Researchers have found evidence which suggests a female bonobo will call out more loudly during sex with another female if her partner has a higher social status or a more important ape is watching.

Bonobos are renowned for a liberal approach to sexual contact, regularly engaging in such activity with members of their own sex.

Males of the great ape species, a cousin to the chimpanzee, are known to touch their genitals together after a fight.

Scientists from Emory University in Atlanta observing female bonobos watched 674 sex acts or incidents including “genital contact” during the study in the Democratic Republic of the Congo.

‘Communication during sex among female bonobos: effects of dominance, solicitation and audience’ found the copulation calls made by females were different depending on who their partner was and who could hear them.

Researchers suspected lower-ranked female apes would be more eager to have sex with other, higher-ranked female apes and more vocal about their success when they did.

The study authors Zanna Clay and Klaus Zuberbühler wrote: “We reasoned that if sexual interactions were part of a social strategy to affiliate with other females and functioned to develop social bonds then low-ranked females should engage in and solicit more sexual interactions compared to high-ranked females.

“Moreover, they should seek out and prefer high-ranked and socially established females compared to other females.

“If sexual interactions were driven by such social motivations, we expected females to advertise socially important sexual interactions with vocal signals.”

The results, they say, support a hypothesis that females use gay sex acts as a social tool to climb the latter of their peers’ esteem, calling out more depending on the status of their partner and their audience.

They concluded: “Our results are generally consistent with the main hypothesis that genital contacts are used as a means to express social dominance relationships, via asymmetric patterns in performance, initiation and calling behaviour.

“Unlike chimpanzees, bonobos appear to lack a formal vocal signal of submission, greeting and willingness to interact.

“Copulations calls may provide a means for females to exert some of these functions.”

The bonobo population is estimated at between 29,500 and 50,000 individuals.

Along with the chimpanzee, they are humanity’s closest relative in the animal kingdom.