After years of observation, mountain gorillas have shown there’s much about them that we don’t know. In popular movies, they show gorillas using chest beating as a sign of challenge, however that is not true. Edward Wright, a primatologist, spent about 3 years observing 500 chest beats from 25 silverback mountain gorillas. Using acoustic monitoring, they were determined it was to compare body sizes. This tells us more about their social life, the first was that larger animals were at lower frequencies that could travel half a mile. When they beat their chests, air sacs underneath their larynx reverberate from the kinetic energy, causing it to create a sound, and the bigger the male the louder the sound. They assume it is to show how big and dominant the gorilla is, keeping rivals away from their social group. It’s believed that it is also a calling sound, so other gorillas in the dominant gorilla’s social group can identify which silverback it is. The second idea was that even though the sound depth and body size were correlated, body size and frequency of chest thumping was not. The dominant gorillas didn’t pound their chest any less then the smaller gorillas, concluding that it could be to diffuse fights, instead of provoking them. When smaller males hear the sound of the dominant gorilla’s sound, they return the sound, showing to the dominant gorilla there is no match physically due to the higher frequency of the chest beating sounds. How chest beating sounds affects the female gorillas is not as well studied, but scientists have suggested that males beat their chest more when females in the group enter estrus, suggesting that it is because of reproduction. Future studies will show if the chest beating will act as a siren’s song and pull away females from other social groups.