Nature
PUBLISHED
You might think the chest beating of male gorillas is perhaps one of the most iconic examples of peacocking since peacocks themselves. However, new research has revealed that the gorillas' chest beating behavior isn’t quite as showy as first thought. Research published in the journal Scientific Reports has concluded that the non-verbal means of communication is actually an honest representation of a male mountain gorilla’s size, accurately portraying their competitive ability as opposed to exaggerating it.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Chest beating in itself represents an interesting branch of non-human communication, as it’s not actually a vocalization but a physical action that can be seen but also heard. Impressively, some male mountain gorillas’ thumping has carried over a kilometer demonstrating that females needn’t be in eyeline of the gun show to pick up on its message
To reach their conclusion, the researchers of the new study used photogrammetry to record the sound of chest beating. This carried the benefit of not having to get up close and personal with the incredibly strong, but also potentially dangerous, male mountain gorillas in the Dian Fossey Gorilla Fund in Volcanoes National Park, Rwanda. Unfortunately, even this proved challenging as they still needed to be in the right place at the right time to pick up the chest beats, which aren’t all that long in duration.
Their results revealed that peak frequencies were lower in the larger male mountain gorillas, while smaller males had a higher peak frequency. Low frequency sounds travel further than high frequency sounds, meaning bigger males that are probably more formidable competitors can be heard from further away. This is helpful for similar sized or smaller males that can use the information to decide if it’s worth taking on a competitor or cutting their losses and backing off.
This is reflected in previous research carried out by the same team that found larger male mountain gorillas aren’t just socially dominant, they also have better reproductive success compared to smaller males. It’s likely then that females too glean information from chest beating sounds that can help them decide on a worthy mate.
"The gorilla chest beat is one of those iconic sounds from the animal kingdom, so it is great that we have been able to show that body size is encoded in these spectacular displays,” said Edward Wright, first author of the study from the Max Planck Institute for Evolutionary Anthropology, in a statement.
