Aggression in dogs

Aggression is a normal part of the way animals behave. People often only consider aggressive behaviour in dogs to be a problem when it results in biting. However, aggression includes 'grumbling', growling, snarling, teeth-baring and snapping at the air (without making contact). Bites can vary from light touches to inflicting serious injury.

Canine aggression FAQs

Clinical animal behaviourist David Ryan answers our FAQs about canine aggression. The Association for the Study of Animal Behaviour recognises this advice as best practice.

What is dog aggression?

Aggression is the outward expression of an emotion and can be used to communicate various intentions by the dog. Rather than being something that switches on and off suddenly, aggression is part of a range of behaviours that dogs have available to them to deal with life’s everyday challenges. Many of these behaviours are passive and it's only when the dog changes from trying to avoid a situation – through things like moving away or showing that they're not happy – to actively trying to manage the situation, that we term it 'aggression'.

Why are dogs aggressive?

Dogs are aggressive in response to unfolding events. Any dog has the ability to use aggression, but it's always dependent on what they believe is happening to them. When a dog uses aggression it’s almost always because they think they’re under some form of threat – to their personal safety, something (or someone) they value highly will be taken away, or they're being prevented from doing something they really want to do, which causes frustration. Aggression can be used to control or reduce this challenge. Theoretically every single dog, if pushed far enough, can and will use aggression.

Are some dogs naturally aggressive?

Although it might seem that some dogs are born to be aggressive, it's more accurate to say they're born with inherited tendencies that might, if not controlled, make aggressive behaviour more likely.

As aggression is always a response, usually to a threat, there's no reason why a dog can't learn alternative responses. If these responses are controlled throughout the dog’s life, starting with breeding from well-balanced, healthy parents and continuing with learning good social skills as a puppy, there's no reason why any dog should learn to use aggression inappropriately.

Because of the way some types of dogs have been bred, some puppies will need more careful nurturing than others to ensure they don't grow up to use aggression inappropriately.

If dogs don't have the right kind of experiences at any time in their life, they can learn that aggression can solve problems for them. Once learnt it can become the dog’s first choice of ways to solve problems. This kind of dog may appear 'naturally' aggressive, but they're actually responding to the combined effect of the learning experiences they've had over their lifetime.

Are some breeds of dog more aggressive than others?

There are inherited ways of behaving that are particular to some breeds or types of dogs, that make it more likely for individuals to grow up to use aggression where others would not. Because no two dogs are exactly the same, individuals will differ too. In every breed there'll be individuals who use aggression inappropriately, and others who won't.

Aggression is not a single characteristic. However, there are breeds of dogs that have historically been used for specific purposes, such as for fighting dogs or other animals, or for guarding. While these breeds may not be any more likely to show aggression, because of their physical and temperamental attributes if they do show aggression it's likely to have more serious consequences. Persistence in attack coupled with strong jaws can cause serious injuries.

Guarding breeds have been selected to show aggression when threatened, but the levels of threat always have to be learned through experience. If you were to take a puppy from a very defensive guarding breed and bring them up correctly, the dog wouldn’t necessarily show aggression except in the most extreme circumstances. If you were to take a puppy from the least defensive breed and bring them up badly, they could very well turn out to be extremely aggressive in all kinds of circumstances.

What are the signs of aggressive behaviour?

Each individual dog will use aggression in the circumstances that they believe appropriate, and use the degree of aggression they believe to be appropriate for each encounter. What they believe to be appropriate will depend on what they've learned previously.

Averting or reducing a challenge can be done in many non-aggressive ways. It's only when the dog believes these won’t work, or that aggression will be more effective, that it’ll be used.

Dogs communicate mainly through body language. They have a wide range of non-aggressive signals and postures that they exhibit when they want us to stop doing whatever it is that they don't like.

These 'threat aversion' or 'threat reduction' signals include gestures that show they're uncomfortable, like yawning, lip-licking, averting their gaze, turning their head away, dropping ears, crouching, low wagging or tucking their tail under and rolling over on their back. These are sometimes termed 'submissive' but the intention is the same as aggression – to stop whatever is happening – and if they don’t work the dog may escalate their communication more actively.

