Weird & Wild

Why Are Elephants and Other Animals So Wrinkly?

For African elephants, baggy skin keeps them cool in the hot sun.
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African elephants' wrinkles help them keep cool.


When you write a column called Weird Animal Question of the Week, it's inevitable that you get some smart-aleck inquiries. Recently someone asked me: "What happens when you put anti-wrinkle cream on an elephant?" (See National Geographic's elephant pictures.)

Any self-respecting pachyderm would turn up its trunk at such an offer. That's because those fabulous folds help keep the big mammals cool, Kathleen Garrigan, spokesperson for the African Wildlife Foundation, said via email.

Elephants have few sweat glands and can't use them for regulating their body temperature, so they disperse heat in other ways, including through their baggy skin. (See "It's Time to Accept That Elephants, Like Us, Are Empathetic Beings.")

"The elephant's wrinkled skin traps moisture in the hollows, which means it takes longer for the moisture to evaporate, thus keeping the elephant cooler for longer," Garrigan said.

"This helps explain why savanna elephants, who are exposed to the hot sun on the open savanna, tend to be more wrinkled than their forest elephant cousins, who are better able to keep cool under the forest canopy," she said.

African elephants are also more wrinkled than their forest-dwelling Asian relatives. Both species have sparse body hair, and a 2012 study in PLOS ONE showed that these hairs also assist the giants in dissipating heat.

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The loose skin of naked mole rats (pictured, an animal in South Africa) helps them burrow underground.


More Than Skin Deep

Elephants aren't the only creased creatures that benefit from wrinkles.

Take the naked mole rat, whose saggy skin makes moving around easier.

"All burrowing rodents have loose skin because they live in confined tunnels and need to turn around, virtually inside their skins," Bruce Patterson, curator at the Field Museum in Chicago, said via email.

The slack skin is more noticeable on naked mole rats, which "look funny because they're hairless."

Well, nearly: They do have sparse hairs that allow them to sense their surroundings. Blind and nearly cold-blooded, the African rodents stay safely underground, where the sun's warmth penetrates the shallow parts of their tunnels, Patterson said.

Naked mole rats are known for another reason: They live long, cancer-free lives, whereas mice and rats don't live long and have high rates of cancer.

In 2013, the journal Nature reported the chemical properties that make naked mole rat skin stretchy may also play a role in keeping them cancer-free. (See "Naked Mole Rats Unable to Feel Burning Pain.")

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The sharpei (pictured) likely got wrinkles from selective breeding.


Ironing Out Scientific Wrinkles

Wrinkles may be marks of character, but you'd be hard pressed to find anyone who would call them cute ... unless they're on a dog.

And the most famously furrowed dog is the Chinese sharpei.

In 2008, researchers at the Universitat Autònoma de Barcelona discovered a genetic mutation in the purebred that gives them their wrinkled appearance—increased production of a naturally occurring compound called hyaluronic acid.

The canine likely got its distinctive wrinkles from selective breeding, Joshua Akey, a genome scientist at the University of Washington in Seattle, said via email. (See your dog pictures submitted to National Geographic.)

Akey led a 2010 study published in the Proceedings of the National Academy of Sciences that analyzed the genomes of ten dog breeds. His team found 155 genomic regions that could have been affected by selective breeding, including a variation in the HAS2 gene, which affects wrinkling of the skin.

"You can think of it as a mutation that turns the faucet ... resulting in the production of more HAS2, which is the enzyme that makes hyaluronic acid," he said.

According to the American Kennel Club, sharpei wrinkles are "limited to the head, neck, and withers" in adult dogs; the breed is more wrinkly overall as puppies.

Anyone else want to call no fair on that?

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