Repellent activity of nesting trees in the Sebitoli chimpanzee community of Kibale National Park, Uganda
Abstract
Every night, like other great apes, chimpanzees (Pan troglodytes) build a “nest” by folding and intertwining plant branches. As nighttime is a key period when female mosquitoes are feeding and may transmit diseases, chimpanzees may have developed strategies to avoid biting at this time. Indeed, a previous survey showed that they use nesting sites and height in the trees where fewer female mosquitoes are present compared to other places where they feed during the day. As some of the chimpanzee communities studied have a preference for trees in which to build a nest, we suggest that a complementary strategy could be to choose leaves that emit insect repellent aromatic substances to reduce bites risk. To test this hypothesis, we first analyzed 24 months of nesting data to determine the 12 most preferred nesting trees in the Sebitoli community of Kibale National Park in Uganda. Secondly, we hydro-distillated leaves from those preferred trees to compare them to the 10 most common trees in their habitat and yet not preferred for nesting. The essential oils obtained was tested against females of the African mosquito, Anopheles gambiae. We discovered that out of the 12 nesting trees, 8 showed repellent activities, 7 were irritant (vs 3 and 5 respectively in common trees) and none were toxic. This study is one of the first evidence that chimpanzees could choose their nesting trees according to their biological and chemical properties, a potential inspiration for human health.