More active signals may still incorporate submissive parts, but will include things like the baring of teeth, narrowing of eyes, raising of the hairs on the neck and back, shifting of weight to allow escape, growling, snarling and sometimes barking or snapping. These signals will become more and more active if the threat does not reduce, as the dog believes the only way they can ward off the danger is through force, and they can end in biting.

Some dogs’ communication is hampered by the way they look. For example, a dog with a short tail may not use it very successfully and a dog with a lack of facial expression, low-hanging ears or lots of hair may have difficulty making themself understood. Some dogs learn over time that the more subtle gestures don't work – people often don't pay them much attention – and so go straight to the more obvious ones such as bites. Some dogs may feel that the danger in front of them is so threatening that they have no time for 'small talk' and have to go straight to the top.

All of these dogs may use aggression without the smaller communication signs that we recognise and because of that it may not be easy to predict when they're about to bite. So, while many dogs give off lots of warning that they're not happy with the situation and if you don't leave them alone they may bite, a few other dogs appear to bite unpredictably. The 'unpredictable' bites are simply the result of the dog deciding the lesser signals are not appropriate for the circumstances.

My dog is aggressive, what should I do?

Sit down and work out the circumstances that caused the aggression so you can avoid them in the short term. What you do next depends on when, or towards what or whom, your dog is aggressive. Some dogs will only be aggressive in one context and others will show aggression in lots of contexts. The more often and the more contexts in which your dog is aggressive, the more difficult it's likely to be to treat.

For example, if your dog defends high-quality food with aggression, but shows no aggression over ordinary food, you may be able to deal with it by simply not giving them their favourite food. However, the use of aggression can escalate quickly and the more that dogs use it the more they're likely to use it in the future, so getting help early is crucial.

Aggression can be a sign that your dog is not well. Illness can cause grumpiness and intolerance, so it's essential that you have your dog checked by a vet. If they’re given a clean bill of health they’ll be able to refer you to a qualified, experienced dog behaviourist who'll be able to guide you through changing your dog’s behaviour.

Should I tell my dog off when they’re aggressive?

No. Telling a dog off will be seen as a punishment, as will smacking, ‘scruffing’ them by the neck or pinning them down. All of these will be seen by the dog as very threatening. Aggression is a dog’s response to what they think is a threat. When your dog is already in an aggressive frame of mind, telling your dog off or otherwise punishing them will make them feel even more threatened and cause conflict with you. It may even make the dog direct a much greater level of aggression towards you. They may go from growling to biting because they can see no other way out of the confrontation.

Punishing a dog for showing small signs of aggression, such as growling, may stop it. However, if they have no way of showing that they feel under threat they will hide their emotions until they can't contain them any longer, resulting in what appears to be 'unpredictable' aggression, where the dog misses out all the lower communication and goes straight to biting.

Changing an aggressive response is all about understanding why the dog feels that way and then changing that feeling, not about telling them off for the way they feel.

Are male dogs more aggressive than female dogs?

Both male and female dogs have the ability to show aggression but the statistics show that 'entire' (not neutered) male dogs are more likely to show aggression than female dogs or neutered males. Unfortunately this isn’t the easy answer it might appear to be. Entire male dogs are likely to be more competitive over things they value than are either females or neutered males. They may be more confident in their ability to control things they think are important and that may lead them into conflict in situations in which their owners expect them to defer, or do as they're told.

For example if a puppy regularly muscles their litter-mates away from food, they may form the idea that they can take food whenever they want. This may lead them to think they're entitled to any food that is on the floor. Because they control their litter-mates, they expect to control other similar situations as well. If they then fail to control food, because their owner stops them, the frustration and anger they feel may turn to aggression, leading them to use aggression to defend food they've 'found'. In their view they’re defending something they believe is theirs.

While it's entirely possible that female dogs and neutered males may show the same behaviour, the extra competitiveness of some entire males make them more likely to do so. Male dogs are not more aggressive than females, but their competitive tendencies might bring them into conflict with their owners more, which may result in aggression if not handled properly.

Will neutering my dog make them less aggressive?

