Polar bear conflict risk behaviour is shaped by maternal, individual, and environmental effects, not heritability

Leah Kathan, Evan S Richardson, David McGeachy, Stephen D Petersen, Vicki Trim, Ruth Rivkin, Colin Garroway

As ecosystems transform under the combined pressures of climate change and human activity, interactions between humans and wildlife are becoming increasingly common. Human-wildlife conflict is often managed by either targeting repeatedly involved individuals or modifying the conditions that make conflict more likely. Choosing which approach to emphasize depends partly on whether individual differences in conflict risk are persistent and genetically inherited or arise mainly from maternal and environmental effects. In the Western Hudson Bay subpopulation of polar bears (Ursus maritimus), lengthened ice-free seasons have extended fasting periods and increased the likelihood of nutritionally stressed bears entering human settlements. We investigated the genetic, maternal, and environmental contributions to conflict risk behaviour in this subpopulation using five decades of capture records and a six-generation pedigree of 4,634 individuals. We used animal models to estimate the repeatability and heritability of conflict risk behaviour across the pedigree, along with the relative contributions of additive genetic variation, maternal effects, and the environment to conflict risk behaviour for different age classes of polar bears. Conflict risk behaviour exhibited low heritability for all age classes, and was moderately repeatable in older, independent bears, but not in young, dependent bears. Maternal effects were stronger in dependent than independent bears, and observation year explained substantial variation in both age classes. Our findings indicate that conflict risk behaviour is shaped more strongly by maternal and environmental effects than by additive genetic variation, supporting proactive management of the conditions that promote conflict rather than relying primarily on responses directed at individual bears.