Republished content: Read the original post

In some parts of the world, tourists get up close and personal with wildlife by boat.

In Malaysia, for example, groups of visitors climb aboard motorboats to approach proboscis monkeys along riverbanks. While tourists might enjoy the intimate encounters, the animals are stressed by the disruption, new research finds.

“Primate ecotourism with motorboats is rapidly growing in various rainforests, including in Malaysia, and we wanted to learn more to what extent these motorboats might have a negative effect on wild primates, specifically proboscis monkeys,” lead author Marina Davila‐Ross from the University of Portsmouth in the United Kingdom, tells Treehugger.

Researchers knew visitors were becoming more common, but so far, no one studied whether human interaction stressed the animals.

“Due to anthropogenic changes to the environment, humans will most likely continue to have increasing access to wild populations of nonhuman primates and other wildlife, causing further challenges to their existence,” the researchers write.

“Partly resulting from such changes, ecotourism is one of the fastest-growing tourism sectors. Ecotourists, who regularly get close to wildlife, can increase disease transmission and cortisol levels in primate populations, suggesting a damaging effect of ecotourism on wildlife.”

For their analysis, researchers studied six groups of proboscis monkeys living in remote areas along rivers and streams in Sabah, Malaysia. Each group consisted of one male and multiple females.

The proboscis monkey (Nasalis larvatus) is named for its prominent long nose. The species is listed as endangered by the International Union for the Conservation of Nature (IUCN) Red List with population numbers decreasing.

They pass much of their day resting and feeding, but also spend time being vigilant and performing stress-related behaviors.

When Motorboats Approach

For their work, scientists conducted an experiment with monkeys in a remote area along the Kinabatangan River at the Lower Kinabatangan Wildlife Sanctuary. There are an estimated 2,000-3,000 proboscis monkeys in the sanctuary.

They approached groups of monkeys under three conditions at different speeds and travel distances: fast-close, slow-close, and slow-far conditions. For fast-close, they approached 40 meters in 10 seconds at a speed of 14.4 kilometers per hour. For slow-close, they approached 40 meters in 40 seconds at a speed of 3.6 kilometers per hour. And for the slow-far condition, they approached 20 meters in 20 seconds at a speed of 3.6 kilometers per hour.

In each scenario, they compared any stress-related behaviors demonstrated by the monkeys before the boat approached with after the boat started moving toward the animals.

They found the monkeys exhibited more stress-related behaviors like gazing at the boat, moving backward, hiding in the leaves, and repeated scratching. They displayed these behaviors longer in the fast-close and slow-close conditions.

The findings were published in the International Journal of Primatology.

Ecotourism Recommendations

Davila-Ross says the findings are similar to studies on birds and sea mammals, which suggest that stress is a universal response when a loud boat approaches and appears threatening.

The researchers propose guidelines for primate tourism in riparian (riverbank) areas where motorboat speeds should be no more than 4 kilometers per hour within 100 meters [328 feet] of the monkeys.

“It is also important to keep a distance from the monkeys, preferably no closer than 60 meters away from the monkeys (based on the impact of the slow-close condition, where we traveled for 40 meters),” Davila-Ross says.

“However, further empirical, policy-focused research is needed to better understand the impact of tourists and boats on proboscis monkeys and other primates.”

The study offers the first evidence that nonhuman primates demonstrate stress-related behaviors when even just one motorboat nears them, researchers say.

“Motorboat travel becomes particularly problematic when it involves multiple loud tourist boats, potentially causing the monkeys to leave their safe sleeping sites and to flee deep into the forest as it gets dark, where they could be faced with higher risk of predation,” Davila-Ross says.

“The results from this study might be helpful for tourists, allowing them to modify their behaviors when visiting these and other primates, and when encouraging guides to follow the guidelines in riparian areas.”