1Anthropology, Boston University, 2Earth and Environment, Boston Univeristy, 3Biology, University of Tanjungpura
April 12, 2018 , Texas V/VI
Animal-mediated seed dispersal is important for promoting forest regeneration and sustainability. Animal movement influences the distribution of seeds across the environment, resulting in spatially aggregated seed dispersal patterns. Animal seed dispersal patterns likely play an important role in the spatial structuring of tree populations: where a seed disperser moves influences the seed distribution. Environmental parameters that shape a disperser’s movement also influence the spatial distribution pattern of their seed dispersal. Orangutans are highly frugivorous and have been shown to disperse intact viable seeds. GPS locations were recorded for all orangutan defecations (n=1721) from 2014 to 2016 at the Cabang Panti Research Station in Gunung Palung National Park (GPNP), Indonesia. Our pilot research at GPNP measured seeds in fecal samples (n=98 fecal samples) and demonstrated that orangutan fecal samples do have intact seeds in more than 95% of their feces. A kernel density map was made using the defecation data to calculate the spatial density distribution of the defecations. A geographically weighted regression model (GWR) analyzed how well spatial parameters (altitude, slope, distance to river, and normalized difference vegetation index) predict the spatial density distribution of orangutan seed dispersal. All parameters in the GWR were statistically significant (R2=0.80, p<0.001) and showed low values for collinearity. The results show that orangutan seed dispersal is aggregated in space and the seed dispersal pattern is significantly shaped by environmental variables. This study provides us a better understanding of how the environment plays a role in determining animal behavior which influences the seed spatial distribution.
Funders include the National Science Foundation (BCS-1638823), National Geographic Society, US Fish and Wildlife (F15AP00812), Leakey Foundation, Disney Wildlife Conservation Fund, and Nacey-Maggioncalda Foundation.