Scientists have seen chimpanzees creating "music" -- that includes hooting and throwing rocks at trees -- then walking away.

Primatologists from the Max Planck Institute for Evolutionary Anthropology in Germany have conducted some of their own experiments, mimicking the chimps, to determine whether the behavior is some type of communication, according to the study published Wednesday in Biology Letters.

The researchers also noticed the chimps that practiced accumulative stone throwing (AST) didn't throw them at any old type of tree; they returned to the same species time and again. They have seen the behavior in four groups of chimps in Libera, Guinea-Bissau, Guinea and Ivory Coast.

"We predicted that chimpanzee AST tree species produce sounds that have energy concentrated at lower frequencies and a greater resonance since these impact sounds would be optimal for long-distance communication," the scientists write in their study.

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The footage can be seen below.

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The researchers then used algorithms, according to the study, to get information on three aspects of the trees: the wood's internal friction, the hardness of the tree at impact point and the modal response of the tree to the impact.

Ammie Kalan, a primatologist at the Max Planck Institute and co-author of the study, said she doesn't think the chimps are just hooting and throwing rocks for fun.

"Play behavior is a little less structured, a little more impromptu," she told Science Magazine.

A zoologist at the University of St. Andrews in the U.K. who was not involved with the study, Andrew Whiten, said it could be significant that only certain chimps do it -- despite the plentiful number of trees available.

"This suggests the behavior is a local cultural tradition," he told Science Magazine.