Browsing by Subject "chimpanzee"

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    Exploring the form and functions of chimpanzee pant-hoots from basic evolutionary principles.
    (2022-06) Desai, Nisarg
    Researchers have studied chimpanzee vocal communication extensively, focusing on evidence of parallels with human language. This approach has been effective in encouraging vocal communication research and providing some insights about the evolution of language. However, it has obscured our understanding of non-human animal communication by motivating researchers to adopt a problematic conceptual framework that uses complex linguistic phenomena as models for simpler primate vocal communication mechanisms. An approach focusing on basic evolutionary principles involves studying the intimate connection between form and function to obtain insights about the biological and evolutionary origins and mechanisms of traits. Such an approach, when employed for studying chimpanzee vocalizations, may be more fruitful in revealing fundamental factors that may shape their vocalizations. This dissertation extends our knowledge of the forms and functions of chimpanzee vocal communication. I first explored different acoustical and statistical analysis methods for describing the form of vocalizations. Next, I studied connection of the form of chimpanzee vocalization, the pant-hoot, to its possible functions. Using audio recordings and behavioral data from two chimpanzee communities in Gombe National Park, Tanzania, and one chimpanzee community in Kibale National Park, Uganda, I tested if the variation in chimpanzee calls is explained primarily by (i) community membership, or (ii) by individual traits such as age, rank, and health, and (iii) if any of these acoustic cues predicted male mating success. Individual traits better explained the acoustic variation in pant-hoots than community membership. Acoustic variation also reflected male mating success. These findings suggest that sexual selection is a key evolutionary force shaping chimpanzee vocalizations.
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    The Socioecology of Chimpanzee Foraging and Food-associated Calling Behavior
    (2015-06) O'Bryan, Lisa
    Social-living is complicated. Living in groups can provide greater protection from predators, promote discovery and defense of food sources and improve access to mates. On the other hand, it can increase susceptibility to predators or pathogens and incite competition for resources. Because of these trade-offs, social systems can display high levels of diversity, both on an evolutionary time-scale as well as in response to short-term variation in social and ecological pressures. In this dissertation I investigate the foraging and food-associated calling behavior of chimpanzees (Pan troglodytes) in order to better understand the causes and consequences of grouping behavior. Chimpanzee social groups display high levels of short-term variability in both size and composition. Furthermore, individuals produce specific vocalizations in foraging contexts that are believed to further modulate these parties. Thus, this system provides a prime opportunity to examine the costs and benefits of sociality and how individuals respond to these trade-offs. Using a combination of captive experiments and observational field studies, I examine chimpanzee foraging decisions, the trade-off between foraging and socialization and the social and ecological correlates of food-associated calling behavior. Results from these studies expand current understanding of the foraging and social behavior of chimpanzees and suggest an alternative function for their food-associated rough-grunt vocalization. Furthermore, they highlight the challenges and benefits of social-living and the tactics individuals can employ to manipulate their social landscape.