Quantifying acoustic and temporal characteristics of vocalisations for a group of captive African elephants Loxodonta africana

In order to increase understanding of African elephant vocal communication and to standardise the terminology used to describe vocalisations, this study examined acoustic and temporal characteristics of 983 vocalisations from 2 male and 6 female captive African elephants. Recording collars were used to monitor vocalisations and videotape to simultaneously record behaviour, allowing for unambiguous attribution of sounds to individuals, even in close proximity. Eight acoustically distinct categories of calls were defined in terms of structural characteristics; two of these categories are described for the first time. Low-frequency vocalisations containing infrasonic components were predominant in this localised communication context and showed a gradation of variation in acoustic structure and duration. Most calls were part of temporally closed exchanges between individuals and coincided with short-distance interactions. In addition, male-female choruses and non-musth rumbles from males were documented, suggesting that the African elephant vocal repertoire may be more complex than previously reported.