Demographics of a Geographically-Isolated Population of Threatened Salamander (Caudata: Ambystomatidae) in Central Illinois

Amphibian populations that use small isolated wetlands are often small in size, susceptible to stochastic extinction processes, and have little to no contact with other populations. One can ascertain the persistence of such populations only by obtaining data that allow the prediction of future changes in population’s size, and propensity to achieve a sustainable number of individuals. The number of metamorphosing larvae leaving a pond predicts the viability of a salamander population, and thus, the number recruited into the terrestrial adult population. The Jefferson Salamander, Ambystoma jeffersonianum, is a listed threatened species in Illinois, occurring at fewer than 15 ponds statewide. In 2004 and 2005, individuals at an isolated breeding pond in Lincoln Trail State Recreation Area (LTSRA) were captured using a drift fence-pitfall trap array. Once captured, we determined sex, measured snout-vent length, and using a unique combination of toe clips, marked the salamanders. We also determined the number of egg masses, average percentage of successfully hatched eggs, and number of juveniles leaving the pond. We incorporated this information into a matrix for a stage-based population model. Model simulations predicted that on average, the population at the LTSRA pond would persist for four more years, with survivorship from larvae to juvenile being the most important parameter. Increasing survivorship during the larval period increased abundance as well as average persistence time. Active management at the breeding pond to increase the time available for successful metamorphosis might facilitate persistence of the salamander at this site