Wipe a hippo's face, and you get something akin to sweat, reports researcher Yoko Saikawa, a scientist with Keio University in Japan.
Sure, it's not produced by sweat glands like human sweat. Nevertheless, it serves the same purpose. Like sweat, it helps control a hippo's body temperature, explains Saikawa.
When the stuff is fresh, it is colorless like sweat. But in hippos, the mucus gradually turns red, then brown.
In their study, Saikawa and his fellow researchers wiped a hippo's face and back -- then tested the red mucus in their laboratory. As they filtered the mucus, red and orange pigmented solutions emerged. "We named the red pigment 'hipposudoric acid' and the orange 'norhipposudoric acid,'" Saikawa writes. The study appears in this week's issue of Nature.
The pigments are in the ultraviolet range, indicating that they "may act as sunscreens," he explains. The red pigment also acts as an antibiotic, protecting the hippo's skin from infections, he explains.
There's just one problem. Once they're off the hippo, these pigments become unstable and turn into solid, brown gunk within a few hours. What factor in the hippo's mucus keeps the stuff from changing form? That's yet to be discovered, says Saikawa.
Hippo sweat poses no immediate threat to the sunscreen industry -- at least not until the secret hippo ingredient is found.
SOURCE: Saikawa, K. Nature, May 27, 2004; vol 429: p. 363.