Communication and spatial cohesion of the African elephant, Loxodonta africana

Abstract

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This dissertation is divided into 3 chapters that explore various aspects of communication in African savanna elephants and how this communication is used to maintain the cohesion of family groups. The first chapter presents a series of seismic playback experiments conducted in Etosha National Park, Namibia. Building on previous research, which showed that seismic correlates of acoustic signals are produced when elephants produce low frequency rumbles, we played back just the seismic correlates of elephant warning calls to family herds visiting a waterhole in the park. As a result of this stimulus the elephant herd spent significantly less time at the waterhole and herd spacing decreased significantly, thus indicating that the elephants were able to detect the seismic signal. Chapter Two focuses on acoustic communication. Specifically, it categorizes rumbles that were recorded in Kruger National Park, South Africa, into discrete rumble types. Previous researchers have described a number of different rumble types by associating these rumbles with specific behaviors. Recently others have quantified the physical differences between 8 call types used by African elephants. This chapter focused on the most common of these call types, the rumble. By extracting various acoustic parameters and submitting them to cluster analysis we show that there are indeed distinct rumble types and furthermore, that those rumble types have significant associations with specific group behaviors. The final chapter takes a more holistic approach to communication and how it is used for a specific purpose. As elephants move they will often spread out large distances while feeding, and yet the family group is found in each other's presence most of the time. By following a family group in Kruger National Park, this research quantified the relative importance of multiple modes of communication in maintaining the cohesion of this group. It was determined that acoustic communication is by far the most probable method of maintaining cohesion, while visual and chemical communication did not play a large role for this purpose. It is also possible that seismic cues could be used as well, although this will need further study