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The secret language of elephants: Males use deep rumbles to signal 'let's go' to their pals, study finds
Elephants are already known for their remarkable human-like level of intelligence.
But a new study shows males in groups convey a sophisticated message - although to human ears it sounds like a primitive grunt.
Adult male African elephants emit a deep, resonant growl to their herd mates to say it's time to move to another spot, experts say.
Amazing audio captured by the biologists reveals this so-called 'let's go rumble' is repeated throughout the herd 'like a barbershop quartet'.
Adult females are already known to use the let's go rumble, but new recordings document the technique in males for the first time.
Scientists have documented male elephants using 'let's go' rumbles to signal the start of group departures
The new study was led by Caitlin O'Connell-Rodwell, a research associate at Stanford University's Center for Conservation Biology.
'These calls show us that there's much more going on within their vocal communication than has previously been known,' she said.
The experts studied African bush elephants (Loxodonta africana) at the Mushara waterhole in Etosha National Park, Namibia, one of the largest national parks in Africa.
Although the African bush elephant is a social mammal that travels in a herd, these groups are composed of females and their offspring.
Males leave the herd when they reach maturity – around the age of 10 to 19 years old – and as adults, usually live alone or in small 'bachelor' groups.
The experts studied elephants at the Mushara waterhole in Etosha National Park, Namibia, one of the largest national parks in Africa
African bush elephant males (pictured) leave the herd when they reach maturity - around the age of 10 to 19 years old - and as adults, usually live alone or in small 'bachelor' groups
At Etosha National Park, the experts used recording equipment including buried microphones and night-vision video cameras to capture movements and vocalizations, inaudible to human ears.
They noticed that the distinctive rumble preceded departures from the waterhole – suggesting that it had an important meaning.
Generally, the rumble would first come from the most senior or dominant male in a group before the other males would repeat it as if in agreement.
Each elephant would wait for the preceding call to nearly finish before adding their own – creating a harmonious, turn-taking pattern akin to a barbershop quartet.
The findings are particularly surprising because males are typically considered to have loose social ties, according to O'Connell-Rodwell and colleagues.
'We found that this vocal coordination occurs in groups of closely associated, highly bonded individuals and rarely occurs between looser associates,' they say.
The 'let's go' rumbles observed in male elephants bear striking similarities to those previously recorded in female elephants.
In fact, the team hypothesize that male elephants likely learn the behaviour when they are young before they leave the herd.
'They grew up in a family where all the female leaders were engaging in this ritual,' O'Connell-Rodwell said.
Three spectrograms depicting three different male elephant coordinated departure rumble vocalizations. A spectrogram is a graph that displays the strength of a signal over time for a given frequency range
Male elephants, typically considered to have loose social ties, engage in such sophisticated vocal coordination to trigger action
'We think that as they mature and form their own groups, they adapt and use these learned behaviors to coordinate with other males.'
Unfortunately, populations of African elephants have plummeted over the last century due to poaching, retaliatory killing for crop raiding and habitat fragmentation.
Care must be taken to avoid hunting older socially connected male elephants, as their removal could disrupt social cohesion and mentoring structures within elephant populations.
'These findings provide further support that mature males, and perhaps certain individuals such as those leading the LGR events here, are important for male elephant society,' the team write in their paper, published in PeerJ.
'Additional variables, such as group size, rumble rate, or level of bondedness, might also impact departure duration and warrant further investigation.'
Another recent study found African bush elephants call each other by name – in other words, they use unique sounds depending on which elephant they were communicating with.
The findings suggest elephants may be capable of abstract thinking, making them much more socially complex mammals than previously thought.