Resistance and Resilience of A Stream Salamander To Supraseasonal Drought

Abstract

Drought represents a significant stressor to aquatic animals. However, empirical data regarding the response of many aquatic animals, particularly amphibians, to drought are limited. The southeastern United States experienced a supraseasonal drought in 2007-2008, which provided an opportunity to examine the resistance and resilience of salamanders to drought. In this study, we used 5 yr of presence-absence data at 17 first-order streams and 61 mo of mark-recapture data at one stream to examine the effects of drought on occupancy and vital rates of the salamander Desmognathus fuscus (Northern Dusky Salamander). We tested three hypotheses regarding the effects of drought: larvae would decrease in occupancy during drought conditions, but adult occupancy would remain stable; adult temporary emigration rates would be greatest during supraseasonal drought conditions; and adult survivorship would be equal or nearly equal during nondrought conditions and drought conditions due to higher rates of temporary emigration. We found that adult salamander occupancy remained stable through the 5 yr of sampling; however, larval salamander occupancy decreased by an average of 30% during the supraseasonal drought. We found that adult temporary emigration probabilities were twice as high during supraseasonal drought conditions than during nondrought or typical drought conditions. Monthly survival of adults was relatively high during nondrought (S ¼ 0.89 6 0.02), typical drought (S ¼ 0.97 6 0.02), and severe drought conditions (S ¼ 0.90 6 0.01). Our findings suggest that high survivorship of adult D. fuscus likely buffers the negative effects of drought on larvae and high rates of temporary emigration allow adult salamanders to be resilient to supraseasonal drought conditions.