Sexual Anatomy of Female Cetaceans: Art and Science Contribute Insights into Functionality

Abstract The relationship between sexual selection and the diversity and rapid evolution of male genitalia has been well-documented across many animal taxa, while the morphological variability of female genitalia has received comparatively little attention. Female whales, dolphins, and porpoises possess unusual flaps, folds, and blind sacs in their vaginas, which vary among taxa and may serve several functions. We review the relationship between form and function of these unusual vaginal structures in cetaceans and discuss evidence that supports or refutes various functional hypotheses. A compilation of three-dimensional vaginal endocast models, contemporary high-resolution photographs of dissected reproductive tracts, and detailed anatomical illustrations ranging over 175 years are used to highlight the diversity of forms and fill in gaps in taxonomic knowledge. We discuss the complementary nature of anatomical illustrations and modern analytical and visual tools and how they can help us better understand the evolution of such unusual morphological structures. We identify opportunities for future studies in cetacean genital evolution and discuss the insights they may provide into mating strategies of cetaceans.