Driving down the long, winding lane to her home, Pam could see a white flash darting through the pasture.  A pit rose up in her stomach as she feared the worst. Less than an hour ago, she had brought home an adorable yearling miniature donkey as a companion for one of her retired horses.  Little Olivia, the donkey, was the picture of cuteness; white and fluffy with black spots and the longest donkey ears. Not bigger than your average Labrador Retriever, Oliva had been unloaded from the trailer, greeted by the family, and placed in a pen attached to the barn. Pam then had to run out to pick up her son from a play date, and instructed the rest of her children to keep the dogs in the house until she got back and could supervise introductions between Olivia, the dogs, and her other horses.

Unfortunately, one of the dogs had gotten out and she was arriving home to a scene of pure chaos.

As Pam toward the scene, she could see Olivia sprinting in a panic, with her dog Roscoe hot on her heels. Olivia ducked under a fence as Roscoe repeatedly bit into her hind legs. Once under the fence, Olivia suddenly and unexpectedly stood her ground and pinned the dog by standing on his back. The yearling then proceeded to kick the dog and bite the back of his head. This little donkey was not going down without a fight.

Pam jumped into the mix, restraining the dog under her foot and desperately trying to push the angry little donkey off of him, but Olivia was in full-out fight mode and wouldn’t budge. “I think she would have killed him if I hadn’t shown up,” Pam said. Leaning against the fence, she began pressing her other foot against the donkey, finally managing to shove her off of Roscoe. The donkey wheeled around and bit Pam on the calf, then ran away. “Get a lead line!” Pam yelled at her son.

Roscoe’s injuries were minor, so she tied him to the fence and went to check out Olivia’s wounds. The yearling had bites to three of her four legs and puncture wounds to her throat. Pam quickly called the emergency vet. Olivia would recover, but the trauma of the attack would stay with her for a long time.

This was not the first time Roscoe had gone after one of Pam’s animals. She adopted the mixed breed dog at the local animal shelter when he was just 8 weeks old and even then he had the urge to chase. As a puppy, he would sneak into the pasture with her five horses and begin running at them.  The little red dog would disappear into a herd of thundering hooves. “I can’t watch. He’s going to be trampled,” Pam told her husband.  Roscoe and the family’s other dog were free to roam their expansive Colorado farm, and surprisingly, he remained unscathed—most of the time.

When Roscoe was 10 months old, he came into the house through his doggy door, revealing a bloody mouth. Five of his front teeth were barely hanging from his gums. A trip to the vet showed that his hard palette was fractured. The teeth had to be pulled and Roscoe’s mouth was put back together with reconstructive surgery.  Although no one saw it happen, the vets assumed an injury this severe could only have happened with the force of a horse’s hoof.

You would think Roscoe would lose the urge to chase after getting his teeth kicked in, but you would be wrong. The family installed an invisible fence to prevent him from accessing the pasture and barn area.  Roscoe soon grew into an adult dog weighing 60 pounds, and at that size, posed a much greater threat.

Yet more than a year passed by without incident, until the day Pam brought Olivia the donkey home. It was only after the attack that Pam realized she had forgotten to put Roscoe’s invisible fence collar on that day. He had come out of the house to find a new, perfectly-sized prey animal for his chasing pleasure.

That’s when I was called in. As a certified dog trainer who specializes in aggressive or hard-to-train dogs whose owners are at their wit’s end, I frequently help owners whose dogs like to chase or harass livestock, wildlife, or people.



Roscoe’s case is not unusual. Dogs are predators by nature. Horses, donkeys, deer, rabbits, and squirrels, just to name a few, are all prey animals. Predators are born hunters and even though the cute little fluffy pup that you share your home with looks a lot different from a wolf, many of our pet dogs have retained the same prey drive that keeps their wild cousins alive. They are hard-wired to chase and selective breeding has increased the tendency in some types of dogs.

Hunting, tracking, and herding are all types of predatory behaviors. When your dog chases a ball or shakes a stuffed toy, this is a type of predatory behavior.  When Greyhounds at the track or Sight Hounds on a lure course chase the little stuffed bunny, they do this because of prey drive.  Sometimes dogs with high prey drive will direct their attention to chasing cars, runners, or cyclists. Sometimes they will choose to chase your horse.



