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Asian Elephant Social Communicative Behavior: 2007 Fieldwork & Acoustic Analyses
All figures and text.
Achievement/Results
Shermin de Silva, IGERT trainee and biology graduate student at the University of Pennsylvania, has recently developed a research program studying wild, free-ranging Asian elephants (E. Maximus) in Udawalawe National Park (UWNP), Sri Lanka. This park, roughly 325 sq. km, is home to one of the highest densities of Asian elephants anywhere in Asia. Despite their size, we know very little about these intelligent social mammals. De Silva’s primary interest is to describe the Asian Elephants’ social structure and vocal communication, but also to explore the ecological factors that have shaped both Asian elephant society and its communication system. De Silva takes an unusual approach to this research: in addition to the traditional field research, she, with the help of her colleagues, has begun to apply acoustic analysis techniques traditionally used for human speech to the extraction and classification of elephant calls. (See Figure 1.)
De Silva’s work is part of a larger research and education effort at The University of Pennsylvania to establish itself as a leader in the emerging interdisciplinary field of Language and Communication Sciences. De Silva’s academic and field training are being administered under the direction of her advisors, Penn Professors Dorothy Cheney and Robert Seyfarth, renowned experts in non-human primate communication and social cognition. De Silva’s traineeship is supported by The University of Pennsylvania’s graduate training program in Language and Communication Sciences (LCS), funded by an Integrative Graduate Education and Research Traineeship (IGERT) grant from the National Science Foundation (IGERT 0504487, Dynamics of Communication in Context, PI: Trueswell). This IGERT program brings together students and faculty from diverse backgrounds and expertise who share an interest in understanding the computational and neural underpinnings of linguistic and nonlinguistic communication.
The primary ambition for this IGERT is to create a community of scholar-scientists with the conceptual reach and technical expertise to integrate the computational, cognitive and neuroscientific study of communication, be it characterized as human-linguistic, animal or machine. By bringing together faculty and students with such diverse skill sets, we hope to produce a new generation of scholars with unique combinations of expertise that make them not only special in their own sub-discipline but relevant to a larger community, by creatively combining ideas, techniques and analyses in ways previously not considered.
The existing knowledge of acoustic communication in elephants is based primarily on research on just three wild African elephant populations (Amboseli National Park (Tanzania), Etosha National Park (Namibia), central African forests) and one captive African elephant herd (Disney’s Animal Kingdom, Orlando FL). Little is known about the vocal repertoire of Asian elephants (Elephas maximus). Only about 30 calls have been published for African savannah elephants (Loxodonta africana), and only nine calls for Asian elephants.
De Silva has recently changed this situation. Together with her local counterparts, de Silva has created an identification catalogue of around 300 females, and recently begun to work on males, having already counted up to 100. This is quite a bit higher than the population that was expected to live in this relatively small reserve, generating a lot of local curiosity and interest in her work. Data is gathered by spending the whole day (10-12 hours) in the field, usually driving or looking for shade near a grazing, bathing, playing, or sleeping group of elephants. De Silva and her colleagues do this several times a week, and have been monitoring continuously since June 2006. They mark locations of all sightings via GPS and try to follow animals they recognize for as long as they stay visible. They also audio- and video- record calls whenever they occur, including infrasonic sounds. (See Figures 2 & 3.) Currently de Silva has returned to the University of Pennsylvania campus to continue her academic studies. She is currently enrolled in the Mathematical Foundations II course, which is part of the IGERT training initiative. With the help of IGERT faculty who teach this course (Linguists Mark Liberman and Stephen Isaard), de Silva has categorized by quantitative acoustic parameters, basic call types and modifications of these call types. In order to determine if acoustic variability within and among call types is functionally relevant, calls by known individuals are being associated with social context and behavior. Comparisons of acoustic communication in wild and captive elephants may provide insights into the ecological role such communication plays. (See Figures 4, 5 & 6)
De Silva is also collaborating with Sharon S. Glaeser from Portland State University to compare recordings of wild elephants to those of captive ones at the Oregon Zoo. They have found apparent repertoire disparities among the two types of groups. These comparisons could help zoos enrich the lives of their charges, while shedding light on the functions of these calls among their wild relatives.
Address Goals
De Silva’s work has many levels of importance. In addition to documenting the social and communicative behaviors of a little understood species, this work serves as a comparative connection to other animal communication and social systems, including, birds, non-human primates and human primates. This comparative work is crucial to understanding what is and isn’t unique about the human linguistic system, but also serves to better reveal the putative evolution of communication systems within and across species. The University of Pennsylvania IGERT program in Language and Communication Sciences is designed to offer the experimental, observational, and quantitative skills necessary to tackle this important research endeavor.
