Guest post by Robin A. Smith, Duke Lemur Center

The fancy neck charm this lemur is wearing is no fashion accessory. Weighing in at just under an ounce, it’s a battery-powered data logger that measures light exposure and activity levels continuously over many days.

In a study to appear in the American Journal of Physical Anthropology, Duke researcher Ken Glander and colleagues  at  Rensselaer  Polytechnic  Institute’s  Lighting  Research  Center  (LRC)  outfitted twenty lemurs at the Duke Lemur Center with the special gadgets — called Daysimeters — to study the animals’ daily ups and downs.

The five species in the study — mongoose lemurs, Coquerel’s sifakas, ringtail lemurs, red-ruffed lemurs and black-and-white lemurs — wore their new jewelry around the clock for a week while they went about their regular routine of lounging, leaping, napping and climbing trees.

Sifaka with dosimeter

Sifaka with a light-and-motion dosimeter looks like Flava Flav

Lemurs in this study are generally more active during the day than at night. But when the researchers downloaded the data, they found that several species also stirred after dark, and all of them took periodic rests during the day — often retreating to a shady spot for a midday siesta.

The results could help researchers understand the sleep disturbances common among people with Alzheimer’s or other forms of dementia, and whether light therapy could help reset their internal clock for a more solid night’s sleep.

For their next experiment, they’ll use a lighting fixture custom-built by the Lighting Research Center to find out how different light-dark cycles — similar to seasonal changes in day length or the waxing and waning of the moon — affect patterns of rest and activity in two groups of ringtail lemurs:  one consisting of younger animals that are less than two years old, and another over twenty.

“We’re not saying that lemurs have dementia,” Glander said. “But we think that lemurs can tell us something about how some animals manage to stay healthy despite having segmented sleep.”

CITATION: “Measured daily activity and light exposure levels for five species of lemurs,” Rea, M., et al. American Journal of Physical Anthropology, 2013.