Why would my dog fight with dogs he has never met?
Aggression between unfamiliar dogs can be due to fear, hierarchal competition, possessive behavior or protective behavior over territory or owner. Aggression between dogs can result in injury to dogs and/or to the people trying to separate them. The behavior can consist of growling, snarling, barking, lunging, snapping, and biting.
Fear based and defensive aggression toward unfamiliar dogs
This aggression is very common in aggressive encounters with other dogs. The diagnosis is based on the body postures and reaction of the dog when faced with another dog. However, these postures and reactions may change over time depending on the consequences of the interaction. For example, if the dog learns that the aggressive display stops encounters, the behavior tends to increase in intensity and the body postures may become more confident. Therefore it is important, not only to observe the expressions and posturing at the present time, but also those from the initial few encounters. The fearful dog will often have the tail tucked, ears back and may lean against the owner or attempt to get behind them. They may be barking at the approaching dog, while lunging and backing up at the same time. Often the dog is avoiding eye contact. This behavior can be precipitated by previous aggressive attacks from which the dog could not escape and sustained injury. In other situations the owner creates tension via leash tightening responses that signal the dog that the approaching dog is of concern. In addition if the owner is frustrated, anxious or worried about the dog’s behavior, then the dog is likely to pick up on the owner’s reactions and associate them with the approach of the other dog (rather than their own behaviors. Thus the dog becomes even more defensive. Owners that try and calm their aggressive dog may serve to reinforce the actions the dog is engaging in at the time, , while those that threaten or punish the dog in an attempt to stop the behavior, will only serve to heighten the dog’s fear and anxiety in relationship to the stimulus. Good control can help to calm the dog, while owners who have their dogs restrained on a leash (especially with a choke or pinch collar) and have poor control often have highly defensive dogs. Dogs that are restrained on a leash or tied up are more likely to display aggression when frightened, because they cannot escape.
Dominance motivated aggression between unfamiliar dogs
This aggression can be elicited by dominant or assertive gestures or postures from either dog. These can include placing head or feet, on the back of the other dog, dominant body postures such as eye contact, and high tail and stiff legged approach. If one of the two dogs does not show appropriate appeasing or submissive responses toward the other dog, then aggression might ensue. Owners may inadvertently heighten the anxiety and arousal by the way in which they respond such as when they pull and tighten or correct with the leash or when they use threats or disciplinary techniques. These may signal to the dog that the impending approach is problematic. Leash restriction also does not allow the dog to react with a complete rate and range of responses including body postures, approach and withdrawal.
Problems may escalate quickly in dogs that are anxious or fearful and in dogs that lack good social skills with other dogs. For example if the assertive or dominant expressions and gestures frighten the other dog, either dog may become defensive and aggressive. Conversely, the signaling dog may not be reading the signals of the second dog and might increase the intensity of its displays, perhaps to the point of aggression, even when the other dog shows deferential behavior. This can lead to the second dog becoming defensively aggressive. While a pack hierarchy can generally be maintained within a social group of familiar dogs with a minimum of fighting through actions, posturing, and visual and vocal signals, this does not necessarily work when unfamiliar dogs are meeting and greeting for the first time. In addition, changing circumstances and environments on walks, behavioral genetics, lack of sufficient socialization to other dogs, previous experience and the wide array of differences in physical appearance and behavior between breeds and individuals may compound the problem and increase the uncertainty and anxiety. For example, smaller dogs might repeatedly “attack” larger dogs that are attempting to avoid interaction while dogs of near equal dominance and those of the same sex are most likely to compete for dominance. Some extremely bold or assertive dogs will fight rather than back down when challenged. Assertive dogs may be over-assertive and/or overprotective if the owners do not have good verbal and physical control. If the dog pulls the owners along during walks, it will take the lead in reacting to stimuli that it meets along the way, rather than looking to the owner for direction and reassurance.
Territorial aggression toward other dogs
This aggression is primarily exhibited when unfamiliar dogs are on the resident dog’s property, or what the aggressor considers 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. See our handout on protective and territorial aggression.
