Population estimation, spatial ecology, and health status of eastern hellbenders in Indiana.

摘要

The eastern hellbender (Cryptobranchus alleganiensis alleganiensis ) is a member of an ancient salamander family comprised of three extant species. They require cool, swift flowing rivers and streams with rocky substrates and abundant large, flat rocks for shelter. Once commonly found in many rivers and streams in the eastern United States, the hellbender has experienced precipitous population declines and is now rare or extirpated throughout much of its historical distribution. While the exact cause of the declines is unknown, habitat degradation is suspected as the primary stressor. In Indiana, the hellbender's distribution has been reduced to one low density population in the Blue River in southern Indiana.;Many studies have focused on various aspects of hellbender ecology; however, most have focused on populations characterized by considerably higher density of animals. Individual behaviors may differ as a result of varying densities and habitat conditions. With this study, we intend to elucidate the behaviors of the hellbender under demographic and environmental conditions, which differ considerably from previous studies and hope to identify potential factors contributing to their decline. Our objectives were to: (1) estimate population abundance and structure, (2) investigate the home range, movement patterns, and habitat use, and (3) evaluate the physical health of the population and its surrounding environment in order to develop a better overall understanding of the problems facing the population.;Surveys were conducted in September 2007, June 2008 -- October 2008, and July 2009 -- September 2009. Blood was drawn from all individuals for blood chemistry analysis. Twenty-one hellbenders were implanted with radio-transmitters at eight sites and water quality was examined at a subset of seven of these locations. Eighty-eight hellbenders were captured during surveys. Using the Jolly-Seber model, we estimated a population density of 0.06 individuals/100 m2 for our study sites. Minimum convex polygon (100%) home range estimates were larger than reported in previous studies and home ranges for males were significantly larger than for females'. Most plasma chemistry parameters were similar between sexes and comparable to other reported populations. Vitellogenin was found to be an accurate means for gender identification up to two months prior to the breeding season. Our study represents a portion of an ongoing comprehensive assessment of hellbender ecology and will provide valuable information for future management efforts.