Wapiti. Elk. North American red deer. Whatever you choose to call them, their shrieks biting through the forest or tearing across the plains can sound worryingly like the other-worldly wails of a Ringwraith, ripped straight from the pages of the Lord of the Rings.
The similarity between those bone-chilling voices and the cries of the wapiti has long perplexed scientists, curious as to how such a big animal could produce such a high-pitched sound, but new research published Wednesday in the Journal of Experimental Biology throws some light on the paradox.
It turns out the wapiti does indeed utter the low roar one would expect from a creature of its stature, but that deep rumble is usually overshadowed by the other sound it makes, a bugle sound likely produced using a separate mechanism.
“One key element encoded in vocal information is about size – bigger animals tend to have lower frequency vocalizations, while smaller ones have higher,” says lead author David Reby of the University of Sussex, UK, in a telephone interview. “If you look at most large deer, they follow that rule. In the case of wapiti, their vocalization pitch is what you would expect from very tiny animals.”
The phenomenon has been studied before, but a satisfactory explanation had so far eluded scientists. This latest effort was prompted by postdoctoral fellow Megan Wyman’s trip to New Zealand, where she made some high-quality recordings of the calls in question.
Previous work had focused on the wapiti’s larynx – the voice box – and had assessed that it was capable of producing bellows as high as 1,000 Hz in pitch. But the wails from the wapiti reach far higher, up to 4,000 Hz.
Through the analysis of spectrograms – tools that produce visual representations of sounds – the researchers were able to establish that two separate sounds were being made.
“They use a low-frequency roar, but also a whistle,” explains Dr. Reby. “The fact they’re doing both simultaneously is quite unique. There are some similar cases, but usually one of the sounds lies in the ultrasonic range.”
Fortune smiled on the team, when a colleague at France's Muséum National d'Histoire Naturelle made contact to say that a male wapiti from that institution had passed away, offering Reby the chance to take a closer look at the mechanisms involved.
While the work was still inconclusive as to how the higher calls are actually produced – though they did come away with two theories – the scientists have some shrewd guesses as to their purpose.
One possibility is that the whistles communicate information about an individual’s size, with a bigger lung capacity providing the ability to make higher-pitched whistles.
But Reby suggests that the most likely explanation lies in the long distance these wails can travel – helpful in the hunt for a mate.
“People will tell you they hear the bugle calls many miles away, whereas they don’t hear the low roar,” says the professor. “Thus the animals can be detected by potential partners far away.”