Abstract
There is increasing evidence of indirect effects of hunting on populations. In species with sexually selected infanticide (SSI), hunting may decrease juvenile survival by increasing male turnover. We aimed to evaluate the relative importance of direct and indirect effects of hunting via SSI on the population dynamics of the Scandinavian brown bear (Ursus arctos). We performed prospective and retrospective demographic perturbation analyses for periods with low and high hunting pressures. All demographic rates, except yearling survival, were lower under high hunting pressure, which led to a decline in population growth under high hunting pressure (λ = 0.975; 95% CI = 0.914–1.011). Hunting had negative indirect effects on the population through an increase in SSI, which lowered cub survival and possibly also fecundity rates. Our study suggests that SSI could explain 13.6% of the variation in population growth. Hunting also affected the relative importance of survival and fecundity of adult females for population growth, with fecundity being more important under low hunting pressure and survival more important under high hunting pressure. Our study sheds light on the importance of direct and indirect effects of hunting on population dynamics, and supports the contention that hunting can have indirect negative effects on populations through SSI.
Highlights
Understanding the population dynamics of exploited species is essential to determine sustainable harvest rates for wildlife populations
We found that adult females were the most important groups affecting population dynamics, having the highest elasticities and explaining the most variation in l
The relative contribution of survival and fecundity to the variance of l changed with hunting pressure, with fecundity being more important under low hunting pressure and survival being more important under high hunting pressure
Summary
Understanding the population dynamics of exploited species is essential to determine sustainable harvest rates for wildlife populations. In species with SSI, harvesting males can have an indirect negative effect on the population by reducing juvenile survival [4,21]. The goal of this study was to assess the direct and indirect effects of hunting through SSI on the dynamics of a brown bear (U. arctos) population. We expected (P2) that hunting would have an indirect negative effect on population growth through SSI, owing to lower cub survival. By evaluating the importance of cub survival, a proxy of SSI, for population growth, we aimed to better understand the effects of behaviour on the population dynamics of a long-lived wild mammal species. This cub mortality is thought to be caused by SSI, which is promoted by the male turnover created when males die during the hunting season [12,35,36,37]: when a resident male is killed, he will be replaced by a male who is probably unrelated to cubs present in the area, leading to an increase in SSI [12,13]
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