The ultimate sunscreen

The hippos' secretions are a mixture of pigments that function both as sunscreen and antibiotic.

The colourful secrets of hippopotamus sweat have been uncovered. Researchers have identified the chemicals responsible for the timeless myth that hippopotamus sweat blood.

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The blood red secretion is a familiar sight to anyone who has come face to face with a hippo.

"It's all over their back, face and behind their ears. It really does look like blood is pouring down them, "Craig White, a zookeeper at Whipsnade Wild Animal Park in Britain was quoted by Nature as saying.

Kimiko Hashimoto and his colleagues at Kyoto Pharmaceutical University, Japan, revealed that hippos' secretions are neither blood nor sweat, but a mixture of pigments that function both as sunscreen and antibiotic. This mixture keeps hippos' cool and protects them from the harmful effects of the sun.

The hippos tend to produce more of the 'Scarlett Sweat' when on dry land rather than when they are in water, bolstering the idea that the secretions are similar to sweat. However, other experts have suggest that it works like waterproofing.

Hashimoto's team used gauze swabs to collect the fluid from the faces and backs of two hippos, Satsuki, a female, and Jiro, a male, living at Ueno Zoological Garden in Tokyo.

The Japanese team analysed the chemical make-up and found two pigments, one red and one orange, which they christened Hipposudoric Acid and Norhipposudoric Acid, respectively. It is these compounds that give the hippos their ruddy appearance.

The researchers then set about testing the theory that pigments function both as a sunscreen and an antibiotic. They concluded that the compound does shield hippos from harmful ultra-violet rays.