New Study: Gorillas Use Chest Beating to Prevent Conflict, Not Provoke It
A gorilla’s chest beating is an incredible sight, but new research based on years of observation of mountain gorillas shows there’s much we never understood about this iconic acoustic.
Since people first went to see King Kong or encountered Donkey Kong from the Mario Bros franchise, most might say male gorillas beat their chests with their fists as a sign of challenge or triumph.
But it seems to serve several functions – a challenge not necessarily being one of them.
Edward Wright, a primatologist at the Max Planck Institute, observed 500 chest beats from 25 different silverback mountain gorillas in Rwanda’s national parks between 2014 and 2016. Using acoustic monitoring equipment, he and his colleagues determined that chest thumping was an honest demonstration of body size, hinting at several organizational aspects of gorilla social life.
The first is that larger animals were recorded at lower frequencies which could travel half a mile. By flexibly adjusting the voltage and the rate at which saltwater flowed through the system, the researchers developed a system that adjusts to variable sunshine while not compromising on the amount of fresh drinking water produced.
By beating their chests, air sacks underneath their larynx reverberate from the kinetic energy, producing a sound, and the bigger the male, the deeper the sound. This is believed to broadcast how big and dominant a male gorilla is as a means of keeping rival males away from their social group.
Furthermore, it’s believed that each thump may act as a calling card, with members of a dominant male’s group being able to identify the silverback from this sound.
The second aspect was that while sound depth and body size were correlated, body size and frequency of chest thumping instances did not—the dominant males didn’t pound their chest any more than their smaller rivals. This presented Dr. Wright and his colleagues with a fascinating suggestion—the chest thumping is used to diffuse fights, rather than provoke them.
Even if you’re likely to win a fight, there is still quite a high-risk factor,” Dr. Wright told National Geographic. “These are large, powerful animals that can do a lot of damage.
How the chest thumps affect the female half of gorilla society is even less well-studied, but the scientists knew at the initiation of their observations that males beat their chest more when the females in their social group enter esterus, and that larger males make deeper calls which were both found to correlate to reproductive success.
Future studies will examine whether a large male’s chest beating can act as a siren’s song as it were, and pull females away from other social groups.
In conclusion, the iconic behavior of gorilla chest beating plays a crucial role in communication, social hierarchy, and reproductive success within gorilla communities.
Maeva B.