Q: One of the challenges with equine pain management is often simply detecting a horse in pain and to what extent. From a behaviorist's point of view, what signs might indicate a horse is in pain, and what can owners do to better pick up on them?
A: I have come to view undetected pain, the misunderstood behavioral manifestations of physical discomfort, along with the "if we can't find a source of pain, it must be just bad behavior," as one of the biggest persisting threats to domestic horses' welfare.
You would think that a reasonable, caring, and observant caretaker ought to know when a horse is uncomfortable or painful, and we sure would think an equine veterinarian doing a good physical examination would be able to recognize that a horse is physically uncomfortable. Certainly for many injuries and medical conditions signs of discomfort are clear enough that caretakers recognize pain immediately, and we or our veterinarians can quickly pinpoint the likely cause. But very often horses suffering from painful conditions are fairly stoic and their discomfort is difficult to detect. And often owners and managers working with their horses day-to-day pick up on changes in behavior and complain that something is wrong, but neither they nor their veterinarians identify a cause. The difficult truth is that horses can and often do "hide" pain for a long time. While we certainly know that horses--just like people--vary in their threshold for exhibiting behavioral changes in response to painful injuries and conditions, in general horses qualify among species as "stoic to the max."
The more we study horses the more we realize that their pain, even when fairly significant, can go undetected for a long time. And it makes perfect sense with what we know of how horses evolved as an open-plains grazing prey species. In that situation there is an obvious advantage to the individual and to the herd to behave as normally as possible in the face of physical discomfort, so as not to call the attention of predators to any frailty. Those that did the best job of hiding pain from a survivable condition were then more likely to avoid predators and to survive to pass on those tendencies. Now that we are looking after domestic horses, however, this has become an unfortunate welfare disadvantage.
A modern tool that has taught us the most in this regard, and can often help us identify and understand painful horses, is video. Simply review a video recording of a horse in his environment over a period of time--with people present, without people, when other animals are around, and alone. It still amazes me how much you can learn from such a simple and inexpensive noninvasive tool and how behavior can vary throughout the day and night as the horse's environment changes. It is not at all unusual for a horse to show clear signs of discomfort except when people are present. They are either distracted from the discomfort or might "buck up" and appear completely normal when people are around. Then when the people leave, they seem to let down their guard and show more continuous discomfort. Or the opposite can be the case; a horse in pain might appear more comfortable when his environment is quiet--no people or other animal activity--and then during the busy time of the day, or at times when he anticipates work, he shows more behavioral signs of discomfort.
Another important step in this regard, of course, is better understanding among caretakers and veterinarians of the subtle signs of discomfort in horses. They also benefit from a better understanding of behavior changes in horses due to discomfort as opposed to behavior quirks or misbehavior. My hope is this understanding will improve in the next few decades as more veterinary behavior specialists and Certified Applied Animal Behaviorists include horses in their practices, teach in veterinary schools and horse management programs, and instruct the horse caretakers (e.g., through extension service programs).
So, what are some of the behavioral signs of physical discomfort in horses?
- Putting ears back or turning head back repeatedly without an external stimulus attracting attention;
- Repetitive tail swishing, raising the tail off the perineum (region between the thighs encompassing the anus and genitalia), or slapping against the perineum;
- Frequent shifting of weight on the limbs, either from side-to-side or fore to hind;
- Lifting a leg or kicking toward the abdomen;
- Kicking out to the back or side;
- Stamping or pawing at the substrate or into the air, aside from scenarios such as when waiting for feeding or turnout;
- Rubbing any part of the body against objects;
- Self-biting or -nipping;
- Standing for rest with front legs not squarely under the body;
- Repeated deep stretching;
- Flehmen response (lifting the upper lip) outside of the usual sexual or marking context;
- Excessive yawning;
- Repetitive head shaking, flipping, or bobbing;
- Abnormal postures when resting, urinating, or defecating;
- Trembling, muscle fasciculation (twitching), or tremors;
- Leaning against a wall or other object when resting;
- Grunting, groaning, or squealing;
- Repeated sighing;
- Teeth grinding;
- Frequent lying down and getting up, with or without rolling;
- General crabbiness around people or herdmates, as if saying, "I don't feel well, and don't bother me";
- Unwillingness to do usual work;
- Hyperresponsivity (unusual jumpiness or spookiness);
- Restlessness or uneasiness;
- A change from normal eating style to either picky eating or to food urgency and bolting of feed;
- A glassy eye or dazed or dull look, which can be associated with pain-induced endorphin release.
This is certainly not a complete list, but it probably includes the most common behaviors strongly suggesting physical discomfort or a neurologic cause.
In my experience it's pretty common for the signs of particular sources of discomfort to vary between horses, so once you determine that the horse is uncomfortable it might take some effort to localize the source. That's where I find video so helpful. Watching it at various speeds can often point you toward the source of discomfort. In fast-forward you can see the horse's discomfort behavior over and over in rapid succession. You can also slow down to frame-by-frame and go over it as many times as needed to focus on the ears, the legs, the tail, etc., to gain clues as to what precipitates a tail slap or a sudden head movement or ear position.
When you put your mind to it, detecting a horse in pain is not as much work as it seems, and it is very satisfying to watch a horse that has been uncomfortable for a long time finally get relief. Not only do the specific discomfort responses stop immediately, but any of the secondary behavioral changes also usually subside.
About the Author
Sue M. McDonnell, PhD, is a certified applied animal behaviorist and the founding head of the equine behavior program at the University of Pennsylvania's School of Veterinary Medicine. She is also the author of numerous books and articles about horse behavior and management.