George Murray Levick, an explorer with the Scott Antarctic Expedition, spent the summer of 1911-12 making detailed notes on the breeding cycle of Adélie penguins. Male penguins, he was surprised to discover, regularly had sex with other males, but this fact was deemed too shocking to include in the official expedition report and it was another 50 years before it was noticed in the scientific literature.
Today, same-sex sexual behavior has been reported in a wide variety of species, but a new analysis suggests a gap remains between how often it happens and how often we hear about it. A survey of animal scientists found they widely observe, but rarely publish, same-sex sexual behavior in primates and other mammals.
Karyn Anderson, the first author of the survey and a graduate student in anthropology at the University of Toronto, said: “This appears to be due to a perception by researchers that same-sex sexual behavior is very rare. However, we found that this was commonly observed by our survey participants.”
Of 65 researchers working on 52 different species, 77% observed same-sex sexual behavior, such as mounting or genital stimulation, but only 48% collected data and only 19% published their findings, according to the study in PLOS One.
Certain species, such as penguins and Japanese macaques, have become poster animals for same-sex couplings, but tend to be portrayed as outliers. The latest analysis highlighted observations of same-sex copulations in many species with no previous reports, including mole rats, squirrels, mongoose, ring-tailed coatis and several monkeys.
Anderson said the perception that same-sex sexual behavior is rare in animals has fed into a narrative that it is “unnatural” in humans. “I think that record needs to be corrected,” she said. “One thing I think we can say with certainty is that same-sex sexual behavior is widespread and natural in the animal kingdom.”
Respondents said they were not influenced by sociopolitical concerns, but many noted that journals were biased against publishing anecdotal reports compared to systematic studies.
Josh Davis, of the Natural History Museum in London and author of A Little Gay Natural History, said: “About 1,500 species have been observed to exhibit homosexual behaviour, but this is certainly an underestimate as it is found in almost every branch of seen the evolutionary tree – spiders, squids, monkeys.
“There is a growing suggestion that this is normal and natural for almost every species,” he added. “It’s probably more rare to be a purely heterosexual species.”
Prof Paul Vasey, a psychologist at the University of Lethbridge in Alberta, has been studying female homosexual behavior in Japanese macaques for more than three decades. “I can say with certainty that in some populations, like the one I study, female homosexual behavior is relatively common,” he said, adding that in many species it is probably less common and difficult to study quantitatively.
In the past, same-sex sexual behavior has often been labeled a “Darwinian paradox” – apparently at odds with the evolutionary pressure to survive and reproduce. However, there is increasing evidence that some same-sex sexual behaviors may have evolutionary advantages. In black swans, male-male couples frequently court each other, steal eggs, raise chicks together and are more successful in ensuring the survival of these chicks than heterosexual swan pairs.
Julia Monk, an ecologist at the University of California, Berkeley, said animal behavior can become a prism through which humans attempt to make sense of their own nature. “I don’t believe we should be bound by what animals do or don’t do to set standards for human behavior,” she said. “But I think it’s important to better examine how animals live, and question how much our understanding of the natural world is limited by our own social imagination.”