Predatory aggression can be extremely difficult to work with. Management by keeping the dog leashed or securely fenced is always the safest option, but it limits the owner’s ability to enjoy outdoor activities in natural environments where you may encounter other animals. If you have a dog prone to chasing, he should never be left unsupervised with prey animals. If you are unable to watch the dog, keep him indoors or in a fenced area.



If you have any hope of calling your dog away from a potential chase, he must have a basic understanding of the foundation skills:

      1. Heel
      2. Sit
      3. Down
      4. Stay
      5. Come
      6. Leave it

    Address this training outside of the chase issue first to ensure he is responsive to your commands.

    Gradually increase the distractions while you practice with your dog until he is able to pay attention to you even in the presence of prey animals. For example, have the first lessons inside your home, then inside your yard, then graduate to the dog park. And remember, if you only require your dog to obey you when you are in training mode, he will have a tendency to ignore your commands the rest of the time. Be sure to require your dog to listen to you and practice self-control throughout the day. In this way, he will find you a worthy and relevant leader.



    Now that your dog understands what your verbal commands mean, it is your job to learn to read his body language, which includes eying and stalking. Chase behavior is frequently triggered by common actions in the prey animal, including:

        1. Quick or jerky movements
        2. Fear
        3. Struggling or limping
        4. Injury
        5. Yelping
        6. Running

      Some dogs also learn that by barking at or harassing a horse, they can cause him to move, creating the opportunity to chase.  Many people respond to their dog chasing by yelling, screaming, threatening the dog or offering him treats to stop chasing. None of these techniques will work because once the dog is in full prey drive, he no longer hears you. He has tunnel vision of sorts, and you wind up sounding like the school teacher from Peanuts. Chasing is part of a natural sequence of predatory aggression including:

          1. Scan
          2. Eye
          3. Chase
          4. Bite
          5. Shake
          6. Hold
          7. Kill
          8. Dissect.

        The key here is catching your dog as early as possible in this sequence, preferably while he is still on number 1 or 2.  If you become aware of your dog’s body language, you can interrupt the behavior before the dog has begun to chase.

        For instance, if you see your Border Collie beginning to crouch down in order to stalk your horse, this is the time to interrupt. Clap your hands loudly, call him over to you, and put him on a down / stay where you can supervise him.  If you break the sequence early enough, you can prevent the chase from ever starting. Once the dog has begun to chase, it will be difficult,if not impossible, to distract him from the chase.

        Prey drive is so hard-wired into the dog’s DNA, it is much more than just a behavior problem.  It is his natural instinct.


        FIX #4 – E-COLLAR

        I live and work just outside Boulder, Colorado. We are blessed with 43 thousand acres of open space surrounding our city, much of it accessible for hiking and trail riding. I spent years on this land assisting Colorado law enforcement agencies as a certified canine search and rescue dog handler for missions in this area and around the state. In addition to lost hikers, our expanse of Colorado wilderness gives dogs here more than ample opportunity to harass horses, prairie dogs, deer, elk, and cattle grazing on these public lands. This is strictly forbidden and has kept me very much in demand as a dog trainer.

        Through years of experience working with more than a thousand dogs, I have found that the most effective way to reach a dog that has shifted into prey drive is by using a remote collar. Remote collars, also called electronic or e-collars, use an electronic stimulation to communicate with the animal. Often this is the only method that will snap a dog out of a prey driven event once he has gone into full-on chase mode. It allows the handler to get the dog’s attention just long enough so that he stops momentarily as if to say, “Are you talking to me?”  During this moment, you can redirect the dog to a more appropriate behavior such as coming to you.

        Before ever using an e-collar to correct a specific behavior, it is important to introduce the collar to the dog and teach him the language of the collar. By this I mean we introduce the collar to the dog at the lowest possible level at which he feels the stimulation. The e-collar feels much like a vibration or a hum. I will begin hitting the button on the e-collar at the same time I issue a command to the dog. In this way, he learns the collar is an extension of my voice. He should not be upset by this process. If he is, you have increased the level on the collar too high.

