December 5, 2013
Cave Sleeping A Regular Occurrence For Madagascar Lemurs: Study
April Flowers for redOrbit.com - Your Universe Online
A team of researchers led by the University of Colorado Boulder has discovered that some ring-tailed lemurs regularly return to the same limestone chambers to sleep. The findings, published in Madagascar Conservation and Development, are the first proof of the consistent, daily use of some caves and crevices for sleeping among the world's primates.Michelle Sauther, University of Colorado anthropology Associate Professor, said that ring-tailed lemurs might opt to sleep in the caves for several reasons. Safety from predators might be a primary reason for the cave-sleeping behavior, but it can also 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 human activities like deforestation.
"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."
Ring-tailed lemurs, which are only found in Madagascar, have likely been sleeping in caves for millennia. It is only now being recognized as a regular behavior, however. Other primates, including the endangered Fusui langurs, slender, long-tailed Asian monkeys roughly 2 feet tall, have been documented sleeping in caves, but only as a direct result of extreme deforestation, moving from cave to cave every few days. There have also been isolated reports of South African baboons sleeping in caves.
Ring-tailed lemurs are easily recognizable because of their characteristic, black and white ringed tails, which can be twice as long as their bodies. The lemurs weigh around 5 pounds and are up to 18 inches long from head to base of tail. The small primates, with fox-like snouts and slender frames, are highly social, congregating in groups of up to 30 individuals. They are unusual among lemurs, according to Sauther, spending most of their time on the ground feeding on leaves and fruits and socializing.
In "gallery forests," which form as corridors along the rivers, ring-tailed lemurs mainly sleep in the canopies of tall trees. In "spiny forests," however, most of the trees with woody stems are covered in rows of spines, making them uncomfortable, as well as dangerous, sleeping sites because predators can easily climb them. The research team documented the lemurs’ habit of cave sleeping behaviors in the dry spiny forest habitat adjacent to limestone cliffs.
The team observed the cave-sleeping behavior at the 104,000-acre Tsimanampesotse National Park and the Tsinjoriake Protected Area in southwestern Madagascar between 2006 and this year. Field observations were combined with motion-detector cameras to chart the behavior and movements of 11 different troops of ring-tailed lemurs.
The first clue the team uncovered was the lemurs’ presence on limestone cliffs adjacent to spiny forest trees or on the ground when Sauther's research team arrived at the study sites early in the morning.
"They seemed to come out of nowhere, and it was not from the trees," she said. "We were baffled. But when we began arriving at the study sites earlier and earlier in the mornings, we observed them climbing out of the limestone caves."
The lemurs' primary predator is a cat-like, carnivorous mammal known as a fossa. Endemic only to Madagascar, the fossa is closely related to the mongoose and may weigh up to 20 pounds. Sauther said that fossil records show a cougar-sized relative of the fossa became extinct as recently as several thousand years ago. This predator likely preyed on lemurs as well.
The research team found evidence that some early ancestors of humans in South Africa might also have lived in these caves to protect themselves from predators. Hominid remains going back several million years were found inside or near the limestone caves, and some fossil bones have evidence of damage consistent with the bite of saber-toothed cats.
"We think cave-sleeping is something ring-tailed lemurs have been doing for a long time," she said. "The behavior may be characteristic of a deep primate heritage that goes back millions of years."
Sauther collaborated with Associate Professor Frank Cuozzo of the University of North Dakota, Ibrahim Antho Youssouf Jacky, Lova Ravelohasindrazana and Jean Ravoavy of the University of Toliara in Madagascar, Krista Fish of Colorado College in Colorado Springs, Colo., and Marni LaFleur of the University of Veterinary Medicine in Vienna. Their efforts were funded by the 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.
Cuozzo, a former CU-Boulder student, co-directs the Beza Mahafalay Lemur Biology Project in southwestern Madagascar with Sauther. The Project is centered at the roughly 1,500-acre Beza Mahafalay Special Reserve, and focuses on how climate- and human-induced change affects lemur biology, behavior and survival.
Field observations made by faculty and students from the University of Toliara in Madagascar helped Sauther's team. Sauther regularly leads research teams made of undergraduate and graduate students from CU-Boulder to Madagascar, including students from CU's Undergraduate Research Opportunities Program, which provides hands-on research and fosters student-faculty relationships.
"I never thought I would have a chance as a CU undergraduate to conduct research in an exotic place like Madagascar," said former UROP student Anthony Massaro, who was part of a team that trapped ring-tailed lemurs, measured their physical characteristics including dentition, and released them back into the wild. "Dr. Sauther and Dr. Cuozzo mentored and guided me through the process of creating and conducting a unique research project."
Unfortunately, habitat destruction such as deforestation is increasing in many parts of Madagascar. Trees are being harvested for cattle forage, construction materials and firewood in southern Madagascar. The mining of limestone for the production of cement, fertilizer and other products is increasing in the same region. The International Union for the Conservation of Nature's (IUCN) Species Survival Commission has listed the ring-tailed lemur as an endangered species.
"Madagascar is a challenging place to conduct research," said James Millette, a doctoral student working with Sauther to study how the tooth wear of lemurs relates to their foraging behavior. "Part of our job is to work with local communities, because without the support of these people there would be no lemur conservation. We consider Beza, where we have been working with the community for several decades, to be a real success story."