Genetic Mark-Recapture Population Estimation in Black Bears and Issues of Scale

Abundance estimates for black bears (Ursus americanus) are important for effective management. Recently, DNA technology has resulted in widespread use of noninvasive, genetic capture-mark-recapture (CMR) approaches to estimate populations. Few studies have compared the genetic CMR methods to other estimation methods. We used genetic CMR to estimate the bear population at 2 study sites in northern New Hampshire (Pittsburg and Milan) in 2 consecutive years. We compared these estimates to those derived from traditional methods used by the New Hampshire Fish and Game Department (NHFG) using hunter harvest and mortality data. Density estimates produced with genetic CMR methods were similar both years and were comparable to those derived from traditional methods. In 2006, the estimated number of bears in Pittsburg was 79 (95% CI = 60-98) corresponding to a density of 15-24 (95% CI) bears/100 km(2); the 2007 estimate was 83 (95% CI = 67-99; density = 16-24 bears/100 km(2)). In 2006, the estimated number of bears in Milan was 95 (95% CI = 74-117; density = 16-25 bears/100 km(2)); the 2007 estimate was 96 (95% CI = 77-114; density = 17-25 bears/100 km(2)). We found that genetic CMR methods were able to identify demographic variation at a local scale, including a strongly skewed sex ratio (2 M: 1 F) in the Milan population. Genetic CMR is a useful tool for wildlife managers to monitor populations of local concern, where abundance or demographic characteristics may deviate from regional estimates. Future monitoring of the Milan population with genetic CMR is recommended to determine if the sex ratio bias continues, possibly warranting a change in local harvest regimes. (C) 2011 The Wildlife Society.