Amphibian decline is a major concern worldwide, and a lack of basic ecological and life history information for many species significantly limits our ability to evaluate the degree and possible causes of such declines, and to develop effective conservation strategies for threatened and endangered species. Not only is there a shortage of adequate long-term datasets necessary for robust analyses of population variability, but the elusive nature and obscure microhabitats of many species make it difficult to collect even the most basic natural history data. In a series of observational and experimental studies, I employed both traditional and novel ecological methodologies to examine environmental correlates of temporal population variability, foraging ecology and anti-predator behavior in endangered Barton Springs Salamander (Eurycea sosorum) from Austin (Travis County), Texas. Though headwater springs are typically thought of as habitats with relatively stable environmental conditions, I discovered that E. sosorum population abundance was strongly influenced by periodic extremes of rainfall that affect cycles in spring flow rates, water temperature, and other physico-chemical variables. I also found that population dynamics in E. sosorum are highly consistent with those expected for organisms with a storage effect life-history strategy, in which a few long-lived females capable of high fecundity and prolonged survival in subterranean habitat during adverse environmental conditions may be sufficient for population persistence. In addition, juveniles may use subterranean habitat as a thermal refuge. Using stable isotope analyses and macroinvertebrate prey censuses, I determined that at the population level, adult E. sosorum exhibits high electivity for planarian flatworms (Dugesia sp.). This would not have been detectable using traditional methods of dietary analysis such as stomach or fecal content analysis because Dugesia are soft-bodied animals. Additionally, stable isotope analyses revealed that adult E. sosorum exhibits inter-individual diet variation and is capable of diet switching. Finally, I discovered that anti-predator behavior in E. sosorum is influenced more strongly by visual and bioelectric cues from potential predators, but not olfactory cues. This is the first known demonstration of anti-predatory response mediated only by bioelectric stimuli in an amphibian, and one of very few to observe this phenomenon among aquatic vertebrates. / text

The Jollyville Plateau Salamander (JPS), Eurycea tonkawae, is a species of salamander endemic to Texas, the United States. It is a candidate for protection under the Endangered Species Act. This report assesses the JPS population abundances at Lanier Spring, Long Hollow Creek at Wheless Spring, and Ribelin Spring in Austin using a mark-recapture method. The maximum likelihood estimation method was used to obtain the population size estimates under two models, the M₀ model and the M[subscript t] model. The M₀ model assumes that every animal has the same capture probability in the population for each sampling period while the M[subscript t] model allows capture probabilities to vary by time. Simulations were performed by using an MCMC algorithm based on the M₀ model. Between 2007 and 2009, the population size estimates for JPS (>16mm snout-vent length, (SVL)) at Lanier Spring varied between 86 and 554 under the M₀ model, between 80 and 549 under the M[subscript t] model, and between 76 and 564 using MCMC simulations. During 2007 monitoring periods, the population size estimates for JPS (>16mm SVL) at Ribelin Spring varied between 105 and 236 under the M₀ model, between 104 and 196 under the M[subscript t] model, and between 105 and 265 using MCMC simulations. During 2007 and 2008 monitoring periods, the population size estimates for JPS (>16mm SVL) at Wheless Spring varied between 368 and 1087 under the M₀ model, between 339 and 1075 under the M[subscript t] model, and between 411 and 1098 using MCMC simulations. Different estimation methods yielded consistent estimates. No clear population trends were detected due to the big fluctuations in estimates in this study. / text

Large-scale land uses such as residential wastewater discharge and coal mining practices, particularly surface coal extraction and associated valley fills, are of particular ecological concern in central Appalachia. Identification and quantification of both large-scale land use and microhabitat alterations to ecosystems are a necessary first-step aid in mitigation of negative consequences to biota. In central Appalachian headwater streams absent of fish, salamanders are the dominant, most abundant vertebrate predator providing a significant intermediate trophic role. Stream salamander species are considered to be sensitive to aquatic stressors and environmental alterations with past research having shown linkages among microhabitat parameters, and large-scale land use such as urbanization and logging to salamander abundances. However, there is little information examining these linkages in the coalfields of central Appalachia. In the summer of 2013, I visited 70 sites (sampled three times each) in the southwest Virginia coalfields to collect salamanders and quantify stream and riparian microhabitat parameters. In an information-theoretic framework I compared the effects of microhabitat and large-scale land use on salamander occupancy and abundances. My findings indicate that dusky salamander (Desmognathus spp.) occupancy and abundances are more correlated to microhabitat parameters such as canopy cover than to subwatershed land uses. Brook salamander (Eurycea spp.) occupancy show negative associations to large-scale land uses such as percent recent mining and percent forested. Whereas Eurycea spp. abundances are negatively influenced by suspended sediments, stream bank erosion and stream substrate embeddedness. Management implications of these findings include erosion prevention and control as well as protection and management of riparian habitats. However, quantifying physical environmental quality such as stream and riparian habitat often can be quite difficult, particularly when there are time or fiscal limitations. In order to accurately assess stream and riparian habitat in a time- and cost- effective manner, the U.S. Army Corps of Engineers (USACE) developed a functional condition index (FCI) assessment for streams that measures 11 stream and riparian parameters along with watershed land use to calculate three different scores: a hydrology score, biogeochemical score, and habitat score (Noble et al 2010). Using the salamander data from 2013, I then analyzed the FCI scores using collected occupancy and abundance analyses. Both analyses supported the Habitat FCI score as it had strong correlations with both occupancy and abundance of three Desmognathus spp., and support the use of the USACE protocol for stream and riparian habitat assessment. / Ph. D.