During deep hibernation, an Olympic marmot’s heart rate can slow to three beats per minute.
Olympic marmots are deep hibernators native only to Washington’s Olympic Mountains. As winter approaches, they retreat into communal burrows, where their body temperature falls below 40°F and their metabolism drops sharply. The extremely slow heartbeat helps conserve energy while the animals live on fat stored during summer.
This is not the marmot’s normal heart rate: three beats per minute describes an especially deep hibernation state. Olympic marmots periodically rewarm themselves, roughly every ten days, but they do not eat or drink during the hibernation season. Adults generally emerge in May, while young marmots may remain underground until June.
A related misconception is that all winter-sleeping mammals hibernate in the same way. Bears, for example, remain much warmer and are easier to awaken; marmots undergo a far deeper physiological slowdown. The species became Washington’s official endemic mammal in 2009.