The Curious Case Of The Horses Who “Hibernate”

What’s more, the researchers say, the Yakut horse population quickly developed adaptations to its frigid environment. Specifically, modern Yakut horses are small in stature with compact bodies and short legs, conformation that helps conserve body heat. They also grow thick winter coats, which help insulate them from cold.

A surprising finding

Finally—and perhaps most interesting—Yakut horses appear to adjust metabolically to extreme cold. The researchers observed that the horses enter a “restful” state characterized by low body temperature, slow heart rate and reduced metabolic activity for hours at a time during winter. This response, called torpor, helps bears, squirrels and other animals cope with periods of cold and low food availability, but it had not previously been documented in horses.

Extended torpor, lasting for several days or weeks, is sometimes described as hibernation. Even as their metabolism slows during the harsh winters in their region, Yakutian horses remain active, entering a state that some researchers call “standing hibernation.”

Normally, an evolutionary response to environmental pressure plays out over thousands of years. However, the international research team determined that the Yakut horses made these adaptations in about 100 equine generations, one of the most rapid adjustments to extreme environmental conditions documented in animals.

These findings, say the researchers, could help to improve our understanding of how animals adapt to climate change and aid in the development of selective breeding programs that produce animals better suited to cope with extreme environments.