Physiological and behavioral adaptations of impala to anthropogenic disturbances in the Serengeti ecosystems

Abstract

Anthropogenic activities are causing biodiversity loss at an unprecedented rate and attempts to ameliorate our impacts have largely failed. This thesis aimed to contribute to our understanding of how anthropogenic activities affect wildlife populations, using physiological and behavioural indices as a window into the status of a wild ungulate population. We used various remotely-sensed proxies of both direct human disturbance (i.e. land use area, settlement density, and distance from a pro- tected area) and environmental conditions (i.e. forage quality, temperature, and rainfall) to test how these disturbances affected the physiological state (i.e. glucocorticoid and thyroid hormone concentrations), behaviour, and demography of impala populations in the Serengeti ecosystem, Tanzania. We found that impala showed significant variation in hormone concentrations in response to both direct human disturbances and changes in environmental conditions. However, hormone concentrations were much more strongly affected by variation in the environment, such as forage quality and temperature, than by direct human disturbances. Impala populations in land use areas which allow more exploitation showed behavioural and demographical changes that could lower population persistence. These results suggest that, although human activities do have a significant impact, with climate change becoming increasingly pervasive, climate and land use change are likely to be the biggest long-term threats to impala populations in the Serengeti ecosystem. Therefore, we suggest that managers focus on conserving larger natural systems, well beyond the boundaries of few strictly protected areas. Additionally, this thesis shows the advantages of combining both behavioural, physiological, and remote-sensing methods to obtain a more complete picture of the threats facing wildlife populations, disentangling their responses to disturbances, and the fitness implications of those responses. However, one should always consider the physiological, ecological, and evolutionary context of the biological methods used to inform conservation research. It is my hope that future work will recognise this complexity and design studies and interpret results with this in mind.