PS 7-77 - A decade-long demographic study of a spotted salamander population in central Ohio

Monday, August 8, 2016
ESA Exhibit Hall, Ft Lauderdale Convention Center
Rebecca N. Homan, Department of Biology, Denison University, Granville, OH
Background/Question/Methods

Amphibians are among the most highly threatened groups globally. For salamanders, eastern North America represents a region of significant diversity and significant concern in terms of issues of habitat loss, disease, and climate change. The more we know about longer-term demographic fluctuations and microhabitat choices of salamanders in this region, the better informed our management plans can be. I studied a population of spotted salamanders (Ambystoma maculatum) from January 2005 through August 2014 at a temporary pond in the Denison University Biological Reserve. Continuously for those ten years, my students and I monitored breeding population sizes, sex ratios, recruitment rates, and modeled survival and recapture rates, in an attempt to understand the demographic variability in a population relatively undisturbed population of salamanders. 

Results/Conclusions

We found that breeding population sizes fluctuated over time, ranging from a low of 399 to 1061 breeding adults per year. Adult sex ratios were consistently male biased, ranging from 1.33 to 3.87 M:F. Interestingly, male breeding population sizes declined significantly over this ten year window (r2 = 0.60, p = 0.009), apparently driving nearly significant declines in overall breeding population size (r2 = 0.39, p = 0. 053) and M:F sex ratios (r2 = 0.34, p = 0.07). Juvenile recruitment was also highly variable, with peak recruitment of 0.98 juveniles per female, but no recruitment in three of ten years. Variation in recruitment seemed to be due primarily to pond hydro-period, with early drying years resulting in low to no recruitment. However, recruitment in 2012 was negatively impacted by a confirmed ranavirus outbreak. Annual survival estimates ranged from 0.27 to 1.00. Annual recapture rates varied by sex, ranging from 0.22 to 0.93 for females and 0.16 to 0.67 for males. Overall, we found that our population, though largely undisturbed by habitat loss, was impacted by disease, and was experiencing both declines in males as well as declines recruitment rates, leaving us concerned about its long-term stability.