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It is one of the animal kingdom's best-known showmanship: a gorilla stands upright and frenetically slaps its chest with its cupped hands.
The unique drumming can be heard a kilometer further.
However, this is more than just showing off - unlike what the main characters in Hollywood blockbusters suggest.
Researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig have now found:
The breast drumming gives information about the size of the gorillas.
“The gorilla breast drumming is a really iconic sound from the animal kingdom.
It is therefore great that we can now prove that gorillas transmit information about their own height in this spectacular way, ”explains primatologist Edward Wright in a press release from the Max Planck Institute.
Source: Jordi Galbany / Dian Fossey Gorill
For their study - published in the journal "Scientific Reports" - the researchers recorded the drumming of a total of 25 free-living male mountain gorillas in the Volcanoes National Park in Rwanda and evaluated them with regard to the number of beats, duration and frequency.
In addition, the scientists used photogrammetry to determine the size of the animals.
Using photos, they measured the width of the back with lasers and were thus able to infer the body size.
It turned out: the bigger the gorilla, the deeper the sound of the chest drumming.
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So the behavior is not just macho, it also provides actual information that the monkeys cannot manipulate.
The gorillas stake their territorial claims by drumming and want to intimidate their competitors.
Should they dare a confrontation or should they prefer to run away?
They also want to impress females with it.
Because size is also decisive for success or failure for women.
Well roared gorilla!
Source: Dian Fossey Gorilla Fund
Also interesting: the primates drum in different rhythms, their beats vary in speed and frequency.
This could indicate that the breast drumming can each have individual signatures
Edward Wright, first author of the study from the Max Planck Institute for Evolutionary Anthropology
In other words, each male may have his own style.
However, further studies are necessary to confirm this assumption.