A field study of wild mountain gorillas was conducted to elucidate details of sexual initiation required for an interpretation of the increased frequency of copulation during the menstrual cycle, in comparison to the wild, that occurs when this species is tested in traditional laboratory pair tests. Although females in the wild played a clear role in establishing and maintaining proximity to the male and assertively presenting for copulation, all female presenting was preceded by some form of behavior by the male. Although originally described as male aggression in the laboratory tests, such behavior now appears to be male sexual initiative, elicited by female proximity. The exaggerated form and frequency of the display in the laboratory, and the increased copulation during the cycle that ensued, are likely due to 1 placing females in proximity to a male daily, rather than on 2—3 days of estrus as occurs in the wild, and 2 the inability of the female in the laboratory to withdraw from male proximity during pair tests in a single cage. In addition to clarifying the data on laboratory pair tests, the data on wild gorillas have relevance to the captive breeding of gorillas.

By Ewen Callaway. Female gorillas use sex as a tactic to thwart their rivals, new research suggests. Pregnant apes court their silverback male to stop other females conceiving. Her team chronicled the sex lives of five female western lowland gorillas and one silverback almost every day for more than three years. This kind of competitive behaviour may even help explain how humans evolved into a mostly monogamous species, she says. Bonobos treat coitus like a handshake, while female chimpanzees mate during pregnancy and outside fertile periods, or oestrus, to gain support from males and to protect against infanticide.

Female gorillas have been documented engaging in lesbian sex for the first time. The behaviour was observed by scientists during a research trip to the Rwandan section of the Virunga mountain range in central Africa. The wild mountain gorillas, observed by a team led by Dr Cyril Grueter of the University of Western Australia, are believed to gain pleasure from having sex and may do it when they have been rejected by males.

When it comes to getting down and dirty in the rainforest, it seems hot-blooded female gorillas are the ones for steamy action. Associate Professor Dr Cyril Grueter, a primate expert from the University of Western Australia, is reported to have stumbled on the homosexual behaviour while studying the feeding ecology of the mountain gorillas in Rwanda. Two separate groups were studied and out 22 females, 18 were found to engage in sexual activity with other females, including engaging in genital rubbing. The reason for the behaviour seems to have no other function than sexual arousal, believe academics. Dr Grueter has been working with the Dian Fossey Gorilla Fund and it was while on an month field trip that he began studying what was behind the female homosexual activity.