Shoreline distribution and landscape genetics of bears in a recently deglaciated fjord: Glacier Bay, Alaska

Abstract

To further knowledge of mammalian colonization patterns following deglaciation, I used occupancy modeling to estimate black and brown bear shoreline distribution of Glacier Bay and how these distributions relates to the number years of land exposure and post glacial plant and stream succession. I also conducted microsatellite genetic analysis of brown bear hair and tissue to determine contemporary population structure throughout the park and how it relates to landscape features and surrounding populations. Closed forest cover within 1 km of the study site was a strong positive predictor of black bear occurrence. Brown bears were detected at 100% of sites although their use was highest in recently glaciated and old growth forest areas, and lowest in young forests. The shoreline of Glacier Bay hosts brown bears from three geographically overlapping distinct populations, one of which is likely composed of the original colonizers following glacial retreat that were isolated long enough to undergo genetic drift. The southern portion of Glacier Bay fjord and the Fairweather Mountain range are barriers to dispersal. Evidence of range expansion and recent migration indicate that brown bears are still actively colonizing Glacier Bay.