Long Distance Communication in Forest Elephants
Elephants live in fission-fusion societies which means they form large social groups that frequently break up and reunite¹. Subgroups can travel significant distances from each other and savannah elephants have been documented using low frequency rumbles to communicate with each other over long distances². Langbauer and his colleagues estimated that these vocalizations, which are too low for humans to hear, can travel up to four kilometers². A recent study³ by the Elephant Listening Project (ELP) sought to determine if forest elephants utilize a similar system.
In this study ELP researchers Peter Wrege and Daniela Hedwig asked how far elephant calls could be detected by other elephants in the dense rainforests of Central Africa³. They set up nine sound recorders at varying distances from a forest clearing in Ivindo National Park, Gabon. These devices recorded the vocalizations produced by elephants frequenting the clearing, along with ambient noise (bird song, wind etc.). The data showed that under normal forest conditions vocalizations could be heard at only 0.8 kilometers from their source. The vocalizations’ strength decreased with distance from the calling animal and, for half of them, the harmonics structure dissipated at just 100 meters. This was partially caused by the sound waves being broken up as they bumped into forest objects. Furthermore, each call has multiple components of different frequencies. Since lower frequencies travel farther than high frequencies, portions of the vocalization are lost as it covers more distance. The end result is that animals hearing a call don’t obtain the full information originally contained in it. This is the equivalent of hearing a sentence with missing words. Interestingly, although the vocalizations dissolved quickly, the dissolution happened at a slower rate than the researchers expected. This was because the sound waves bounced off of forest objects and combined to form stronger ones that were more robust³.
Since the vocalizations couldn’t travel very far the researchers concluded that forest elephants likely don’t utilize them to the same extent as savannah elephants and there is probably little long distance communication between forest elephant subgroups³. One potential explanation for these results is that forests contain more obstacles to sound travel, in contrast to open grassland. Forest elephants are also significantly smaller than savannah elephants and therefore produce weaker calls, which typically travel shorter distances than louder ones. Study design may also be an important factor. Most savannah elephant experiments were conducted in optimal conditions with little ambient noise. Forest elephant calls were estimated to be capable of travelling as much as 13.3 kilometers in a similar setting³.
This research increases our understanding of forest elephants’ communication systems and how they navigate their environment. Such knowledge is critical as it allows us to assess their needs and predict how human activities could adversely impact their behavior patterns. This information could be incorporated into conservation plans and help to better secure the elephants’ future.
¹Wittemyer, George, Iain Douglas-Hamilton, and Wayne Marcus Getz. “The socioecology of elephants: analysis of the processes creating multitiered social structures.” Animal behaviour 69, no. 6 (2005): 1357–1371.
²Langbauer, William R., Katharine B. Payne, Russell A. Charif, Lisa Rapaport, and Ferrel Osborn. “African elephants respond to distant playbacks of low-frequency conspecific calls.” Journal of Experimental Biology 157, no. 1 (1991): 35–46.
³Hedwig, Daniela, Maya DeBellis, and Peter Howard Wrege. “Not so far: attenuation of low-frequency vocalizations in a rainforest environment suggests limited acoustic mediation of social interaction in African forest elephants.” Behavioral Ecology and Sociobiology 72, no. 3 (2018): 33.