Canine Rage Syndrome, it can be a difficult condition to work through as identifying triggers almost seems impossible. Commonly occurring in dogs between the ages of 1 to 3 years old, idiopathic aggression is characterized by sudden, explosive episodes of aggressive behaviour that appear to have no apparent stimulus. Some owners have reported that their dog’s eyes appear to be glazed over just before an outburst occurs, which could be an indication of the freeze response and hard stare that dogs often give right before an attack. When the situation is looked at more closely with the help of a veterinarian and behaviour professional, there is usually an underlying reason or cause for the aggression related to resources, seizures, or damage to the area of the brain that controls behaviour. In true cases of idiopathic aggression, the prognosis for the dog is often poor and for safety reasons euthanasia will likely be suggested.

  • Pain Related Aggression

Undiagnosed pain or illness in dogs can result in aggressive behaviours that may appear to come out of nowhere. A dog who is suffering with an illness may at first display signs of aggression low on the canine ladder of aggression, but quickly escalate to more overt warning signs if those go ignored, or if the pain from their condition worsens over time. A study by Tomas Camps that was published in the Journal of Veterinary Behaviour found that dogs who were already displaying aggressive behaviours towards their owners before the onset of pain were demonstrating aggression in a wider variety of situations (when food was taken away, when an attempt was made to move them from an area where they were sleeping, and when there was an attempt to make them something they did not want to do) once they were experiencing pain. Dogs who did not display aggressive behaviours before being afflicted with a painful condition demonstrated aggressive behaviours in situations where someone was attempting to control them. These dogs were also more impulsive and would skip the lower warning signs often given before a snap or bite occurred in an attempt to prevent further pain or discomfort. One specific disorder, hip dysplasia, was found to be a key factor in large dogs showing aggressive behaviour. The problem becomes worse quickly as often the dog is experiencing pain in smaller amounts long before there is a diagnosis and treatment is offered.

  • Redirected

There are times when a dog can become so highly aroused, fearful and /or frustrated in a situation that it may turn and begin to unleash the aggression towards something/someone else nearby. For example, a dog who has been charged by another dog may react aggressively and a fight ensues. Should a person attempt to break up the dogs it is possible that the dog, as it is being removed from the situation, experiences an increasing level of frustration due to the fact that it can no longer reach it’s original target and it may turn and bite the person. Emotional arousal has become so intense that it needs a release, and the target of the aggression shifts to the being that interferes in the moment. On leash, a dog who normally displays fear aggression towards other dogs or people while out walking, may also experience the same frustration and resort to turning and taking out its aggression on its owner. In either case, the target of the initial aggression was, or became, unreachable and so the dog turns to the next closest thing. Redirected aggression can also occur between two dogs, or a dog and another species. Two dogs in the same household who are allowed out into the yard where they bark through the fence at a dog or person on the other side, may end up in a fight themselves. A dog alone who is behaving aggressively in the same situation may turn and take out its aggression on a passing cat or other animal who might happen to get a bit too close. When dogs are playing together and a new dog shows up that causes a bit of tension with one, play may stop for a moment while the dogs warily check each other out. Should an attempt be made to re-initiate play again, the unsure dog may turn and attack its former play mate, as the tension is redirected to what took attention away from the original target. Both male and female dogs are equally likely to display this type of aggression, as are young and older dogs.

Understanding Communication

Dogs and humans do not speak the same language, and yet they are among our closest companions. Humans rely largely on our verbal capabilities to communicate with others and we obviously cannot count on dogs to respond in kind. Understanding more about how dogs communicate what they are thinking and feeling with each other and with us is something that we will strengthen our relationship with them. We will be more effective coaches, behaviour professionals and guardians, our dogs will be happier and less mis-understood and there will be fewer misunderstandings that could lead to a person or other animal being harmed.

In a podcast presented by The Animal Training Academy, Patricia McConnell discusses how communication needs to be looked at from two different perspectives – that of the sender and the receiver. Our dogs are giving us information all the time with their body…the way they hold their tail, position their body, hold their ears, tense or relax their face and whether (and how) they vocalize. That is only one part of the communication. Becoming adept at interpreting a dog’s communication effectively is important for anyone living, or working, with dogs. By knowing the signs of a dog showing stress, fear, happiness etc. we can be better at figuring out how they may be feeling at any given moment and then work to actively reinforce behaviours that are preferable to an aggressive response.

A large number of behavioural problems involving aggressive displays reported by owners can actually be chalked up to someone mis-understanding what a dog is trying to say with regards to how they feel in a situation, and/or the failure of a person to do what is needed to help the dog in the moment. Our dogs experience the world through the same five senses as we do, however, the order of importance of those senses to a dog and their communication is different from ours. Jan Windsor, in her live presentation ‘Sense and Sensibility in Dogs’ explains that for humans, our senses in order of importance are: sight, hearing, smell, touch and then taste, whereas for a dog they are: smell, sight, hearing, touch and taste. This is huge in understanding our dog’s behaviour and ensuring that we are doing what we can to enrich their lives and work with them in a way that is relevant to them.

As dogs have domesticated, they have become much more ‘subtle in their skills’ than wolves as far as using signals to communicate with one another (Rugaas, 1997). By learning the subtle signs that dogs use we can see that a tucked tail is showing they are fearful of something and get them away from the situation, we can notice the tight lips and hard stare of a dog who is being pushed too far and may resort to biting and work to change the situation before that happens and we can see when our dog is getting a bit too worked up by something and take them away to help them calm down. It really is not fair for us to expect a dog to learn and understand our language (‘sit’, ‘down’, ‘stay’ etc.) and not reciprocate by working to understand theirs. We cannot approach communicating with our dogs as we would with other humans. Considering how we move, hold ourselves, speak, approach, and then respond to our dogs will help our dogs live their best and happiest life. It can make the difference between preventing aggressive behaviours from ever happening and having to deal with the aftermath once they have begun.

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