This really depends on the reason that your dog is aggressive. Neutered male dogs are less likely to show aggression, but this is probably because they don't learn to use it in the first place. Once aggression is learnt as a response to a situation, neutering a male dog (also called 'castrating') is unlikely to have much effect. Castrating dogs before they start to show aggression may well reduce the future likelihood of some individuals becoming aggressive, but once they’ve learned that aggression is a successful response, the learning doesn't go away. There's also strong anecdotal evidence that neutering a male dog can actually make some forms of aggression worse.

Female dogs show less aggression than male dogs in general, but neutering a bitch will not affect aggression unless it's driven by female hormones, for example nest guarding in false-pregnancy. Again there's evidence that neutering a bitch can make some forms of aggression worse.

If your dog, either male or female, is not showing any signs of aggression, neutering them may make them less likely to show aggression in the future, but there’s no guarantee. If your dog is already showing aggression you need a professional behavioural opinion as to exactly what the cause is before considering neutering as an option.

Will playing rough games with my dog make them aggressive?

Studies show no connection between playing rough games with your dog and aggression, but one way dogs test their ability to win competitions is through rough games. If your dog plays rough games with you they're less likely to inhibit their behaviour towards you at other times. If your dog defers to you, obeys you when you ask and you're happy with your relationship, there's no need not to play any type of game. If your dog is showing aggression, particularly towards you or other family members, playing rough games may well be contributing to it.

My dog is aggressive and I've been told to assert my dominance over them. Should I do this?

Relationships with pet dogs are far too complicated to be defined as simply either dominant or subordinate. 'Asserting dominance' is an outdated concept that modern behaviourists don't think is an appropriate way of interacting with our pets.

If your dog is aggressive you may well need to adjust your relationship to take them under your control, but this shouldn’t be done in the confrontational manner suggested by 'asserting dominance'. Things such as 'staring them out', shaking them by the scruff, rolling them over, holding them down, 'Alpha rolls', holding their jaws, smacking, or any form of physical punishment, at best may do little good and at worst will severely worsen aggression in your dog.

Even less brutal interventions thought to support dominance, such as making them eat after you or standing in their bed from time to time have little basis in science and are unlikely to have a positive effect on aggression.

I have a new puppy. What should I do to prevent them from becoming aggressive?

Unfortunately, breeding from parents who show aggression and the effects of very early upbringing could establish a tendency to use aggression before new owners even see their puppy.

Assuming you’ve done the right thing by researching the kind of dog that fits your lifestyle and buying from a reputable source, you'll have been to see the puppy with their mother, brothers and sisters and established that they're happy and contented. From birth, the puppies should have been regularly interacting with people in a normal family environment, not shut away in a barn or shed. Always try to see a pup in their home well before the day on which you pick them up, so you can walk away if the conditions aren’t right. Remember, you could be caring for this dog for the next 20 years.

There's no reason for a dog to become aggressive because you have a new child, but children bring with them a huge change in your circumstances that may have an effect on how you relate to your dog. You may not have time to walk them as much, or be hampered by a pram when you do; lack of sleep might make you a little less tolerant and maybe a little grumpy; you may not be able to stroke your dog as much because you have a baby on your knee. None of these things may have a direct impact that causes aggression, but they may make your dog more unsettled.

I have a new child in the family/on the way. Will my dog become aggressive?

It's a good idea to prepare your dog for the changes before they actually happen, so you can gauge their reaction. Dogs who have no experience of children and babies may take longer to adjust than those who are familiar with them.

Bring out the cot and pram before the baby comes home so your dog can get used to them, and you can play the noises that babies make (crying could be quite worrying for a dog that has never heard it before). When the baby comes home, don’t exclude your dog but allow them to see, hear and smell the new arrival, under strict supervision of course, so they can understand more easily that there's nothing to be worried about.

It's also a good idea to teach your dog to sit on a 'day-bed' (such as a blanket or cushion) where they can relax out of harm’s way. The bed should be in the same room as you, but away from where you will be busy with the baby. Train them to sit on the bed or give them a chew when they go there, to give you freedom to attend to the baby when you need it.

The little noises that babies make and their uncoordinated wriggling actions can remind some dogs of prey, so it's vitally important never to leave dogs unattended with babies, no matter how safe and friendly you may think they might be.

Learn more about dogs and children.

If a dog shows signs of aggression towards me, what should I do?

