Aggression Towards Unfamiliar Dogs

How can I prevent my dog from becoming aggressive with other dogs?

Prevention starts with puppy training and socialisation. Early and frequent pleasant association with other dogs will enable your pet to learn how to recognise and interpret canine interactions and reactions. This can be very helpful in the prevention of aggression to other dogs.

When your young dog is interacting with other dogs it is important that you have good control and that you are relaxed yourself. Your dog will take contextual cues from you, and will be calmer and less anxious in the presence of other dogs when you are relaxed but in confident control. It is helpful if your dog knows how to reliably respond to instructions to sit, stay and quiet. These should be taught first of all in the absence of other dogs, using a reward based system (see handouts on puppy training). If your dog is physically stronger than you it can be helpful to fit him with a head collar to give you additional control during meetings with other dogs, especially when out on walks. It is going to be important for your dog to meet other dogs in a calm and controlled manner and this will be easier to achieve if you have good physical control. However, the way in which you achieve that control is important and you should avoid any methods which could give your dog a negative experience, through pain or discomfort, which could then become unintentionally associated with the other dog.

Why is my dog aggressive to other dogs?

Before being able to determine the reason for “aggressive” behaviour it is important to have an accurate description of exactly what is happening between the dogs. The behaviour can consist of growling, snarling, barking, lunging, snapping and/or biting and the prevelance of one or more of these responses may indicate a different underlying motivation. Aggressive behaviour can result in injury to dogs and/or to the people trying to separate them. Every case of “aggression” should therefore be taken very seriously.

Some canine play can be very boisterous and if one dog does not want to play in the same way, this can sometimes result in overt aggression. This mismatch of play behaviour is more likely if either of the dogs has been poorly socialised and/or there has been excessive human intervention in canine play. For example, if a dog has always been told off for approaching other dogs or has been pulled away from a playful encounter by an over cautious owner, it will often learn negative associations with encounters with other dogs or may become frustrated at not being able to initiate or complete playful interactions. The behaviour that is displayed in these situations is not rooted in true “aggression” and is often misinterpreted by human observers. It can also lead to a great deal of social embarrassment which results in owners being reluctant to walk their dogs in highly populated areas.

True “aggression” between unfamiliar dogs has many causes and the most important step in developing a treatment strategy for these cases is developing an understanding of the emotional state of the dogs involved.

Confrontational signalling

If a dog exhibits confident gestures or postures to an unknown dog, which does not show deference in the way in which the individual expected, this can lead to an escalation of threats from both dogs. Socially confident gestures include placing the head, or feet on the back of another dog, body postures such as high tail and stiff legs and direct eye contact. Owners may inadvertently exacerbate the problem by tightening the lead and giving vocal cues, which heighten arousal. The owner’s actions may also signal to the dog that an impending approach is problematic. Lead restraint inhibits the dog’s ability to react with a normal repertoire of responses including body postures, approach and withdrawal. It is important to remember that spacing is very important in the avoidance of aggression. Some dogs will fight rather than back down when challenged, but aggression may also occur because the dog is unable to retreat to a safe distance. Although confident displays may be a source of physical conflict when two dogs are meeting each other for the first time, hierarchies between known individuals are normally established through posturing communication and not fights. Fear and anxiety and/or learned factors more usually contribute to an initial attack. Dogs may feel the need to give an aggressive display if the owner shows signs of apprehension and does not appear to be in control of the situation. It is therefore important that the owner establishes a relationship with their dog, in which the dog feels relaxed and protected in the company of its owner, and does not feel the need to take the initiative. 

Territorial aggression toward other dogs

This term simply describes the context in which the aggression is displayed. For example, when unfamiliar dogs are on the resident dog’s property or what the aggressor perceives as his territory. Some dogs get highly aroused at the sight of other dogs on their territory and may jump fences, or go through windows or doors to get to the intruder. In order to deal with this sort of problem it will be necessary to determine the underlying emotional state of the dog and the emotional basis for its aggressive display.

To reduce the risk of territorial behaviour around the property, it is helpful for your dog to be frequently taken out of the home environment and for canine visitors to frequently come to the home during puppyhood. It is important to prevent your dog from engaging in prolonged and out of control aggressive displays both in the home and the garden. Aggressive displays include barking, lunging, fence running, jumping on doors, windows and fences. An essential lesson for any dog is to "quiet" and settle on command, and this must be taught by remaining calm yourself. 

Fear and anxiety based aggression toward unfamiliar dogs

Aggression due to fear or uncertainty about a situation is very common when aggressive encounters occur between dogs. The diagnosis is made based on the body postures and reaction of the dog when faced with another dog. It is important to gather information about the body language at all stages through the development of the behaviour and not just the postures that are being shown at the time when an owner asks for help. This is because the body language can change over time as the dog becomes more confident that its aggressive display is able to protect it from the approach of the other dog.