Learned components of aggression
Learning and conditioning aggravate most forms of inter-dog aggression. Should threats or aggression result in the retreat (or removal by the owner) of the other dog the behavior has been successful. If the owner tries to calm the aggressive dog this may only serve to reward the aggressive responses. One of the most common mistakes is to punish the dog that is showing aggression toward other dogs. This usually serves to heighten the dog’s arousal, and teaches the dog that the stimulus (other dog) is indeed associated with unpleasant consequences. Many owners, in an attempt to gain more control, then increase the level or type of punishment (e.g. prong or electronic shock collars), which further heighten the dog’s arousal and in some cases may lead to retaliation and defensive aggression toward the owners. Unfortunately, owners may be confused by the fact that at least initially these products may suppress the undesirable behavior. However, this does not mean that these techniques are working since even if the response has been inhibited, the negative association might be becoming more intense. 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. In short, if the owners cannot successfully control the dog and resolve the situation without heightening the dog’s anxiety or increasing its fear, the problem will escalate with each subsequent exposure.
How can I prevent my dog from becoming aggressive with other dogs?
Prevention starts with puppy training and socialization. Early and frequent association with other dogs will enable your pet to learn proper interactions and reactions to other dogs. This can be very helpful in prevention of aggression to other dogs. Socialization must occur with other dogs that are calm and communicate well with other dogs and should progress to a variety of shapes, sizes and personalities. Ear carriage, eye contact, tail position and even body postures may be difficult to “read” if there are significant size disparities or if one or both of the dogs has cropped ears, hair that covers the eyes or a docked tail.
You must have good control of your dog. This means that your dog will take contextual cues from you, and may be calmer, less anxious and less likely to be protective in the presence of new stimuli. Moreover, the dog should reliably respond to commands to ‘sit’, ‘stay’ and ‘quiet’ so that appropriate responses can be reinforced rather than undesirable responses getting punished.. If necessary, the dog may need a head halter to give you additional control. When in situations where the dog may encounter other dogs, a leash is necessary.
For territorial behaviors, what is most important is to prevent the dog from engaging in prolonged and out of control aggressive displays both in the home and yard. Aggressive displays include barking, lunging, fence running, jumping on doors, windows and fences. These types of behaviors should be discouraged and prevented by blocking windows if needed and going outside with the dog to prevent them. Using a leash and head collar both indoors and outside will increase control and allow you to interrupt aggressive responses and redirect the dog to more appropriate ones. One important component is teaching your dog a ‘quiet’ command for barking (see handout on Barking and head halter training).
My dog is already aggressive to other dogs. What can I do?
First and foremost, you must have complete control over your pet. This not only serves to calm the dog and reduce its anxiety, but also allows you to successfully deal with each encounter with other dogs. Leashes are essential and the use of head collars and/or muzzles are strongly recommended for dogs that will be in situations with multiple dogs. Because of the potential for injury, liability and increasing the intensity of the problem, a behavior consultation would be advisable to structure the following plan. Until you have more control and a treatment plan in place all encounters with other dogs must be avoided.
Begin by establishing reliable responses to basic obedience commands. If the dog cannot be taught to display a relaxed ‘sit’, ‘stay’, ‘come’ and ‘heel’ (see our handout on settle exercises), in the absence of potential problems, then there is no chance that the dog will respond obediently in problematic situations. Reward selection can be critical in these cases, since the dog needs to be taught that obedient behavior in the presence of the stimulus (other dog) can earn the dog-favored rewards (for most dogs this is a food treat such as cheese, small pieces of hot dogs etc.). The goal is that the dog learns to associate the approach of other dogs with rewards. Long term treatment consists of desensitization (gradual exposure) and counter-conditioning the dog so that the approach of the other dogs leads to a positive emotional response. (see our handouts on behavior modification and on fear and panic of animals and people). In training terms the dog must be taught to display an appropriate, acceptable response when other dogs approach (e.g. ‘sit’, ‘watch’, ‘relax’) which can be reinforced (differential reinforcement or response substitution). This must be done slowly, beginning with situations where the dog can be successfully controlled and rewarded and very slowly progressing to more difficult encounters and environments. The first step is to perform training for its favored rewards, in a situation where there are no dogs present and the owner is guaranteed success. Food or toy prompts can be used at first, but soon the rewards should be hidden and the dog rewarded intermittently. The selection of favored food or toys is essential since the goal is that the dog will learn that receiving these favored rewards is contingent on meeting other dogs. A leash and headcollar can be helpful to increase control and aid in compliance with training. During this pre-training exposure to other dogs should be avoided since ongoing expression of the behavior tends to reinforce it.
