Heavily hunted wolves have higher stress and reproductive steroids than wolves with lower hunting pressure

Human-caused harassment and mortality (e.g. hunting) affects many aspects of wildlife population dynamics and social structure. Little is known, however, about the social and physiological effects of hunting, which might provide valuable insights into the mechanisms by which wildlife respond to human-caused mortality. To investigate physiological consequences of hunting, we measured stress and reproductive hormones in hair, which reflect endocrine activity during hair growth. Applying this novel approach, we compared steroid hormone levels in hair of wolves (Canis lupus) living in Canada's tundra-taiga (n=103) that experience heavy rates of hunting with those in the northern boreal forest (n=45) where hunting pressure is substantially lower. The hair samples revealed that progesterone was higher in tundra-taiga wolves, possibly reflecting increased reproductive effort and social disruption in response to human-related mortality. Tundra-taiga wolves also had higher testosterone and cortisol levels, which may reflect social instability. To control for habitat differences, we also measured cortisol in an out-group of boreal forest wolves (n=30) that were killed as part of a control programme. Cortisol was higher in the boreal out-group than in our study population from the northern boreal forest. Overall, our findings support the social and physiological consequences of human-caused mortality. Long-term implications of altered physiological responses should be considered in management and conservations strategies.