Monitoring behavior changes in your dog and knowing when to seek help

Young dog wearing red collar with humane in background

Sudden behavior changes in your dog can be concerning, whether it’s an aversion or fear of something they used to enjoy — think rough-housing with other dogs or daily trips to the local dog park — or a new habit that’s appeared out of the blue, like barking out the window or guarding their toys. Most dogs’ behavior will change over time, but those shifts can still catch many pet parents off-guard.

Just like humans, our dogs’ personalities are shaped by a combination of physical and mental factors. That’s why we teamed up with an Animal Humane Society Veterinarian and Behavior Specialist to help inform what’s at the core of your pup’s personality and what you should do if you notice a change in their behavior.

Below are the top three reasons for common behavioral changes pet parents notice in their canine companions, and what you can do about them.

Top reasons for behavioral changes in pets

Reason #1: Aging

Dog age to human age conversion chart

We’ve all heard the analogy that one dog year is akin to seven human years. But that’s not quite accurate. Our dogs go through so many physical and mental changes in their first few years of life that it’s actually equivalent to more than 20 human years. Imagine growing from a bouncing baby to a college graduate in just two years — of course your personality and preferences would change along the way! The same is true for our canine companions.

Around one to three years of age, many pet parents begin to notice their pup’s personality is changing. Perhaps they are more selective about what dogs they’ll play with at the dog park, or they’ve lost interest in highly physical games like tug or playful wrestling. It’s important to remember, although your furry friend is still young in your eyes, they’re maturing at an incredible pace.

“Even if you’ve spent hours socializing and training your dog, behavior changes can still occur, especially as they age,” explains Behavior Specialist Lauren Sorenson. Part of what makes your dog who they are is ingrained in their DNA — it’s out of your control. Be patient with your dog as they come into their own. “Don’t force them to partake in activities they no longer enjoy, and instead, work on finding new habits and routines you both love.”

Reason #2: Physical factors

Whether you suspect an injury or illness might be behind your dog’s troubling new behavior or not, a trip to the vet is always the first step. In addition to running bloodwork and other diagnostics that most behaviorists will require before working with your pup, your vet will ask you a variety of questions to get to the bottom of what’s going on, including whether or not you think your furry friend is in pain.

“Pain is one of the most common physical reasons for behavioral changes in dogs,” says AHS Veterinarian Dr. Angelica Dimmock. “For instance, a dog who’s developing arthritis may seem more tired than normal or could appear grumpy when moved. A dog with a toothache or gum disease might stop eating or take up a new habit of gnawing on things.”

So how can you tell if your pet is in pain? It’s helpful to assess your dog at home where they are most comfortable so you can give your vet the best information possible.

Holding a dog's paws

Dr. Angelica shared these tips for a brief at-home check-up:

  • Ask your dog to sit, stand, and lay down. Does your dog object to any of these movements? Take note of any stiffness or shaking during this process.
  • Next, very gently turn your dog’s head to the left and right, then up and down. You can also lead their gaze with a tasty treat.
  • Run your hand down your dog’s spine and note if they shy away at any point.
  • Touch their ears, paws, and take a peek at their teeth if you feel comfortable. Do you notice any cuts or debris? Does anything look red or swollen?
  • Lastly, bend and straighten each of their legs. Never pull or push in a way that your dog doesn’t seem comfortable with, and skip this step if your pup has been limping or won’t bear weight on her leg as you could make her injury worse.

This at-home check-up of your dog will help you bring the best information possible to your vet. It’s also a great routine to practice to help desensitize your dog to these types of physical touch, which are common in medical exams. Plus, it can help you monitor your pet’s health as they age.

Reason #3: Mental factors

We expect a lot from our dogs, from following us on every adventure to accepting our friends, family, and other pets without hesitation. Occasionally, these changes can overwhelm our pups and lead to alterations in their behavior.

Sometimes it’s easy to discern the cause of your dog’s stress: a big move, a new pet, unfamiliar friends or family in your home during holidays. Other times it’s harder to understand what’s happening in your pet’s mind.

“No matter what the cause of your pet’s anxiety, one training principle will always hold true,” promises Lauren. “Use positive reinforcement! Punishing your dog for being scared, stressed, or anxious can lead to further problems down the road.”

So if your pup is barking at strangers out the window since you moved to a new house on a busy corner, don’t reprimand her by yelling or swatting her away. These negative interactions only further her concern that strangers are bad or scary. Instead, sit with her by the window, and each time someone walks by, give her treats, pets, and encouragement. Over time, she’ll build a positive association with the thing that previously triggered her.

A dog looking over a fence

Change is the only constant

Every animal changes over time. Perhaps the best advice is to remember there’s something unique and wonderful about every stage of your pet’s life. From their bouncy and boisterous puppy phase to their sweet and serene senior years — your dog is your constant companion and best friend. The changes you go through together make the relationship you share even more special.


The tips above are not a replacement for speaking with your vet or trainer. If you’re concerned about your dog’s health or behavior, it’s always best to contact the professionals who know your pet best.

For caring, compassionate advice and resources to address all your animal concerns.

Contact the Pet Helpline