Initially, the fearful dog will often have the tail tucked, ears back and may lean against the owner or attempt to get behind them. These animals may also send mixed social signals, including elements of appeasement and confidence. They may be barking at the approaching dog while backing up at the same time. Often the dog is avoiding eye contact. This behaviour may be precipitated by previous aggressive attacks from which the dog could not escape and sustained injury, but is perhaps more commonly associated with owners attempting to punish the dog when it encounters other dogs, often because the owner misreads the situation. For example, it is very common for owners to confuse an alert upright posture with a “dominance” display and yank the dog back using the lead and/or tell the dog off. This negative response from the owner in the presence of other dogs can signal to the dog that it is better to avoid other dogs and prevent them from coming too close (because it associates them with punishment from the owner). This association then results in a vicious circle of aggressive display and punishment based in a miscommunication between dog and owner. In these cases, owners and dogs need to learn to relax around other dogs and work on establishing a positive based relationship between themselves. Once this has been achieved work can begin on changing the dog’s perception of other dogs so that they can see them as a potentially positive encounter rather than as a threat.

"Initially, the fearful dog will often have the tail tucked, ears back and may lean against the owner or attempt to get behind them. These animals may also send mixed social signals, including elements of appeasement and confidence."

Owners that try to calm their aggressive dog, rather than punish it, may also serve to reinforce the aggression, by inadvertently signaling that this behaviour is appropriate. They may also encourage more general defensive behaviour in the presence of the owner. Defensiveness may also be encouraged by an owner’s understandable anxiety around dogs as the problem develops. If the presence of other dogs causes the owner concern the dog has twice the reason to make sure that they stay well away. Good, effective, confident but relaxed control can help to calm a dog, while having a dog tightly restrained on a lead (especially with a choke chain) with poor control can often result in very defensive dogs. Dogs that are restrained on a lead or tied up are more likely to display aggression when frightened, because they cannot put enough distance between themselves and the perceived problem.

Learned components of aggression

As should be apparent from the above, learning and conditioning aggravate most forms of inter-dog aggression. Common elements of learning include the following:

• If the dog finds that his threats or aggression result in the retreat (or removal by the owner) of the other dog, the behaviour will be reinforced. 
• If the owner tries to calm the aggressive dog or distract it with food treats, this may serve to reward the aggressive behaviour. 
• Attempts at punishing a dog that appears aggressive toward other dogs, usually serves to heighten the dog's arousal, and teach the dog that the stimulus (other dog) is associated with unpleasant consequences. Many owners, in an attempt to gain more control, then increase the level or type of punishment (e.g. ever more severe jerks on the lead) which further heighten the dog’s arousal and in some cases may lead to retaliation and defensive aggression directed at the owners. 
• If the dog to dog interaction results in pain or injury to one or both dogs, the dogs will quickly learn to become more fearful and aggressive at future meetings.

If you cannot successfully control your dog and resolve the situation without heightening the dog’s arousal or increasing its fear, the problem will not resolve and will most probably worsen over time.  

My dog is already aggressive to other dogs. What can I do?

First and foremost, it is important to address the emotional state of your dog and work to increase relaxation and confidence so that you reduce the anticipation of threat. The aim is to reduce your dog’s negative state of arousal so that it is in a better position to learn new associations with other dogs, and be taught appropriate behavioural responses in their presence.

In addition it is important that you establish good control over your dog. This not only serves to calm your dog and reduce its anxiety, but also allows you to successfully deal with encounters with other dogs. Leads are essential and the use of head collars and/or muzzles (which have been correctly introduced) is strongly recommended for dogs that will be in situations where they need to encounter multiple dogs. 

• Begin by establishing a reliable association between relaxation and reward. Wait until your dog is spontaneously relaxed and work to associate the passive delivery of a high value treat with this state of relaxation. You are then ready to put the relaxation behaviour on to a cue, such as settle, which can be used to guide your dog into a relaxed state.
• It can also be helpful to increase your dog’s compliance with obedience commands. If he cannot be taught to sit, stay, come and heel, in the absence of potential problems, then there is no chance that the dog will respond obediently in problematic situations. 
• Choice of reward can be critical. It is important to use your dog’s favourite treats. These should be restricted at other times, since your dog needs to learn that relaxed and obedient behaviour, results in his favourite treats. 
• In order to change your dog’s perception of other dogs a programme of desensitisation (gradual exposure) and counter-conditioning to the approach and greeting of other dogs, is required. This must be done slowly, beginning with situations where the dog can be successfully controlled and rewarded, and then very slowly progressing to more difficult encounters and environments. You may need a specifically prescribed schedule of stages to help you with this and you would be well advised to seek appropriate professional assistance. The rewarding of relaxation using favoured rewards to reinforce a relaxed state, in a range of situations where there are no dogs present and little else by way of distraction, is a necessary first step. Food or toy prompts can be used at first, but soon the rewards should be hidden from view and your dog rewarded intermittently. The selection of favoured food or toys is essential since the goal is that the dog will learn that receiving these favoured rewards is dependent on relaxation in the presence of other dogs. 

