Cooperative Fish and Wildlife Research Units Program: Vermont
Education, Research and Technical Assistance for Managing Our Natural Resources

Of the threats facing amphibian populations today, habitat transformation due to land-use is among the most pressing. Although conservation of pond-breeding salamanders clearly requires protection of breeding ponds and their surrounding habitat, little is known about the effects of land use and other factors on the occurrence of salamanders in the dispersal/terrestrial phase of their life cycle. To determine these effects, we surveyed populations of Eastern Newts (Notophthalmus viridescens) at 551 stations across Vermont, and modeled salamander distribution as a function of environmental variables hypothesized to influence site occupancy. We developed a set of 12 models based on seven a priori hypotheses of site occupancy. We hypothesized that occupancy was influenced by 1) amounts of available habitat types, 2) arrangement of these habitat types, 3) geographic position, 4) housing density, 5) road density, 6) short term changes in habitat distribution, or 7) habitat structure at the stand-level. We used a single-season occupancy model to rank and compare the 12 models. 232 Eastern Newts were detected at 82 of 551 stations. Of the 12 models, amount of habitat within 0.5 km of the survey station best represented the field data. Strong effects were indicated for developed land (-), open water (+), and forest (+) cover. Given a survey station with average forest and open water characteristics, stations with > 5% developed land classes within a 0.5 km buffer had a very low probability of occupancy. Further research is needed to determine the direct role of development on occupancy patterns.