Patricia Wright: Climate Change Pushing Greater Bamboo Lemur Closer to the Brink of Extinction

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A new study from world’s leading lemur expert paints a grim picture for future of dietary specialists like the critically endangered Greater Bamboo Lemur.

Greater Bamboo Lemure

Similar to the giant panda, the Greater Bamboo Lemur eats the tough culm (trunk) of bamboo, and only does so during the dry season, but it prefers bamboo shoots which are more nutritious.

Human disturbance of tropical rainforests in Madagascar, including wildfires, burning and timber exploitation, have led to reduced rainfall and a longer dry season, further pushing the Greater Bamboo Lemur to the brink of extinction. Findings are published in a new study from primatologist and lemur expert, Patricia Chapple Wright of Stony Brook University, evolutionary biologist Jukka Jernvall of University of Helsinki in Finland, and colleagues. The study is entitled Feeding Ecology and Morphology Make a Bamboo Specialist Vulnerable to Climate Change, in the Oct. 26 online edition of Current Biology.

Researchers have evidence to suggest that, as the climate changes, Madagascar’s Great Bamboo Lemur will gradually be forced to eat culm, the woody trunk of the bamboo, for longer periods of time throughout the year. Ultimately, they suggest based on an analysis of anatomical, behavioral, paleontological, and climate data, this dietary constraint is impacting the Greater Bamboo Lemurs’ ability to thrive, reproduce and shortens its lifespan.

Wright, a primatologist, anthropologist and conservationist, and colleagues including Jernvall;  Sarah Zohdy, an assistant professor of disease ecology at Auburn University; Stacey Tecot, associate anthropology professor at University of Arizona; Alistair Evans, an associate professor  at Monash University in Australia; and Jussi Eronen, a researcher at University of Helsinki, first showed that the Greater Bamboo Lemurs are equipped with highly complex and specialized teeth, just as giant pandas are — the only other mammal capable of feeding on culm. Those teeth make it possible for them to consume and survive on woody culm for parts of the year.

On the ground in Madagascar
To find out more about the Greater Bamboo Lemurs’ feeding habits, the researchers spent hours watching them in their natural habitat in Madagascar’s Ranomafana National Park over a period of 18 months, collecting more than 2,000 feeding observation in all. Those data showed the lemurs spend 95 percent of their feeding time eating a single species of woody bamboo. But they only eat the culm from August to November, when dry conditions make tender shoots unavailable.

According to the research findings, these rainfalls are changing annually. Over the past two years, Wright says, there has been a three month delay in the rainy season and new tender shoots that Great Bamboo Lemurs use for sustenance are appearing in January and February — 14 days after the first rainfall. Since new offspring are born in November, the delayed rainy season is dangerously affecting the survival of the baby Greater Bamboo Lemurs because of lack of nutrition available for both the mothers and offspring.

“This is why, for extreme feeding specialists like the Greater Bamboo Lemur, climate change can be a stealthy killer,” said Wright. “Making the lemurs rely on a suboptimal part of their food for just a bit longer may be enough to tip the balance from existence to extinction.”

A characteristic of bamboo-feeding mammals is that most are considered threatened by extinction. In Asia, both giant and red pandas have much diminished geographical ranges and similarly, in Madagascar, the two larger bamboo lemurs, the Greater Bamboo Lemur and the Golden Bamboo Lemur, have highly restricted distributions within the island. In fact, once the most broadly distributed lemur in existence, the Greater Bamboo Lemur is now one of the most critically endangered of all lemurs, with only an estimated 800 in the wild.

“By studying specialists like the Greater Bamboo Lemur, we can identify the different ways that climate change can cause extinction,” Jernvall said. “And if we do not study these endangered species now, they may go extinct before we know all the reasons why, and we’ll be less able to protect what remains.”

The research also projected that the dry season on the island will lengthen, meaning less nutritious and more mechanically demanding bamboo for the lemurs to consume, which is a serious issue.

“Thirty years ago these new shoots would come in December; now they don’t start until February,” Wright said. “These challenges can translate to decreased life span, increased tooth wear, and decreased birth rate. All of this adds to the lemur’s already serious predicament: their population is in the hundreds and they’ve already suffered decades of poaching and habitat destruction due to human encroachment.”

Finding a Solution
To combat the various issues confronting lemurs, Wright and her team at Stony Brook’s Centre ValBio in Ranomafana National Park, have begun a project to strategically reforest and rebamboo areas of the island. Because portions of the lemur population have been cut off from each other due to deforestation, Wright and colleagues are planting corridors of bamboos with the goal to connect the lemur’s isolated populations and expand their habitats. They are also planting trees endemic to Madagascar and native species that are economically viable and important to the Malagasy people such as wild pepper, vanilla, chocolate and coffee in the shade under those trees.

“90 percent of Madagascar’s natural habitat is gone,” said Wright. “When it’s gone no one can live there — not animals or people. The most important thing we can do in this case is to stop the burning of the forests and also of the denuded areas. Using the approach presented in the study, we are able to identify locations where this species may be viable if they are also protected from habitat loss and hunting.”

“Tropical forests count! They are the lungs of our planet,” Wright added. “Some of our primate cousins on the edge of extinction are being severely affected by climate change issues.  We are determined to finding solutions on how we can stop the destruction of the tropical forests in Madagascar and beyond.”

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