Elephants tell human friend from foe by voice
Pinpointing predators Elephants are able to distinguish between friendly humans and those more likely to pose a threat, based solely on vocal cues, new research shows.
The study, published today in the Proceedings of the National Academy of Sciences, examines the extent to which African elephants use human voice cues to determine not only ethnicity, but also finer-scaled differences in gender and age.
The team of researchers from the UK and Kenya studied 47 different elephant family groups living in the Amboseli National Park.
Humans pose the most significant threat, other than lions, to elephants living in this area, but different ethnic groups pose different levels of danger.
"Maasai pastoralists periodically come into contact with elephants over access to water and grazing for their cattle, and this sometimes results in elephants being speared, particularly in retaliation when Maasai lives have been lost," write the authors.
"In contrast, Kamba men, with more agricultural lifestyles, do not typically pose a significant threat to elephants within the National Park, and where conflict occurs outside over crop raiding, this largely involves male rather than female elephants."
Past research has shown that elephants showed a greater fear reaction to garments worn by Maasai men, and their typically red-coloured fabric, than those worn by the Kamba.
In this study, the researchers were able to demonstrate that the elephants could reliably discriminate between ethnic and age groups based on their response to voice recordings from Maasai and Kamba men, women and boys.
When the elephants heard the playback of Maasai adult males, they behaved much more defensively, with more investigative smelling, bunching and retreating, than when they heard Kamba voices.
They also reacted more strongly to adult males than to adult females or to young male voices.
The elephants were even able to distinguish the original sex of the speaker when the voices were digitally altered to resemble the acoustics of the opposite gender.
McComb says this kind of resynthesising was sophisticated enough to fool the human ear, but the fact that the elephants could still pick and respond to the original gender of the voice suggested they were using different acoustic cues to characterise the speaker.
"They're very good at making these distinctions, which are very important to them when it comes to ultimately to survival and reproductive success," says McComb, professor of animal behaviour and cognition University of Sussex.
Another finding from the study is that older matriarch elephants are better at distinguishing the true level of threat and so reacted less to the voices of young Maasai boys than did younger matriarchs.
"In our previous work, we had found both in the social domain and when we did experiments with lion playbacks, families with older matriarchs were actually better at pin-pointing the most threatening situations," says McComb.
The researchers also noted quite different defensive behaviour in this study compared to previous studies involving playbacks of lion roars.
"Elephants very rarely attempted to approach when faced with human stimuli; instead, reactions involving defensive bunching, retreats and investigative smelling were much more common," the authors wrote.
"Whereas an aggressive mobbing response can prove very effective in driving off lions, it is unlikely to success against humans armed with spears and would instead put the family group in great danger."
The authors say the findings should prompt similar studies in other animals that have a long history of co-existence with humans.