Causes of Canine Reactivity: Why Does My Dog Bark, Snarl, and Snap?

Updated: Apr 6


Dogs bark and snarl for all sorts of reasons. Sometimes it's because they're excited, frustrated, sometimes it's because they're afraid, and sometimes it's because they're angry. But what causes canine reactivity in the first place? In this blog post, we'll discuss some of the most common causes of canine reactivity and provide tips on how to prevent it.


“Reactive” is a word that's gaining popularity in the dog training community — but what exactly does it mean? Karen Overall, M.A., V.M.D., Ph.D., a specialist in Applied Animal Behaviorist, define reactivity as the "abnormal" (higher-than-normal) intensity of the reaction to a specific trigger (such as another animal or person.) Typically, we an increase in these categories when the reaction is labeled "abnormal":

  • Alertness hypervigilance)

  • Restlessness (motor activity)

  • Vocalization (whining, barking, howling)

  • Systemic effects (vomiting, urination, defecation)

  • Displacement or stereotypic behaviors (spinning, tail or shadow-chasing)

  • Changes in the amount or type of attention the dog gives the trigger

The term "abnormal" is crucial to Dr. Overall's definition. When their owners arrive home, when they see other dogs, when a cat passes by the window, or when someone knocks on the door, many dogs get excited. The reactive dog does not merely become ecstatic; he spins out of control to an extent that puts themself or others in danger.


One of the most common causes of canine reactivity is fear. Dogs may be afraid of other dogs, people, or even objects. They may not have been socialized well as a puppy but it's equally possible that there is a genetic predisposition to be fearful. If your dog is afraid of something, it's important to help them feel safe and secure. You can do this by providing a safe space for them to retreat to when they're feeling scared or overwhelmed (such as a designated area or their crate). Just by helping your dog feel safe, you can greatly reduce the level of stress they feel that causes them to become aggressive.


Another common cause of canine reactivity is excitement or frustration. This occurs when a dog wants something (to greet another dog, for example) but is prevented from getting access to it by leash restraint or some sort of barrier. This can lead to barking, lunging, and even snapping. The best way to prevent this type of reactivity is to provide your dog with opportunities to socialize safely in environments that are considered "neutral territory" and with dogs that are well socialized but use a fence for protected contact first BEFORE an actual in-person greeting.


Finally, dogs can become reactive when they are fearful and may seem "angry" when they are in a state of reactivity. They may bark and lunge when they encounter something they're afraid of. In serious cases, they do make contact and bite another animal or person. It's important to remember that fearful dogs are not being "aggressive." Yes, they are exhibiting aggressive behavior, but the problem is mostly based on fear. They're simply acting out of fear and trying to protect themselves. If you have a dog with this issue, please seek professional help. This problem is the most dangerous and has the most potential for a lawsuit. For safety reasons, it is best to avoid circumstances that elicit aggressive behavior as you work with a qualified professional. With the proper training, your dog can learn to trust people and feel less fearful around them. If you think your dog may be reactive, the first step is to consult with a veterinarian or professional animal behaviorist to rule out any possible medical causes. There are medical conditions that can change behavior and severe behavior problems can affect the body. The two go hand in hand so it's important to reach out to make an appointment with your vet and rule out medical causes first


Remember, there are several possible causes of canine reactivity, and it often depends on the individual dog. Some possible causes include prior traumatic experiences, lack of socialization or human interaction, genetic disposition, health problems, and more. It's important to work with your veterinarian, board-certified veterinary behaviorist, and qualified trainer to determine the root cause of the problem so they can address it and teach the dog to offer a different behavior that is more appropriate.

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