Electronic Theses and Dissertations

Piel, Alexander Kenneth. (2014). Savanna Sounds : : Using Remote Acoustic Sensing to Study Spatiotemporal Patterns in Wild Chimpanzee Loud Vocalizations in the Issa Valley, Ugalla, Western Tanzania. UC San Diego: Anthropology. b8854970. Retrieved from: http://escholarship.org/uc/item/8cd9h1kd

Researchers who study unhabituated animals face a daunting task, that of locating and monitoring elusive subjects and, sometimes, conditioning them to human presence. With savanna-woodland chimpanzees (Pan troglodytes) in western Tanzania, this challenge is further exacerbated when one considers their hypothesized home range is over ten times larger than forest-dwelling populations and they live at one tenth the density. Consequently, alternative methods to study these apes are needed, especially to test hypotheses concerning behavioural adaptations necessary to cope with marginal, open-habitat conditions. Results have implications for extant apes living in these drier habitats, and Plio-Pleistocene hominins that would have faced similar environments. We designed and deployed an acoustic remote sensing system to continuously monitor chimpanzee vocalizations across space and time from April 2009 - February 2010. Results from a playback study examining sound propagation in the study area showed that sound carries farther through woodlands, slopes and mountain edges than from plateaus or through thicker, forest vegetation. Spatiotemporal analyses of chimpanzee loud calls revealed that individuals produced loud calls from non-random places and times, including exhibiting dawn and dusk peaks and during moonlit nights. Contrary to some of our hypotheses, we found no relationship between when chimpanzees call and optimal sound propagation conditions. Rather, the best predictor of when a vocalization was produced was the presence of a preceding call, both in predicting a call itself, and also from where it was emitted (e.g. in the same valley as the previous call). Significantly more calls were produced in the northern part of their range during the dry season, and more in the southern part, during the wet season. Additionally, mean monthly call rate (number of calls/day) correlated strongly with monthly mean nest party size, suggesting that vocalizations are a reliable predictor of grouping behaviour. Whilst this dissertation describes spatiotemporal vocalization patterns, results from this terrestrial, remote passive acoustic monitoring have numerous other applications. These include using precise caller localizations to test hypotheses concerning the role of vocalizations in movement coordination, and establishing ecosystem-wide savanna soundscapes, to assess acoustic niche partitioning