Origins of Dog Reactivity

I’ve worked with thousands of clients over the years, specifically for reactivity, and consistently, most of my clients blame themselves. It breaks my heart. Not only because I know that in most cases reactivity is a result of more than one element, but also because it can result in pet parents getting caught in a cycle of blame and shame. And this never helps our dogs, or ourselves!

I thought I would break down some of the reasons for dog reactivity that likely have nothing to do with you! Keep in mind, it is almost ALWAYS a combination of genetics and environment (nature vs nurture) so we can never point to one influence solely. I also don’t want this article to make you feel like there is no hope for your dog; know that there are almost always opportunities for us to improve behavior and welfare for your dog!


Selective breeding has resulted in why our dogs have certain features. There is a reason why Great Danes are the size and stature they are and Miniature Poodles have a specific coat texture and come in different standard colors. These are physical attributes, but you’ve likely heard of the term “temperament” - an animal's nature, especially as it permanently affects their behavior. While some breeders pay special attention to temperament, so many dogs are not bred as a result of a focused program. Stray dogs, backyard breeders and puppy mills… these dogs are not selected for reproduction for temperament. That does not mean they are any less deserving of love, kindness and adoptive homes. What it DOES mean, is that we need to have realistic expectations and understand that puppies are never blank slates and that adopting a dog means that they also come with an individual set of genetics and history.

“Researchers have identified a new genomic region and anxiety-related candidate genes associated with fearfulness in dogs. Findings support their hypothesis that fearfulness and anxiety are hereditary traits in dogs, and there may be shared factors underlying anxiety in both humans and dogs.” 

Maternal Stress

Stress triggers the release of hormones like cortisol into the bloodstream and during a dog's pregnancy, this can affect the unborn babies as it is transferred via the placenta to the unborn pups. It changes the set point of the puppies’ stress response system, alters the quality of maternal care leading to a great impact on the behavior of the puppies. An adult dog that is fearful or anxious ideally would not be bred, not only because of the genetic component but the additional impact that this behavior has during pregnancy and whelping.

Dogs that are living in stressful environments are at risk for having puppies that may have behavior challenges. This is why responsible breeding and foster homes for rescues and shelters that aid in reducing stress are so important!


Oftentimes we cannot control the environment we live in and the events that occur. What is important is how that environment is interpreted and processed for your dog. The most sensitive development period will be that early socialization period before 14-18 weeks. How different was that environment vs the one we are bringing them into to live? Were there negative or stressful situations that occurred? This will impact your dog and their associations as they develop.

An unpredictable environment will result in stress for many animals. A very busy environment can be sensory overload for some dogs. We often see “trigger stacking” with dogs that are exposed to too many stimuli that are overwhelming without enough time to decompress from these singular events, leading to an escalated response such as a bite. We can imagine a cup that continues to fill with each event, eventually overflowing. 

In an ideal world…

… we would have responsible and ethical breeding practices and not hundreds of thousands of strays and abandoned dogs. But, sadly we don’t. This information is important for a few reasons; 1. If we are adopting, we can have realistic expectations and 2. If you are thinking about bringing a dog into your home, research where the dog is coming from and any history provided, and 3. Know that there is always a possibility that reactivity may occur despite your best efforts and sourcing your dog from the best situation. We cannot control all factors. 

I do want you to know that all is not lost if your dog is reactive, no matter the reason! We can always make improvements to help you and your dog. Reach out to me and let’s start working on a plan. 

© copyright 2023 by Bravo Dog Training Inc.

Dog behaviorist and dog behaviour consultant in vancouver, north vancouver, west vancouver, british columbia

© copyright 2023 by Bravo Dog Training Inc.

North Vancouver and Vancouver dog trainer and behaviour consultant