- A recent study into same-sex behavior in primates finds that social organization and ecological factors, including climatic conditions, influence this behavior.
- In gorilla groups, same-sex relations can help strengthen social bonds, study lead author Chloë Coxshall told Mongabay, reducing competition and facilitating access to mates and resources.
- Gorilla groups typically consist of a dominant adult male, several adult females, and their offspring. If the dominant male has the exclusive right to mate with all females of the same group, sometimes this polygamy pushes the females to leave this family to look for other females with whom they develop intimate relationships, Malagasy primatologist Jonah Henri Ratsimbazafy said.
- Same-sex behavior doesn’t appear to have the same place in the lives of different primate species or even at various times for the same population, the study suggests. So species-specific research is needed, according to the study authors.
The fact that primates other than humans engage in homosexual behavior is well-documented. A recent study in Nature Ecology & Evolution digs deeper into the factors influencing the prevalence of this behavior.
Of the 491 nonhuman primate species considered in the paper, 59 were found to engage in same-sex behavior. This behavior is more likely to occur among species that live in drier climes, experience heightened food insecurity, and face greater pressure from predators, the researchers suggest, based on analyses of patterns across 23 species.
Same-sex interactions are also more likely when there’s a significant difference in body size between male and female members, and in primates with longer lifespans. A more complex and stratified social structure is also a predictor of this behavior.
Gorillas are an example where social configurations play a role. This genus of primates includes two species: the western (Gorilla gorilla) and eastern gorillas (Gorilla beringei). Gorilla groups, which include anywhere from 20 to 50 members, typically consist of a dominant adult male (the silverback), several adult females, and their offspring.
“Same-sex sexual behavior in gorillas has been associated with reconciliation and strengthening social bonds,” Chloë Coxshall, a doctoral student in biology at Imperial College London, U.K., and lead author of the study, told Mongabay. “Reconciliation reduces the likelihood of further aggression, which reduces risks of injury or fatalities and promotes group cohesion.”
She added that stronger social bonds can be crucial for survival by reducing competition over “resources such as food or mates.”
If the dominant male has the exclusive right to mate with all females of the same group, sometimes this polygamy pushes the females to leave this family to look for other females with whom they develop intimate relationships, said Jonah Henri Ratsimbazafy, a Malagasy primatologist who studies lemurs. Ratsimbazafy wasn’t involved in the recent research.
In rhesus macaque populations in Puerto Rico, previous studies show that males have sexual relations with each other in order to form coalitions, which would perhaps allow them to have access to more females and, therefore, a chance to sire more offspring.
Homosexual behavior doesn’t appear to have the same place in the lives of different primate species or even at various times for the same population, the research suggests.
“Given the study’s results on harsh environments influencing same-sex behavior, I would recommend future research into climate change and conservation to understand how the expression of this behavior varies over time in changing climates or in extreme climatic events, which may occur more frequently with climate change,” Coxshall told Mongabay.
She suggested that further species-specific hypotheses would need to be tested. While the study authors recommended an analysis on similar lines for humans, they warned against extrapolating the results of the present study to human societies.
Banner image: A mountain gorilla, a subspecies of the eastern gorilla, in Virunga National Park in the Democratic Republic of Congo. Image by VALENTIN NVJ via Wikimedia Commons (CC BY-SA 4.0).
Citations:
Coxshall, C., Nesbit, M., Hodge, J., & Savolainen, V. (2026). Ecological and social pressures drive same-sex sexual behaviour in non-human primates. Nature Ecology & Evolution. doi:10.1038/s41559-025-02945-8
Clive, J., Flintham, E., & Savolainen, V. (2023). Same-sex sociosexual behaviour is widespread and heritable in male rhesus macaques. Nature Ecology & Evolution, 7(8), 1287-1301. doi:10.1038/s41559-023-02111-y
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