        During this introduction phase, I will review all of the dog’s basic commands.  When working on the come command specifically, it is important to think of the e-collar as a way of putting pressure on the dog from a distance. With your dog on a long leash, lunge line or retractable leash, call him to come to you and hit the button on the e-collar simultaneously. As soon as he moves in your direction, come off the button and praise the dog. You are removing the pressure the moment the dog makes the right choice. Away from you = pressure. Towards you = release.

        At first, the dog may not understand what you are asking. This is where your long leash comes into play. You will use it to coach the dog into the right behavior. If he does not come the first time you call, command him to come a second time but continue hitting the button on the e-collar until he begins to move in your direction. Use your long leash to gently draw the dog into you. As soon as he takes one step in your direction, even if it was because you are pulling him your way, come off the e-collar button and praise your dog lavishly. You may even want to reward come with a food treat or play with a favorite toy.

        Repeat this until your dog begins to understand that coming towards you is a good deal, but refusing or pulling away is a bad deal because it keeps the pressure on.  I will usually spend a couple of weeks improving the dog’s foundation skills and gaining off-leash control before setting him up with a prey-drive trigger.

        Now that the dog understands the language of the e-collar and is clear what each command means, I will move onto his chasing issue. Keep in mind, as the dog’s arousal level increases, you will need to increase the level on the e-collar. Using a muzzle and leash during these initial interactions will help to keep the other animals safe.


        Redirecting Roscoe

        In the case of Roscoe, I began working him muzzled and on-leash at a distance of about 100 feet from Olivia the donkey.  Olivia was also on a lead line as she obviously had become very distrustful of the dog and somewhat aggressive towards him. Working the dog at a distance that keeps him under threshold is very important at first.

        At 100 feet, Roscoe would look at Olivia with interest but had not gone over into prey drive. Each time he would look at the donkey, I would command him to “leave it” and “heel” while hitting the button on his e-collar. Since we had previously worked on these behaviors, he would redirect his attention to me, which I rewarded with praise and bits of chicken.

        With another handler walking Olivia, we gradually began decreasing the distance between the dog and the donkey.  Within 30 minutes, dog and donkey were walking calmly side by side.

        Over the course of several more sessions, we were able to drop both animals’ lead lines and allow them to be free near one another. Be aware, Roscoe remained muzzled during these encounters. It is important to work up to allowing the dog to make a mistake. If he is forever tightly controlled around his trigger animal, you will never have an opportunity to create a teachable moment.

        During one training session, Olivia got a wild hair and jumped quickly to the side, gave a little buck, and began cantering off – all trigger behaviors for a predator. The quick movements triggered Roscoe’s predatory aggression and he immediately gave chase.  Quickly, I called him to leave it and come using the e-collar but due to his increased arousal level at that moment he did not respond right away. I incrementally increased the level on his collar and continued to call, until I got his attention. This left Roscoe with a strong memory that chasing the donkey was not so fun. He now understands how to remove the pressure—by moving closer to his handler and giving up the chase.

        It’s been more than a month now that Roscoe has not harassed Olivia. Prior to training, he would stand just outside his invisible fence boundary and bark at her. He now no longer barks at the little spotted donkey and has stopped all chasing of the horses and is generally much more obedient for his family. I would never suggest leaving Roscoe loose or unattended around any other animals, but his prey drive is now manageable enough that he remains a healthy and active part of his family. E-collars are not the answer to every behavior problem in dogs, but when dealing with predatory aggression, they are by far the most effective.

        Next month, we’ll go more in-depth on how to read a dog’s body language in order to determine if it might pose a threat to you or your horse, as well as what to do if a dog that’s not your own comes after your horse while on a trail ride or anywhere else.

        Bernadette Pflug, CPDT-KA is a professional dog trainer in Louisville, CO who is certified in the E-Touch & Force Free Method ™; and is a professional member of both the APDT (Association of Pet Dog Trainers) and IACP (International Assoc. of Canine Professionals). Bernadette owns two horses, three dogs and enjoys Dressage and trail riding.

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