Compulsive Urinating on Hay

Q: My 10-year old Paso Fino gelding has a very strange habit. He consistently and sometimes frantically urinates on his hay. I have placed his hay deep in the corner of his stall, and he will squeeze his body into the corner to urinate on his hay. If the hay is placed in a hay net he will circle around and around his stall, releasing short bursts of urine, kicking the walls as he is circling around his stall. He does eventually settle down and eat his hay, but always after this type of display.

I purchased him from a bad situation of neglect. He was in a small paddock with a very aggressive/dominant gelding. My gelding had tons of scrapes, scabs, and scars all along his neck and back. The other gelding appeared very well-fed, whereas my gelding was extremely underweight.

Could this be some sort of "marking" behavior?  

Joy from Ohio


A: I'm not aware that anyone has figured out why some horses urinate on hay. Marking is one thing the behaviorists talk about when this subject comes up, but it's not known for sure. In the case of your horse, marking seems to be as plausible explanation as any I've heard proposed. Another reason discussed that makes sense in some cases has been that in circumstances without adequate bedding to prevent urine splashing, a horse might urinate on hay. But in the case of your horse, I presume there is bedding available and his behavior when a hay net is presented would be hard to understand.

I have also heard of the explanation that urination on hay is the horse's way of commenting on the quality of the forage, which is likely an overly anthropomorphic idea. Horses don't appear to urinate on undesirable forage in other circumstances, and for horses that I have seen do this behavior, the quality of the forage did not appear to alter the behavior, and they ate the hay after urinating on it.

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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