04 - may - 19


Hippos form a family comprising several species of certatiodactyl mammals relatively genetically close to cetaceans and to a lesser extent suids (or pigs designate a family of artiodactyl mammals whose common characteristics are having canines developed and legs terminated by four tabs like warthogs, bush pigs …) and ruminantia (herbivorous mammals that ruminate like sheep, goats, antelopes …).

They were traditionally classified in the ungulates before phylogenetic studies revealed them as cetartiodactyls. Many species have disappeared but there are still two living: the best-known species, the hippopotamus called amphibian and the dwarf hippopotamus.


Hippos are typically aquatic animals with barrel-shaped bodies. Their legs form pillars. The legs of the dwarf hippopotamus are slenderer and clearly more suitable for walking.

Its four fingers are free, not being connected by a membrane and the nails are pointed.

This allows it to adhere well to the soil, even if it is uneven, in its living environment consisting of backwaters and wet undergrowth. Hippos have a big head with a wide mouth that can open up to 180 degrees, with imposing tusks inside which can measure more than 60 cm in male amphibious hippos. Their eyes, ears and nostrils are placed at the top of the head.

Their nostrils can close by contraction when they dive. Likewise, their ear canals get blocked when they move underwater. The two hippopotamus species differ in particular in the shape of the ears, the browbones are much more pronounced in the amphibian hippopotamus.

The male’s testicles are found inside the abdominal cavity (like in the rhino). Males are known to have a more grayish appearance than that of females which have a hue turning towards purplish.


Hippos do not have sebaceous glands and sweat glands. The only way they can regulate their internal temperature is the loss of trans epidermal water. Their skin is glabrous and secrete, to protect themselves from the sun, a kind of reddish natural sunscreen sometimes called “blood sweat”, although it is neither blood nor sweat. This mucus with hydrating power, initially colorless, turns orange-red after a few minutes, and finally becomes brown.

Two different and extremely acidic pigments have been identified in the secretions, a red and an orange. The red pigment is hipposudoric acid and the orange pigment norhipposudoric acid.

It has been discovered that the red pigment inhibits the growth of pathogenic bacteria, which suggests that the secretion has an antibiotic effect. The absorption of light by these two pigments is maximum in the ultraviolet range, which is equivalent to the effect of sunscreen.

As hippos secrete these pigments all over the world, it does not seem that it is their food that is the source.

Instead, animals can synthesize pigments from precursors like the amino acid tyrosine.


The hippopotamus is present on practically the whole extent of the Gabonese territory. It can mainly be seen in 2 national parks :

– le parc national de MOUKALABA DOUDOU
– le parc national de LOANGO