The image of a gorilla thumping its chest is one of the most iconic images associated with gorilla behaviour, but what does it mean? The scientific community has set to work and, to find it out, they have studied a dozen social groups of mountain gorillas in Rwanda’s Volcanoes National Park.
The study, published in the journal Scientific Reports, is led by Edward Wright and Martha Robbins of the Max Planck Institute for Evolutionary Anthropology. Researchers from the Dian Fossey Foundation, George Washington University, Goethe University Frankfurt and Professor Jordi Galbany of the Faculty of Psychology at the University of Barcelona have also participated.
Mountain gorillas live in social groups where there are usually one or more males competing with other males in the same and neighbouring groups. The beats, which are both visual and acoustic signals, reliably indicate the gorillas’ body size to their social group and neighbouring groups. Larger and more competitive males emit beats with lower frequencies so:
- Rival males may be intimidated by the sound of these long-range blows, which can be felt up to a kilometre away, allowing some gorillas to prudently decide not to engage in combat.
- Females may use it to choose potential mates.
The team also discovered a large variation in the number of strokes and the duration of the chest beat among different males. Does each individual have its own code? This may be another object of study that the scientific community will surely discover.