Another study using long-distance playback experiments to determine the range over which elephants can recognize a particular caller found that behavioral responses fade at 2.5km (McComb et al, 2003).
3.0 Long-distance Vocal Recognition.
Langbauer et al, (1991) found behavioral differences in elephants to long-distance playback calls of various vocalization types. For example male elephants responded much greater vocalizations of females than did family groups, while baby elephant distress call elicited a strong response in adult female elephants. McComb et al, (2000) used long-distance playback experiments to show that African elephants have the ability to distinguish between infrasonic vocal calls of known and unknown family and bond members. Reactions of elephants to playback calls of familiar and unfamiliar individuals varied greatly. Measurements of positive reactions were responding with a contact call or approaching the signal source. Where a playback of an unfamiliar elephant was used, all recorded reactions showed no positive response. The highest response was a contact call given by elephants in response to playbacks of a familiar family or bond group member. Elephants showed uneasiness to playbacks from unfamiliar elephants indicating the possible use of infrasonic calls for conflict avoidance. Also the orientation of elephants in the direction of the signal and approaching calls of familiar family or bond group members shows the use of infrasonic calling in locating a lost member. .
4.0 Atmospheric Conditions .
Low-frequency sound is better suited to long range communication as it attenuates much less than high-frequency sound. Garstang et al. (1995) studied the effects of atmospheric conditions on the range over which low-frequency sound could be communicated. The temperature gradient between very hot days and cool night time stratifies the air at the ground surface and these conditions allow enhanced propagation of low-frequency sound (Garstang et al, 1995).
