摘要：Effective conservation needs a solid baseline of animal distribution, density, and abundance data to base management strategies on and evaluate the effectiveness of conservation efforts on the species of interest. For many species it is not feasible to directly count individuals, and scientists are forced to use indirect methods that can provide estimates of density and abundance. For orangutans nest counts are the most often used indirect sign of presence. Models used for density and abundance estimates are based on a set of assumptions about the observations. Here we analyze the effect of several factors (distance to transect, height, decay stage, and observer experience) on the probability that an orangutan (Pongo abelii) nest is found along a line transect. The results indicate that all factors significantly influence nest detection. Orangutan density estimates varied between the teams with the lowest estimate being approximately 83% of the highest estimate and orangutan density showed a positive correlation to experience level. We use these results to propose a new approach to determine orangutan density that should reduce variation between density estimates from nest surveys and therefore should lead to more reliable between-survey comparisons for orangutans and potentially other great-ape species.
