Maximizing Sampling Efficiency and Minimizing Uncertainty in Presence/Absence Classification of Rare Salamander Populations

摘要

Effective sampling of pond-dwelling larval stages of the federally- listed flatwoods salamander (Ambystoma cingulatum) requires sufficient knowledge of when larvae are present and how best to sample them. The primary objective of this study was to maximize field sampling efficiency of flatwoods salamanders and minimize the uncertainty associated with declaring absence after repeated non-detects. Our approach was to evaluate sampling method efficiency, the relationship between pond habitat and larvae residency, and the effect of sample design on sampling success. We surveyed salamander larvae and pond habitat at Fort Stewart military installation for three years and at several locations in Florida on a limited basis. Our studies on method effectiveness demonstrated that the most time efficient and cost effective sample method is dipnetting. Larvae were detected at one pond at Fort Stewart in 3 of 4 years of the study, but not at 59 other ponds that were sampled. These detections represent the only observations of successful breeding in a natural wetland in Georgia since 1999. Our inability to find larvae in more than one pond at Fort Stewart confirms what appears, based on historic capture records, to be a significant decline in flatwoods salamander abundance at Fort Stewart. To better predict annual variation in pond residency, we developed a model that uses rainfall data and likely growth rates to predict hatching dates and period of pond residency. With two years of data that likely represent the extremes of pond residency in Georgia we found that date of hatching can occur as early as the first week of January and as late as the first week of March and, that in some years, larvae may be found in the pond as late as the end of May. We recommend that the most opportune time of year to sample flatwoods salamander larvae is during the second and third months after a pond fills to at least half, typically sometime within February to April.