Acoustic structure and variation in mountain and western gorilla close calls: a syntactic approach

Gorilla close calls exhibit a complex, combinatorial structure with five intergraded acoustic unit types that form 159 distinct combinations. This syntactic approach reveals non-random flexibility in vocalizations, challenging traditional discrete-graded distinctions and expanding understanding of combinatorial systems beyond long-distance calls. The study compared mountain gorillas (Bwindi Impenetrable National Park, Uganda) and western lowland gorillas (Bai Hokou, Central African Republic), identifying subtle but significant differences linked to environmental and social factors. Findings suggest these vocalizations may serve nuanced social functions, offering new avenues for studying ape communication.

Hedwig, D., Hammerschmidt, K., Mundry, R., Robbins, Martha M., & Boesch, C. (2014). Acoustic structure and variation in mountain and western gorilla close calls: a syntactic approach. Behaviour, 151(8), 1091–1120. https://doi.org/10.1163/1568539x-00003175