Home-Range Use and Activity Patterns of the Red Langur (Presbytis rubicunda) in Sabangau Tropical Peat-Swamp Forest, Central Kalimantan, Indonesian Borneo

Knowledge of a species' ranging patterns is vital for understanding its behavioral ecology and vulnerability to extinction. Given the abundance and even distribution of leaves in forested habitats, folivorous primates generally spend less time feeding; more time resting; have shorter day ranges; and require smaller home ranges than frugivorous primates. To test the influence of frugivory on ranging behavior, we established the activity budget and home-range size and use in a highly frugivorous population of the Borneo-endemic colobine, Presbytis rubicunda, within Sabangau tropical peat-swamp forest, Central Kalimantan, and examined relationships between fruit availability and ranging patterns. We collected 6848 GPS locations and 10,702 instantaneous focal behavioral scans on a single group between January and December 2011. The group had the largest home-range size recorded in genus Presbytis (kernel density estimates: mean = 108.3 ± SD 3.8 ha, N = 4 bandwidths). The annual activity budget comprised 48 ± SD 4.0% resting; 29.3 ± SD 3.9% feeding, 14.2 ± SD 2.5% traveling, and 0.4 ± SD 0.4% social behaviors. Mean monthly day-range length was the highest recorded for any folivorous primate (1645 ± SD 220.5 m/d). No significant relationships existed between ranging variables and fruit availability, and ranging behaviors did not vary significantly across seasons, potentially owing to low fluctuations in fruit availability. Our results suggest that colobine monkeys maintain larger than average ranges when high-quality food resources are available. Their extensive range requirements imply that protecting large, contiguous tracts of habitat is crucial in future conservation planning for Presbytis rubicunda. © 2013 Springer Science+Business Media New York.