The first time you see a proboscis monkey (Nasalis larvatus), you might be hit with a mix of fascination, joy and perhaps some confusion: muscular limbs attached to a pot-bellied torso, with its namesake trunk hanging like a small but bulbous red banana from the center of their faces (at least the males).
These social — and endangered — monkeys spend most of their time squatting in the forest canopy, grazing on leaves and fruit and occasionally launching themselves from tree to tree. They’re a highlight for any wildlife tourist, especially along the banks of the Kinabatangan River in Malaysian Borneo, where motorized skiffs bring visitors close enough to feel like they’re part of a fellow primate’s troop, if only for a moment.
Wildlife tourism is increasingly seen as a way to raise awareness around conservation issues and provide local communities with a source of income that’s contingent on the protection of ecosystems. But boats like those on the Kinabatangan may be troubling for proboscis monkeys, according to a study published online Feb. 25 in the International Journal of Primatology.
“Collectively, our findings suggest that the approach of a single motorboat induces stress in proboscis monkeys when approaching them as closely as 60 [meters, or about 200 feet] from the other side of the river, regardless of the speed of approach,” Marina Davila-Ross, a researcher in comparative psychology at the University of Portsmouth in the U.K. and one of the study’s lead authors, said in an email to Mongabay.
Davila-Ross had been doing research in this part of the Malaysian state of Sabah at the Danau-Girang Research Centre, which sits on the banks of the Kinabatangan. She knew proboscis monkeys are a perennial tourist favorite, and a troop often attracts boats on the river like filings to a magnet. So, she and her colleagues from Cardiff, Danau-Girang and the Sabah Wildlife Department decided to test whether a whirring motorboat approaching the riverbank below their canopy hideouts caused any discernible change in their behavior.
Lead Image: Two male proboscis monkeys in Malaysian Borneo. Image by Rhett A. Butler/Mongabay.
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