Abstract

Similar to terrestrial mammals, male-female sexual behavior is significant for the survival and continuation of certain cetacean species. However, non-reproductive mating behaviors, i.e. homosexual behaviors and masturbation, are widespread in all mammals. Therefore, it would be interesting and helpful to better understand the reproduction of cetaceans by further investigating their non-reproductive behaviors. We investigated male and female non-reproductive behaviors in a captive population of Yangtze finless porpoise including three males and four females. Fourteen sexual behaviors were defined in our sexual behavioral ethogram, and the occurrence frequencies and dyads of each non-reproductive behavior were recorded. Over half of the sexual behaviors were non-reproductive behaviors (3887 times, 69.87%); homosexual behaviors occurred 3633 times (65.31%) and masturbation was recorded 254 times (4.57%). Most homosexual behaviors were performed between males (3438 times, 94.63%). The dyads AFU & TAO (1921 times, 55.88%) were the most active dyads involved in male-male sexual behaviors, and most of these behaviors (1543 times, 80.32%) were cooperative by counterpart. The male homosexual behaviors are thought to be related to the gang coalition or training. One female-female pair (F7 & F9; 117 times; 60.00%) performed the most frequent homosexual behaviors. None of the female-female sexual behaviors were rejected by the counterpart. Female homosexual behaviors, however, may have something to do with company or communication.