Indicators of Stress & Reproduction for Management Considerations in Abundant Deer & Endangered Ferrets

Increasing urbanization and changing landscapes result in wildlife facing challenges that humans try to manage. In over-abundant wildlife, the goal is to reduce population size, whereas in threatened or highly inbred populations, the goal is to increase populations and maximize fitness. I studied two North American mammals with disparate conservation goals and management concerns – the abundant white-tailed deer (Odocoileus virginianus; deer) and the endangered black-footed ferret (Mustela nigripes; ferret). Deer populations are high, especially in suburban habitats where they over-browse plants and can negatively interact with humans. Ferret populations are small and threatened with extinction. They require extensive management and ex situ breeding efforts for reintroduction across wild habitats. Using non-invasive laboratory and field-based assays, I examined behavioral and physiological indicators of stress and reproduction to understand factors contributing towards fitness and to inform wildlife management. First, I studied hair cortisol concentrations of deer from managed and unmanaged Chicagoland forest preserves. Urbanization does not influence deer stress if animals have adequate resources. Culling as a management strategy also maintains herd health and reduces nutritional stress. Second, I examined how the lack of mate selection in ferret breeding programs influences fitness. Captive ferrets are paired via pedigree, missing out on important mate exploration and odor communication that occurs in the wild. To study mate preference and success, I examined traits that influence both odor and fitness – behavior, endocrine function, and gut microbiota. Ferrets were given different soiled odor cues from potential mates. Scent investigation, the most prominent behavior, was highest for females closer to estrus and males with elevated testosterone levels. There was no preference for specific individuals. Ferrets likely prefer additional traits that we did not measure, and they may aim to seek out multiple mates. Gut microbial diversity increased with age, especially after the first year when ferrets are paired. Increasing opportunities for natural behaviors and social interactions may benefit ferret microbial health and mating success. Management for both species should consider hormonal and behavioral indicators of fitness as invaluable insights into the physiological and psychological state of individuals and populations.