Interspecific Comparison of Reproductive Strategies

Abstract

Knowledge of cetacean life history, morphology, and social behavior provides clues to the niche-specific adaptations that have evolved to maximize reproductive fitness. An essential component of a species’ life history is mating, particularly the sex-specific mating strategies that have evolved. Mating strategies vary within and among species reflecting phylogenetic constraints and the interplay of selective forces molding each species’ adaptations. The suite of cetacean mating strategies that have evolved ultimately determines how a species’ mating system operates. Thus, mating systems provide a unifying framework to compare and contrast cetacean strategies for reproduction and mating. Theory predicts that the degree of sexual size dimorphism (SSD) and the relative testes size of mammalian species will be good indicators of their mating system. However, interspecific and intraspecific variability in SSD and relative testes size reveal unique tradeoffs made in response to evolutionary pressures and ecological processes that result in exceptions to the theoretical predictions. In this chapter, we review current knowledge of cetacean reproductive biology and how that information furthers our understanding of their mating systems.