INDIVIDUAL VARIATION IN MAMMALS

The study of individual variation offers an underexploited wealth of o pportunities for mammalogists. This paper addresses recent development s in the study of both intra- and inter-individual variation. After re viewing several methods (e.g., intraclass correlation, product-moment correlation and confirmatory factor analysis) for quantifying intra-in dividual consistency or repeatability, we discuss how these measures o f repeatability can serve as guides for appropriately defining traits and how they may be helpful in ensuring that appropriate statistical m odels are used (e.g., in accounting for measurement errors in regressi on analyses). We discuss three aspects of inter-individual variation; phenotypic selection, alternative individual strategies and phenotypic integration, and quantitative genetic analyses. The value of these ap proaches for studying inter-individual variation is illustrated with r ecent examples from the literature. Finally, we discuss how many field studies of mammals may be well poised to exploit the unique insights that can be gained from studying individual variation.