From 2016 to 2019, scientists observed a group of macaques to see how they used stones as tools. The behavior of the primates was filmed.
Unexpectedly, the researchers discovered that the monkeys not only used stones as tools, but also as sex toys; they went on to publish their findings in a study.
It turned out that males and females of different age groups used stones to satisfy themselves, but there are differences between groups of macaques. As it turns out, female monkeys are more picky in choosing stones, while young males "played" with stones more often, and indiscriminately.
Some populations of macaques also regularly play with stones without sexual overtones. They wear them, rub surfaces with them and beat them against each other.
According to the study, this odd behavior can only be observed in certain groups of the animals.
The new study is based on previous work published in the journal Physiology & Behavior in 2020. Then researchers first proposed a hypothesis about the use of sex toys by male macaques, and now scientists have studied females, as well as studied the potential motivation of macaques of both sexes.