Twig-assisted masturbation in Balinese long-tailed macaques

What is it about?

We documented evidence of twig-assisted masturbation by Balinese long-tailed macaques, living in Ubud, Indonesia. This population is known to customarily engage in genital stone-tapping and stone-rubbing. However, masturbation using other objects has never been reported in this population and species. We observed repeated and extensive twig-assisted masturbation in one adult female and one adult male. We also recorded three instances of twig-assisted masturbation in three additional individuals. Our results indicate that this behavior is not accidental and may be sexually motivated; that is, it may be another form of tool-assisted masturbation in this primate population. This report provides a valuable addition to the increasing literature on the use of tools in behavioral innovations pertaining to self-care, comfort, and possibly pleasure.

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