Behavioural and ecological predictors of dispersal outcomes in red squirrels

Abstract

Dispersal is one of the most important life-history events facing an individual, but how and why individuals arrive at the decision to leave home is largely unknown. This decision has immediate and lifelong fitness consequences. Therefore, understanding how individuals make dispersal decisions is key to dispersal theory and fundamental to species management and recovery. Using North American red squirrels (Tamiasciurus hudsonicus), I examine the drivers and consequences of dispersal at the individual and population level. During prospection (the time between leaving the natal site and settlement), movement was greater when there were more local competitors (juveniles of the same age within 130 meters of the focal individual), while the location of territory acquisition was closer when local adult density was higher (adult territory holders within 130 meters of the focal individual). These effects were phenotype-dependent, with aggressive juveniles, whose behaviour develops over ontogeny, settling closer to their natal site. I further found that red squirrels exhibited sex-biased dispersal and that the benefits and costs to dispersal after settlement were sex-dependent and extended across generations. Collectively, this thesis demonstrates that the drivers of juvenile dispersal are phenotype- and environment-dependent, and suggest that lifetime fitness and intergenerational effects must be considered to better understand what factors drive dispersal.