Date of Award
Master of Science (MS)
Concerns over worldwide declines of amphibians, including some to extinction, has increased the urgency for understanding how amphibians interact within local environments and across regional landscapes. Hypotheses for declines include anthropogenic destruction and fragmentation of amphibian habitat, introduction of exotic predators and competitors, increased ultraviolet (UV-B) irradiation, acid precipitation, environmental contamination by pollutants, harsh climatic conditions, over harvesting, and infectious disease. Three different types of models were developed for the northern leopard frog (Rana pipiens), gray tiger salamander (Ambystoma tigrinum diaboli), and gray tree frog (Hyla versicolor/chrysoscelis complex) populations inhabiting the Sheyenne National Grassland (SNG) in southeastern North Dakota. The SNG is a relatively large (283 km2) and contiguous piece of tallgrass prairie embedded in a landscape dominated by agriculture, though the predominant land use on the SNG is grazing by domestic livestock.
Although amphibians often occur in a metapopulation typ~ structure where individual wetlands represent patches, continued fragmentation and isolation of habitat will cause populations to go extinct if colonization is not sufficient to offset local extinction. Because many factors may influence habitat use and occupancy of amphibian populations, best subsets logistic regression was used to develop occupancy and extinction models for these amphibian species using a whole suite of variables related to wetland hydroperiod, wetland isolation, patch quality, and landscape complementation.
Bly, Bartholomew L., "Population Dynamics of Three Amphibian Species Across the Sheyenne National Grassland of Southeastern North Dakota" (2004). Theses and Dissertations. 3198.