Once the dog responds quickly and is receiving rewards on an intermittent basis, training should progress to low-level exposure to other dogs. If the owner’s training and the rewards are not sufficient to control the dog in the absence of the other dogs, then utilizing a leash and head collar, selection of more motivating rewards, and seeking the assistance and guidance of a behaviorist should be considered. The next steps in desensitization and counter-conditioning rely on a stimulus gradient. In other words your dog needs to be controlled, (preferably with leash and head halter) and respond to commands and rewards in the presence of gradually more intense stimuli. Start low and mild and work up to gradually more intense. The key is to have a dog that is sufficiently calm so that it can learn. By training the dog for rewards in the absence of the stimulus, using a head halter, and beginning exposure training with low enough levels of the stimulus, your dog should be calm enough to focus, settle and learn that the other dog is not a threat. In fact, with counter conditioning (favored rewards paired with association with the stimulus) your dog should begin to enjoy meeting and greeting other dogs. If your dog remains too fearful, excited, aroused or out of control, you need to consider further training prior to exposure, a head halter (if you are not already using one), lower levels of stimulus exposure (e.g. a less intense starting point for desensitization) or perhaps drugs to help your dog calm and focus. (see below)
Begin with a calm and well-controlled second dog, in an environment where your dog is least anxious or threatened, and at a sufficient distance to get your dog to respond to your commands. Gradually the dog is exposed to dogs at closer distances and in more familiar locations. Using the head halter and a prompt (lure reward, favored toy, set of keys) it should be possible to keep the dog focused on the owner and sufficiently distracted. While dogs with fear aggression may improve dramatically, dogs with dominance-related aggression that are trained in this manner do not necessarily get better about greeting other dogs, but should learn to walk calmly with their owners and not initiate fighting behavior.
Dogs that are exhibiting territorial aggression should be retrained in much the same manner, but the gradient of stimuli will need to be adjusted. Begin in the front hall or on the front porch with no other dogs around. Then with the dog controlled in the hall or on the porch, other dogs could be brought to the perimeter of the property. Over subsequent training sessions, the dogs could be brought closer to your dog, or your dog could be moved closer to the other dog. (See our handout on Behavior Modification – desensitization, counter-conditioning, differential reinforcement and flooding).
Another way to disrupt the undesirable response and get the dog’s attention is to use an air horn, shake can or citronella spray collar. In fact, if the dog barks prior to the aggressive display, a citronella spray bark collar will be activated by the dog’s barking insuring immediate timing and disruption so that once the barking is inhibited, the behavior may not progress. Once the inappropriate behavior ceases, and you get your dog’s attention, the dog should be redirected to an appropriate behavior such as play. The greeting should be repeated, until no threats or aggression is observed.
Success can be achieved in a number of ways, but head halters are generally the most important tools. Head halters provide enough physical control that the desired behavior can be achieved (sit, heel) since pulling up and forward, turns the head toward the owner and causes the dog to retreat 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 prompt. A second hand can guide the muzzle under the chin to insure eye contact and help to calm the dog. Rewards can and should be given immediately for a proper response (sitting, heeling), by releasing tension on the leash. If the dog remains under control with the leash slack, the reward (toy, food, affection) should be given, but if the problem behavior recurs, the leash should be pulled and then released as many times as is necessary to get and maintain the desired response. The dog’s anxiety quickly diminishes as it learns that the other dog is not to be feared, that there is no opportunity to escape, that its responses will not chase away the other dog, that responding to the owner’s commands will achieve rewards, and that the owner has sufficient control to achieve the desired behavior (which further calms the dog). Also since there is no punishment or discomfort that might further aggravate the situation and rewards are not being given until the desired behavior appears, fear and anxiety will be further reduced (See handout on head halter training).
Are there drugs that can help the treatment program?
Occasionally, for fear aggressive dogs in particular, anti-anxiety drugs may help to calm the dog enough so that the retraining session is successful. Dogs that are too highly aroused may be unable to focus, settle and learn that other dogs are not a threat. For situations where the problem has become highly conditioned and intense, antidepressants may be useful for regaining control. In most cases however, the best calming influence is a head halter, good owner control and some strong rewards.