Salamander Movement Propensity Resists Effects of Supraseasonal Drought

Abstract

Movement can act as an effective strategy used by amphibians to avoid detrimental environmental conditions, particularly drought. However, due to the unpredictable nature of droughts, evaluating the patterns and consequences of movement has rarely been investigated. In 2007–2008, the southeastern United States experienced a supraseasonal drought that resulted in 110 yr low flow levels among the first-order streams. In this study, 61 months of mark–recapture data collected from one first-order stream were used to examine the effects of drought on the movement frequency distribution, survival, and growth rates of adult Desmognathus fuscus (Northern Dusky Salamander). We hypothesized that salamanders would demonstrate a higher propensity to move during supraseasonal drought conditions and that moving salamanders would experience higher survival and growth rates. We found that salamanders were more likely to move immediately after the drought compared to the pre-drought and drought conditions. Although movement frequency was low during the drought, survival was higher for individuals who moved during drought conditions in comparison to individuals who remained in their original capture location. Although our model did not detect a trend, salamanders experienced slightly higher growth in the post-drought conditions compared to drought and pre-drought conditions. In addition, during the post-drought, salamanders that moved had slightly higher growth rates compared to salamanders who remained in their original capture location. Our results suggest that adult salamanders were potentially displaying an adaptive movement strategy to resist drought conditions by moving away from affected (i.e., dry) areas within the study stream. In addition, movement was likely utilized to access replenished resources in other areas after the severe effects of the drought ended. Therefore, both in-stream and riparian barriers that impede movement may inhibit resilience of stream amphibians during severe droughts.