Asian elephant calls are more flexible than previously thought

By using an acoustic camera that visualizes sound pressure, a team of researchers from the University of Vienna has investigated the calls of Asian elephants. The analysis revealed that the animals emitted their low frequency “rumbles” mainly through their trunk, or through their trunk and mouth simultaneously, and only rarely through the mouth alone. 

Since elephants have the longest nasal elongation in the world, it is not surprising that their low-frequency, partially infrasonic rumbles resonate deeper when emitted through their long trunks. According to the researchers, these vocal tract resonances – known as nasal pronunciations in human languages – play a crucial role in animal communication, by allowing them to encode more information and enhance the transmission of the calls over long distances.

Humans form vowels through their tongue positions, lips, and mouth. By opening the velum and letting air stream through the oral and nasal cavities simultaneously, humans “nasalize” the sound of vocals, a feature which in many languages (such as French or Hindi) can change the meanings of words, as in the case of beau [bo] meaning “beautiful” in French and the nasalized bon [bõ] meaning “good.” 

Scientists have long thought that mammals have far less flexibility to modify their vocal tracts and thus the timbre of their calls. Although in animals calls often differ solely by being emitted through the mouth or nose, in the case of Asian elephants the situation appears to be more complex.

“To our surprise, the acoustic camera also clearly showed calls that were emitted through the mouth and nose simultaneously. The resonance spectra of these calls were very similar to the ones described in human nasal vowels,” said study lead author Veronika Beeck, a cognitive biologist at the University of Vienna.

These findings suggest that mammal calls may be more flexible than previously though. While it is well known that acoustic communication plays a critical role in social systems, such as the complex matriarchy of elephants, further research is needed to clarify the exact function of the mixed mouth-and-trunk calls that Asian elephants emit. 

The study is published in the journal Animals.

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By Andrei Ionescu, Earth.com Staff Writer