In its study, published in the journal Scientific Reports, the team notes that both male and female chimps, and even juveniles, were observed partaking in the stone-throwing, adding that it's "likely that it has some cultural elements."
Kehoe theorizes that the behavior might be a sort of showy display of power, or the rock piles could serve as a geographical signpost.
Most interesting, however, is the possibility that the behavior may indicate that the trees themselves are of deeper significance to the chimps - a notion, Kehoe points out, humans are quite familiar with:
"Indigenous West African people have stone collections at 'sacred' trees and such man-made stone collections are commonly observed across the world and look eerily similar to what we have discovered here."
Watch footage of the chimpanzee behavior in its entirety below.