First observation of fellatio by a wild non-estrus adult female chimpanzee on an adult male, and subsequent meat sharing in Mahale

Sociosexual behaviors such as mounting and genital touch have been extensively reported in chimpanzees. However, there are a small number of reported cases of fellatio, with only a few cases between captive juveniles or adult males. In this study, fellatio from a non-estrus adult female to an adult male holding bushpig meat were observed for the first time. After a series of sociosexual behaviors including fellatio, the meat was shared through begging behavior from the female to the male, suggesting that the series of displayed sociosexual behaviors may have occurred to reduce tension, so that the female could then make a smooth transition to begging behaviors. In addition, the fact that fellatio displayed between male and female in a context similar to previously reported cases of fellatio between adult males suggests that the social bond-strengthening effect of fellatio can also function between an adult male and female.