Discoveries

September 14, 2022

Tools and Toys

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Some animal species are able to use stones and sticks as tools for their own survival.

For example, chimpanzees use sticks to collect termites, while sea otters use rocks to smash snails.

Researcher Camilla Cenni and her colleagues discovered that long-tailed macaque monkeys in Bali, Indonesia, have figured out a novel use of their stone tools, namely self-gratification, the New York Times reported.

The macaques are known to handle stones for a number of tasks but previous records have shown that they also sometimes use them without any particular purpose or function – a phenomena scientists describe as “playful manipulation.”

Cenni’s team closely observed the stone-handling actions of 173 monkeys. They noted in a new study that young males would frequently rub or tap the stones around their genitals, more than the adult males.

This “tool-assisted masturbation” was more common during sexually charged situations, such as when they or another macaque nearby was soliciting a mate or showing signs of sexual arousal.

Although using rocks sounds extremely uncomfortable, researchers countered that the animals didn’t display any sign of pain or distress.

They theorized that the monkeys accidentally engaged in this self-gratifying behavior while using stones. If confirmed, that would support the hypothesis that the use of tools may have originated from the playful manipulation of objects.

“There might be a transformational effect from play to tool use,” Cenni explained.

This story originally appeared in the September 14, 2022 newsletter, The Time To Choose.