This article focuses on the low frequency rumble calls of African elephants. The authors believed the elephants were using these calls as social signals to indicate their location and distance from other members of the herd. They explain that elephant herds break up into smaller groups and travel large distances looking for resources. After a period of time, they come back together and reform the main group, demonstrating fission-fusion herd behavior. In order to find each other again, the elephants need to make contact calls that signal proximity as well as their individual identity to make sure they are associating with the right animals and reforming their original group. Rumble calls are the likely solution for this problem because their low frequency allows them to propagate the large distances of over a kilometer that elephants can be separated, and they do not go through much attenuation in the environment. To test whether this is really the function of rumble calls, the researchers used audio recording systems on collars on elephants at Disney’s Animal Kingdom. This allowed them to take measurements on the vocalizations and record which individual was calling when. They also used GPS and video recording to record the elephants’ movements after calls were made. This would show whether the animals moved toward (were attracted) or away from (avoided) the calling elephants. Then they developed movement ratios based on distance between individuals after different timesteps after the original call. The researchers also analyzed the data on whether rumble calls were answered by other elephants in the group. The results were that there was significant approaching when the animals started out far away from each other, but this movement was not significant when they were already close. Additionally, elephants in high affiliation groups showed more movement toward the caller than elephants with a low or moderate affiliation with that caller. There was also increased approaching the caller when the moving elephants gave reply calls after one minute. With this evidence, the authors concluded that the rumble calls do function to dictate spatial relationships and movement between subgroups of a large herd of African elephants.

This study relates to what we have learned in class about social integration and communication. Since the authors showed in one section of the study that approaching or avoiding is a response of the level of association between different animals, the elephants must be able to discriminate individuals based on rumble calls. While the signal serves a spatial function, it is not a spatial recognition mechanism because there is not a fixed area to recognize. Therefore, it is most likely a familiarity mechanism. It is also enables the herds to coordinate movement when coming back together after finding resources.

Leighty, K. A., J. Soltis, C. M. Wesolek, and A. Savage. 2008. Rumble vocalizations mediate interpartner distance in African elephants, Loxodonta africana. Animal Behaviour, 76(5), 1601-1608.