Air Date: Week of June 4, 2004

Living on Earth’s Susan Shepherd reports on the all-natural sunscreen secreted by the hippopotamus.

Transcript

CURWOOD: Just ahead: one man’s roadkill is another man’s trophy—that is, if you’re a taxidermist. First, this note on emerging science from Susan Shepherd.

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SHEPHERD: If we had the same sweat glands as the hippopotamus, we’d have little use for the sun blocks and anti-infection creams cluttering our medicine cabinets. Japanese researchers studying the secretions of Hippos say these hairless river horses literally sweat sunscreen. And this slow-setting lather doesn’t just protect them from the hot equatorial sun – it doubles as an antiseptic to help heal wounds as well.

Scientists at the Kyoto Pharmaceutical University in Japan recently discovered the sweat salving powers by analyzing swab samples taken from Hippos at a Tokyo zoo. They found the Hippo sweat is made up of two pigments – one red, called “hipposudoric acid”, and the other orange, dubbed “norhipposudoric acid.”

At first the Hippo’s sweat is a colorless, sticky liquid, but it gradually turns blood red and then darkens as the pigments bond to form a polymer. This plastic shell of sorts that absorbs ultraviolet light, just like commercial sunscreens. Scientists found the red pigment also makes a good antibiotic, which may explain why Hippos, when nicked and cut from their frequent scraps with rivals, don’t seem to get infections. But researchers are not rushing to parlay this sweat science into any human-friendly skin applications. That might be because Hippo body odor is far smellier than our own.

That’s this week’s note on emerging science, I’m Susan Shepherd.

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CURWOOD: And you’re listening to NPR’s Living on Earth.

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