| Summary: | Understanding how wildlife populations respond to selection pressures imposed by environmental and anthropogenic conditions is important in wildlife management. Sport harvest, habitat alteration, climate change and population density are all selective pressures that may affect individual fitness, population dynamics and ultimately population viability. Our knowledge of how management practices and the multitude of ecological conditions are affecting the evolution of wildlife populations is extremely limited. I analyzed a 25-year data set on horn growth and age of bighorn sheep rams in two populations in the southern interior of British Columbia. I examined how harvest regulations, weather, and habitat degradation affected horn length of harvested bighorn rams. I found that age-specific horn growth can predict the age at which rams are harvested: rams with rapidly growing horns are harvested at younger ages than rams with slow-growing horns. Management regimes that result in an average harvest age much below the reproductive peak of males, are based on a minimum horn or antler size and remove mature reproductive males disproportionately to subordinate males are likely to have a selective effect. I found that over 25 years of records, the age-adjusted horn length of bighorn sheep rams in the South Okanagan declined by 10%. That decline could be attributed to intense selective hunting, as well as severe habitat deterioration that became worse over time. In addition, ram horn growth was slowed in years with hot summer temperatures, suggesting that weather in summer may be important in horn growth. We know little about how wildlife populations are reacting and changing to novel selection pressures, such as introduced species, human-induced habitat and climate change. In general, wildlife management regimes aim to maintain large, healthy populations and attempts to harvest wildlife at a sustainable level. Management actions, however do not necessarily meet the intended goals. Knowledge of biological systems allows us to ask and answer important questions about the directions of adaptations in natural populations. My research examines possible selective pressures on a wildlife population over a short time period, considering management strategies, habitat change and climate and suggests that human actions may have resulted in evolutionary change. While wildlife management has contributed well to population dynamics and habitat relationships, it cannot ignore the possible evolutionary consequences of human behavior and management strategies that can result in rapidly occurring genetic change. In order to develop sustainable harvests, potential evolutionary consequences must be considered.
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