Population, genetic and behavioral studies of black bears Ursus americanus in southeast Alaska.

摘要

I studied population, genetic and behavioral aspects of black bear ( Ursus americanus) in the temperate rainforest of Southeast Alaska. At a landscape level, I used population genetics to investigate black bear movement in the Alexander Archipelago and mainland of Southeast Alaska. I found that geographic structure defined by salt water and glaciers curtails black bear movement, to the extent that most regions have significantly genetically differentiated black bear populations. I found that black bears in Southeast Alaska cluster into seven genetic types. I also found that two larger, nuclear genetic clusters of black bears in Southeast Alaska correspond, geographically, to the two ancient mitochondrial lineages of black bears. This perhaps indicates that the nuclear genome retains a genetic signature of the secondary contact of these two lineages. I also studied black bear vagility on a much smaller scale---at the level of riparian areas of salmon spawning streams. I used genetic tagging to demonstrate that the group of bears using these streams is in demographic flux throughout the course of the salmon stream, and that a high number of individual bears use these streams. The persistence of intact salmon streams in Southeast Alaska likely contributes to high black bear population density. In a final aspect of my dissertation research, I used tetracycline biomarking to estimate the population size of black bears on Kuiu Island to be 1.5 bears/km2. This estimate is among the highest recorded bear densities.