Dorothy M. Fragaszy, spoke to an ECWG dinner on Oct. 15, 2018 on “Hercules with a tail:  Stone tool use in wild bearded capuchin monkeys.”

 She described how wild capuchin monkeys living in Fazenda Boa Vista Piauí, Brazil; a dry forest habitat, routinely use stone hammers to crack open very resistant palm nuts after they place the nuts on stone or log anvils.

She said this is an impressive accomplishment given that the monkeys as adults weigh 1.8 – 4.4 kg, and the stones they use can weigh up to 3 kg.

The speaker’s work shows that these monkeys choose stones, nuts, and anvil sites selectively, and display finely honed skill in cracking the nuts, including precise positioning of the nut on the anvil, precise handling of the stone hammer, precise control of the trajectory of their strikes, and modulation of the force of their strikes in accord with the condition of the nut following the previous strike.

These features of tool use in humans are unexpected in nonhuman primates, let alone small monkeys from South America, according to conventional views. Stone tool use by capuchin monkeys opens up a new reference point for understanding skilled tool use across species and evolutionary time.

Fragaszy is a Professor of Psychology and Chair of the graduate program in Behavioral and Brain Sciences at the University of Georgia.

She is a primatologist and comparative psychologist who has studied nonhuman primates in laboratory and natural settings. She is past president of the American Society of Primatologists and International Primatological Society.

She has documented several ways in which these monkeys use stone hammers skillfully, and how young monkeys acquire this traditional skill over the course of many years.