ANNUAL VARIATION IN HABITAT SELECTION - PATTERNS CONCEALED BY POOLED DATA

I reviewed 43 papers published in The Journal of Wildlife Management (JWM, 1988-91) that examined habitat selection of terrestrial vertebrates by comparing habitat use with availability. My objective was to determine whether annual variation in habitat selection was typically considered in these studies. Most studies (84%) recognized the potential for variation in habitat selection on a seasonal scale, by either restricting investigations to one season or analyzing data separately for individual seasons. In contrast, 72% of the 39 studies that spanned >1 year pooled data on habitat use among years, evidently without testing for annual variation and without presenting use data for individual years. Most studies (56% of 43) lasted 2 years. I present an example for female black bears (Ursus americanus) that illustrates the misleading inferences that can result from pooling data among years. The value of most selection studies is limited by their short duration and by the common approach of assuming resource use is static on an annual scale.