Broad-scale genetic monitoring suggests density-dependent dispersal in a large carnivore

Abstract

Characterizing patterns and drivers of dispersal is fundamental to our understanding of animal ecology and ultimately informing species conservation and management strategies. In this study, we used microsatellite data from 3941 individual black bears Ursus americanus occupying 73 spatially distinct sampling areas across a large heterogeneous landscape to characterize dispersal via gene flow directionality. We fit spatial models to quantified gene flow to test hypotheses regarding drivers of putative dispersal patterns. Specifically, we tested the relative influence of food productivity gradients, bear density, and bear harvest on dispersal. We also evaluated differences in gene flow patterns within and between sexes to assess sex-biased dispersal. We found evidence suggestive of positive density-dependent, male-biased dispersal. Our data show evidence of a relationship between dispersal and broad food productivity gradients. Specifically, male bears displayed preferential dispersal towards mixed deciduous forests with higher food productivity relative to less productive boreal forests. Given the dense sampling scheme across a continuous population, occupying a large heterogeneous landscape, these results provide key insight as to the likely drivers of dispersal patterns in a wide-ranging mammal.