Hong Kong (CNN) -- Gorillas put off their food and stressed out orangutans, could nature tourism be bad for wild animals' health?
It's an idea that has been suggested in a recent report that tested for stress hormones in orangutan excrement.
Researchers from the University of Indiana and eco-tourism group Red Ape Encounters spent 14 years studying two apes in Sabah, Malaysia, which were used to seeing humans. By testing the animals' feces they found that the orangutans' stress levels were higher than normal the day after coming into contact with humans.
"As for the unknown wild orangutans that we were also able to gather samples from, we found numerically, but not statistically, higher stress hormone levels in these animals following contact with researchers than in the habituated animals," said Michael Muehlenbein, of Indiana University and one of the authors of the report. Read More