Introduction

We use the phrase resource selection to mean the process that results in animals using some areas, or consuming some food items, and not consuming others. In some studies, resources are defined using mutually exclusive categories such as ‘wooded/nonwooded’ in a habitat study or ‘invertebrate/ plant/bird/mammal’ in a diet study. In other studies, resources are defined using variables that are not mutually exclusive and that define different aspects of the resource such as elevation, aspect, distance to water, and cover type. In some studies, only use is measured. In many others, availability of the resources is also measured and analyses are conducted to determine whether the resources are used in proportion to their availability or whether some are used more – and some less – than would be expected if resources were selected independently of the categories defined by the investigator. In this Chapter, we concentrate on methods in which resources are assigned to mutually exclusive categories because this approach has been by far the most common in behavioral ecology. However, studies in which resources are defined using multivariate approaches are discussed briefly, and we urge readers to learn more about this approach since it can be formulated to include the simpler approach but offers considerably more flexibility.

The investigator has great flexibility in defining use. In the case of habitat studies use may mean that an area is used at least once during the study or (less often in practice) used more than some threshold number of times, or used for a specific activity (e.g., nesting). When the population units are possible prey items, used items might be those attacked, consumed, partly consumed, etc.