Evaluating genetic capture‐recapture using a chimpanzee population of known size

Abstract

ABSTRACTGenetic capture‐recapture (CR) estimates of population size have potential for aiding the conservation and management of rare or elusive animals. To date, few studies have explored the performance of genetic CR estimates by implementing them in a population of known size. We evaluated the accuracy and precision of genetic CR estimates by genotyping fecal samples collected opportunistically over the territory of a well‐studied group of approximately 190 previously identified and genotyped eastern chimpanzees (Pan troglodytes schweinfurthii) in Kibale National Park, Uganda. We compared the performance of genetic CR estimates based on 3‐month and 3‐year sampling periods to explore the impact of lengthened sample periods, which are expected to increase accuracy and precision of estimates but also increase the chances of violating population closure assumptions. We compared the effects of using spatial and non‐spatial models and equal or heterogeneous detection probabilities upon estimates. Over the 3‐year period, we detected 54% of the group members and produced population size estimates with more accuracy and narrower confidence intervals than the 3‐month sampling period. The population remained effectively closed over the 3 years and detection heterogeneity was linked to age but not sex. Non‐spatial methods estimated group size more accurately than spatially explicit methods, which had a stronger tendency to underestimate population size. This study suggests that genetic CR may produce accurate and precise population size estimates if substantial effort is allocated to sample collection and genotyping. © 2016 The Wildlife Society.