Firstly, discontinue whatever it is you're doing. Aggression is the dog’s way of warning you to stop. Secondly, stand still. Movement towards an aggressive dog may be interpreted as a threat, and movement away may make the dog bold enough to bite. Stand still and take stock of what's happening. If the aggression stops, think about what caused it and avoid doing the same thing again. If it's your own dog and you're stuck in the situation, try to distract them with something positive, such as picking up their lead, or asking them to sit for a treat. If it continues, or if it's a strange dog, see below ('What should I do if a dog attacks me?').

If this is your dog, you probably need professional help because you haven't been able to prevent this happening, so you're unlikely to be able to improve it. You may well be too close to the problem to take a detached view.

Is it possible to predict if a dog will be aggressive in the future?

There are factors that make it more likely that a dog will use aggression in the future which can be used to estimate the likelihood that they will do so in particular circumstances. For example, if a dog has bitten their owner the last nine times they've tried to take a toy away from them, the likelihood that they'll do so on the tenth attempt is very high. With a detailed history of how an individual dog has behaved in the past, a professional dog behaviour counsellor may be able to estimate the likelihood of whether the dog will be aggressive in similar circumstances in the future. This is not the same as being able to predict aggression. Almost all of the relevant factors depend upon knowing what has happened in the past. Without these precise details it's impossible to predict future aggressive behaviour.

Dogs use aggression in response to what they see as a threat. If the dog has never felt sufficiently threatened, they may never have felt the need to use aggression. When a sufficient threat arises any dog may decide, there and then, to use aggression. In dogs with a history of aggressive behaviour it's possible to estimate the chances of future aggression. In dogs with no history of aggression, or an unknown history, it's virtually impossible to be certain.

How do I know if a dog is about to bite?

Most dogs will give plenty of warning that they're going to bite. They may give 'leave me alone' signals like licking their lips, yawning, turning their head or trying to walk away; they may be even more obvious with signals such as raising the hair on their neck and back, growling, snarling, showing their teeth and barking. Don't make the mistake of thinking that a wagging tail means they're friendly – a wagging tail can mean lots of things, including 'I am about to bite'!

The most obvious signal will be a snap at the air in front of you, which is not a 'miss' but a warning that the next one will make contact. 'Unpredictable' biting is never without a cause, but the reason may be hidden from us by the dog’s previous experiences. Biting is usually the last thing a dog wants to do, but they can learn that it's the only way out of a situation. Such a dog may learn that in a certain situation it's useless to try all the other signals, because they've never worked before, and may go straight to biting as a guaranteed way of reducing the threat. Alternatively the threat may be so sudden and close that the dog feels they have no option other than to bite.

What causes a dog to attack?

Dogs can attack for a number of reasons, but all can be traced back to the basic threat. It's important when viewing this to do so from the dog’s perspective. Dogs can feel threatened by lots of different things depending on what their breed was originally developed to do and their upbringing. Dog breeds that were originally bred to be guards may be more inclined to attack if they feel their territory is threatened. Even if we know the postman does not pose the same threat as a burglar, the dog treats them the same.

Dog breeds that were originally bred to retrieve game may be more inclined to defend things they have in their possession, whether it's their own toy, or something they've 'stolen'. The threat may even come from trying to stop them doing something they enjoy. Dogs that have had bad experiences, for example of being attacked by other dogs, may feel threatened by new dogs they meet. Dogs may even attack because they're hurt or in pain.

What should I do if a dog attacks me?

The dog is almost certainly attacking you because they consider you to be a threat in some way. There are two main priorities to ensure your own safety: firstly to physically protect yourself and secondly to reduce the threat to the dog so they stop the attack. Using strategies that combine these two priorities will afford you most protection:

