A study published in the scientific journal behavior is the first to bring records of homosexual behavior in capuchin monkeys of the genus Sapajus out of captivity.
According to the main author of the research, biologist Henrique Rufo, a doctoral candidate at the Department of Experimental Psychology at the Institute of Psychology (IP) at the University of São Paulo (USP), who studies the social learning of capuchin monkeys, there were four episodes of for a few seconds among six different monkeys, part of the group of 33 individuals of the Sapajus libidinosus species that live in the Tietê Ecological Park, in the East Zone of São Paulo.
Rufo says that the observations happened in an unplanned way during an experiment carried out as part of his master’s research. He placed two acrylic problem boxes with a few holes in the top and luscious inside in the environment where the monkeys live, seeking to analyze how the animals would use tools to access food and how this learning would spread socially.
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While the monkeys were being recorded, there were four occasions in which a male monkey approached another male who was interacting with one of the boxes, mounted him and began engaging in sexual acts.
According to Rufo, the idea of publishing these records came up when the magazine behavior issued a call for papers on anecdotal reports (i.e., experiments with a number of cases too small to support a scientific conclusion that can be generalized) within the field of animal behavior.
Until then, there was only published record of homosexual behavior in Capuchin monkeys of the genus Sapajus in captivity, where males were observed mounting other males when these were reintroduced to the group after a separation.
Sexual interactions between monkeys of the same sex are common
Although the new findings are only anecdotal, the author explains that they are valuable for raising initial hypotheses that can be systematically investigated later. One is that the observed cases include juvenile monkeys mounting adult monkeys, suggesting that perhaps sexual behavior between males in this species does not play a role in establishing dominance.
Sexual interactions between primates of the same sex (which may involve mounting, touching, oral stimulation, or displaying the genitals to a specific target) are very common in nature.
Behaviors of this type have already been observed in several species, such as chimpanzees, baboons, mandrills, langurs, bonobos, gorillas, orangutans in Africa and Eurasia, as well as marmosets, spider monkeys, squirrel monkeys and capuchin monkeys themselves, in the Americas.
These interactions can have the most diverse social functions. In golden and squirrel monkeys, mounting and displaying genitals, respectively, are associated with dominance relationships, but this does not seem to be a key factor for most species.
Bonobos, for example, use sex to request food sharing and to manage conflicts, calming down or serving as reconciliation after a fight, something also observed in capuchin monkeys of the genus Cebus.
“Seeing that there are few works directed at the field of sexual behavior between individuals of the same sex in monkeys in the Americas, this article can serve as a kick-off for other more in-depth studies in the discussion on the sexual behavior of primates”, explains Rufo, who states have plans to get in touch with other researchers in the field to compile several specific records like this one into a more complete work with the potential to indicate more solid conclusions.
The research was carried out with funding from the State of São Paulo Research Foundation (FAPESP) and a master’s scholarship from the National Council for Scientific and Technological Development (CNPq), having been carried out under the guidance of Professor Eduardo Ottoni, who also sign the article.