Spatial and temporal patterns of water loss in heterogeneous landscapes: using plaster models as amphibian analogues

Water balance is critical to survival, growth, and performance of many terrestrial organisms because it can influence foraging time, limit dispersal, and curtail courtship activities. Water loss can vary in time and space across the landscape, and can also be modulated by behavior. Amphibians are particularly sensitive to water loss because their skin provides little to no resistance to evaporative water loss. Our study sought to quantify rates of water loss across a heterogeneous landscape using plaster of Paris models as analogues for the Western Slimy Salamander (Plethodon albagula Grobman, 1944). Models were validated within a controlled laboratory setting prior to field deployment, and were shown to approximate rates and magnitudes of water loss observed in living salamanders. In the field, we tested both adult-and juvenile-sized models, and found that juvenile-sized models lost water at a greater rate under all contexts. The rates of water loss measured at night (1.5%/h-4.5%/h) was nearly half of those measured during the day (2%/h-10%/h). Rates of water loss were greatest on ridges with southwestern aspects during the day (5%/h-10%/h) and lowest in ravines with northeast aspects at night (1.50%/h-3.75%/h). The results of spatial and temporal patterns of water loss corroborate field observations of salamander activity patterns and distribution across the landscape, providing a physiological mechanism driving fine-scale habitat use and distribution. Although we tested plaster models as analogues for salamanders, this approach should be generalizable to other amphibian taxa, providing an efficient means of measuring rates of water loss in the field under biologically meaningful contexts.