Beating of My Chest  

In Life: Season 1 Episode 10, David Attenborough explores the social interactions and behavior of various primates that live around the world. Particularly in the Congo Basin, many populations of Western Lowland Gorillas (Gorilla gorilla gorilla) inhabit the dense rainforest. Living in family packs, gorillas are led and protected by one silverback male. As the dominant figure of the social group, the silverback male ensures the safety and stability of his members [2]. In the documentary, Attenborough states that silverback males beat their chests to maintain their territory since one family may be living in close vicinity to other family groups around the area.

While chest beating may be immediately associated with aggression, the display may only be used as an alert or cautionary system. Oftentimes, silverback males of one family group may be related to surrounding silverback males, and interaction between different groups is not uncommon [1]. Therefore, the display of chest beating may only be a request for other groups to stay within their own territory. In other situations, chest beating from a silverback male is an act of dominant assertion over its resources, especially access to females [3]. Overall, there is little aggression between these related silverback males, and maintaining friendly kin relations also benefits the younger males, who are trying to attract other females in order to form their own packs [1].

Although related silverback males may use chest beat displays to communicate with surrounding groups and ultimately to avoid aggressive interactions, other involuntary intergroup signals such, as odor displays, also influence interactions between silverback males [4]. During encounters between silverback males, they release odors of different intensity in order to communicate their intentions. Greater intensities often indicate a threat, and mild odors indicate the desire to avoid conflict [4].

All animals have their own ways of communication. Whether it is through chest beating or the involuntary release of odor, gorillas seek to protect their family groups in order to assure the successful passing down of their genes.

by Elizabeth Teng

Life, Season 1 Episode 10, starting at approximately 16 minutes and 44 seconds from beginning

References

1. Brenda JB, Doran-Sheehy DM, Lukas D, Boesch C, & L Vigilant. 2004. Dispersed male networks in Western Gorillas. Current Biology 14: 510-513.
2. Margulis SW, Whitham JC, & K Ogorzalek. 2003. Silverback male presence and group stability in gorillas (Gorilla gorilla gorilla). Folia Primatologica 74: 92-96.
3. Pullen K. 2005. Preliminary comparisons of male/male interactions within bachelor and breeding groups of western lowland gorillas (Gorilla gorilla gorilla). Applied Animal Behaviour Science 90: 143-153.
4. Masi S & S Bouret. 2015. Odor signals in wild western lowland gorillas: an involuntary and extra-group communication hypothesis. Physiology & Behavior 145: 123-126.