Fellatio by Fruit Bats Prolongs Copulation Time

Tan M, Jones G, Zhu G, Ye J, Hong T, et al. 2009 Fellatio by Fruit Bats Prolongs Copulation Time. PLoS ONE 4(10): e7595. doi:10.1371

Abstract

Oral sex is widely used in human foreplay, but rarely documented in other animals. Fellatio has been recorded in bonobos Pan paniscus, but even then functions largely as play behaviour among juvenile males. The short-nosed fruit bat Cynopterus sphinx exhibits resource defence polygyny and one sexually active male often roosts with groups of females in tents made from leaves. Female bats often lick their mate's penis during dorsoventral copulation. The female lowers her head to lick the shaft or the base of the male's penis but does not lick the glans penis which has already penetrated the vagina. Males never withdrew their penis when it was licked by the mating partner. A positive relationship exists between the length of time that the female licked the male's penis during copulation and the duration of copulation. Furthermore, mating pairs spent significantly more time in copulation if the female licked her mate's penis than if fellatio was absent. Males also show postcopulatory genital grooming after intromission. At present, we do not know why genital licking occurs, and we present four non-mutually exclusive hypotheses that may explain the function of fellatio in C. sphinx.

from the discussion

We speculate that the female C. sphinx licks the male penis to increase penile stimulation, stiffening the penis and maintaining the male's erection. At the same time, the female's saliva may increase lubrication, thus facilitating intromission and thrusting. In combination, these features may prolong copulation in C. sphinx.

So in a similar way to the anthropoid primates, the C. sphinx females (like most animals) are not passive during copulation but rather communicate with the male, in this case by licking his penis. We propose a series of adaptive hypotheses to explain genital licking in C. sphinx. First, genital licking may lubricate the penis or increase penile stimulation, prolonging the duration of copulation. Prolonged copulation might assist sperm transport from the vagina to the oviduct, or stimulate secretions of the pituitary gland in the female and hence increase the likelihood of fertilization. Second, prolonged copulation might be a method of mate-guarding, because the mates would normally segregate after copulation to form unisexual groups which persist throughout the non-breeding season. Third, fellatio may confer bactericidal benefits and assist in the prevention of sexually transmitted diseases (STDs) both to females, and to males that lick their own penis briefly after copulation. Saliva has a protective repertoire that goes beyond antibacterial activity to include antifungal, antichlamydial, and antiviral properties as well. Finally, genital licking may facilitate the detection and identification of MHC-dependent chemical cues associated with mate choice.

Thanks to Dieter L. for the link