Food-Associated Calling in Gorillas (Gorilla g. gorilla) in the Wild

Many nonhuman primates produce food-associated vocalizations upon encountering or ingesting particular food. Concerning the great apes, only food-associated vocalizations of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) have been studied in detail, providing evidence that these vocalizations can be produced flexibly in relation to a variety of factors, such as the quantity and quality of food and/or the type of audience. Only anecdotal evidence exists of eastern (Gorilla beringei) and western gorillas (Gorilla gorilla) producing food-associated vocalizations, termed singing or humming. To enable a better understanding of the context in which these calls are produced, we investigated and compared the vocal behavior of two free-ranging groups of western lowland gorillas (Gorilla g. gorilla) at Mondika, Republic of Congo. Our results show that (a) food-associated call production occurs only during feeding and not in other contexts; (b) calling is not uniformly distributed across age and sex classes; (c) calls are only produced during feeding on specific foods; and (d) normally just one individual gives calls during group feeding sessions, however, certain food types elicit simultaneous calling of two or more individuals. Our findings provide new insight into the vocal abilities of gorillas but also carry larger implications for questions concerning vocal variability among the great apes. Food-associated calls of nonhuman primates have been shown to be flexible in terms of when they are used and who they are directed at, making them interesting vocalizations from the viewpoint of language evolution. Food-associated vocalizations in great apes can offer new opportunities to investigate the phylogenetic development of vocal communication within the primate lineage and can possibly contribute novel insights into the origins of human language.