Stress and Reproductive Hormones Reflect Inter-Specific Social and Nutritional Conditions Mediated by Resource Availability in a Bear-Salmon System

The study investigated the impact of salmon availability on stress and reproductive hormones in grizzly and black bears in coastal British Columbia, using hair samples from 69 grizzly bears and 68 black bears. It found that grizzly bears consuming less salmon had higher cortisol levels, indicating nutritional stress, while black bears' cortisol levels were more influenced by social competition due to salmon availability. Testosterone levels generally decreased with increased salmon availability, suggesting reduced competition. The research highlighted species-specific differences in nutritional needs and social behavior, emphasizing the importance of resource availability in affecting bear physiology and proposing a model for further research on wildlife responses to environmental changes.