A. There are many good reasons to provide a physical or man-made shelter of some type for horses on turnout. Weather extremes can be challenging, and shelters offer convenience and benefits when we work with our horses. Man-made shelters can also be essential when we have a sick or old infirm horse. But, shelters can be difficult to manage. They need to be safely constructed, kept clean, and spacious enough for all horses in a group to use in order to decrease agonistic encounters.
There is scant experimental work on what domesticated horses need or would choose with regards to physical shelter. But if we survey the research and observations that are available, we can say that most acclimatized, healthy horses can be provided an outdoor living environment with only natural shelter, such as trees.
Horses have physiological adaptations to the environment as it varies over the seasons. A thin hair coat in the summer, along with sweating, allows heat dissipation. A thick hair coat and the loft of the hair in the winter provides insulation and protects skin from wetting. But horses can also adopt behaviors that allow them to maintain comfort according to ambient conditions, known as “behavioral thermoregulation.”
Variation in landscape is important in successful outdoor living. Both feral and domestic horses choose over a course of a day or across seasons what we estimate are the best micro-habitats. For example, the Assateague ponies occupy different areas on the island in summer and winter. Horses use ponds, salt marshes, and non-vegetated areas to keep cool and avoid insects in the summer. Trees and shrubs provide both windbreak and overhead protection from precipitation. I observed horses in Iceland—kept on expansive, treeless pastures—use the natural upheavals of the ground, forming mounds and ditches, as windbreaks.
Movement, foraging, and digestion help horses metabolically maintain warmth. Resting and nonforaging time has been described in many groups of horses as increased during the summer or concentrated during the warmest parts of the daytime in all seasons. Horses tend to huddle or stand resting close more during hot weather, probably for group tail-swishing and insect avoidance, as well as to keep cool by not exercising. We don’t seem to see huddling so much in inclement weather, but when horses are in an exposed area, we do see them adopt a characteristic posture with their heads low and hind-ends to the wind.
It is generally recommended that heavy precipitation combined with wind creates the greatest thermoregulatory challenge for horses. Camie Heleski, PhD, an equine science professor and researcher at Michigan State University, reported the rare use of a physical shelter by groups of primarily Arabian horses mostly when there was windy-snowy and windy-rainy weather. Yet I have followed tracks in fresh snow to see where ponies sought shelter near and within dense shrubs, leaving a man-made shed completely unused. Also, anecdotally, I’ve observed my ponies use their run-in shed for shade and shelter much more in the hot, high insect months of the summer, rather than during the cold winter months.
So with or without physical shelters available, horses rely on the natural variations in landscape and habitat in order to physiologically and behaviorally cope with environmental challenges. A farm management scheme that has these variations in the landscape, gives horses freedom of movement, and provides adequate grazing or supplemental forages should allow acclimatized, healthy horses to do well without a man-made shelter.