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Ecotours aimed at saving monkeys are likely stressing them out, study finds

Two male proboscis monkeys in Malaysian Borneo.

Two male proboscis monkeys in Malaysian Borneo. Image by Rhett A. Butler/Mongabay.

  • A recent study reveals that tourist boats approaching troops of proboscis monkeys in Malaysian Borneo cause the animals stress, even when the boats travel at slow speeds.
  • The research reveals something of a universal response, closely tracking similar findings from ecotourism operations focused on other animals such as birds and whales.
  • 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.
  • Scientists say this type of research can form the basis for guidelines aimed at minimizing the effects of ecotourism on animals, especially as its role in conservation grows.

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.

Rainbow over the Borneo rainforest and Kinabatangan River. Proboscis monkeys spend most of their time squatting in the forest canopy, grazing on leaves and fruit. Image by Rhett A. Butler/Mongabay.

“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.

Individual monkeys from several groups in the Lower Kinabatangan Wildlife Sanctuary had been fitted with GPS collars for a previous study, which aided the team in finding and identifying different groups. When the monkeys were in sight, the researchers recorded the group’s behavior with video cameras. The boat drivers then chose one of three different approach conditions: fast and close, quickly traveling 40 m (131 ft) toward the group; slow and close, moving the same distance but at about a quarter of the speed; or slow and far, slowly driving just 20 m (66 ft) in the direction of the monkeys.

Team members then recorded the changes in the way the monkeys were acting, looking for anything that might indicate the boat’s presence was perturbing them.

Researchers found that motorized boats cause stress to proboscis monkeys in the trees along the banks of the Kinabatangan River in Malaysian Borneo. Image by John C. Cannon/Mongabay.

Both the fast-close and slow-close approaches elicited heightened attention from members of the monkey group and other behaviors such as scratching and aggression toward other monkeys, indicating they found the approaching boats bothersome. The fast-close approach led the monkeys to cut short the time they spent feeding more so than either the slow-close or slow-far approaches.

The team made the faster approach slowly enough so it wouldn’t cause the monkeys to flee into the forest. But Davila-Ross cautioned that tourist boats might still be capable of unsettling the monkeys enough to force them to move away from the river’s edge and into areas where they could be more susceptible to predators like the Sunda clouded leopard (Neofelis diardi).

Ikki Matsuda, a primatologist and associate professor at Japan’s Chubu University, said that despite the relatively small number of observations in the research, it was still “a very important study.”

“[I]t is the first step towards developing quantitative guidelines for tourism by boat in Sabah,” Matsuda, who was not involved in the study but did review it prior to publication, told Mongabay in an email. “Future research, including comparisons with more touristy areas and combined with endocrine analysis, will make the impact of tourism more apparent.”

The proboscis monkeys’ response to the team’s slow-far approach indicates a potential avenue for tourism operators who want to avoid disturbing the species. Davila-Ross said the research supports parameters for primate tourism that include keeping speeds under 4 kilometers per hour (2.5 miles per hour) once a boat is within 100 m (330 ft), and then getting no closer than 60 m.

A herd of Borneo elephants. The researchers are working on a study examining how tourists affect the Kinabatangan’s population of Borneo elephants. Image by John C. Cannon/Mongabay.

Heather Leasor, currently a data archivist with the Australian National University, wrote her doctoral thesis on proboscis monkey tourism in Sabah. She said those sorts of guidelines could benefit the region’s tourism operators as well.

“If the monkeys get too stressed and act out of the ordinary or flee regularly then tourism in the area could be negatively impacted,” Leasor, who was not involved in the current study, said in an email. The reduced chances of seeing proboscis monkeys could then in turn hurt those who depend on the region’s tourism economy, she added.

Davila-Ross and her colleagues are working on a study examining how tourists affect the Kinabatangan’s population of diminutive Borneo elephants (Elephas maximus borneensis). More broadly, what the team learned from the proboscis monkeys fits with research on other animals, ranging from birds to whales, in different environments. That suggests “that stress is a universal response across animals when a boat approaches — a large, loud, and artificial object moving towards them is likely to be threatening,” she said.

This growing body of research suggests that wildlife tourism must be done carefully with guidelines aimed at minimizing harm to animals if it is going to be part of an effective conservation strategy.

Banner image: Two male proboscis monkeys in Malaysian Borneo. Image by Rhett A. Butler/Mongabay.

John Cannon is a staff features writer with Mongabay. Find him on Twitter: @johnccannon

Citation:

Davila-Ross, M., Pople, H., Gibson, V., Nathan, S. K., Goossens, B., & Stark, D. J. (2022). An approaching motor boat induces stress-related behaviors in proboscis monkeys (Nasalis larvatus) living in a riparian area. International Journal of Primatology, 1-21. doi:10.1007/s10764-022-00277-z

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