Gorillas beat their chests to size each other up, researchers say

Chest-beating behaviour in male gorillas allows them to signal their size and avoid fights with larger rivals

It is a trope used in films from King Kong to Tarzan - a male primate standing upright and beating its chest, sometimes with a yell and often with more than a dash of hubris.

But it seems the pounding action is less about misplaced bravado than Hollywood would suggest: researchers studying adult male mountain gorillas say that while chest-beating might be done to show off, it also provides honest information.