You're riding along when your horse spooks, then freezes: Head held high, ears flicking back and forth like bug antennae. Your heart pounding, you strain to hear what he's listening for but, as seconds pass in silence, come to the conclusion that your horse is hearing things.
He is hearing sounds that you can't hear. Understanding how your horse's hearing differs from yours and how his reaction to sounds differs, too, can give you valuable insights into his behavior. It can help you anticipate and perhaps avoid a dangerous spook, or reduce his anxiety in such noisy environments as horse shows.
The Sound of Silence
Like all animals (including you), your horse has binaural hearing, meaning his ears can hear sound concurrently. His external ears, known as pinnae, act like satellite dishes to capture sound waves and funnel them to his inner ears. Because of the large, cuplike shape of his pinnae, especially when compared to your small, flat ones, very little sound spills out of them, so he can capture noises you might miss.
Another reason your horse can detect sounds you can't is his ability to hear a wider range of high-frequency tones, such as the ultrasonic squeak of a bat. For a prey animal, which he is, this hearing acuity makes sense. In his natural environment (open plains), other animals, including predators, are the only things besides weather that generate noise. Predators generally don't vocalize when stalking prey, so your horse is hard-wired to listen for the sounds of stealth--the snap, crackle and pop of grass and twigs under, say, a mountain lion's paws.
These telltale rustlings contain high-frequency sounds, which your horse uses to locate the direction from which they came by gauging which ear hears them first and at what intensity. Unlike animals that can hone in on a precise location, your horse needs only an approximate indication of where the sound erupted, so he can prepare to run in another direction. If the sound tells him action may be warranted, he'll follow with eye movement, then finally raise and turn his head so he can better focus, freezing his body so as not to give away his position. (You've probably seen grazing horses do this. You'll notice they also quit chewing, the better to hear.) If he perceives danger, he'll likely spook and run.
Ah, the spook. Then there's the spin. And let's not forget the bolt. These equine survival tools underscore the fact that your horse not only hears differently from the way you do but also can react quite differently to sound. That's because horses have a very strong emotional response to whatever sensory input they might receive. And the emotion is fear. Fear triggers your horse's flight mechanism (and puts you in danger of being run over, into, or away with). We humans often curse it, but that hair-trigger response is an important thing to have. A horse doesn't want to be brave. If he is, a lion is likely to eat him. His best shot at survival is to run first and think later.
If you spend much time around horses, you've likely noticed that some, like some people, are more "emotional" or reactive than others. One horse may spook at the slightest sound; his "Steady Eddie" barn mate takes everything in stride. Male horses may react more strongly to sound simply because they're traditionally the herd watchdogs. They don't necessarily hear any better than females do, but they feel a need to alert "their herd" to perceived danger. That's why some horses suffer more anxiety than others at shows or in any new environment. A strange place can put your horse on high alert for danger, causing him to be emotionally aroused and to make his reaction to noise even stronger than it would be in a familiar setting. If he's of the "bombproof" variety, his anxiety may not result in undesirable behavior. But if he's reactive by nature, it could not only hamper his performance but harm you.
You can help reduce your horse's reactivity by blocking out a majority of the noise with earplugs. Tack stores and tack-supply catalogues carry equine models. Or you can make your own using thick wads of cotton or 1-inch black yarn balls (which are nearly invisible in the ear), available at art-supply stores. Wherever you ride, keep an eye on your horse's ears to help avoid a possible spook. They'll signal where his attention is directed. For instance, if you see a piece of plastic blowing to the left and you're wondering whether he sees it, look at his left ear. If the open part of that ear swivels toward the bag (a movement called the Pryer Reflex), he's tuning into it. If he's afraid of bags, picking up on that ear movement gives you time to direct his attention elsewhere and maybe avert a spook.
Hearing Loss in Horses
Like you, your horse can lose his ability to detect sound as he ages. Age-related hearing loss in humans begins at about age twenty (roughly the same point as age five for a horse), starting with the higher frequencies and working down the scale. High-frequency hearing loss isn't generally obvious in humans until sometime after fifty (equivalent to fifteen for a horse). But because your horse has a wider range of high-frequency hearing than you do, he can lose more of it before you notice a lack of response to sounds you hear.
If you suspect a hearing problem in your horse consult your veterinarian. Although we have no way yet to compensate for age-related hearing loss in horses, your vet might find another cause that can be treated. For instance, tick infestations, ear mites, and ear infections can have a negative impact on hearing. Whatever the cause, if your horse has a hearing loss, you'll need to make some management changes for safety and even if his hearing's fine, these practices are a good idea. Always speak to him before you approach, so you don't startle him and be sure he heard your alert by monitoring the direction of his ears: One or both should flick toward you. In addition, check his ears weekly for signs of insect infestation or infection (redness, scratching, hair loss on the ear that could indicate rubbing).
The more tuned in you are to your horse's hearing, the better off you'll both be.
A professor of psychology in the Laboratory of Comparative Hearing at Ohio's University of Toledo, Dr. Rickye Heffner has specialized in mammal hearing since 1976.
This article first appeared in the August 2000 issue of Practical Horseman magazine.