Once your dog responds reliably to cues for relaxation and commands for obedience, and is receiving rewards on an intermittent basis, the treatment programme should progress to include low level (i.e. distant) exposure to other dogs. If your dog is still highly aroused in the presence of the other dogs, then consideration should be given to:

• The underlying emotional state – make sure that adequate ground work has been done to decrease your dog’s negative state of arousal before any practical introduction to other dogs begins.
• The distance between the dogs – make sure that you begin introductions at a distance that is great enough to not induce any negative reaction from your dog.
• Using dogs with whom your dogs gets on well – it can help to begin the introduction process with dogs that are familiar and do not lead to a negative reaction. This allows your dog to rehearse the introduction situation without any negative emotional responses.
• The need for a head collar to control your dog’s focus of attention – if a head collar is to be used it must be introduced carefully before it is used in the treatment context.
• Your own body language – pay attention to your own emotional state and make sure that you are as relaxed as possible.
• Increasing the value of the rewards and making sure that the timing of delivery of rewards is accurate.
• The need for further expert assistance and guidance – ask your veterinary surgeon for advice.

The next steps in the desensitisation and counter conditioning programme rely on a stimulus gradient. In other words gradually bring your dog closer to other dogs while rewarding it for being relaxed. It is important to give your dog clear signals so he knows what to do and can earn rewards in the presence of gradually more intense stimuli. A critical point comes when your dog starts to let other dogs into his personal space (about 2 metres). You must make sure that all dogs are safely controlled at this time, using a muzzle as necessary. With time and patience he should learn to accept other dogs.

Tips for success

Begin with a calm, and well-controlled second dog, in an environment where your dog is less anxious or threatened. Keep the dog at a sufficient distance so that your dog remains relaxed. Stay close to your dog so he will respond to your commands. 

Ultimately the aim is for your dog to learn to be relaxed in the presence of the other dogs such that there is no need for a display of aggressive behaviour. In the early stages it can be helpful to teach your dog an alternative behaviour to perform when it sees another dog, such as looking toward you, but this is an interim stage in the treatment process and not the ultimate goal. The aim of treatment is to change your dog’s emotional reaction to the other dog and not just its behavioural response.

The head collar can be helpful as a means of offering you a higher level of physical control, which enables you to direct your dog into acceptable behaviours such as the sit or heel in the presence of other dogs during the early stages of treatment. Pulling up and forward, turns the head toward the owner and causes the dog to move into a sit position. With the dog’s head oriented toward the owner and away from the other dog, lunging and aggression can be prevented, and the dog will usually settle down enough to see and respond to the owner. Rewards can and should be given immediately for a correct response (sitting), and tension reduced on the lead. If your dog remains under control with the lead slack, the reward (toy, food, affection) should be given, but if the problem behaviour recurs, the lead should be pulled and then released as many times as is necessary to get and maintain the desired response.

Remember that it will also be necessary to continue the evaluation of your dog’s emotional state. You need to be careful not to simply suppress the reaction to other dogs by overlaying it with an appropriate behaviour (such as looking at you) since this will not result in a long lasting solution to the behavioural problem. The long term strategy needs to involve working to reduce your dog’s level of anxiety and to reward relaxation in the presence of other dogs. 

What is the outlook for this problem?

Aggression is a normal behaviour and therefore it is never cured but it can be managed to minimise risk. Dogs with fear aggression may improve dramatically and learn to greet other dogs; but dogs with more assertive behaviour posturing will need a lot of reconditioning and expert assistance will frequently be needed. For many owners the ability to meet a number of other dogs under controlled circumstances can be a limiting factor in terms of success. It may be necessary to enlist the help of an appropriate local training facility but you should take professional advice before doing this as inappropriate introductions could make your dog’s behaviour worse.

Are there drugs that can help the treatment programme?

When the aggression toward other dogs is rooted in fear or anxiety, certain drugs may help to reduce the level of emotional arousal so that the behaviour modification can be successful. For situations where the problem has become highly conditioned and intense, certain antidepressants may be a useful aid, but the value of these must be considered carefully by your vet on a case by case basis. In most cases however, the best solutions involve increased relaxation and self confidence on the part of your dog, confident owner responses and some powerful rewards.