Why Do Dogs Show Aggression To Other Dogs

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Do you own a four-legged Jekyll and Hyde? A dog that is sweet as pie to you and your family, and even to strangers, but lunges like a crazy animal when another dog passes by? Or maybe your dog is one of the inscrutable canines that is best friends with the neighbor dog one moment, and mortal enemies the next. So from where does this behavior come, and how do you stop it? Any interaction between dogs is a form of communication, so it is important to first understand how your dog perceives other dogs. But why does your dog attack other dogs and the neighbor dog does not? There are some common threads among all dogs, but the reason most relevant to your canine companion will depend on his history and temperament as well as his biology.  

The Root of the Behavior

Evan MacLean, an anthropologist and psychologist from the University of Arizona, believes that hormones may be at least partially responsible. He and his team recently published a study in Frontiers in Psychology, where they discuss the relationship between the hormones vasopressin and oxytocin and canine social behavior. The team found that dogs who have a more even temperament tend to have more oxytocin in their blood, while those who are more aggressive have more vasopressin. MacLean recognizes that hormones are only part of the picture, however. Many dogs shift toward aggression when they feel threatened in some way. For some dogs, even the sight of another canine is enough to come across as a threat. Other dogs only respond aggressively if a fellow canine encroaches on their territory, attempts to claim dominance, or appears to be competition for resources such as food or toys. In some cases, two dogs may simply be in a personality clash, which can happen in dog society just as it happens among humans.

Some dogs may be more prone to aggression because of their temperament, history, or situation. If your dog had a bad experience with other dogs when he was young, and even if his first owners didn't socialize with other dogs, he may be fearful of other dogs and thus more aggressive as an adult. Some dogs also tend to feel more insecure when they are leashed or fenced, which makes them more aggressive to other dogs when in those situations. Regardless of the source of conflict, the aggression itself is an attempt by the attacking dog to claim or re-claim dominance. This rarely happens suddenly. Most dogs will give another dog a warning sign, such as a growl or a baring of the teeth, to show that the other dog's behavior is not okay. Typically, this will only escalate to aggression if the other dog fails to show submission.

Encouraging the Behavior

There are probably many inscrutable behaviors in your dog's repertoire, but aggression may be one of the most frustrating and scary. You may worry that your dog will do harm to the other dog, the other dog's family, himself, or your loved ones. Your instinct to stop the behavior is spot on, but there are effective and ineffective ways to go about it. First, you as the human need to stay calm at all times. If you show fear or anger, your dog may become more upset and his aggression could become worse. Instead, work your way up to calm interactions with dogs that your canine companion perceives as safe. Experts recommend first walking past other dogs, then spending some time in the presence of another dog, engaged in a safe and enjoyable activity.

Many dogs are motivated by treats, so you can try carrying some in your pocket whenever you expect to be around other dogs. If you instead offer treats when another dog is approaching or nearby and your dog acts calmly, you can build up positive associations. The most important thing is not to punish your dog if he shows signs of becoming aggressive. This causes the dog to associate the other animal with punishment and only worsens the insecurity, which can make aggression worse. If your dog is having real difficulties being calm in the presence of others, you may want to hire a professional trainer.

Other Solutions and Considerations

In rare cases, a dog's aggression may come from a neurological condition or the onset of a disease that is causing your dog physical discomfort. If you suspect that something about your dog is not quite right or typical, do not hesitate to make an appointment with your veterinarian. In addition to examining your dog to see if he is in pain or otherwise uncomfortable, he or she may order an MRI to screen for a neurological condition that may be causing unusually high aggression levels. Your veterinarian may also choose to evaluate whether your dog may have an underlying anxiety that is contributing to the aggression. If so, the vet may be able to prescribe a medication such as a serotonin reuptake inhibitor or a benzodiazepine.


Whatever the reason for his behavior, training your dog out of aggression can be a challenging process. Be patient with yourself and your dog, and remember that any animal's anger is usually a manifestation of fear. If you can help your dog to feel more comfortable around other dogs in a variety of situations, taking your dog out will be much less stressful for both of you. It may be a dog-eat-dog world out there, but your little buddy doesn't have to be a part of it!