Vervet Vocal Repertoire in an Impacted Environment at Gorongosa Park: Implications for the Evolution of Human Language

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The vervet monkey (Chlorocebus pygerythrus) is well-known for its use of functionally referential predator-specific alarm calls. As well as being of interest in their own right, due to their apparent similarity to human words, the alarm calls of vervets have frequently been discussed in regard to the evolution of human language - being especially relevant to the debate around a vocal versus gestural mode of origin for advanced human communication. Can the beginnings of our language be traced back to a simpler form of vocal communication such as that present in the vervet monkey, or was non-verbal communication the springboard from which language first developed? Critiques of the vocal origins hypothesis focus on the assumed lack of flexibility of non-human primate vocal communication and, following the principle of parsimony, early human vocal communication. However, various observations indicate that non-human primate vocal communication may be far more adaptable and complex than was once thought. The vervets of Gorongosa National Park, Mozambique, present a unique opportunity for further investigation of the flexibility of vocal communication in a free-ranging primate. Following the civil war in Mozambique, the leopard (Panthera pardus) - a natural predator of the vervet - has experienced a severe decline in population at Gorongosa National Park. Restoration programmes are underway and plans are in place to reintroduce the leopard to the park in the near future. In the meantime, the current population of vervets lack their main predator. This 'quasi-experimental' situation provides a unique opportunity to study the adaptability of vervet vocal production and perception in response to an ecological shift in predation risk. What happens to the vocal repertoire of this primate species in the absence of one of its vocal signal targets? Is the alarm call traditionally associated with leopards absent in these populations, or is it flexibly produced and interpreted accordingly upon perception of other threats? Furthermore, will vervet communication change as leopards are reintroduced to the area, and how will this impact other species in the park, such as baboons (Papio ursinus/cynocephalus), which would normally make use of the vervet alarm calls to predict threats? In 2019, after undertaking the necessary arrangements and refining my research methods, I will head to Gorongosa, and, through observation of the vervet monkeys, seek to answer these questions. In doing so, I will shed light on the flexibility of vervet monkey alarm call production and perception, and primate vocal communication more broadly, which in turn will inform models of the origin and evolution of human language. Vervet monkey troops exposed to various levels of predation will be selected and compared for several months over the course of the planned leopard reintroductions. Vocalisations and subsequent responses (of vervets and neighbouring baboons) will be recorded through focal follows and ad libitum sampling techniques, whilst detailed information will be collected on the context of the calls, including the presence of predators, the number of other conspecifics visible, and the demographic factors of the signaller. By adopting these fieldwork methods, I shall gain all the necessary information to conduct analysis of the collected data and establish answers to my research questions, irrespective of the scale of the reintroductions.As well as directly contributing to the study of primate communication and the origin of human language, the project will be conducted in close collaboration with the leopard reintroduction programme, leading to increased focus on the restoration of the park, and benefitting the ongoing conservation projects; as well as providing opportunities for the local community, and expanding our knowledge of the very much understudied vervets of Gorongosa through behavioural observations and census taking.