Gorillas beat their chests as a form of non-vocal communication, often in response to threats, to establish dominance, or to assert their territory. This behavior is known as “thumping” or “pounding” and is a common display in gorillas, especially silverback gorillas, which are the alpha males of their groups.
Here are a few specific reasons why gorillas might engage in chest beating:

1. Dominance and Status: Silverback gorillas often chest-beat to assert their dominance within the group. By demonstrating their strength and size, they can scare off potential threats and solidify their position as the leader.
2. Warning and Intimidation: Gorillas may beat their chests to warn off rivals or intruders. It’s a way to communicate power and can serve as a deterrent without necessarily resorting to violence.
3. Mating Display: In some contexts, chest beating can be a part of a mating display. Silverbacks may do this to attract females or to establish their fitness as potential mates.
4. Emotional Release: Gorillas, like other animals, may have emotions that need expressing. Chest beating can be a way to release stress or frustration, even if its primary purpose is not communication.
5. Territorial Marking: Gorillas may also chest-beat to mark their territory. By making their presence known, they can inform other groups of gorillas to stay away.

Chest beating involves the gorilla standing upright or slapping its hands on its chest while sometimes vocalizing grunts or roars. The vibration from the impact of their hands creates a deep, reverberating sound that echoes through the jungle. This behavior is an integral part of gorilla social dynamics and plays a key role in maintaining group structure and hierarchy.