It has been discovered recently by the researchers that chimps living in the forests of West Africa are showing some unusual behavior. It has been seen that adult chimps throw rocks at trees for no apparent reason. They throw the rocks at the tree while yelling and then run away. Even though the researches are not sure why chimps throw rocks at trees, they seem to have some clue. It is believed mainly by the researchers that the reason chimps throw rocks at trees is that it makes long-lasting and resonant sounds.
Discovery of this unusual behavior
The researchers from Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, initially discovered this unusual behavior in chimps three years ago. According to the researchers, this behavior seemed to be localized. It means that these actions were performed mainly by the chimps in adherence to serve a local tradition. It felt more like a part of some rituals to the researchers. Although, the researchers could not figure out what purpose this ritual or tradition would serve to the champs.
Experiments conducted on chimps
To further understand this unusual behavior in chimps, the researchers started conducting experiments on them. To understand the interest of chimps in throwing rocks at trees, the researchers’ team went to the same areas with microphones. They installed microphones to capture the sounds and movements of chimps when they throw stones. While waiting for the chimps to throw stones, the researchers’ team themselves started throwing rocks at trees just for fun.
But, when the chimps hurled the rocks, it was analyzed that they liked throwing rocks on the trees that made lower but longer-lasting sounds. The trees that chimps threw rocks at were mostly the ones that had less exposed roots.
Findings of the experiments
Later on, the team published their findings in Biology Letters. The research stated that the low-frequency sounds move further in the surroundings and are better for long-distance communications. The resonant sounds also stay for a longer time in the environment. So, one assumption is that chimps might throw rocks at the trees for communication.
The real reason why chimps throw rocks at trees is still not known to the researchers. Because if chimps throw rocks at trees to communicate, choosing the tree that made the loudest sound would be more effective. Or, they could also drum the trees to make a loud noise and communicate with chimps that are far away.
But, the researchers saw that chimps only threw rocks at the same trees and never chose new ones. So the researchers assume that the location of the trees might be an essential factor. It is believed that maybe the location of those trees has some connection with the nearby sources of water and food. The chimps might use the sound of rocks hitting the trees as a signal to find food and water.
While the reason is still not apparent, you can assume the above-stated factors as the cause.