Photograph by Michael Nichols, National Geographic Creative

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A yawning mountain gorilla shows off its fangs.

Photograph by Michael Nichols, National Geographic Creative

Why Do Plant-Eating Gorillas Have Big, Sharp Teeth?

We're delving into the choppers of the animal world for Weird Animal Question of the Week.

For Weird Animal Question of the Week, we’re sinking our teeth into two reader queries about animal choppers.

First we have six-year-old Henry from Denver, Colorado, who asked: “Since gorillas are herbivores, why do they have such big teeth?”

First off, teeth aren’t just for chomping flesh. Gorillas eat a lot of heavy twigs and bark, which requires tough teeth—particularly molars—to grind all that tough plant material, according to Peter Emily, founder of the Peter Emily International Veterinary Dental Foundation. The organization, based in Colorado, provides dental care for domestic and captive animals worldwide.

What about the gorilla’s long, sharp canines? They’re used for display, in particular “to defend against external threats, as well as fend off other male gorillas competing for dominance,” Kathy Garrigan, of the African Wildlife Foundation, said via email.

Emily notes that with the exception of humans, all primates have those long canines. (Read about how our teeth evolved.)

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An African elephant, Malalka, shows off its tusks in Kenya’s Tsavo East National Park.


Continuing the tooth trend, reader Danny Huynh wondered, “Why are elephant tusks hollow?

Tusks may “look like canines that have become long,” but they’re actually the elephant’s incisors—the narrow teeth at the front of the mouth, Emily said.

And, like our own teeth, a tusk has a hollow chamber containing blood, nerve, and pulp tissue that keep the tooth nourished and strong. (Also see “Elephants Use Their Trunks to Ace Intelligence Tests.”)

A part of the tooth called the apex, which is located in the jawbone, “allows plenty of space for the pulp that lets the tooth grow,” Alexander M. Reiter, of the University of Pennsylvania School of Veterinary Medicine, said via email.

When an animal loses a tusk, “all the soft tissue inside of it will have disappeared, and then it appears as if the tooth has always been hollow.”

Hippo Root Canal

In his four decades of animal dentistry, Emily has seen some of the world’s weirdest choppers. (Also see “The Real Story of ‘The Incredible Dr. Pol.’”)

“They are made the same—with enamel, dentine [hard, calcified tissue], and a ligament to support them inside the jawbone”—but the shape and size can vary wildly, he said.

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A toothy wolf eel emerges from its rocky den.

The wolf eel, for example, “has a whole row of teeth right in the roof of his mouth,” called palatal teeth, in addition to long canines. Both types are ideal for crushing crabs and other crustaceans. (You can see a wolf eel’s upper jaw in this photo.)

Emily hasn’t worked on a wolf eel, but “I’ve done root canals on hippos,” he said.

It’s not easy: A normal dental drill won’t work on hippos’ large, round, ever-growing incisors, which means you “have to cut the nerve out with a scalpel.”


That’s all in a day’s work for Emily, who will even do dentistry on animals with no teeth.

Birds, for example, use their beaks for feeding and numerous other functions, and may have problems if a beak doesn’t fit together quite normally (think a human overbite). (See “Rare ‘Smiling’ Bird Photographed in Colombia.”)

Emily has made appliances to straighten the crooked beaks of birds, as well as prosthetics to repair broken beaks so they can function properly.

“Human have orthodontics,” he said. “This is ortho-beakics.”

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