Responses of captive African elephants to playback of low-frequency calls

Abstract

We conducted a series of playback trials with captive African elephants to identify behaviors that might indicate perception of calls by conspecifics. Our findings were as follows. (i) The elephants responded clearly to playbacks of prerecorded low-frequency elephant calls. Responses included, in rough sequence, lifting and stiffening of ears, vocalization, walking or running towards the concealed speaker, clustering in a tight group, and remaining motionless ("freezing"), with occasional scanning movements of the head. The occurrence of each of these behaviors increased substantially immediately after the playbacks. (ii) Elephants responded both to full-bandwidth playbacks and to playbacks of calls in which most of the energy above 25 Hz was filtered out, simulating the effect of frequency-dependent attenuation over distance. (iii) Elephants did not respond to a pure-tone control stimulus similar in frequency and intensity to the filtered elephant calls. Thus, the observed responses to elephant calls were not merely responses to an unexpected stimulus, but probably indicate recognition of a biologically meaningful signal.