Homosexual behavior among bonobos and other animals is becoming a vibrant field of study for modern academics.
If you ask a random person what they know about bonobos, the answer will probably be “That’s the ape that has a lot of sex, right?”. Yep, that’s the one! In recent years, a new generation of scientists are helping us to understand more about bonobo sexual activity, including same-sex sexual behavior (SSSB).
Same-sex behavior is more common than you think
But bonobos aren’t alone. In fact, SSSB has been recorded in more than 1,500 animal species, ranging from doodlebugs to albatrosses, from dolphins to bison. For the first time ever, citizen scientists have photographed two humpback whales engaging in sexual activity. What is even more interesting is that both whales were male.
Although 1,500 seems like a large number, undoubtedly it is greatly understated. A recent study reported SSSB among mammals is widely seen but seldom reported. While 77% of scientists had observed SSSB, just 48% collected data on it, and only 19% had published papers about it.
What accounts for this imbalance? Researchers say they didn’t report SSSB because the behaviors were rare or because it wasn’t a research priority. Perhaps it wasn’t a research priority because of the scientific focus on Darwinian theories of reproductive success. If you think there are no evolutionary advantages to SSSB you might be less likely to study it. Some researchers may have been embarrassed by the topic or received pushback from university administrators.
Evolving science and society go hand-in-hand
Scientific views on SSSB have changed dramatically over time, reflecting shifts in society. In 1911-12, Arctic explorer George Murray Levick refused to document SSSB by penguins in his official report. In the 1970s, a theory was SSSB among animals was due to a lack of suitable opposite-sex partners. A few decades later one proposed explanation was “practice”, as if SSSB was just training for procreative sex.
Western secular society is different today. About 70% of people in North America and Western Europe support same-sex marriage, or marriage equality. A new generation of scientists have grown up in this more accepting environment and now study SSSB among animals. At least one suggested that the basic assumption about heterosexual behavior – that it’s the ancestral norm – may be incorrect.
This increased knowledge about SSSB among animals is coming out of the academic journals and into mainstream media. Eliot Schrefer’s young adult book Queer Ducks (and other animals) has reached a younger audience, letting them know about the diversity of sexual behavior in the natural world. In an interview with NPR he said one of the first animals he had to mention in his book was the bonobo.
The ‘make love, not war’ ape
Bonobos are arguably the animal best known for SSSB. The most common SSSB observed in bonobos is female genito-genital rubbing. Males engage in mounting, penis fencing, and rump and scrotum rubbing. Oral sex, tongue kissing, and genital massaging have also been documented.
Suggested explanations for the behavior include greeting, forming social bonds (including alliances), conflict resolution, post-conflict reconciliation, dominance, and simple enjoyment. As the late scientist Frans De Waal famously put it, “For these animals, sexual behavior is indistinguishable from social behavior.”
A commonly cited example is sex and food, which has been documented in both captive and wild populations. A group of bonobos finds a large fig tree or are given sugar cane. In the excitement, high-ranking females rub genitals before feeding, perhaps to avoid squabbles over who gets to eat first. When two males fight over a female, they have been seen reuniting and scrotal rubbing. This is “kiss and make up” after a fight, bonobo-style.
Queer studies for primates?
Primates are most studied for SSSB, and for good reason. In addition to chimpanzees and bonobos, other primates exhibiting SSSBs include stumptail macaques, pigtail monkeys, and baboons. Primates are our closest living relatives, and people wonder if we can learn about ourselves by studying them. Was ancient humanity like the male-dominated and violent chimpanzees, or were we like the female-led and cooperative bonobos? Did ancient humans engage in SSSB to resolve conflicts like the bonobos do?
We may never have a definitive answer, but undoubtedly more researchers will visit Lola ya Bonobo and wild troops to see what they can learn. We think we understand them now, but there will surely be surprises to come. And who knows? Maybe what we learn about SSSB among bonobos will tell us something about ourselves.
Blog author David J. Cord is the author of five books and has been published in 10 languages. As a journalist he covers Nordic innovations and public policy for an international audience. He is a firm believer in nature conservation and thinks bonobos can teach us a lot about ourselves.
Monk, Julia D., et. al., An alternative hypothesis for the evolution of same-sex sexual behaviour in animals, Nature, 2019, https://www.nature.com/articles/s41559-019-1019-7
Kuta, Sarah; These photos are the first to show humpback whales mating – and both are males; 2024; https://www.smithsonianmag.com/smart-news/these-photos-are-the-first-to-show-humpback-whales-mating-and-both-are-males-180983890/
Anderson, Karyn A., et. al., Same-sex sexual behaviour among mammals is widely observed, yet seldomly reported: Evidence from an online expert survey, PLOS, 2014, https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0304885#sec003
Ibid.
Devlin, Hannah, Animal homosexual behaviour under-reported by scientists, survey shows, The Guardian, 2024, https://www.theguardian.com/science/article/2024/jun/20/animal-homosexual-behaviour-under-reported-by-scientists-survey-shows
Weber and Vogel, 1970, cited in Homosexual Behaviour in Animals: An Evolutionary Perspective and edited by Volker Sommer, 2006.
Manson, Joseph H., Nonconceptive Sexual Behavior in Bonobos and Capuchins, International Journal of Primatology, 1997, https://link.springer.com/article/10.1023/A:1026395829818
Gallup, LGBTQ+ Rights, https://news.gallup.com/poll/1651/gay-lesbian-rights.aspx
ILGA Europe, What the data says about the acceptance of LGBTI people in Europe, https://www.ilga-europe.org/blog/data-acceptance-lgbti-people-europe/
Yeoman, Barry, Same-Sex Behavior Among Animals Isn’t New. Science Is Finally Catching Up, National Wildlife Federation, 2023, https://www.nwf.org/Magazines/National-Wildlife/2023/Summer/Conservation/Same-Sex-Behavior-Animals-Science
Pfeiffer, Sacha; What ‘Queer Ducks’ can teach teenagers about sexuality in the animal kingdom; 2022; https://www.npr.org/2022/05/29/1101224759/what-queer-ducks-can-teach-teenagers-about-sexuality-in-the-animal-kingdom
Sommer, Volker (ed), Homosexual Behaviour in Animals: An Evolutionary Perspective, 2006
Palagi, Elisabetta, et. al.; Mirror replication of sexual facial expressions increases the success of sexual contacts in bonobos; Scientific Reports; 2020; https://www.nature.com/articles/s41598-020-75790-3
Frans B. M. De Waal, Bonobo Sex & Society, Scientific American, 1995
Ibid.
Hamilton, Jon, Some generous apes may help explain the evolution of human kindness, NPR, 2021, https://www.npr.org/sections/goatsandsoda/2021/03/20/978868116/some-generous-apes-may-help-explain-the-evolution-of-human-kindness
Hare, Brian, and Woods, Vanessa, Being gay is natural: Just ask bonobos, Live Science, 2014, https://www.livescience.com/44464-bonobo-homosexuality-natural.html