Minimum resource requirements support population persistence; however, ecologists and conservationists often want to identify factors that improve biological outcomes of animals. The population-level approach common in wildlife-resource studies limits our ability to draw inferences about the importance of resources and other factors by failing to link them with individual fitness. Measuring individual-based biological outcomes and resource use helps determine variation in mechanistic relationships between animal fitness and behavior. I suggest using direct metrics of resource use such as food consumption and distance traveled, to avoid errors with estimating resource availability. I summarize these concepts in an analytical framework for modeling relationships between resource use and fitness to guide readers toward effective study designs. I also describe constraints on an animal’s ability to use resources freely, which must be considered when modeling these relationships to account for additional sources of variation in biological outcomes. I investigated effects of resource use on body condition, survival, and reproduction using field data from four species of vertebrates. I found that using multiple predictor metrics to model biological outcomes allows comparison between factors affecting fitness. In general, factors more closely relating to energetics (e.g., movement pattern or distance traveled) were more useful predictors of animal outcome than metrics of habitat use or selection. Management and conservation efficiency can be improved by focusing efforts on preventing detrimental risks and threats, and supporting less stressful access to beneficial resources rather than supporting average population habitat use without consideration of biological outcomes. Improving the study of ecology depends in part on our efforts to seek finer-scaled mechanistic observations of relationships among individual organism behavior, resource use, and biological outcomes that improve our understanding of population-level resource ecology. Melding current techniques to obtain detailed evidence of how habitat is used at an individual level will allow us to relate resources to fitness for more efficiently understanding an animal’s ecology and improving conservation and control of populations. While we will continue to manage for populations, we must not lose sight of the individual variation that drives natural selection if we want to fully understand variation in resource-outcome relationships.