The role of behavior in influencing headwater salamander responses to anthropogenic development
Cecala, Kristen Kimberly
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Evolutionary theory predicts that animals have evolved to move in response to a suite of cues that maximize animal survival and growth while minimizing risk of injury or mortality. When humans modify environments, new conditions can suddenly yield maladaptive behavioral responses to cues that were adaptive in undisturbed environments. Changes in behavior can alter animal movement patterns impacting patterns of occupancy among habitats and fragment populations. My objectives were to determine which environmental features best predict salamander occupancy in an exurban region of the southern Appalachian Mountains and describe the behavioral mechanisms driving observed stream salamander distributions. Headwater streams generally have dense canopy cover that limits direct light penetration and regulates temperature and humidity known to affect salamander behavior. Therefore, I predicted that canopy cover would be an important predictor of stream salamander occupancy and behavior. A regional survey of stream salamander occupancy was conducted in the Little Tennessee River basin with the Coweeta Long Term Ecological Research site. Of a ! ! variety of factors and scales, upstream riparian forest and canopy cover were the two most important predictors of stream salamander occupancy. Because deforestation increases light penetration to streams, I performed controlled laboratory and field experiments to determine if salamanders exhibited consistent behavioral responses to light under a range of environmental conditions and experience with high-light environments. Salamander larvae generally exhibited negative phototaxis that was exacerbated by the absence of refuge. Individuals with prior experience with high-light conditions exhibited weaker responses to light suggesting that salamanders may be capable of adapting to high-light environments. Lastly, we tested whether negative phototaxis could negatively influence natural behaviors in a field environment by surveying homing behavior across canopy gaps. All salamander life stages were unwilling to cross even small canopy gaps. Because streams are bisected frequently by canopy gaps for a variety of purposes, the accumulation of these small land-use changes and their effects have the potential to profoundly reduce connectivity among populations even in the absence of additional habitat alteration. This dissertation demonstrates the importance of considering the consequences of behavior in determining how disturbance influences populations.