AskNature

“The rust-colored perspiration of the hippopotamus does more than keep the animal cool. Hippo sweat contains pigments that act as both sunscreen and antibiotic. Researchers at Kyoto Pharmaceutical University in Japan identified two such pigments, the red hipposudoric acid, and the orange norhipposudoric acid. Both are conjugated three-ring structures. The two compounds absorb light in the UV-visible range (200-600 nm) and so are thought to protect the hippo’s dermis from the sun. Additionally, low concentrations of hipposudoric acid inhibit the growth of bacteria. Both compounds are highly reactive, and tend to polymerize when removed from the hippo and/or a water source. An unknown agent in hippo mucus keeps the compounds from polymerizing for several hours, even after the hippo sweat dries.” (Courtesy of the Biomimicry Guild)

“The efficient sunscreen activity of NH and HP stems from their broad absorption in the UVA and UVB regions of the spectrum.” (Galasso and Pichierri 2009:2543)

“Although the fluid secreted by the hippopotamus (Hippopotamus amphibius) is not strictly sweat as it is produced by the subdermal glands, it acts like sweat in helping to control body temperature. It is also thought to be antiseptic…What is the function of these pigments as far as the hippopotamus is concerned? Their spectra in the ultraviolet/visible range (200–600 nm; see supplementary information) indicate that they may act as sunscreens. The red pigment 2 also has antibiotic activity: at concentrations lower than that found on the hippopotamus’s skin, it inhibits the growth of the pathogenic bacteria Pseudomonas aeruginosa A3 and Klebsiella pneumonia.” (Saikawa et al. 2004:363)