Scientists have discovered that some ring-tailed lemurs in Madagascar regularly retire to limestone chambers for their nightly snoozes, the first evidence of the consistent, daily use of the same caves and crevices（裂缝） for sleeping among the world's wild primates. The ring-tailed lemurs may be opting to sleep in caves for several reasons, said University of Colorado Boulder anthropology Associate Professor Michelle Sauther, who led the study. While the cave-sleeping behavior is likely important because it provides safety from potential predators, it also can provide the primates with access to water and nutrients, help to regulate their body temperatures during cold or hot weather and provide refuge from encroaching（渐渐渗入的） human activities like deforestation, she said.

"The remarkable thing about our study was that over a six-year period, the same troops of ring-tailed lemurs used the same sleeping caves on a regular, daily basis," she said. "What we are seeing is a consistent, habitual use of caves as sleeping sites by these primates, a wonderful behavioral adaptation we had not known about before."

A paper on the subject appeared in the November issue of the journal Madagascar Conservation and Development. Funding for the project came from Primate Conservation Inc., the International Primate Society, the American Society of Primatologists, the National Geographic Society, CU-Boulder, the University of North Dakota, Colorado College and the National Science Foundation.

Although sleeping in caves by ring-tailed lemurs -- which are found only in Madagascar -- has likely been going on for millennia, it is only now being recognized as a regular behavior, said Sauther. The endangered Fusui langurs, slender, long-tailed Asian monkeys roughly 2 feet tall, also have been documented sleeping in caves but as a direct result of extreme deforestation, moving from cave to cave every few days. There also have been isolated reports of South African baboons sleeping in caves.

Ring-tailed lemurs are easily identified by their characteristic, black and white ringed tails, which can be twice as long as their bodies. They weigh roughly 5 pounds with a head-body length of up to 18 inches and are highly social, congregating in groups of up to 30 individuals. Sporting fox-like snouts（鼻子） and slender frames, they are unusual among lemurs, spending a considerable amount of time on the ground feeding on leaves and fruit and socializing, said Sauther.