Same-sex sexual behaviour is far more prevalent in mammals than research would suggest because scientists often don't report the behaviour when they witness it in the field, according to a University of Toronto Scarborough study.
Sixty-five wildlife biologists, ecologists and mammologists were surveyed for the study, which was published in PLOS One. Most of them said they declined to publish accounts of same-sex sexual behaviour because they felt the behaviour was an anomaly too rare to be worth reporting, or wasn't a research priority of their lab.
These results suggest that the paucity of reports of same-sex sexual behaviour among mammals is attributable to a bias against anecdotal evidence.
"We realized some species we had observed engaging in same-sex behaviour were not included in other published reports and we wondered how often other researchers were witnessing it and also not publishing," says study co-author Karyn Anderson, a PhD candidate in U of T Scarborough's department of anthropology. "We decided the best way to get at this information was to go directly to the source."
Researchers surveyed for the study said they had seen same-sex behaviour (defined as mounting or other genital contact) in nearly 80 per cent of the 54 species they completed surveys on, which ranged from monkeys to elephants. Yet, about 80 per cent of the researchers never published their data.
There were even 17 species on which there was no research stating that they engaged in same-sex behaviour even though experts witnessed it.
"Some respondents reported observing encounters that lasted close to an hour, while others said they had only seen it a few times or very briefly in many years of observation," says Anderson, who is completing her PhD in the lab of Associate Professor Julie Teichroeb.
When asked why they chose not to collect or publish their findings, none of the researchers reported a discomfort with homosexuality or any prejudice against it.
The study collected demographic information on its respondents too, though nothing was found to impact likelihood of recording or reporting, including their career stage, the animals they studied, and whether they identified as part of the LGBTQS+ community.
A quarter of the respondents said they didn't report same-sex sexual activity because they had other research goals they needed to prioritize or because they weren't leading the studies and didn't determine what was included.
Responses also backed the theory that popular ideas about the role of same-sex behaviours have led researchers to lump it into other categories in their data collection, with many recording it as instances of establishing dominance, playing or creating social bonds. Only 22 per cent of respondents classified it as a unique behaviour.
Most researchers reported they chose not to record or report because existing evidence on same-sex sexual activity is too dominated by eye-witness accounts.
Anderson notes the bias is a feature of Western approaches to wildlife biology, pointing out that Japanese primatologists, for example, tend to place more importance on researchers' narrative accounts than their Western counterparts.
"At some point anecdotes were no longer considered rigorous enough for some publications, but they can tell us important things about overarching trends," Anderson says. "One monkey engaging in same-sex behaviour isn't necessarily going to tell us a lot about its evolution or function, but if all animals engage in it, that's a whole different story."
The study notes that other misconceptions of "rare" behaviours have been disproven once researchers began studying them in a more structured, formal way - such as when wild chimpanzees were found to feed their young by chewing up and spitting out their food, akin to birds.
"I hope this encourages scientists to publish on their observations of behaviours that they perceive to be rare," Anderson says.