Stop moving towards the dog. If you’re at home, stand still. If you’re out walking, jogging or cycling and a dog approaches you, you’ve probably inadvertently entered what they consider to be their territory. If they run towards you but not barking or growling, they may just be checking you out and after a quick sniff to determine you're no threat may leave you alone. Stand still and let the dog sniff. Don't try to touch the dog, or make sudden movements, but speak reassuringly. Keep standing still and they’ll lose interest and leave. If they're barking or growling, they consider you a threat that must be dealt with and will be unlikely to leave.
Stay calm. Indoors, or if you’re walking or jogging, stand still and face the dog, slightly angling your body away from them. Keep your body relaxed and on your back foot. You want to give the impression you're leaving calmly. Don't try to shoo away, hit or kick the dog as you'll be increasing the threat, and will increase the possibility of a full attack. Talk to the dog calmly in a pleasant tone of voice. Tell them you mean them no harm and that you're leaving. If you’re cycling, dismount and place the bike between you and the dog – this allows you to slowly wheel it far enough away to remount. Don't try to outpace the dog as this may encourage them to chase you.
Get something as solid as possible between you and the dog. Indoors this may be furniture, a chair, coffee table or even a cushion. If you're in a street or park it may be a bench, a lamppost or litter bin, or even a bag or your coat. If you're cycling, use your bicycle as above.
Watch the dog, but don't stare into their face. Turn your head slightly to one side and downwards. Watch them very carefully out of the corner of your eye.
You may need to move, either behind something or to get away from the dog. If the dog does not end up attacking, walk slowly backwards or sideways. Don't let the dog get round behind you; keep moving gently so that you continue to present a half side/front view of your body. Don't make sudden movements or run, just walk slowly away from the dog – they’re not likely to pursue you very far. Keep walking and talking up to the point at which the dog loses interest in you. If you must get past the dog, try to circle round, keeping at least the original distance between you.
If the dog does attack, try to hold something between you and the dog, such as your bag or coat. Fend off rather than try to fight back. Very few dogs go for a serious attack and after a snap-bite they'll be content that you’re leaving. Don't scream or yell. If you know there are people within hearing distance, call to them for help. Stay on your feet and don't corner yourself. Continue to walk slowly away, backwards or sideways, looking down and sideways, talking reassuringly, fending off if necessary and aiming to place solid objects between you as you leave.

How can dog attacks be avoided?

Firstly by choosing a puppy sensibly and bringing them up correctly you'll be able to minimise the aggression they're likely to show. However, although most dogs go through their entire life without ever showing any signs of attacking anyone, every dog has the ability to attack if they believe the circumstances warrant it.

Secondly, by knowing the dog. Have they shown signs of aggression before? Are they generally grumpy or even uncharacteristically grumpy today? Do they dislike particular things such as being leant over or disturbed in their bed? Are they intolerant of children or of hands reaching to their food bowl? Do they have a toy that they really like to keep? Every dog has preferences that they may be prepared to defend. If you know exactly how a dog is likely to react in a situation, you can avoid or cut short any aggression by controlling the circumstances. Although this may not be an ideal long-term solution for a dog showing a high risk of aggression, it will prevent injury while you seek professional help.

Finally, there will usually be warning signs. The dog will often try to leave the situation, or otherwise avoid the threat in some way, before resorting to attack.

Pay close attention to their body language. A slight stiffening of posture may be the first or only clue. Only by taking notice can you hope to understand what the dog is going to do next. Canine communication is a language like any other: you need to learn it so you can effectively understand your dog.

If a dog bites a person or another animal, should they be put to sleep?

What is more important is how much danger the dog may be in the future. To know that will require a full understanding of why they bit. Some dogs may be so dangerous that the only safe option is to put them to sleep, but the majority of episodes of dogs biting can be both explained and controlled.

A professional pet behaviourist will have the qualifications and experience to tell the difference between dogs that can be changed and the ones beyond help.

How will a professional pet behaviour counsellor stop my dog being aggressive?

Because each dog and owner are different no two interventions will be exactly the same and, although they may follow the same scientific principles, ways of changing each dog’s behaviour will be tailored to the individual circumstances.

Where to go for help

It's important that you use a behaviour expert with the appropriate knowledge, skills and experience to treat your pet. Anyone can call themselves a dog behaviour expert, but many don't possess up-to-date knowledge or the necessary skills required to treat pets with behaviour problems. Inappropriate or outdated advice or methods may adversely affect your pet’s welfare and even make your pet’s behaviour problem worse – so always do your research and make sure the behaviourist you have chosen has the right qualifications.

For any behaviour problem involving aggression, it's important to have your dog checked by a vet. Aggression can be a sign that your dog is unwell and any good behaviourist will want to rule this out first.