Was your dog playful with other dogs but suddenly found themselves getting into scuffles? Or perhaps they started lunging at other dogs while on a walk?
Maybe they were always friendly with strangers but now growl when someone tries to approach?
Why now? What changed?
Here are a few scenarios showing how a dog can develop unpredictable behaviors over time, especially as they mature:
The Dog That Was Friendly with All Dogs but Suddenly Turned Reactive
While it may feel like your dog became reactive overnight, it usually doesn’t happen that way—unless they were recently attacked by another dog, which can trigger immediate fear or insecurity around other dogs.
What is more likely, however, is that your dog was giving off very subtle signs of discomfort/uncertainty in situations where other dogs were present. As they matured, they began to develop more confidence and acted on those emotions, i.e. lunging, growling, and barking.
The Dog That Will Only Let Some People Pet Them but Not Others
This situation shares similarities with the scenario above, with a few slight differences. Some dogs simply need time to build trust with people. They aren’t as naturally trusting as other dogs, and that’s completely OK.
Lack of exposure—or, alternatively, an overabundance of socialization during puppyhood—can lead to a dog that doesn’t want to be petted all the time or has trouble trusting others.
For a dog like this, think about interactions with people in terms of “consent”. Did your dog consent to being petted? Or did the other person approach when your dog seemed nervous?
This is why reading your dog’s body language, in the moment, is so important. If your dog looks nervous, anxious, or overwhelmed, advocate for them and allow interactions only once they appear calm and comfortable. This helps build trust in your relationship and reduces the likelihood of your dog reacting toward a stranger—or worse, biting.
The Dog That Was Potty Trained but Suddenly Started Having Accidents
It can seem odd when your dog was doing great with potty training and then suddenly has an accident inside your home.
This often happens when there’s a sudden change in your dog’s environment, such as a big move cross-country or into a new home that feels unfamiliar. More importantly, big changes at home usually result in changes to your routine with them. When their routine is disrupted, your dog may struggle to predict when they’ll be taken outside to relieve themselves and, as a result, may start having accidents again.
It’s not just about the move itself—disruption in their routine is a major factor. One which will trigger changes in the other, and vice versa.
For example, if you recently moved, try to get your dog back on track by being as consistent as possible with the times each day that you take them outside.
Equally make sure you’re rewarding them often for making the right choices!
In Closing
Dog behavior isn’t always as unpredictable as it seems. If you’re struggling with the “why” behind sudden changes like the ones listed above, try to identify any trends that might have led to the shift in their behavior. Did they get into a scuffle with another dog? Did a person spook them recently? Have there been any changes to their routine?
Answering these questions will usually provide you with a good starting point to work from!
Nicolas Angione is the founder and head dog trainer at Hope Gables Canine, based in Fairfield County, CT. Inspired by his own dog's reactive journey and rehabilitation, he left his career behind to become a dog trainer. After years of shadowing other dog trainers in the industry, he started his own practice, which has successfully helped hundreds of dog owners, both domestic and abroad, regain peace and harmony with their dogs. Many of these success stories, dog training tips, and more can be found on their Instagram and YouTube pages.
