The Horse Who Chewed on Fences
The question is not, “Can they reason?” nor “Can they talk?” but “Can they suffer?”
Let’s bring in the proverbial Martian to observe human behavior. And let’s suppose that communication with such an interplanetary being proves impossible, because our languages don’t mesh. How will the Martian possibly understand us, when all it has to go on is what it sees with its own three eyes?
Our Martian comes around a corner and suddenly confronts a man pounding his head against a brick wall. By observing this behavior, the thought might arise in the Martian’s mind, Something is wrong here. Such a conclusion arises naturally, and no common language is necessary.
We folks who study animal behavior are in much the same boat as our space alien visitor. Veterinarians share no common verbal way to communicate with animals, because our languages don’t mesh. In order to understand what’s going on, we humans in the white lab coats are limited to our observational abilities. Yet determining things about animals without verbal communication is what we veterinarians do best. The verb “to vet” derives from “veterinarian.” To vet means to examine thoroughly and extrapolate from what we see. That’s always how we doctors seek to function. And just like the Martian, we recognize certain emotional states in animal subjects.
Yet, if we’re scientists, we must not say no. Here is the voice of traditional science: If it can’t be measured, it isn’t real. If you want to be a “real” scientist, you can’t ascribe any quality to animals that you can’t measure. Emotions are the realm of humans. Remember Morgan’s Canon? I am not allowed to suggest a cocker spaniel feels sadness when its owner dies. Or that a cat demonstrates happiness when she greets her human companion. No, no, no. We are supposedly looking at the mere mechanical workings of wind-up toys.
Some horses indulge in the strange repetitive behavior called “cribbing.” You can find disturbing videos of it on the Internet. Whenever and however you encounter cribbing, it’s the equivalent of the Martian confronting the human headbanger. Anyone with intelligence concludes instantly that something is seriously wrong.
I knew about cribbing, but I still reacted strongly the first time I saw it. An otherwise healthy-looking palomino mare with the fabulous name of Poker’s Queen Bee, was positively addicted to biting her stall.
Every few seconds Poker would lean forward and anchor her teeth in the edge of the stall door. Her incisors dug powerfully into the wood. Then she would lean backward and swallow hard, making a loud grunting sound—a behavior called “wind-sucking”—as she pulled with all her might on the stall.
The pathetic fallacy would have us believe that Poker was crying out against her captivity. It was as if she was trying to pull apart her stall. Let me outta here!
Cribbing is indeed a condition of confinement, the product of an unnatural lifestyle with fettered natural outlets. More specifically, though, the issue lies in the eating department. In the wild, horses never crib—and not just because they don’t live in stalls. Free-ranging horses graze for 60–70 percent of their day. Cribbing represents a frustrated response that becomes ingrained. Horses that crib are reacting to a lack of an opportunity to graze on grass.
But we don’t have to know all this to understand Poker’s behavior on a more basic level. Even a child (or a Martian) would comprehend the situation after witnessing her bite, lean, and grunt. Something is wrong here.
Poker’s owner, a Boston-based business executive, was concerned about Poker’s health. The practice wears down teeth and can lead to digestive disturbances, such as life-threatening colic. Understandably, she also found the behavior annoying.
Vets with little feel for animal behavior have developed various vile treatments for cribbing. They’ve implanted brass rings in the offending animal’s gums, or had the horse anesthetized in order to surgically sever its neck muscles. They’ve even tried boring holes in its cheeks. These painful, worse-than-useless techniques stem from the automaton model of animal behavior. It is as if those vets were considering a mechanical toy that was broken. Surely simply bending this spring there or adjusting that ratchet there will do the trick.
Step back a minute and consult your common sense. Brass implants? Sliced muscles? Drilled cheeks? Common sense responds: Are you kidding me? These measures are not only ineffective. They’re inhumane. It’s as if the Martian were to strap a brass plate onto the head of the poor guy bashing his head against the wall. Um, no, that won’t do.
Owners of cribbing horses become frustrated enough to try almost anything. Some take the behavior personally, concluding their horses are just being brats, cribbing simply in order to spite them. Nothing could be further from the truth. But cribbing does have far-reaching physical consequences. Horses that indulge in it fail to thrive and cribbing decreases the animal’s value in the marketplace. This alone can have perilous consequences for a horse. Off to the slaughterhouse or glue factory!
