Same-sex behavior among animals is being underreported, study finds

By Rosa Rahimi, CNN

(CNN) — Same-sex sexual behavior has been observed in more than 1,500 animal species, but a new study has found that it is massively underreported by researchers.

Observations of this same-sex behavior in animals, such as sexual mounting and genital touching, date back to the 1700s and 1800s. But research on the subject only progressed in the 20th and 21st centuries.

In a study published Thursday in the journal PLOSOne, a team of researchers at the University of Toronto, Northwestern University and the University of Warsaw found that experts who study animal behavior are underreporting and rarely publishing their observations of same-sex sexual behavior.

The study surveyed 65 experts and found that 77% of them observed same-sex sexual behaviors in the species they studied. But only 48% collected data on these behaviors and even fewer – just 18% – had published papers on these findings.

“Many respondents reported that their lack of recording data or publishing on SSSB [same-sex sexual behavior] was due to a perception that it was very rare,” Karyn Anderson, a PhD candidate in evolutionary anthropology at the University of Toronto, who led the study, told CNN. “When looked at on a broader scale, we found instead that it was very commonly observed by our survey participants.”

The notion that these sexual behaviors are rare in the animal kingdom has been, and continues to be, used in debates about the ethics of human homosexuality, the study noted.

Anderson says that their study, like others on same-sex sexual behavior in animals, has found that this behavior is in fact “widespread and natural in the animal kingdom.”

Yet homosexual behavior continues to be newly discovered among different species. In 2018, the first report of sex between male spider monkeys was recorded. That same year, two male Gentoo penguins made headlines for “adopting” an egg that had been abandoned by a male-female penguin pair.

The field appears to be ripe for future research –– of the species identified as engaging in same-sex behaviors in the survey, nearly 39% had no prior reports of these behaviors, according to the authors.

Josh Davis, a science writer for the Natural History Museum in London and author of the book “A Little Gay Natural History” was not surprised by the study’s findings, but says he found it “quite exciting” to have the data to prove these numbers.

“Homosexual behavior, it’s been officially recorded for around 1,500 species of animals, but I think for a long time most people have suspected that this is most likely a huge underestimate,” he told CNN. “Because it’s found in almost every branch of the evolutionary tree… from beetles and butterflies, to lizards and squirrels.”

By identifying this gap in the research, Anderson says she hopes other mammalogists will be encouraged to publish their studies of same-sex sexual behaviors.

Why so underreported?

While the authors hypothesized that discomfort or socio-political reasons may contribute to the underreporting of same-sex sexual behaviors, they didn’t find this to be the case among the researchers they surveyed.

Instead, respondents told them it could be because these sexual behaviors were rare or not a research priority for their lab. Most of their observations would be considered “anecdotal” rather than the result of systematic study, perhaps making scientific journals less inclined to publish their findings.

Davis added that there have been other obstacles that get in the way of documenting same-sex behaviors among animals.

“Historically, there has definitely been fears from researchers that if they were to publish on these behaviors, they might then get associated with those behaviors,” he said, though it has “got better over time.”

Another challenge for researchers is when they observe sexual activity in species, it might not always be clear of the animal’s sex. “There is an underlying assumption that when they’re seeing it, they’re watching a male and a female,” said Davis.

“The biggest take away from this research is that same-sex sexual behavior is widely observed within mammals, but not widely reported,” explained Anderson, who added that “this could be true for other behaviors which are perceived to be rare but are found to be more common when looked at on a broader scale.”

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