Hippopotamus amphibious - Red sweat
The name ”hippopotamus” comes from the ancient Greek for “river horse.” Hippos are actually more closely related to whales and dolphins than horses.
The scientific name of the common hippopotamus is "Hippopotamus amphibious", which reflects its dual existence in water and on land. Hippos don’t have sweat glands. They spend much of their day in water or wallowing in mud to escape the hot African sun, although they will come on to land to lie down if the temperature is not too hot. Their eyes and nostrils are located high on their heads so that they can stay partially submerged in water but can still see and breathe. At dusk, when it’s cooler, hippos become active. They eat mainly grass and spend up to six hours feeding during the night. They may travel as far as six miles looking for food.
Hippopotamuses can live for up to forty to fifty years, but their wild populations are under pressure. There's still much to learn about these animals, but they are difficult to study due to their aggressive tendencies and their fondness for traveling underwater.
Hippo skin is virtually hairless and would soon burn when exposed to intense sunlight, but the skin secretes an oily liquid that acts as a sunscreen. The secretion is colorless to begin with, but quickly turns red.
Two pigments have been found in the skin secretion of the hippopotamus - hipposudoric acid, which is red, and norhipposudoric acid, which is orange. Hipposudoric acid has been found to be strongly anti-bacterial, even at low concentrations. The skin secretion absorbs ultraviolet radiation, and also contains crystalline structures that scatter light.
The hippo's antibiotic sunscreen is intriguing to scientists, who would like to replicate the sunscreen, or at least some of its components, for humans to use.
The International Union for Conservation of Nature (IUCN) has created a seven-category “red list” which indicates how close a species is to extinction. The categories, in order of seriousness, are:
1 - Least Concern
2 - Near Threatened
3 - Vulnerable
4 - Endangered
5 - Critically Endangered
6 - Extinct in the Wild
7 - Extinct
Hippos are classified as “vulnerable” due to the destruction of their habitat as land is cleared for agriculture and for human settlement. The hippopotamus is also hunted for its meat and the ivory in its large canine teeth or tusks.