Hill, Pierson, Bill Johnson, and Michael Dorcas. Utilization of edge habitat by black rat snakes (Elaphe obsoleta). (Poster Presentation)

Rat Snakes (Elaphe obsoleta) can be found throughout the Eastern and Midwestern United States. Within this wide range, populations experience varying degrees of habitat fragmentation due to human development. Such habitat destruction often leads to an increase in “edge” habitats where intact and disturbed areas come in contact. Over the course of 3 years, we tracked the movements of 13 rat snakes on the Davidson College Ecological Preserve, in Davidson, NC, which has numerous anthropogenically created “edge” habitats. Snakes were tracked twice per week. When a snake was located, we recorded its general habitat, microhabitat, behavior, body position, exposure to the sun, and GPS coordinates. Using a geographical information system (GIS) we identified field and forested habitats and overlaid the GPS coordinates of each snake location. Our data indicate that black rat snakes use “edge” habitats more frequently than either field or forested habitats. We hypothesize that “edge” habitat is favorable for rat snakes because it has higher abundances of prey, such as rodents and nesting birds, compared to intact forest. “Edge” habitat may also posses more basking sites and available cover for snakes. We speculate that anthropgenically created “edge” habitat on the Davidson College Ecological Preserve may actually affect black rat snake populations positively.

Thawley, Chris, Bill Johnson, and Michael Dorcas. Effects of seasonal, meteorological, and directional variables on amphibian capture in terrestrial drift fences. (Poster Presentation)

Terrestrial drift fences are often employed to gather baseline data on amphibian and reptile species diversity and relative abundances. Since the spring of 1999, we have monitored two drift fences on the Davidson College Ecological Preserve to evaluate the activity patterns of amphibians and reptiles. Each fence has two arms, one running along the north-south axis and the other along the east-west axis. Over the past five years, 184 reptiles of 16 different species and 363 amphibians of 15 species have been captured, and distinct patterns of diversity and abundance have become clear. Many amphibian taxa are found principally in spring or fall, the two seasons in which the drift fence is monitored. For example, ambystomatid salamanders are captured only in the spring while narrow-mouth toads (Gastrophryne carolinensis) and almost all ranid frogs are captured in the fall. Capture frequency of amphibians also varies with proximate meteorological conditions. There is a marked positive relationship between the number of captures and amount of recent precipitation. The majority of amphibians are captured on the south sides of the two fences, indicating strong directional trends in movement towards a nearby stream. Some amphibian groups, especially Plethodontid salamanders, show patchy spatial distributions, indicating that these animals may not be uniformly distributed. Our data suggest several methods for improving representative data from terrestrial drift fences, such as using multiple smaller fences along different cardinal axes to assure the adequate detection of species that may show strong directional movements and patchy distributions.