Endangered Orangutans: Releasing Captive Populations Is Vital To Species Survival, Researchers Say

The survival of endangered Orangutans hangs in the balance as researchers continue to urge conservationists to reintroduce captive populations back into their natural environments. Habitat loss is the greatest threat to endangered orangutans but keeping the animals from their forest homes could further jeopardize survival of the species as a whole, argue Rutgers University researchers.

To make their argument, Rutgers researchers are pointing to their own recent study of tree dwelling animals in relation to their environmental and nutritional needs. Researchers closely examined the availability of food sources found in tropical rain forests throughout Southeast Asia and concluded that orangutans living in the Tuanan Forest, located in Central Kalimantan, Indonesia, consumed almost 2,500 more calories each day when the availability of fruit was high and more than 800 calories in times of scarcity. This is a drastic difference compared to orangutans living nearby in Sabangau Forest where there is a thick later of acidic peat that makes it harder for nutritious plants to grow. Subsequently, this limits an orangutan's food options and calorie intake. This difference was obvious to researchers, who could instantly distinguish which forest was able to support a healthier orangutan population.

"This study gives us a better understanding of how living in an unpredictable environment can influence the population density of large animals that spend the majority of their time in tress," Erin Vogel, an evolutionary anthropologist at Rutgers University, said in the release. "If animals can't obtain enough energy, reproductive output and population sizes will suffer."

The key to species survival is making sure enough high-energy food is readily available. Knowing which habitats are most beneficial will help conservationists properly release the captive orangutans.

"If you want to increase the populations of this endangered species, you need to make sure they are being reintroduced into suitable habitats," Vogel explained. "It means looking at forests carefully, making sure they are productive, and that there is enough food to eat in terms of caloric gain."

Bornean orangutans are a long-haired, orange-colored ape species that depend on low-protein fruit to survive. This allows them to store fat for when food resources are scarce. On average, female orangutans give birth to one offspring every seven or nine years, a reproductive rate that is directly related to nutrition, Vogel noted.

"This work not only helps us understand why orangutan abundance varies between sites, but also suggests a mechanism through which forest degradation may reduce the number of orangutans that can be supported in an area because of the quality of foods available," Mark Harrison, the managing director of the Orangutan Tropical Peatland Project who worked alongside Vogel, said in a statement. "Such considerations are likely to become increasingly important as orangutan habitat continues to be lost and damaged across Borneo and Sumatra, including by the dreadful forest fires currently blighting the region."

Their study was recently published in the journal PLOS ONE.

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