The population and distribution of orangutans (Pongo pygmaeus pygmaeus) in and around the Danau Sentarum Wildlife Reserve, West Kalimantan, Indonesia Original Research Article

We report estimates of orangutan distribution and population size in and around the Danau Sentarum Wildlife Reserve (DSWR) in West Kalimantan, Indonesia, one of the few areas in Borneo that may still support a large population. We generated estimates in line with each of three proposed definitions for the reserve — its current boundaries, a moderate extension, and a greater extension. Estimates were based on current nest survey methods, adjusted for habitat type variability. Measures of habitat type coverage derived from a GIS developed for the DSWR region. Our estimates support impressions that the current DSWR harbors few orangutans (±200) but the greater extension supports a substantially larger population (>2000). Findings are discussed with respect to distribution (habitat preference), behavior in the DSWR area (migration, local stresses, human tolerance), and habitat protection plans.