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Articles 1 - 3 of 3
Full-Text Articles in Social and Behavioral Sciences
Evaluation Of Landscape Models For Wolverines In The Interier Northwest, United States Of America, Mary M. Rowland, Michael J. Wisdom, Douglas H. Johnson, Barbara C. Wales, Jeffrey P. Copeland, Frank B. Edelmann
Evaluation Of Landscape Models For Wolverines In The Interier Northwest, United States Of America, Mary M. Rowland, Michael J. Wisdom, Douglas H. Johnson, Barbara C. Wales, Jeffrey P. Copeland, Frank B. Edelmann
USGS Northern Prairie Wildlife Research Center
The wolverine (Gulo gulo) is an uncommon, wide-ranging carnivore of conservation con- cern. We evaluated performance of landscape models for wolverines within their historical range at 2 scales in the interior Northwest based on recent observations (n = 421) from Washington, Oregon, Idaho, and Montana. At the sub-basin scale, simple overlays of habitat and road-density classes were effective in predicting observations of wolverines. At the watershed scale, we used a Bayesian belief network model to provide spatially explicit estimates of relative habitat capability. The model has 3 inputs: amount of habitat, human population density, and road density. …
Sampling Designs For Carnivore Scent-Station Surveys, Glen A. Sargeant, Douglas H. Johnson, William E. Berg
Sampling Designs For Carnivore Scent-Station Surveys, Glen A. Sargeant, Douglas H. Johnson, William E. Berg
USGS Northern Prairie Wildlife Research Center
Scent stations usually are deployed in clusters to expedite data collection and increase the number of stations that can be operated for a given cost. Presumed benefits of cluster sampling may not be realized, however, unless cluster sizes are chosen with respect to sampling variation within and among clusters. To encourage and facilitate the use of efficient designs and reporting standards, we used data collected in Minnesota, USA, during 1986-1991 to (1) compare the performance of survey designs with various numbers of stations/cluster; (2) estimate relations between required sample sizes and visitation rates, changes in visitation rates, and error rates; …
Interpreting Carnivore Scent-Station Surveys, Glen A. Sargeant, Douglas H. Johnson, William E. Berg
Interpreting Carnivore Scent-Station Surveys, Glen A. Sargeant, Douglas H. Johnson, William E. Berg
USGS Northern Prairie Wildlife Research Center
The scent-station survey method has been widely used to estimate trends in carnivore abundance. However, statistical properties of scent-station data are poorly understood, and the relation between scent- station indices and carnivore abundance has not been adequately evaluated. We assessed properties of scent- station indices by analyzing data collected in Minnesota during 1986-93. Visits to stations separated by < 2 km were correlated for all species because individual carnivores sometimes visited several stations in succession. Thus, visits to stations had an intractable statistical distribution. Dichotomizing results for lines of 10 stations (0 or ≥ 1 visits) produced binomially distributed data that were robust to multiple visits by individuals. We abandoned 2-way comparisons among years in favor of tests for population trend, which are less susceptible to bias, and analyzed results separately for biogeographic sections of Minnesota because trends differed among sections. Before drawing inferences about carnivore population trends, we reevaluated published validation experiments. Results implicated low statistical power and confounding as possible explanations for equivocal or conflicting results of validation efforts. Long-term trends in visitation rates probably reflect real changes in populations, but poor spatial and temporal resolution, susceptibility to confounding, and low statistical power limit the usefulness of this survey method.