(ANIMAL KINGDOM) Thanks to unusual vocal cords, making that ferocious lion roar is easier than it sounds. New research shows that the lion vocal cord has a layer of fat in addition to a unique shape that makes it a perfect instrument for that famous roar. Read more for the science behind the king of the jungle’s roar and how human babies share this attention-grabbing trait. — Global Animal
New York Times, Ritchie S. King
In the open savanna, a lion’s roar travels up to five miles, proclaiming the extent of its territory: If you can hear it, get out.
It turns out that the strength of the roar is not just a matter of kingly lung capacity. New research shows that lions, along with tigers, have unusual vocal cords that are fine-tuned for making loud and rough-sounding noises even without a lot of respiratory exertion.
Vocal cords consist of two membranes that vibrate to produce sound when the muscles of the voice box bring them close together. In most vocal species (with the exception of birds, which have no vocal cords), the two membranes are slightly curved. But in the large cats, an uncommon layer of fat shapes the cords into flat pads that vibrate more easily.
“It’s an incredibly efficient instrument,” said Ingo R. Titze, a biophysicist, head of the National Center for Voice and Speech at the University of Iowa, and author of the study, which appeared in the journal PLoS One. “You don’t have to kill yourself to make a sound with it.”
To uncover the physics of roaring, Dr. Titze and his colleagues built computer models of the vocal cords of both lions and tigers based on measurements of tissue samples taken from zoo animals that had been euthanized because of old age. The models enabled them to see how different exhalation strengths make the vocal cords tremble.
The researchers discovered that the layer of fat not only helps shape the vocal cords but also makes them vibrate erratically, endowing roars with that rough, mind-hijacking quality. It turns out that human babies also have fattier vocal cords, and Dr. Titze suspects that may make their crying especially attention-grabbing.