Power Napping

(following on from our article  on How Horses Sleep)

I am told that most people need a good, solid eight hours of unbroken rest every night  and you might assume that horses have similar needs. But according to Sue McDonnell, all horses do well with far less sleep than people.

We, typically, spend anywhere from four to fifteen hours a day in standing rest, and anywhere from a few minutes to several hours lying down. Only part of those periods are actual sleep time, taken in brief naps that last a few minutes each. The daily total sleep time for an adult horse may range from a few minutes to a couple of hours. Foals and young horses, like other youngsters, sleep more, moredeeply, and more often than adults.
This pattern is another plus for a prey animal: His sleep can be interrupted repeatedly by predators and false alarms, but he'll still function. Rarely does a horse suffer from true sleep deprivation, says Sue McDonnell. The minimum amount of deep (lying-down) sleep he needs is very small-perhaps an hour in many days. Still, if he doesn't get that minimum, he eventually begins to drift off into what appears to be deep sleep while standing-and buckles at the knees.

People tend to lie their rest in a solid block of time, whereas horses spread theirs out in scattered periods throughout the day and night. According to Sue McDonnell, "For any horse or group of horses, there is usually a recurrent pattern of rest and other activities," such as grazing. The pattern varies with the weather, the season, and what's going on around them. Stabled horses, affected by the activity around them, typically get much of their sleep during the evening and early morning hours. "Horses tend to learn the pattern of the yard," Sue McDonnell says, "and their deepest rest and sleep tend to occur soon after the busy 'people day' ends."

Guard Duty

We sleep best when we feel safe from danger. But the factors that help us feel safe may not be what you think. When we are in your stables with the door closed and locked, you may think we feel safe and secure. But its far more likely that we are feeling isolated and confined - and for a horse, isolation and confinement can be dangerous.

As part of her work , Sue McDonnell has studied the behavior of a semi-wild herd of ponies over time. She says feral horses actually sleep more than stabled horses. They also get more down time: As members of a herd, they're able to relax because one horse acts as a sentinel, standing guard while the rest snooze. "In feral groups, all individuals tend to rest together, eat together, go to get a drink together. The young may get additional rest and sleep during grazing, with the protection of the adults." The adults share the guard duty, so everybody gets to lie down. Solitary adult horses tend to get less deep sleep than horses in groups because, with no horses as sentries, and no other horses to help deal with danger, lone horses feel they have to look out for themselves at all times. In the yards that I have lived in horses stabled next to each other often rest standing against the two sides of their shared stable wall, and take turns in doing guard duty.

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 twenty-four-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 twenty-four 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, Pennsylvania. 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 is based on one that first appeared in the September, 2000 issue of Practical Horseman magazine.