Cribbing was the first behavioral condition I investigated in my career, even before my study of nighttime aggression in dogs like Comet. At that time I was that proverbial Martian, limited in language but clearly grasping the fundamental truth of an animal in distress. Trying to understand the condition, and ultimately seeking to lessen the numbers of horses sold, neglected, or euthanized because of it, my Tufts University colleague, Dr. Louis Shuster, and I embarked upon a study of Poker and other obligate cribbers.
It was early summer in 1984. Lou was then a senior professor of pharmacology at Tufts Medical School. Fifteen years my senior, he had an impressive résumé of work done on the topic of drugs of addiction. His professional standing was recognized by the National Institutes of Health (NIH), which enlisted Lou to help select the proposed research projects worthy of funding. As a scientist, he was head and shoulders above many of his colleagues, including me! I was lucky to have him as a friend and mentor.
A veterinarian paired with a medical professor-researcher: To some, we made for an odd couple: humans is humans and critters is critters and never the twain shall meet. But Lou grasped the principles behind One Medicine and demonstrated a quality that is supposedly a prerequisite for scientific work, but crops up all too rarely in labs and research facilities: he possessed an open mind.
At our invitation, Poker’s owner trailered the horse up to the Cummings School at Tufts in North Grafton, Massachusetts. We brought the mare into the equine ward of our Large Animal Hospital, a bright, cheery place with the sweet smell of hay battling it out with the unmistakable odor of manure. Poker negotiated the rubber-mat-surfaced walkway to her fifteen-by-twenty-foot stall, which featured vertical metal bars on a wood-paneled door. After she explored her stall, she located a wooden crossbar and began—predictably—to crib. The dismal sight of the horse’s obsession at work also triggered a reflexive response in me, one of dismay and urgency. We had to help this poor animal.
Lou and I were aware of being in the presence of a truly magnificent beast, though one who was clearly disturbed. I stroked her neck and did my best to calm her, but she continued to crib. We had to embark upon our investigations with a subject who was in the viselike grip of the very symptoms we sought to alleviate.
Our first step was perhaps the most invasive. To prepare Poker for treatment, we needed to insert an intravenous catheter into her jugular vein. This wasn’t a difficult procedure, since a horse’s jugular is large and easy to locate. (Mongol warriors, who lived more on the saddle than on the ground, would lean over and prick a vein of their mounts, in order to be able to drink the nourishing blood without having to halt.)
The neck catheter was necessary, because we would inject medication through it that we hoped would stop the cribbing. I prepped the area with antiseptic and a topical anesthetic, and then inserted the catheter into the vein. Poker, a stoic by nature, did not flinch during the procedure, barely noticing the incursion. I then capped the device and flushed it with saline. We were ready to go. The white plastic catheter nesting in the furrow of Poker’s neck was an odd sight.
Before medicating Poker, we began a count using a mechanical counter to see how often she cribbed. The horse was relentless. Her rate of crib biting was around 250–300 times per hour. That averaged out to four or five times a minute for the period we studied her. She religiously observed her holy trinity of bite, lean, and grunt. Poker didn’t take too many breaks from cribbing, though occasionally she would saunter around the stall, grab a few mouthfuls of hay off the ground, and then peer out of the stall door, apparently taking in the surrounding environment. But then her obsession would take hold once more. When we plotted her activity on a graph, it showed a straight line upward with no pauses. She barely stopped, even to eat.
Poor Poker. It was distressing, to say the least. Clearly, the animal was in extremis. And we were desperate to make her feel better.
Our first “treatment” was the medical equivalent of a feint. We injected Poker with twenty milliliters of saline, a placebo, to make sure the process of injecting her didn’t itself cause a change in her behavior. The injection made no difference. On she cribbed. The chewing, lunging, and wind-sucking made a constant din.
Next we injected Poker with naloxone, a morphine antagonist drug—that is, a medication that works to cancel out the effects of morphine. It took a few minutes, but her cribbing stopped completely.
The sudden silence after the continuous sound of cribbing seemed almost surreal. It was as if a car alarm had quit after a too-long stretch of loud, annoying noise. Standing there in the sudden silence of the barn at Tufts, Poker’s owner shed tears of joy and relief. We were all moved that the horse’s distress had abated so swiftly.
Lou and I had done it. We had successfully halted a harmful behavior in animals with the administration of a medicine, naloxone, developed for use in humans. But of all the meds in all pharmacies in the world, how had we arrived at that one? The answer involves some explanation.
