Eastern red backed salamanders (Plethodon cinereus) are widely distributed throughout northeastern North America, with the southern portion of the range extending to Virginia and North Carolina. This study characterizes the activity, spatial dynamics, and stress hormone response of a population of P. cinereusin an urban park in Richmond, Virginia. We established six artificial cover board plots and used count and mark-recapture survey methods to regularly monitor salamander activity over a year. At the southern extent, high temperature avoidance is a primary factor determining salamander activity, in addition to moisture limitation. A waterborne corticosterone (CORT) hormone assay was used to test the effect of high temperature exposure on salamander stress responses. We quantified CORT in the Richmond population and compared it to stress responses in salamanders from three other populations across the latitudinal extent of the geographic range.
Results/Conclusions
Local abundance of P. cinereus in the James River Park System was surprisingly high for an urban, coastal plain population. During peak periods of activity, surface salamander densities reached up to 10 salamanders under a single artificial cover board (an area of 0.093m2). Across the three mark-recapture plots, mean local densities were 1.96 – 2.03 adults per m2, with spatial capture-recapture space-use estimates of 3.13–5.08 m2 for females and 5.21–6.83 m2 for males. The activity period of P. cinereus in this location extended from October to May, with surface activity only decreasing during the summer heat from June to September. Across latitude, populations showed elevated CORT levels in response to a temperature ramp from 15°C to 25°C. In the Richmond population, where the mean annual temperature is highest, salamanders showed higher levels of baseline and stress response CORT levels compared to populations from more northern parts of the range. Together, these results indicate that the thermal environment places important constraints on salamander activity and physiological responses.