Threatened Lemurs' Diet Key to Conservation Efforts, Researchers Say

John Roach
for National Geographic News
February 8, 2007
Pristine forests on the African island nation of Madagascar offer the Milne-Edwards' sifaka a rich diet of fruits, seeds,
and leaves, an anthropologist has found.

Logged-over habitat, in contrast, produces mostly leaves for the rare primate to eat.

The Milne-Edwards sifaka is a lemur, a type of primate found only on Madagascar.

There are more than 70 lemur species, and almost all are endangered due to habitat destruction from logging and agricultural slash-and-burn fires. (Related story: "Three New Lemurs Discovered, Add to Madagascar's Diversity" [June 26, 2006].)

Scientists are racing to learn as much as they can about basic lemur ecology so that the Malagasy government can use the data to make informed conservation management decisions before human activity wipes out entire species.

"Are they going to let logging occur in national parks or are they not? Are they going to allow access for firewood collection or not?" said Summer Arrigo-Nelson, a visiting professor of anthropology at the University of Notre Dame.

"Those kinds of questions need scientific data to help us understand what the primate response is."

Arrigo-Nelson's research shows that animals living in unspoiled forest are eating a more nutritious diet than those in disturbed forest, since fruits and their seeds are a potent source of sugars and fats.

"That can potentially have a great impact on their nutritional state, body weight and, in the long term, their survival," she said.

For example, a diet rich in sugars and fats helps females get pregnant, maintain their pregnancies, and produce high-quality milk for their offspring, she added.

Charles Welch is a research scientist at the Duke University Lemur Center in Durham, North Carolina. He lived and worked in Madagascar for 15 years before returning to the U.S. in 2004.

He said that despite a lot of important conservation work on the island, the situation for lemurs remains urgent.

"Progress is not as fast as all of us would like to see," he said. "But there is hope for the future, and the government is committed to making conservation a priority."

Field Research

Arrigo-Nelson's project is part of a long-term monitoring program in Madagascar's Ranomafana National Park.

The program is directed by lemur expert Patricia Wright of New York's Stonybrook University. (Wright is a member of the National Geographic Society's Committee for Research and Exploration. National Geographic News is part of the National Geographic Society.)

Regions of Ranomafana were selectively logged between 1986 and 1989, with as many as 300 hardwood trees hand cut and removed from the forest each day. Wright's program has studied this portion of the forest since 1986.

Arrigo-Nelson, who was a graduate student under Wright, essentially replicated aspects of that study in a pristine site about five miles (eight kilometers) away.

She and her team collected field data in pristine and disturbed habitats between 2001 and 2004. She has also returned for several weeks every June and July.

"One of the things we're interested in doing is just getting the baseline disturbed versus undisturbed comparison down," she said. "We can look at that in the short term—in one-year snapshots—or we can look at it over the time we have all the data."

Arrigo-Nelson used a one-year snapshot to write her dissertation on the effect of habitat disturbance on lemurs. The long-term data, she said, supports her conclusions that lemurs in pristine habitat have a richer diet than those in disturbed habitat.

Welch, the Duke University lemur expert, said Arrigo-Nelson's baseline research is important.

"The more we understand about what the disturbed habitat can support in terms of fauna can tell us a lot," he said. "It can tell us what areas are still worth protecting, what areas are too degraded to merit protection."

More Questions

Arrigo-Nelson hopes to extend her research to address questions on infant mortality in pristine habitat and how lemurs respond as disturbed habitat recovers.

For example, she said, the 20-year dataset from the disturbed forest shows that the lemurs there experience 70 percent infant mortality—only 30 percent survive to adulthood.

"We need comparable data from the pristine forest to tell us whether that's an artifact of disturbance or whether it's just something typical for the species," she said.

Lemurs only breed every two years, so the data collected to date in the pristine forest is too limited to draw any conclusions about infant survival trends yet, she said.

Another interesting question is the response of lemurs to habitat recovery.

Logging in Ranomafana was halted in 1989, and trees that were too small to harvest then are now bearing fruit.

As a result, preliminary data show, the black and white ruffed lemur, a fruit specialist, has begun a slow return to the disturbed forest. (Related story: "African Trees May Be Tied to Lemurs' Fate" [July 26, 2004].)

Arrigo-Nelson said that is a quantifiable—and "hopeful"—sign that the forest is healthier.

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