Oral Attacks

Q: We have an Arabian who, for some reason, has taken to chewing on the horse trailer when we are at a show. He has never done this before. He started gnawing on the fender. We tied him away from the fender, and he started chewing the paint off the side. We are worried he will break his teeth. Why is he doing this and what can we do to break him of this habit? Another horse was there with him as well, so he wasn't alone. We also are trying to come up with an apparatus to keep them away from the trailer while still being tied safely. Any help would be welcomed.

Robin Scudder


A: I don't really know what attracts horses to chew on vehicles, but I have sure seen the behavior develop in otherwise normal, healthy animals. The first time I saw horses damage a vehicle by chewing was on a research study in which we were observing pasture breeding horses on a PMU (pregnant mare urine) farm out on a Manitoba prairie. We had borrowed an old station wagon from the University of Saskatoon fleet to drive around the pasture so we could be sheltered from storms that come up quickly. One morning the entire harem band of Belgian and draft-cross horses we were observing approached our vehicle, investigated with a few sniffs and licks, then orally attacked the vehicle. It was like one started and they all immediately joined in. I'll never forget the sound of their teeth grating across the hood and roof. It could be a form of torture to have to sit inside a car while horses scrape their teeth all around. Once they started chewing on the paint, we had to chase them by wielding a clipboard in one hand and the event recorder in the other. The vehicle seemed as prized a resource as you would imagine sweet feed might have been to a grass-fed herd.

Anyway, every time I see that behavior, I still wonder what the big attraction is for some horses to some vehicles. We have a golf cart that is used to get around our semiferal herd, and it, too, is all chewed up from the occasional paint muncher. The body is mostly fiberglass, and they seem to try to scrape the paint with their teeth. We have not been able to figure out a pattern to who does the chewing or when the vehicle is most attractive.

For any form of pica, as this behavior is called, the nutrition specialists would look for some sort of dietary deficiency. I have known some horses that showed more interest in licking and chewing vehicles that had winter road salt residues and have wondered if the salt was the attractive material. But that certainly has not been the case with the golf cart.

I have not seen a horse break a tooth yet. To prevent the behavior, I would recommend using one of those soft rubber grazing muzzles.

About the Author

Sue McDonnell, PhD, Certified AAB

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.

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