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article imageOrangutans are more resilient than researchers thought

By Subir Ghosh     Sep 25, 2010 in Environment
There is hope yet for the orangutan in forest plantations and sustainably logged forests. Selectively logged forests and timber plantations can serve as habitat for orangutans, and populations of the ape may be more resilient than previously believed.
A team of researchers led by Erik Meijaard of Jakarta-based People and Nature Consulting International has found roughly equivalent population densities between natural forest areas and two plantation concessions in East Kalimantan, Indonesian Borneo.
The researchers found that Bornean orangutans use both secondary forest and acacia plantations for feeding and nesting, although the authors note "it remains unclear whether such landscapes can maintain long-term viable populations."
Meijaard and colleagues, however, admitted that more research is needed to determine how differences in food availability between plantations and natural forests affects orangutan behavior and viability in the long-term.
"The key finding of this study is that orangutans use acacia plantation landscapes," the researchers wrote. "This does not mean that plantations have the same conservation value as natural forests, but, at least for orangutans, they have some value that in the past has not been sufficiently recognised."
"It is too early to know whether these populations are transient individuals in search of new forest habitat, or whether this area is part of a recolonisation process from nearby over-degraded forests. The long-term viability of these populations requires further study."
The total number of Bornean orangutans is estimated to be less than 14% of what it was in the recent...
The total number of Bornean orangutans is estimated to be less than 14% of what it was in the recent past (from around 10,000 years ago until the middle of the twentieth century) and this sharp decline has occurred mostly over the past few decades due to human activities and development.
Tim Strater
The researchers have published their findings 'Unexpected Ecological Resilience in Bornean Orangutans and Implications for Pulp and Paper Plantation Management' in the open access journal PlosOne. The other team members were Guillaume Albar, Nardiyono, Yaya Rayadin, Marc Ancrenaz and Stephanie Speha.
The conservationists wrote, "Objective assessments of species' resilience and adaptability are of crucial importance to develop management recommendations that maximise the long-term survival chances of endangered wildlife, especially when rates of forest conversion are high and human-altered landscapes dominate their range. The orangutan appears to be an especially suitable study object, because of its internationally recognised conservation appeal, but also the strongly emotive aspects of orangutan conservation that can potentially cloud objective conservation assessments."
Roughly 75 percent of Borneo's 50,000 or so orangutans are believed to live outside protected areas. "The conservation implications of these findings are important, suggesting that we must make efforts to enhance the orangutan's chances of survival in plantation forests and the surrounding matrix habitats," the authors wrote.
An adult male orangutan on the Tarantang River  Central Kalimantan.
An adult male orangutan on the Tarantang River, Central Kalimantan.
Marc Dragiewicz
Instead of translocating orangutans when they are encountered within plantations, the scientists instead "recommend solutions that resolve orangutan management issues in situ by trying to reconcile ecological needs of the species with the economic development goals of plantations, for example by increasing the size and interconnectedness of conservation areas and adjacent forested habitat."
The orangutans are the only exclusively Asian living genus of great ape. They are among the most intelligent primates and use a variety of sophisticated tools, also making sleeping nests each night from branches and foliage. They are the largest living arboreal animals with longer arms than other great apes.
Native to Indonesia and Malaysia, orangutans are currently found only in rainforests on the islands of Borneo and Sumatra, though fossils have been found in Java, the Thai-Malay Peninsula, Vietnam and China. There are only two surviving species, both of which are endangered: the Bornean orangutan (Pongo pygmaeus) and the critically endangered Sumatran orangutan (Pongo abelii).
More about Orangutan, Indonesia, Borneo
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