INTERPRETING CARNIVORE SCENT-STATION SURVEYS

The scent-station survey method has been widely used to estimate trend s in carnivore abundance. However, statistical properties of scent-sta tion data are poorly understood, and the relation between scent-statio n indices and carnivore abundance has not been adequately evaluated. W e assessed properties of scent-station indices by analyzing data colle cted in Minnesota during 1986-93. Visits to stations separated by <2 k m were correlated for all species because individual carnivores someti mes visited several stations in succession. Thus, visits to stations h ad an intractable statistical distribution. Dichotomizing results for lines of 10 stations (0 or greater than or equal to 1 visits) produced binomially distributed data that were robust to multiple visits by in dividuals. We abandoned 2-way comparisons among years in favor of test s for population trend, which are less susceptible to bias, and analyz ed results separately for biogeographic sections of Minnesota because trends differed among sections. Before drawing inferences about carniv ore population trends, we reevaluated published validation experiments . Results implicated low statistical power and confounding as possible explanations for equivocal or conflicting results of validation effor ts. Long-term trends in visitation rates probably reflect real changes in populations, but poor spatial and temporal resolution, susceptibil ity to confounding, and low statistical power limit the usefulness of this survey method.