A Salty Compromise: The Behavioral Response of Red-Backed Salamanders (Plethodon cinereus) to Different Concentrations of NaCl, a Prevalent Road Deicer

Many amphibians are bound to a nearby freshwater source such as lakes and vernal pools. Often times, this is because they are fully aquatic; if they are partially terrestrial, they still need freshwater bodies to lay their eggs in a suitable environment. With the constant use of road salt as a deicer during snowing periods, the subsequent runoff has negatively altered nearby soil and water sources. Amphibians, with their permeable skin, are at great risk of desiccation if exposed to a hyperosmotic environment caused by this application. However, some plethodontid salamanders deviate from this restrictive norm by living as dedicated terrestrials. Red-backed salamanders (Plethodon cinereus), a common plethodontid species, have the capacity to relocate to a less salty region whereas freshwater-bound amphibians are mostly confined. Few studies have examined the increased salinity on soil and the potential for terrestrial amphibians to actually react and relocate to a better setting. In this study, red-backed salamanders were placed on a surface that would vary in salinity from 0 to 0.5 M NaCl and the other with aged tap water of 0 M NaCl. As the salinity of the test side increased, salamanders behaviorally responded by spending less time there with the threshold tolerance of about 0.167 M NaCl. To examine their response to multiple regions with different salinity concentrations, they were placed in an enclosed track with 6 patches of salinity from 0 to 0.25 M NaCl for one hour. Although red- backed salamanders had a bias for the end-patches of the tracks, they were able to move from previously preferred patches to patches that contained lower salinity levels. The threshold of tolerance was 0.148 M NaCl for salamanders in this experiment; it differed from the previous 0.167 M NaCl possibly because of a smaller range among applied concentrations. This suggests that red-backed salamanders have the behavioral aptitude to determine which areas have increased salinity and avoid them when apparent. As a result, red-backed salamanders may be able to determine appropriate sites for individual territories and persist as a population. This study provides more insight on the repercussions of road salt on terrestrial amphibians, and will aid in examining the conservation efforts needed for species that are the most at risk of this anthropogenic consequence