Rumble vocalizations mediate interpartner distance in African elephants, Loxodonta africana

The ability to utilize contact calls to facilitate reunions with social partners has been documented in a number of species showing a fission/fusion social organization. Field observations and playback experiments suggest that African elephants use low-frequency rumble vocalizations to reunite with their herd members following periods of fission. Using a digital audio and GPS recording collar system, we documented the production of rumbles and subsequent movements of five adult female African elephants at Disney's Animal Kingdom, Bay Lake, Florida, U.S.A. This recording system allowed us to identify the producer of each rumble and to document the effect of rumbles on the movements of herd members relative to the caller. Our findings provide the first empirical evidence that spontaneously produced elephant rumble vocalizations function in part to mediate the spatial relationships of group members. Overall, the production of rumbles resulted in a net decrease in distance between the caller and her social partners. This approach behaviour was enhanced if the partner was highly affiliated with the caller, if the partner replied with a rumble of her own, and if the pair was initially far apart (≥61 m). Rumble production was likely to result in avoidance behaviour only when there was no rumble reply by the partner and the dyad was close together prior to the initial call. These results suggest that a general function of elephant rumbles is to promote spatial cohesion among separated group members, but they may also mediate a variety of other close-distance social interactions.