Dog Training Case Study: Cat Aggression in a Puppy Mill Breeder Beagle Mix


[The names of individuals in this case study were changed to ensure privacy.]


This case study was conducted as a training regiment for one of my clients, a 1-year-old beagle mix named Harper. The training process documented here not only addresses the behavior of the dog, but the behavior of the resident cat, a polydactyl boy named Winston.

Dog History

Harper was rescued from a puppy mill and adopted shortly before training sessions began. Mark and Kelly were looking for a cat-friendly dog, and per the shelter, Harper was a good match. She never displayed aggression toward the cats at the shelter according to the staff. Before adopting her, Mark and Kelly observed her interacting with the shelter cats directly. They were confident there would be no problems.

Emergence of Behavior

The one thing the owners did not factor in was their cat’s reaction to the situation. Winston had always lived in a one-animal house. He was a quiet but social personality. Harper on the other hand was an excitable, high-energy dog. Every cat she had met to this point was experienced with high-energy dogs. They knew how to tolerate invasion of space.

Upon introducing Winston and Harper, Winston became very nervous. His urge to run at the sight or sound of Harper and his aggressive behavior toward her quickly shifted her high excitement into aggressive behavior. Within a couple days, Winston could not be in the same room as Harper without her growling, baying, and biting at him.

Evaluation and Approach

On first observation, Harper’s behavior toward Winston was very similar to a beagle on a hunt. This was likely caused by the cat’s initial response to run from her, driving her instinct to chase and corner an animal of such size. It was also easy to see that the two animals were feeding off each other’s energy level and behavior. Basically the more excited Harper initially was upon seeing Winston, the more intense his fight or flight response. Both of these reactions resulted in even more excitement for Harper, who would reciprocate the flight response with chase and the fight response with aggression.

Harper also did not have a good grasp of basic obedience or respect toward Mark and Kelly. Since she was a new dog to their home and lifestyle, it was not unexpected; however, to introduce her to their cat properly, respect and attentiveness toward her new owners was essential. Harper needed to know how to behave, and Winston needed confidence in Mark and Kelly.

It became apparent that to address this situation, we would need to not only instill a sense of calm restraint in Harper, but a sense of trust and confidence in Winston toward the owners. Because Winston did not trust Mark and Kelly to keep Harper under control, he had to protect himself however he could.

I decided that taking a more assertive, correcting leadership approach versus positive reinforcement would be necessary in this case. There were three reasons for this:

  1. Harper’s level of excitement and therefore aggressiveness around Winston was too high. The use of treats in this case could come across as reward for her aggressive or over-excited behavior. Even in a calmer state, treats caused Harper to escalate back to the same level of excitement, which we wanted to avoid.
  2. Leading Harper, correcting her as necessary, and taking full control and responsibility of her behavior would provide Winston with confidence and trust in the owners. The more we could take control of Harper, the more subdued Winston became to her presence. The more subdued Winston became, the calmer Harper acted around him.
  3. After discussing different approaches with Mark and Kelly, they personally had more confidence in a leadership approach than a positive reinforcement approach. Since they understood leadership easier and had the confidence to replicate the exercises, we chose to use this approach.

We had two sessions over the course of two weeks to go over the leadership technique and how to execute them in a constructive and progressive way with Harper and Winston. Part of these sessions involved basic obedience with Harper to increase her attentiveness to Mark and Kelly. This included basics like name recognition, commands such as ‘sit’, ‘down’, and ‘stay’, and leash manners, which would all be incorporated into her interactions with Winston.

To start, we kept Harper on a leash while bringing Winston into the room. This allowed Winston to see we had control of the situation and would be able to address Harper immediately. It was clear that Harper could not even look at Winston without escalating. This made the leash imperative at the beginning of her training. The progression of her new interactions with Winston during our sessions was as follows:

  1. At the first sign of assertive or aggressive behavior from Harper, including tension on the leash, I would give her two quick but gentle ‘pops’ on the leash. This corrected her aggressive behavior and redirected her attention to me.
  2. If she did not respond to the tugs, I would use her name along with the tugs to pull her attention.
  3. If this second redirect did not work, I would step between her and Winston and back her away by stepping toward her. This gives Winston more peace of mind that I am taking control of her and addressing her behavior. It also creates more likelihood of Harper giving me her attention instead of Winston.
  4. Once she was a few more feet away from Winston, I would repeat her name to redirect, repeating backing her away and redirecting with my voice until I had her attention.
  5. Upon gaining her attention, I would have her sit and lay down, putting her in a more relaxed physical state.
  6. While in her calmed state laying down, I would move myself from between her and Winston, allowing them to see each other. This becomes Harper’s reward, as I am no longer correcting her behavior. It also shows her that I trust her in this calm state to see the cat.
  7. If Harper re-escalated into barking or lunging at Winston once I moved, she was still too close to Winston to ignore him. I would go back to stepping between them and backing her away. We repeated the process until she could stay calm while in sight of the cat.
  8. Once she could look at Winston while laying down for at least one minute, I would allow her to get up and walk away from the situation. We then came back to repeat the entire process. With each instance, I challenged Harper to stay calm while being closer to Winston.

Winston become much more trusting of Harper and me after about 5 repetitions of this. He recognized that so long as I was in control, Harper was not a threat. He slept in his cat tree for the remainder of the session.

Once Winston was calm and I could trust he wouldn’t run away or insight more excitement from Harper, I began walking Harper around the room on the leash, guiding her past Winston on his tree and correcting her behavior gently as needed. This challenged Harper to keep calm while in motion, not just while laying down.

Final Results

gray-house-dog-training-case-study-harperHarper the once cat aggressive Beagle mix and Winston the cat share some quality time their owner’s lap.

By the end of our second session, Harper and Winston were able to stay calm in the same room. Every day, Mark and Kelly took turns working with Harper. They kept her mentally and physically exercised with long walks treat-finding games. This helped reduce her excitement during training time. A couple of days before our second session, Kelly had them sitting on either end of their living room couch.

About two months after our last session I received a photo from Mark. You can see Harper and Winston sharing Kelly’s lap, with Winston’s paws pressed into Harper’s back kneading away. They continue to be happy, healthy pet-mates to this day.


  • When introducing a new cat or dog to a resident of the opposite species, always consider each animal’s individual personality and prepare to address unforseeable conflict between those personalities. This goes for two dogs or two cats meeting for the first time.
  • Cat-aggressive dogs typically develop this behavior for one of three reasons:
  1. The cat is uncomfortable and aggressive, which creates a similar response from the dog;
  2. The dog is too excited and escalates the cat’s response regardless of the cat’s friendliness with the same results as a.; or
  3. The dog has an instinctual drive to chase or harm small animals.

You must keep these reasons in mind and address your dog’s behavior accordingly. This means calming the cat, calming the dog, correcting the dog, or a combination of the three.

  • Cats and dogs can get along, even if they started off on a bad paw. All it takes is patience and the right approach that will communicate to both cat and dog.

If you are experiencing cat or dog aggression with your dog or any other behavioral issue, please email us at or fill out our contact form to request an in-house or online consultation to start developing your dog’s winning training plan.

Virginia Houser

Virginia Houser

Virginia has been working with dogs for over 15 years. Her greatest passion is training dogs to be the perfect companion for their owners.

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