Glucocorticoid stress hormones and the effect of predation risk on elk reproduction.

摘要: Predators affect prey demography through direct predation and the costs of antipredator behavioral responses, or risk effects. Experiments have shown that effects can comprise a substantial proportion predator's total effect on dynamics, but we know little about their strength in wild populations, physiological mechanisms mediate them. When wolves are present, elk alter grouping patterns, vigilance, foraging behavior, habitat selection, diet. These responses associated with decreased progesterone levels, calf production, reduced population size [Creel S, Christianson D, Liley Winnie JA (2007) Science 315:960]. Two general for reproduction been proposed: stress hypothesis predator-sensitive-food hypothesis. Here, used enzyme immunoassay to measure fecal glucocorticoid metabolite concentrations 1,205 samples collected from 4 populations over winters test is mediated by chronic stress. Across years, were not related predator-prey ratios, calf-cow ratios. Overall, wolf presence better explained changes patterns carry nutritional than concentrations.