This is what an alligator on helium sounds like

Scientists had the reptile inhale the air

as part of an experiment

to understand how they communicate

The outcome?

Something between a grunt and a belch

(SOUNDBITE) (English) TECUMSEH FITCH, CO-AUTHOR OF STUDY “A CHINESE ALLIGATOR IN HELIOX: FORMANT FREQUENCIES IN A CROCODILIAN,” SAYING:

“Our question was whether alligators have vocal tract resonances like human speech. The key is that sound travels faster in helium. This makes the air passages seem shorter, making the resonances higher. So, if you breathe helium and the frequencies shift upward, that shows that they’re resonances. The hard part is getting an alligator to breathe helium.”

Source: Journal of Experimental Biology

Alligator ‘bellows’ are well known

but the function of their vocalizations remains unclear

(SOUNDBITE) (English) STEPHAN REBER, CO-AUTHOR OF STUDY “A CHINESE ALLIGATOR IN HELIOX: FORMANT FREQUENCIES IN A CROCODILIAN”, SAYING:

(REBER INHALES HELIUM) “Our subject was a Chinese alligator. (PLAYS VIDEO OF ALLIGATOR VOCALISATION). We recorded her inhaling normal air and heliox – a helium-oxygen mixture. And here we go, here’s one calling air and one calling heliox (AUDIO PLAYS OF ALLIGATOR VOCALISATION, THE FIRST ONE JUST AIR, THE SECOND WITH HELIUM). They sound different, they look different and this is evidence that also non-avian reptiles have resonances in their vocalizations.”

Video Transcript

[ALLIGATOR GRUNTING]

TECUMSEH FITCH: Our question was whether alligators had vocal tract resonances like human speech, and the key is that sound travels faster in helium. This makes the air passages seem shorter, making the resonances higher. So if you breathe helium, and the frequencies shift upward, that shows that they’re resonances. The hard part is getting an alligator to breathe helium.

STEPHAN REBER: Our subject was a Chinese alligator. We recorded her inhaling normal air and heliox, a helium-oxygen mixture. And here we go. Here’s one calling air and one calling heliox.

[ALLIGATOR GRUNTING]

STEPHAN REBER: They sound different, they look different, and this is evidence that also non-avian reptiles have resonances in their vocalizations.

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