Orangutans instinctively use hammers to strike and sharp stones to cut,
study finds
Untrained, captive orangutans complete major steps in making and using
stone tools

Date:
February 16, 2022
Source:
PLOS
Summary:
Untrained, captive orangutans can complete two major steps in the
sequence of stone tool use: striking rocks together and cutting
using a sharp stone, according to a new study.



FULL STORY ========================================================================== Untrained, captive orangutans can complete two major steps in the sequence
of stone tool use: striking rocks together and cutting using a sharp
stone, according to a study by Alba Motes-Rodrigo at the University
of Tu"bingen in Germany and colleagues, publishing February 16 in the open-access journal PLOS ONE.


==========================================================================
The researchers tested tool making and use in two captive male orangutans (Pongo pygmaeus) at Kristiansand Zoo in Norway. Neither had previously
been trained or exposed to demonstrations of the target behaviors. Each orangutan was provided with a concrete hammer, a prepared stone core, and
two baited puzzle boxes requiring them to cut through a rope or a silicon
skin in order to access a food reward. Both orangutans spontaneously hit
the hammer against the walls and floor of their enclosure, but neither
directed strikes towards the stone core. In a second experiment, the
orangutans were also given a human-made sharp flint flake, which one
orangutan used to cut the silicon skin, solving the puzzle. This is the
first demonstration of cutting behavior in untrained, unenculturated orangutans.

To then investigate whether apes could learn the remaining steps from
observing others, the researchers demonstrated how to strike the core to
create a flint flake to three female orangutans at Twycross Zoo in the
UK. After these demonstrations, one female went on to use the hammer to
hit the core, directing the blows towards the edge as demonstrated.

This study is the first to report spontaneous stone tool use without close direction in orangutans that have not been enculturated by humans. The
authors say their observations suggest that two major prerequisites
for the emergence of stone tool use -- striking with stone hammers and recognizing sharp stones as cutting tools -- may have existed in our
last common ancestor with orangutans, 13 million years ago.

The authors add: "Our study is the first to report that untrained
orangutans can spontaneously use sharp stones as cutting tools. We
also found that they readily engage in lithic percussion and that this
activity occasionally leads to the detachment of sharp stone pieces." ========================================================================== Story Source: Materials provided by PLOS. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Alba Motes-Rodrigo, Shannon P. McPherron, Will Archer, R. Adriana
Hernandez-Aguilar, Claudio Tennie. Experimental investigation of
orangutans' lithic percussive and sharp stone tool behaviours. PLOS
ONE, 2022; 17 (2): e0263343 DOI: 10.1371/journal.pone.0263343 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220216140255.htm

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