According to a study of wild African elephants (Loxodonta africana) in Kenya published in the open-access journal PLoS ONE, elephants produce alarm calls in response to the voices of Samburu – a local tribe from North Kenya.
African elephants at the Amboseli national park near Mount Kilimanjaro. Image credit: Amoghavarsha / CC BY-SA 3.0.
Dr Lucy King from Oxford University with colleagues carried out audio experiments in which recordings of the voices of Samburu tribesmen were played to resting African elephants. The elephants quickly reacted, becoming more vigilant and running away from the sound whilst emitting a distinctive low rumble.
When the scientists, having recorded this rumble, played it back to a group of elephants they reacted in a similar way to the sound of the Samburu voices; running away and becoming very vigilant, perhaps searching for the potentially lethal threat of human hunters.
The study builds on previous research showing that elephants call ‘bee-ware’ and run away from the sound of angry bees.
Whilst the ‘bee’ and ‘human’ rumbling alarm calls might sound similar to our ears there are important differences at infrasonic frequencies that elephants can hear but humans can’t.
“Elephants appear to be able to manipulate their vocal tract to shape the sounds of their rumbles to make different alarm calls,” said study co-author Dr Lucy King from Oxford University.
“We concede the possibility that these alarm calls are simply a by-product of elephants running away, that is, just an emotional response to the threat that other elephants pick up on.”
“On the other hand, we think it is also possible that the rumble alarms are akin to words in human language, and that elephants voluntarily and purposefully make those alarm calls to warn others about specific threats.”
“Our research results here show that African elephant alarm calls can differentiate between two types of threat and reflect the level of urgency of that threat.”
Significantly, the reaction to the human alarm call included none of the head-shaking behavior displayed by elephants hearing the bee alarm.
When threatened by bees elephants shake their heads in an effort to knock the insects away as well as running – despite their thick hides adult elephants can be stung around their eyes or up their trunks, whilst calves could potentially be killed by a swarm of stinging bees as they have yet to develop a thick protective skin.
“Interestingly, the acoustic analysis showed that the difference between the ‘bee alarm rumble’ and the ‘human alarm rumble’ is the same as a vowel-change in human language, which can change the meaning of words. Elephants use similar vowel-like changes in their rumbles to differentiate the type of threat they experience, and so give specific warnings to other elephants who can decipher the sounds,” Dr King said.
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Soltis J et al. 2014. African Elephant Alarm Calls Distinguish between Threats from Humans and Bees. PLoS ONE 9 (2): e89403; doi: 10.1371/journal.pone.0089403
