Sleep Patterns in Horses
Rousting your horse out of his stall at 3:00 AM to braid his mane, put him on the trailer, and haul to a show interrupts his usual sleep pattern. But the interruption is unlikely to affect his performance. If he's used to the show scene, he'll find opportunities to nap here and there during the day. Even if he's on edge all day, in a state of heightened alertness that keeps him awake, he won't lose enough rest to show signs of sleep deprivation. (Horses on 100-mile endurance rides are far less affected by sleep loss than their riders, according to Sarah Ralston, VMD, PhD, of Rutgers University, who's studied these horses-and who's a competitive-trail rider herself. She says they nap at vet checks and get through a twenty-four-hour ride just fine with that.)
Moving to a new barn, variations in turnout and exercise times, and other changes in routine can also disrupt sleep patterns. But horses are remarkably adaptable about sleeping. They can get used to many different situations, even to constant change. Put under lights (to get broodmares cycling or to keep coats short), they soon get used to the long hours of artificial daylight and go back to their usual daily patterns of sleep and rest. Even circus horses, which are moving all the time, don't appear sleep-deprived, says Sue McDonnell. They get to know the daily travel and performance routine, then settle down and rest.
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Horses can become sleep-deprived if they're prevented from lying down and so can't achieve deep sleep. But this won't happen in a day, or even several days; it takes weeks, research shows. And most horses find a way to lie down and sleep, even in situations you might think are less than ideal.
Sue McDonnell has observed wild, semi-wild, and domestic horses in all sorts of settings, including open fields, reserves, box stalls, and tie stalls in Eastern Europe (where this type of stabling is common) and on PMU ranches. (As one of five independent veterinary researchers investigating the comfort and welfare of PMU mares, she's analyzed round-the-clock videos of hundreds of horses, quantifying their every move.) "Horses in properly fitted tie stalls can and do sleep lying down with as great a frequency and total duration as box-stalled horses," she notes. In fact, she says, mares at PMU farms, kept in tie stalls for extended periods so their urine can be collected, have standing and lying-down sleep patterns closer to those of wild horses than do horses in other stabling situations. One reason may be that the mares can see each other and thus feel safe.
Horses have simple needs in bedding, too. They appear perfectly happy sleeping on the ground, even hard ground, as long as it's not very wet or covered in deep mud. Stabled horses don't sleep better for having deep bedding, the round-the-clock observations of Sue McDonnell and other equine behavioral researchers show.
Where bedding and stall flooring can become an issue is in the case of a horse who's older or who has a disability that makes getting up and down difficult. If the surface is at all slippery, this horse may be unwilling to lie down, fearing he won't be able to get up quickly. An older horse may resist lying down to the point that he becomes sleep-deprived. He may sleep better outside, where the ground provides more solid footing, than in a deep-bedded stall.
The bottom line, Sue McDonnell says, is to understand and think of your horse's sleep needs in his terms, not human terms. PH
Sue McDonnell, PhD, is the founding head of the Equine Behavior Lab at the University of Pennsylvania School of Veterinary Medicine. For the past twenty years, she has studied horses and their wild relatives-including zebras, Przewalski's horses, and donkeys--in settings all over the world. Her research has been published in the American Journal of Veterinary Research and other journals.
Where they can, Dr. McDonnell and her fellow researchers at the Equine Behavior Lab videotape their subjects for 24-hour periods. Then they analyze the tapes and quantify each behavior-eating, drinking, sleeping, and so on. Where videos aren't possible, the researchers observe the animals in shifts over 24 hours.
The lab maintains a herd of up to sixty semi-feral ponies at Penn's New Bolton Center large-animal facility in Kennett Square, Pa. Having this group of ponies available has allowed the researchers to track the same animals, as individuals and as a herd, over a period of years.
This article first appeared in the September 2000 issue of Practical Horseman magazine.
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