Why would my dog behave aggressively toward unfamiliar dogs?
Though dogs as a species are considered social, many factors could contribute to a dog’s aggressive response to an unfamiliar dog. For example, some dogs miss being socialized during the sensitive period for socialization, which ends by 14 weeks of age. Without this early comfortable exposure, some dogs develop aggressive behavior when they encounter new dogs.
Sometimes, socialization does not go as planned, and a puppy is unexpectedly frightened by another dog. A long-lasting fear of other dogs can result, and this fear can trigger an aggressive response. Because genetic and early environmental factors contribute to behavior, even well-socialized dogs can develop aggression toward other dogs. (See the handout “Puppy Behavior and Training – Socialization and Fear Prevention” for more information.)
There are other risk factors, such as repeatedly encountering dogs from behind a barrier. The barrier could be a fence, a window, or even a leash—after all, your dog is probably not permitted to meet encountered while on a walk. The aggression that develops in this situation is rooted in frustration and can include components of both territorial behavior and reinforcement-related or learned behavior.
Perhaps your dog does not bark or lunge at most dogs and begins to interact in a friendly manner, playing nicely for a while before showing an aggressive response, such as snarling, barking, or snapping. Aggression during an interaction can be more complicated, as there are many possible reasons for the behavior. One consideration is that your dog could be experiencing pain—have your veterinarian do a thorough examination.
"One consideration is that your dog could be experiencing pain—have your veterinarian do a thorough examination."
A second possibility is that the dogs that trigger your dog to respond aggressively have a different communication style. All breeds do not speak the same language; some use more signals than others. If you look closely, you may discover that your dog tried to communicate that he was ready to take a break and said ‘back off’ in a subtle manner (see body language) but that the other dog did not respond. Dogs may use signs such as leaning away, stepping away, lowering their body, or looking away to try to end interactions. When those signs are ineffective, dogs learn to skip them altogether and instead reach for stronger signals such as barking, growling, and snapping.
It is best to consult a behavior specialist to help with the assessment. Your dog may exhibit aggression for more than one reason. That is, there may be more than one context and diagnosis.
What are some common types of inter-dog aggression?
Fear-based. Initially, dogs show signs of fear though these signs may disappear over time. Signs of fear can include avoiding, looking away, or barking and backing away.
Frustration-based. Dogs bark and lunge toward other dogs when they cannot access the dog. Often, dogs with frustration-based aggression are friendly with dogs they meet without a barrier. Some people refer to this behavior as ‘leash aggression’ or even ‘reactivity’, though those terms do not specify the underlying motivation. Note: a friendly response is not guaranteed, and it is risky and potentially dangerous to remove a safety barrier to ‘test’ a lunging dog.
Territorial. Dogs bark and/or lunge at dogs that approach their home, property, or vehicle.
Reinforcement-related or learned. Dogs experience an innate reward for barking and lunging, especially if they are fearful or territorial. Behaviors that are rewarded will continue and often strengthen over time.
Gender-related. Dogs are only aggressive toward dogs of a specific gender; for example, a male dog who is only aggressive toward other male dogs.
Possessive or resource-related. Dogs behave aggressively when another dog approaches them while they are close to or have something valuable. The valuable item can be food, a toy, or a particular person.
Predatory aggression. Dogs chase other dogs in a non-playful manner, typically with arousal and vocalization. Note: predatory aggression is not the same as predatory behavior. True predatory behavior is not a type of aggression, and dogs are not emotionally aroused, but the behavior is very dangerous.)
Understanding the motivation behind your dog’s behavior is essential to apply the correct treatment.
Are there any specific details that can help with the assessment?
To evaluate your dog’s motivation, it is helpful if you can identify some details about the behavior. Consider, for example, whether your dog gets along with most dogs, which reflects solid social skills. If that is the case, what types of dogs trigger her aggressive response—do you notice the recipient dog is always a certain size, color, or gender? Maybe the other dog shows a particular behavior—high energy, loud, or meek? These factors provide an understanding of the reason for the aggressive behavior and help the behaviorist diagnose and design a more effective treatment strategy.
Also, pay attention to how quickly your dog recovers after an event—a longer recovery suggests a higher level of emotional arousal. Your dog’s treatment plan will include steps to reduce this arousal. Try to notice the point at which your dog becomes alert—freezing and staring are subtle communications that often precede barking and lunging. If your dog reacts to dogs even when they are far away, he may be experiencing anxiety about a potential interaction. Anxiety must be treated so your dog can become less vigilant and learn better.
It is essential to remain objective to avoid a misdiagnosis—a behavior specialist may ask about your observations to determine the cause of the behavior.
"It is essential to remain objective to avoid a misdiagnosis—a behavior specialist may ask about your observations to determine the cause of the behavior."
Why does my dog lunge at me when another dog is in view?
When dogs are very aroused and frustrated, they can lose sight of the focus of their aggression and redirect toward a nearby person or even a companion dog. To avoid injury, minimizing exposure to other dogs is important until treatment is well underway. If you cannot avoid encountering other dogs, consider using a basket muzzle on walks where you might encounter other dogs (see muzzle handout). Since your dog will be vulnerable while muzzled and could be injured should another dog attack, it is important to walk only in areas where other dogs will be leashed and cannot bite your dog.
Do not try to train your dog by giving him commands or corrections while he is lunging at you-- try to stay calm and quiet. Hold the leash steady with just enough tension to keep your dog from physically connecting with your body. It often helps to stand still rather than try to continue moving forward, as pulling on the leash can cause additional frustration and increase the intensity of the aggressive response.
Should I correct my dog when he is behaving aggressively toward another dog?
Punishment-based strategies can contribute to an increased intensity of aggression and should be avoided. Whether your dog is exhibiting redirected aggression and is lunging toward you (see the previous paragraph) or is lunging toward another dog, a correction is likely to increase his arousal and frustration. When you correct your dog, you are engaging in a confrontation—now your dog is fighting two fights, and it will be even more challenging for him to relax and recover from the encounter. (See the handout "Why Punishment Should be Avoided" for more information,)
Another concern with punishment is that when you correct your dog for exhibiting a lower-level signal, such as a growl, snarl, or snap, you teach your dog to abandon safe and valuable communicative signals. Your dog will instead use stronger signals, such as lunging and biting. (See the handout “Canine Communication – Interpreting Dog Language” for more information.)
Your treatment plan will include options for reducing aggression without confrontation. (See the handout “Dog Behavior Problems – Aggression Towards Unfamiliar Dogs Part 2: Treatment” for more information.)