Combined use of mark-recapture and genetic analyses reveals response of a black bear population to changes in food productivity

Abstract

We used mark-recapture analysis to investigate the dynamics of a black bear (Ursus americanus) population in northern Idaho where food availability varies seasonally and annually. We conducted noninvasive genetic sampling (NGS) during 2003-2006 in the Purcell Mountains of Idaho to collect black bear DNA samples for individual identification of bears. We used a combination of both mark-recapture and genetic analyses to evaluate whether variation in vital rates and genetic substructure was a function of changing food productivity in the study area. We found a heterozygote deficiency and detected genetic substructure within a single year, suggesting we sampled multiple subpopulations (a Wahlund effect). Our mark-recapture analyses suggested this pattern was in response to interannual variation in summer berry abundance. This project demonstrated the potential pitfalls of interpreting mark-recapture data over short time periods without ancillary data that can be used to evaluate mechanisms of population change. We found NGS provided information not only for traditional mark-recapture analysis but also complimentary insights into demography gained through genetic analyses. Combining mark-recapture estimates with analyses of population genetics provides a more complete understanding of population dynamics than either method alone, thus improving ecological inferences and effective management.

Citation

McCall, Barbara S.; Mitchell, Michael S.; Schwartz, Michael K.; Hayden, Jim; Cushman, Samuel A.; Zager, Pete; Kasworm, Wayne F. 2013. Combined use of mark-recapture and genetic analyses reveals response of a black bear population to changes in food productivity. Journal of Wildlife Management. 77(8): 1572-1582.