1Department of Anthropology, Rutgers University, 2Center for Human Evolutionary Studies, Rutgers University, 3Fakultas Biologi, Universitas Nasional
April 12, 2018 3:45, Texas V/VI
Male ranging is often assumed to be primarily determined by female distribution, especially in solitary mammals. Whereas ecological and social influences on orangutan ranging have been well documented for females, few studies have investigated factors affecting male ranging patterns. To investigate the factors influencing the ranging patterns of flanged males, we collected behavioral and GPS location data during nest-to-nest follows of 8 adult flanged males from Jul 2013 to Apr 2016 at the Tuanan Research Station in Central Kalimantan, Indonesia. Because flanged males are typically twice the size of adult females, and thus have high energetic demands, we expect that ecological and energetic factors will strongly influence their ranging. We used GIS to generate ranging areas for 5-day follow blocks (N=17) and general linear models to test for the influence of the presence of other orangutans, rainfall, temperature, fruit availability, and the presence of urinary ketones indicating fat catabolism. There was no effect of adult female associations, long calls heard from competitor males, monthly rainfall, or fruit availability on range size, but ranges were significantly smaller during warmer months, and when ketone production was greater. Overall, our results suggest that, at least in the short-term, male range size is most strongly influenced by energetic factors, and appears to be constrained by thermoregulation costs from hot temperatures and during periods of negative energy balance. This work adds to a growing body of work demonstrating the strong influence of energetic stress on both male and female orangutan behavior.
Funding for this research was provided by USAID and the Center for Human Evolutionary Studies at Rutgers University.