The fat-tailed dwarf lemur of Madagascar was known to disappear for long stretches in the wild, but laboratory studies could not confirm whether the animals hibernated. (The image above shows a captive individual.) Kathrin H. Dausmann of Phillips University in Marburg, Germany, and her colleagues studied lemurs in the wild and documented the physiological changes they undergo during their seven-month-long slumber. Unlike other hibernators such as bears, the lemurs do not regulate their body temperature while resting, the team found. Instead, their temperatures fluctuate--sometimes by more than 20 degrees C throughout the day--depending on how much insulation their tree-hole homes provide.
Dausmann and her collaborators write that according to their knowledge, the findings are the first physiological confirmation of prolonged hibernation by a tropical mammal as well as the first proof of hibernation in a primate. Because the decreased metabolism that hibernation affords occurs in lemurs with high body temperatures, the authors note that low body temperature should no longer be included in the definition of hibernation.