Researchers recently tested a new tool used in two captive male orangutans also known as Pongo pygmaeus at Kristiansand Zoo in Norway to observe their behavior.

A EurekAlert! report specified that captive orangutans can complete two major steps "in the sequence of stone tool use" by striking rocks together and cutting them with a sharp stone.

According to new research by the Germany-based University of Tübingen's Alba Motes-Rodrigo and colleagues, neither of the two orangutans had formerly been trained or exposed to exhibitions of the target behaviors.

Each of the two animals was provided with a concrete hammer, a prepared stone core, and two baited puzzle boxes that required them to cut through a rope or a silicon skin to be able to access a food reward.

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Untrained, ‘Unenculturated’ Orangutans Use Hammer, Sharp Stones to Access Food Reward; First Cutting Behavior Observed
(Photo : Pexels/Nathan J Hilton)
A new study showed captive orangutans can complete two major steps ‘in the sequence of stone tool use’ by striking rocks together and cutting them with a sharp stone.


Untrained, 'Unenculturated' Orangutans

The two orangutans both spontaneously hit the hammer against the floor and walls of their enclosure, although none of them directed strikes towards the stone core.

In another experiment, the orangutans were given a human-made sharp flint flake, as well, which one of them used to cut the silicon skin and was able to solve the puzzle. This was the first representation of cutting behavior in the so-called untrained, "unenculturated" orangutans.

To find out if apes could learn the remaining steps from observing others, the study authors showed how to strike the core to make a flint flake to three female orangutans at Twycross Zoo in the United Kingdom. Following the said demonstrations, one female continued using the hammer to hit the core, with blows directed towards the edges as presented.

Spontaneous Stone Tool Use 

This research published in the PLoS ONE journal is the first to demonstrate spontaneous stone tool use minus close direction in orangutans that have not been encultured by humans.

According to the study investigators, their observations propose that two major prerequisites for the beginning of stone tool use, striking through the use of stone hammers and identifying sharp stones as cutting tools, may have existed in the last common ancestors 13 million years ago with orangutans.

The authors explained, their study is the first to present that untrained orangutans can use sharp stones spontaneously as cutting tools.

They discovered too, that they readily get involved in lithic percussion and that this activity sporadically results in the detachment of sharp stone pieces.

Sharp Stone as a Cutting Tool

As indicated in this new research, the earliest hominin stone tool technologies are primarily grounded on the production and use of cutting tools. Nevertheless, according to a similar ScienceDaily report, stone-assisted cutting and the production of the corresponding tools do not exist in wild primates.

A probable explanation for the reason primates do not get involved in stone-assisted cutting is that they can access and process sources of food by other, more cost-effective means.

Consequently, there may be no robust ecological need, and thus no or tiny evolutionary pressure for primates to progress and engage in the sharp stone tool used for cutting.

Nonetheless, the necessity of using sharp stones as cutting tools can be artificially produced to experimentally identify if and how the production and use of sharp stone tools might develop in orangutans and other primates.

Related information about monkeys making tools is shown on Nature Video's YouTube video below:

 

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