Scientists have been studying the physiology and behavior of hibernation for decades. For these studies, researchers collect different types of data, including body mass variations throughout the year, as well as dietary and locomotion adaptations during autumn fattening. They also catalogue physiological changes, such as body temperature, by collecting temperature readings from the abdominal cavity or skin. Scientists also use closed chambers, known as respirometers, to measure the exchange rate of oxygen and carbon dioxide; this reading can identify an animal’s respiration and their metabolic rate. Typically, these studies are done in a laboratory under carefully controlled settings, such as identical diets or feeding regimens.

With the introduction of smaller data loggers to record body temperature—and with better technology to track animals in the wild using radio transmitters—scientists have begun to study animals in their natural habitats. What they found was that more animals than originally expected were using some form of torpor to escape harsh environmental conditions. In 2004, Kathrin Dausmann and her colleagues measured the body temperature profiles of fat-tailed dwarf lemurs in Kirindy Forest, Madagascar. This was the first time that hibernation was documented in a primate. Dwarf lemurs are found in various parts of Madagascar and, depending on where they are found, can hibernate in tree holes (in the dry, deciduous forests in the west) or in underground burrows (in the high-altitude rainforests in the central-east). They have been studied in both locales, as well as at the Duke Lemur Center, which is the only place they are found in captivity.

To learn more about dwarf lemur hibernation, check out the educator’s article in Scientific American. You can also read her personal blog about field work in Madagascar.

Interested in the possibility of human hibernation? Click here to listen to the educator’s interview with BBC for a Radio 4 program.

Dwarf lemurs, like most hibernators, are small-bodied animals that lose heat to the environment quickly. This is because they have a large surface area to volume ratio. Think of your hand on a cold winter’s day. Your hand, if it’s balled up nice and tight, will stay warmer longer. However, if you flatten your hand, it gets colder much quicker. While the volume of your hand stays the same in both instances, the surface area when it’s flattened becomes much greater, leaving more of your hand exposed.

The only exception to the small-body-size rule, as far as scientists know, are bears. However, bears break other rules, too! For example, during torpor, bears only reduce their body temperature a few degrees below their normal temperatures. The body temperatures of other hibernators will drop to just around their surrounding temperatures, which can sometimes be close to 0°C. Bears will also give birth and lactate, which is shown in more detail in this BBC video.

This great article from Science News for Students is full of other great information on hibernation.

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