When turned out on a brisk winter day, does your horse race around the paddock, bucking and kicking up her heels? Or after a spell of rainy weather, is she spirited on the trails and hard to stop? People often declare: “My horse is frisky because it’s cold out!” But how is a horse’s behavior really affected by the weather?
How Horses Stay Warm
When it’s cold, wet, and windy, conserving body heat can be a matter of life and death. Ancestral wild horses adapted to climates with frigid winters and limited food. Some domestic breeds are better suited for cold and wet conditions than others, but most healthy horses can maintain their normal body temperature of about 100°F over a broad range of outside temperatures. When the thermostat dips below 5-10°F—the lower limit of their “thermo-neutral zone”—horses need to adopt various strategies to prevent dangerous loss of body heat.
Lively running, bucking, and other fresh behavior burns calories and isn’t a strategy horses use to stay warm when it’s cold out. Instead, they conserve energy, huddle together, and seek shelter.1, 2 During the summer horses tend to use shelters to protect against biting insects. During winter, they’re more likely to use them to prevent body heat loss when it’s rainy. But they don’t tend to use shelters for warmth when it’s cold and dry.2Smaller horses and ponies are better suited for cold weather because they have less surface area that’s exposed to the elements. A dense winter coat and body fat also provide insulation from the cold; clipping and blanketing keep the horse’s hair short and clean but might interfere with the coat’s natural insulating properties.
Findings from several research studies suggest horses are actually less active when the weather is cold and wet. For example, compared to other times of the year, during harsh cold and rainy Norway winters, Icelandic horses spend less time running and playing but the same amount of time eating, walking, and sleeping.3 Wild Przewalski horses4 and Shetland ponies5 are also less active in winter. Interestingly, they are able to conserve energy by slowing the body’s metabolic processes—a condition called winter hypometabolism—which could be an adaptation to conditions of food shortage and harsh weather. With regular access to food and shelter during winter, most domestic horses have no difficulty maintaining normal body temperature even in locations where the thermostat regularly plunges to frigid levels.