Cribbing is a reaction to stress and the cribbing behavior—while distressing to people watching—actually stimulates the release of endorphins, or soothing, pleasurable brain chemicals. The horse feels better doing it—even though the habit, like many habits, is not good for the horse. The endorphin release reinforces the behavior, so the horse keeps doing it. The horse is, in effect, “self-medicating” to cope with the stress of confinement. The abnormal behavior becomes habitual because the horse is hooked on her own natural, internal morphine—those endorphins.
Naloxone—trade name Narcan—which we used on Poker, is in the news of late as a treatment for drug overdoses. Public health advocates have urged equipping police and emergency medical teams with the drug so that first responders could save thousands of lives. Such sensible measures often run up against crude prejudices: Why should public money be used to rescue drug addicts? But lately reason and logic have pretty much won out. Save lives first. Deal with politics of addiction later.
The idea to treat Poker with naloxone arose from a previous study I’d done with Lou, shortly after I joined Tufts, on “reverse tolerance.” Some animals (most of Lou’s experience was with mice) become increasingly sensitive to morphine’s effects after repeated injections. In other words, they get more affected with every subsequent dose. As with mice, so with horses. Other researchers unwittingly documented the same reverse-tolerance effect in a study performed on Kentucky thoroughbreds.
Reverse tolerance is not well-known in humans. In fact, addicts are commonly understood to develop the opposite effect, acquiring a tolerance to morphine. They become desensitized, meaning they need larger doses to produce the same effect. But that wasn’t what was happening with Lou’s mice, who became increasingly sensitive to morphine, not less. But it turns out that reverse tolerance to various substances does indeed occur in people. After a “drug holiday,” or medication vacation, for instance, amphetamine users can feel increased stimulation (in addict lingo, a “bump”) and a decrease in side effects.
Once Lou and I had figured out how to help Poker, we were able to rescue some horses from a slaughterhouse in Connecticut in order to expand our investigations into endorphins. These horses, too, experienced bumps of their own when given serial doses of morphine: they circled or paced around the edge of the stall, dug at the ground, and mouthed the surfaces in their stall—engaging in cribbing behavior and other stall vices, as equestrians call them.
So if increased sensitivity to morphine triggered these behaviors, then stall vices were likely fueled by nature’s own morphine-like chemicals, endorphins.
Now we needed a way to block the action of endorphins, which is what led us to try naloxone on Poker. Morphine antagonists oppose, interfere with, or halt the effects of morphine and of naturally occurring endorphins. If we gave a cribber a drug that acted as an antagonist, perhaps the medicine would stop the behavior in its tracks. And it worked.
What happened with Poker’s Queen Bee also occurred with many other horses in subsequent trials. The cribbing completely shut down after an injection. For extended periods of time, we could mark “zero cribbing” on our charts.
This first study on cribbing began the kind of inquiry that to this day I still conduct in my life as a veterinarian—formulating a hypothesis, testing it in our trial at Tufts, then reporting the results professionally. All of my studies have been based on a fundamental insight into animal behavior, the profound recognition that we animals share the same neurochemistry. Our minds work in similar ways.
When we started working with Poker, none of us realized that our experience would change all our lives, transform our professional focus, and have far-reaching consequences for the study of animal behavior. Poker Queen Bee’s owner quit her fancy job and went back to Loyola University in Chicago, where she earned a PhD in biochemistry. Dr. Shuster, who had an outstanding career researching addiction to drugs changed his focus to study addiction to bad behaviors.
As for me, well, I had found my true calling: a lifelong study of animal behavior and the pursuit of One Medicine.
Science is sometimes like love, in that the course of research never does run smooth. In the course of our work with Poker’s Queen Bee, we were able to reduce cribbing to zero. Success! Unfortunately, the compulsive actions started up again when the drug wore off. Setback!
With One Medicine we can easily see significant similarities in conditions shared by animals and humans. Obsessive-compulsive disorder, or OCD, for instance, can be considered a condition of degree: that is, normal behavior amped up to an abnormal degree. Human OCD arises out of deep-seated behaviors that are necessary for survival, but are taken to an extreme.
Humans are a hunter-gatherer species. Hunting was necessary for the survival of early hominids. It required some risk taking, but also caution, so that the hunter wasn’t exposed to extreme physical danger. Gathering was also an essential activity for our ancestors. These behaviors are fundamental, and when successful were passed along to successive generations, until it evolved to be programmed into the human brain. These activities are normally employed appropriately when the need arises.
