AZA Professional Members |
African Elephant Vocal Communication
Discoveries
The vocal repertoire of African Elephants |
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The first thing to do when trying to understand the vocal communication system of another species is to figure out how many different types of vocalizations there are. We have found 8 basic types of vocalizations in the adult African elephant vocal repertoire. In that process, we discovered two new vocalizations not previously described by scientists: the ‘croak’ and the ‘rev’. The croak is often heard when elephants are exploring the environment with their trunks, and the rev often occurs when elephants are startled. Although trumpets are the most well known elephant vocalization, ‘rumbles’ are the most common and we know most about them. |
Click here to listen to the croak.
Click here to listen to the rev.
Click here to listen to the trumpet.
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Each elephant has a distinct voice |
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Click here to listen to the rumbles of two different females.
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Although it is difficult for us to detect with our limited hearing, we have shown that our elephants have distinctive sounding voices. We know that voice activated phone systems can understand our voices when we respond to a command such as “say or press one”. Using the same “human speech recognition technology”, our colleagues at Marquette University have developed special software to accurately identify individual elephant rumbles, showing that they have unique voices just as many social animals do. So not only do best friends talk to each other by exchanging rumbles, they probably can also recognize each other by their voices alone. What a great way to keep track of everyone when they are out of sight! |
Best friends exchange rumbles as contact calls |
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Female African elephants are known to produce rumbles in clusters, but since low-frequency rumbles are difficult to detect no one knew for sure who was talking to whom. Using our customized audio-recording collars, we found that females with the strongest social bonds are responsible for these rumble exchanges, sometimes over relatively long distances. When “best friends” are separated from each other and exchange rumbles, they move closer together. These rumbles are like social magnets that keep closely bonded partners from straying too far from each other. It’s the elephant version of a cell phone. |
Click here to listen to the cluster of rumbles.
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Female rumbles may signal their reproductive state to males |
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Click here to listen to a female “mate attraction” rumble.
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There is a lot more information in a rumble besides the differences between individuals. Females appear to have ‘mate attraction’ rumbles that signal their reproductive state to distant males. In the wild, males are solitary and usually only visit females for mating, so it could help everyone if female rumbles indicated something about their current fertility. We found that the cycling females in our herd start rumbling much more than usual a little before ovulation. We have shown that these “pre-ovulatory” rumbles are distinct from “normal” rumbles, involving a lowering of the pitch of the call. Males may listen for these rumbles so they can find females who will soon become ready to mate. But what happens when the male gets into the female herd? When we introduced a male into our herd containing cycling females, the females became less vocal, and males switched to using olfactory cues to determine female fertility. |
This graph shows a female’s hormonal cycle. The black line shows peaks of Luteinizing Hormone, or LH. Unlike most mammals, elephants have two LH peaks per cycle, and the second one results in ovulation. The red bars show how her rumbling increases just before the first LH peak (no ovulation) and remains relatively high up to ovulation, compared to other times in her cycle.
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African elephants express emotion in their voices |
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Click here to to listen to the "temper tantrum" rumbles from a 3-month old female calf.
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When humans are nervous or upset, it is common that their voices get louder, higher pitched and shaky. It turns out that the same thing happens to elephants. Our baby elephants make loud, high pitched rumbles when they are upset, such as when their mothers won't let them nurse. Adult female elephants also express emotion in their voices. When subordinates are approached by dominant animals, they make “nervous” rumbles.
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This graph shows an example of a “calm” rumble, recorded from one of our elephants, Donna, when she was resting, and a “nervous” rumble, which she made when she was approached by a dominant female. Her nervous rumble is higher pitched and shaky, and is louder and longer, compared to her relaxed, “calm” rumble. These nervous rumbles may communicate submission to social superiors or indicate that there will be no aggression.
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Click here to to listen to the nervous rumble pictured in the graph above.
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To learn more about Elephant Communication please visit the links below: |
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