Meeting Abstract

77-6  Wednesday, Jan. 6 09:15  Social and environmental influences on long call behavior of male orangutans HOEPFNER, A.R.*; MORROGH-BERNARD, H.; HUSSON, S.; HARRISON , M.; GOLLER, F. ; University of Utah, Orangutan Tropical Peatland Project; Orangutan Tropical Peatland Project, University of Exeter; Orangutan Tropical Peatland Project; Orangutan Tropical Peatland Project; University of Utah

Long-distance communication in primates is often examined in light of social influences, and less attention has been paid to environmental factors. Given the costly nature of vocal communication, examining environmental influences can help us understand proximate and ultimate mechanisms shaping the use of vocalization for social behavior. Male orangutans produce a long distance call, the long call, which indicates location, direction of travel, caller identity, etc. Multiple social factors may influence calling rate, however, it is not known to what degree environmental factors, such as food availability and weather conditions influence long call behavior. We tested the effects of environmental and social factors on long call rates of Bornean orangutans (Pongo pygmaeus wurmbii) in Central Kalimantan, using long-term behavioral data (2003-2012). We discovered that plant phenology (flowering and fruiting) was the most significant predictor of calling rate. Furthermore, forest productivity, assessed as litter fall data, was significantly correlated with male calling behavior. For social factors, the number of heard long calls influenced calling rate. “Winning” an interspecific conflict greatly increased male long call rate compared to those of individuals that recently “lost” a conflict. In addition, males increased their call rate prior to and during encounters with a female. These data show a clear influence of environmental factors on long calling behavior of orangutans and therefore highlights the importance of examining environmental variables along with social factors in affecting long call behavior.