Study

First Observation of Tool Use in Wild Gorillas

Breuer, Thomas; Ndoundou-Hockemba, Mireille; Fishlock, Vicki

PLoS Biology, 2005

Peer-reviewedfield observationwild

What they did

Long-term observation of western lowland gorillas at a forest clearing in the Nouabalé-Ndoki National Park, Republic of Congo, where animals crossing swampy ground could be watched continuously from a platform.

Studied in: Gorilla gorilla gorilla
Sample size: 2 observed instances by two individual females

What they found

One female used a branch as a walking stick, apparently testing water depth ahead of her while wading. A second detached a small tree trunk, laid it across soft ground and used it as a bridge and as a support while foraging. These were the first records of tool use by gorillas in the wild.

What it means

The authors' reading, and ours. Where they differ, that difference is the point.

How the authors put it

Gorillas are capable of tool use in the wild, and its rarity relative to chimpanzees reflects ecological need rather than an absence of capacity.

How NatureHQ reads it

Two observations, and it would be easy to over-read them or to dismiss them. What they establish is capacity, not custom: gorillas in captivity had long used tools, and the open question was whether wild ones ever needed to. Both recorded uses are postural — depth-testing and support — rather than food-processing, which is the difference from chimpanzees, who crack, fish and sponge routinely. The most plausible reading is that gorilla diet does not require extraction. A gorilla eating leaves and stems does not need a tool to reach them, and a capability that is never called on is not a capability that is absent.

Limitations

Two observations by two individuals; frequency and spread cannot be estimated from this.
Observation was restricted to a clearing, so behaviour in dense forest is unsampled.
Whether the behaviour was learned socially or invented individually is unknown.