But when the behaviors are triggered continuously and out of context, an obsessive-compulsive disorder results. Since staying clean conferred life-and-death survival benefits, washing became a normal, customary behavior, hardwired into us, but people often manifest OCDs as undue fixations about personal cleanliness, with excessive hand washing and showering as well as compulsive skin picking and nail biting. Excess caution can lead to a preoccupation with germs and cleanliness. Too much of a good thing, so to speak. In the same manner, traditional food-storing behaviors transform into the aberrant practice of hoarding. All OCDs reflect excessive expression of basic, species-typical, survival-related behaviors.
Human society has known about OCD for a very long time. Fortunately, the days when such behaviors were ascribed to the work of the devil are over. Nowadays, the condition is considered to be a spectrum of disorders. Human OCD is no longer thought of as linked only to concerns about germs, personal safety, or possessiveness. Other compulsions are included under the same diagnostic tent. The tent is a virtual big top: compulsive shopping, kleptomania, body dysmorphic disorder, bulimia nervosa, anorexia nervosa, obsessive checking, touching, ordering, and arranging, trichotillomania (hair pulling), pyromania (fire-setting), and various paraphilias (extreme sexual behaviors) are now considered by some to be related in their underlying mechanism.
It turns out that these behaviors are based in specific areas of the brain: the limbic system (center of emotions) and basal ganglia (a repository of species-typical, hardwired behaviors). Because of the similarities between human and animal brain function, it’s no surprise that over time we found numerous compulsive disorders in pets. Besides cribbing in horses, such disorders can include compulsive licking and tail chasing in dogs and cats who strip out their hair. At first, the veterinary profession didn’t connect these extreme behaviors to OCD.
A huge gray horse named Mobey, formerly on the Bermuda show circuit, had been retired for constantly bucking his owner. The animal found his way to Tufts, where he was housed in one of our equine wards as a “teaching horse.” Mobey was sincerely loved and admired, and our students performed many, many practice examinations on him. He went a long way toward proving the old adage that an unexamined life is not worth living. Eventually, however, the money ran out to keep him, and he became a candidate for euthanasia.
A single quirk saved Mobey’s life and pulled him back from the edge. He was a confirmed cribber, constantly biting the wooden boards at the front of his stall. If left to his own devices he might have dismantled the whole barn. All we could hear, as we entered the ward, was a great rattling of the stall, followed by the familiar grunting sound as Mobey gulped air.
Lou Shuster and I opted to pay for his keep. We wanted to replicate with Mobey the treatment we had tried with Poker’s Queen Bee. More than that, we aimed for a longer-lasting remedy, one that would extend beyond the temporary fix we had given Poker.
We began our effort by using different morphine antagonists to stop Mobey’s cribbing. Even though we anticipated the same results, they were still remarkable. Each drug worked. After we’d tried a series of different drugs, we arranged for the meds to be delivered by constant infusion using a portable pump strapped to his neck. As long as the infusion remained above a certain level, Mobey did not crib. When we turned the infusion rate down below that level, Mobey would start cribbing again. It was as if we had a radio-controlled horse. Turn the knob to the right and he stopped cribbing. Turn it to the left and he would start up again.
But the solution had its own set of problems. One of the most pressing was that the treatment was not practical, because opioid antagonist drugs are expensive. They cannot be given by mouth because they are rapidly destroyed by the liver. And the effects of a single injection—as opposed to Mobey’s pump infusions—lasted only a short time. Around four hours of cribbing suppression was about the best we could achieve when we administered the injection.
To try to resolve this problem of duration, Lou and I experimented with various long-acting preparations. Taking a cue from the wider world of illicit drug use in humans, we found ourselves applying a “freebase” of the drug directly to mucous membranes inside Mobey’s mouth or nose. Using a long-acting injection of one of the morphine antagonists, we finally did manage to eke out almost a month with no cribbing. The prohibitive cost, coupled with a lack of interest from suitable sponsors, caused our project to end.
The good news is that Mobey was eventually adopted out of Tufts to a local stable. We dodged the need for him to be euthanized, and he lived out the rest of his days in a peaceful environment.
While our early research in cribbing failed to yield an effective long-term treatment for the behavior, it ultimately supported the concept of One Medicine; the medical commonalities between humans and animals. Heartened, I resolved to move forward and investigate problems further. I didn’t realize back then that my research would prove highly controversial. I didn’t fully understand that a certain sector of the human populace would display an aggressive, knee-jerk aversion to the ideas of One Medicine. Scientists and laypeople alike preferred not to be reminded that they were animals, thank you very much, and some were aghast at the news that they shared crucial elements of their physiology with their pets.
I learned my lesson in a memorable and sometimes quite public way.