Using non-invasive techniques to examine black bear (Ursus americanus) abundance in the North Cascades Ecosystem, Washington State

Abstract

Recent advances in non-invasive research methods have facilitated less costly evaluations of bear populations across wide geographic ranges. Non-invasive hair-snagging and genetic tagging allow identification of species, sex, and individual bears without necessitating direct capture or observation. From 2008 to 2011 a large, multi-agency project deployed barbed wire hair-snag corrals to collect DNA samples from black bears (Ursus americanus) in the North Cascades Ecosystem (NCE) of Washington State. Using the genetic and detection data, I examined the influence of human activities and habitat characteristics on bear abundance across heterogenous landscapes of the NCE. Bear abundance was positively associated with the proportion of the landscape in shrubfields, open mesic forests, and dry forests with moderate overstory tree canopy closure. A positive northward trend in abundance existed, but was strongest for female bears. Male abundance was higher on national park lands and did not differ between roaded, frontcountry areas and designated wilderness after accounting for habitat variation. This finding suggests that roadless wilderness areas are not acting as source areas or refugia for bears from human activities. No other research to date in Washington State has examined the influence of habitat and anthropogenic variables on black bears across such a large geographic expanse, and the results of my study should help guide management of black bear populations in the NCE. Effective and science-based management of black bears is especially important given the challenge of maintaining viable populations of long-lived species with relatively low fecundity.