Non-conceptive Sexual Behavior in Cetaceans: Comparison of Form and Function

Abstract

AbstractNon-conceptive sexual behavior (NCSB) is phylogenetically widespread, having been documented in 35 of the 87 extant cetacean species, but function and form of NCSB have not been studied in comparative manner. Many cetacean species engage in NCSB across a wide variety of settings and contexts (e.g., play, sexual, affiliative). NCSB includes both social and non-social sexual behaviors, such as non-social masturbation on the environment or social same-sex thrusting toward a conspecific, but importantly, none of the behavior described as NCSB affords reproduction. While these two general categories encompass all sexual actions, the behaviors are diverse depending on species, social structure, and sex of the individual being observed. Social sexual behavior presumably has individual or social benefits. This chapter organizes what is known about NCSB in cetaceans by summarizing NCSB repertoires from peer-reviewed literature and discussing proposed functions (e.g., practice for reproduction, attracting opposite-sex mates, reducing the reproductive opportunities of same-sex conspecifics, reinforcing dominance relationships, alliance formation, reconciliation, and social tension reduction). Further, the form or behavioral repertoire, the sex of the individuals engaging in NCSB, the environment observed in, and whether NCSB was present or absent in general are noted from each of the articles reviewed. Overall, NCSB behavior observed across species shares similar elements (e.g., thrusting, lateral presentations) in both Mysticeti and Odontoceti. NCSB tends to be more prevalent among sexually immature compared to sexually mature individuals. Additionally, NCSB is more prevalent between male conspecifics compared to females when animals engage in same-sex NCSB. Interspecific NCSB has also been reported for a number of species. While most reports come from toothed whales, the limited observations of baleen whales have also found that many species engage in NCSB, making it likely that NCSB is included in the behavioral repertoire of most cetacean species. NCSB likely aids in forming and maintaining social relations and/or in the development of sexual repertoires in cetaceans, not unlike what has been proposed for primates. We hope this chapter sparks interest in comparative studies of NCSB and sheds light on the similarities of NCSB across species.