Scat shows no scare in a study, published March 15 in PLoS One, that analyzed fecal glucocorticoid metabolite (fGM) levels of Bornean orangutans (Pongo pygmaeus) in the Lower Kinabatangan Wildlife Sanctuary in in the Malaysian state of Sabah between 2008 and 2009. The community-operated organization Red Ape Encounters, which operates there, maintains strict ecotourism guidelines designed to protect the apes.
The research team collected feces samples 24 hours before ecotourism visits, as well as the day of and the day after. Many of the samples came from two orangutans—Jenny, a then-32-year-old female, and Etin, her 11-year-old offspring—both of whom were gradually habituated to encounters with ecotourists over a period of several years. The rest came from four other unidentified orangutans that were not habituated to humans. In each case, the samples collected the day after the encounters showed elevated levels of the stress hormone cortisol. But that wasn't necessarily a bad thing.
"An elevated cortisol level in response to ecotourists would be completely natural and expected," says the study's lead author, Michael P. Muehlenbein, professor of anthropology at Indiana University Bloomington. "It just means an activation of the sympathetic nervous system. Short-term fluctuation of cortisol levels is completely to be expected under most circumstances."
Muehlenbein and his fellow researchers were concerned that the orangutans might have shown extremely elevated levels of cortisol or none at all. That would have indicated levels of chronic stress and a systemic breakdown in the animals, as has occurred in some other species regularly encountered by ecotourists. For example, yellow-eyed penguins (Megadyptes antipodes) have exhibited significantly lowered breeding success in populations exposed to tourism, while ring-tailed lemurs (Lemur catta) showed degraded fur coats. (The paper equates these reactions to post-traumatic stress disorder in humans.)
But short-term fluctuations showed, at least on an fGM level, that the orangutans were not exhibiting signs of chronic stress. "You need the fight-or-flight response," Muehlenbein says. "If you become habituated to a process, and you don't react accordingly when there's a danger, then you have a problem."
Muehlenbein says the fGM test is just one more item in the veterinary or conservation toolbox to make sure that animals encountering humans are healthy. "Cortisol metabolites are very sensitive to a number of things, such as disease, diet and sexual activity. It's not a perfect measure. It should be combined with the other tools that we already have."
According to the paper, tourism accounts for 9 percent of world GDP and can contribute greatly to conservation efforts for rare species. In the case of orangutans, at least, ecotourism done right does not appear to be harming the apes in the process. Red Ape Encounters's guidelines limit visitations to groups of seven and a period of one hour. Sick tourists are excluded, and all visitors must keep a 10-meter minimum distance between themselves and the orangutans.
Muehlenbein is now working at a nearby orangutan rehabilitation center, where he is interviewing ecotourists about their behavior to try to calculate the risk for disease transmission from humans to animals. Apes have been known to catch coughs, colds and other viruses from humans, which can prove fatal. Although this human-to-primate transmission has been documented, there is no conclusive evidence to date of disease transmission from tourists to apes. "We know that a significant number of travelers visit ecotourist sites even though they haven't been well-enough vaccinated or they show signs of illness," Muehlenbein says. Some orangutan tourism sites might habituate their animals more rapidly, overexpose them to humans or even allow people to touch or feed the apes, all of which could contribute to chronic stress and, in turn, make the orangutans more susceptible to human diseases. "Humans pose an undocumented risk. We should put time, money and effort into hiring health professionals at these primate-based destinations and educating tourists about the risk of disease transmission."
Photo: Marco Abis via Flickr. Used under Creative Commons license