An Approaching Motor Boat Induces Stress-Related Behaviors in Proboscis Monkeys (Nasalis larvatus) Living in a Riparian Area

Abstract Primate ecotourism is a fast-growing tourism sector that may have negative effect on wildlife. In riparian areas, tourists can conveniently reach primates via motor boats, but no study has directly examined whether such boats cause stress in primates. Our goal was to test the approach of boat induces stress-related and other behaviors proboscis monkeys ( Nasalis larvatus ), an Endangered species. We studied six one-male, multifemale groups living remote area Sabah, Malaysia, conducted experiment by approaching using three conditions with different speeds travel distances (fast-close, slow-close, slow-far conditions; 7-8 subjects per condition). For each condition, we compared before after started approaching. Feeding, allogrooming aggression were similarly examined, respectively. also observed monkeys’ at times examine age-sex classes differences vigilance, social proximity, allogrooming, play (87 subjects). experiment, displayed for longer fast-close slow-close once than approach. The reduced feeding condition our observational study, males more vigilant females—a behavior likely relate male-male competition group protection. This provides evidence even single moving slowly, humans behaving calmly, negatively affect primate induce stress—an impact be larger tourist boats. shows comparable (speed 3.6 km/hr; closer 60 m), where observed, help develop guidelines areas. Future research examines needed.