Homosexual activity documented in female gorillas for the first time
As part of a study facilitated through the Dian Fossey Gorilla Fund International, a researcher from The University of Western Australia has documented the first detailed evidence of homosexual behaviour in female gorillas.
While bonobos are renowned for their rich sexual repertoire which includes homosexual acts, much less is known about the homosexual behaviour of other Great Apes.
Associate Professor Cyril Grueter from UWA's School of Anatomy, Physiology and Human Biology was conducting a study on the feeding ecology of mountain gorillas in Rwanda when he observed homosexual behaviour in some of the females leading him to delve deeper.
Of the 22 female gorillas studied, 18 were found to engage in homosexual activity such as frottage.
Associate Professor Cyril Grueter said the observations were intriguing and led him to test three (sociosexual) hypotheses that might explain the behaviour- the gorillas' asserting dominance based on social rank, the reinforcing of social bonds or reconciliation after a fight.
"None of the three hypotheses received any consistent support," he said.
"So a more prosaic explanation was considered - that homosexual behaviour reflects elevated arousal, as there was evidence that homosexual behaviour was more frequent at times when females also engaged in heterosexual copulations."
Professor Cyril Grueter observed cases where females directed their sexual attention to other females after the male showed no interest in their advances, so females served as an alternative outlet for their libido.
"Given that all these observations come from wild groups, not gorillas held in captivity, it is obvious that homosexual activity is part of the gorillas' natural behavioural," he said.
"My impression is that these females derive pleasure from sexual interaction with other females." With gorillas closely related to human beings, Professor Grueter said the research may have uses in helping to understand homosexual interactions in humans.
"One thing female gorillas have in common with human women, that has been well documented, is that they can shift from homosexual to heterosexual sex," he said.
The research has been published in the PLOS ONE Journal