A pilot study of the hair-trapping method in Asiatic black bears (Ursus thibetanus): determination of optimal survey period for estimating population size

In order to establish methodology for population estimation of Asiatic black bears using the hair-trapping method, hair-trapping devices were located within a study area, and basic data were collected to determine the optimal survey period for hair sampling. Bear hairs collected were classified as three types (guard hair; G, underfur; U, and intermediate hair; I) depending on hair-bulb thickness. After DNA extraction, six microsatellite loci and amelogenin locus were amplified in order to identify individual bears and sex, respectively. The number of hairs collected by hair-trapping devices decreased dramatically in late August, while those that had lost part of the hair bulb increased after September. The success rate of genetic analysis was over 90% prior to the month of July and rapidly decreased in August. Based on the results of the generalized linear model, it was determined that sampling session had the most significant impact on the success rate of genetic analysis of all the explanatory variables examined. Higher rates of U-type hairs within samples used in DNA extraction resulted in lower success rates of genetic analysis. It was concluded that the optimal survey period for estimating population size using the hair-trapping method was between June and early August.