By Dr. Becker
Hippos spend up to 16 hours a day in the water, and despite their large somewhat-awkward presence on land are graceful, adept swimmers. This gives clues to their origin, although fossil evidence long suggested the hippopotamus was related to an ancient, pig-like mammal.
Over the last decade, however, DNA evidence has suggested that hippos are the closest living relative to whales. What was missing was fossil evidence to confirm what the DNA suggested.
It was thought that hippos' ancestors were anthracotheres, which are long-extinct semi-aquatic mammals, but this ancestor was never found — until now.
Sheep-Sized Hippo Ancestor Discovered
Paleontologists from the University of Montpellier in France were browsing through fossils at the Nairobi Museum in Kenya. They were intrigued by a jaw from an anthracothere, which was found in Kenya's Turkana Basin.
They returned to the site and found a new spot with softer rock that made it easier to excavate. Several teeth from a new anthracothere species were uncovered, and the molars had the unique three-leaf pattern that is similar to molars in modern-day hippos.1,2
The new species, which is thought to have been about the size of a sheep, was named Epirigenys lokonensis — "'epiri' means hippo in the Turkana language and Lokone after the discovery site."3 Discovery News reported:4
"E. lokonensis was not a direct forefather of today's hippo, belonging instead to a side branch. But it lived much closer in time to the ancestor from which they both branched off, thus allowing for inferences to be drawn about the ancient animal.
Dental analysis led the team to conclude that E. lokonensis and the hippo both came from an anthracothere forefather, which migrated from Asia to Africa about 35 million years ago. As Africa was then an island surrounded by water, it likely swam there."
Interestingly, while many people associate Africa with animals like lions and antelopes, these animals came to the continent from Asia. Hippos, on the other hand, first evolved in Africa making them one of the first animals to colonize there. Paleontologist and study co-author Fabrice Lihoreau explained:5
"We filled a gap in the evolutionary history of the hippo, bringing us closer to the point of divergence from their modern-day sister group of cetaceans [i.e., whales, dolphins and porpoises]."
Do Hippos Sweat Blood?
Hippos secrete a red, oily substance that looks sort of like blood, hence the myth that hippos sweat blood. The red substance acts as a skin moistener and sunblock and may even help protect the hippo from germs.6
They spend most of the daylight hours submerged under water to stay cool, then venture onto land as the sun sets to eat. Hippos are herbivores and eat mostly grass — up to 80 pounds a night. According to National Geographic:7
"Considering their enormous size, a hippo's food intake is relatively low. If threatened on land hippos may run for the water — they can match a human's speed for short distances."
There are two species of hippos in Africa. The large hippo weighs 5,000 to 8,000 pounds and lives up to 40 years in the wild. The other species, pygmy hippos, is much smaller — 440 to 600 pounds. Pygmy hippos are solitary and live in the forest, although their range is very limited and they're now rare in the wild.8
"Hippopotamuses are among the most dangerous animals on earth because they are known to charge humans when threatened.
Unfortunately, since their habitat is mostly gone, they are forced to forage among crops, which in turn causes them to come face to face with angry farmers.
It is during these interactions with humans, as well as unwary fishermen, that hippos and humans come together, a situation that will almost always end in death.
Despite its speed, size and aggression, the hippo is no match for a human with a powerful gun, so it's usually the hippopotamus that loses her life."
Hippos Are Disappearing
Many large herbivore species are disappearing, and this includes the hippopotamus. Habitat loss due to human encroachment, cultivation, and deforestation is a major concern.
Hundreds of hippos are also killed each year due to human-wildlife conflicts, although ditches or low fences present a simple way to deter hippos from entering cropland.11
Hippos are also valued for their meat and ivory, making them prime targets for hunters and poachers. The International Union for Conservation of Nature and Natural Resources (IUCN) Red List classifies hippos as a vulnerable species, which is one step before endangered. According to IUCN:12
"The most recent population estimates suggest that over the past 10 years there has been a 7–20% decline in Common Hippo populations.
Over three generations (approximately 30 years), it is likely the population reductions will exceed the 30% size reduction considering both past and future.
Although the causes of the population decline are known (exploitation and habitat loss), the threats have not ceased nor is there evidence the threats will be removed in the near future."
If hippos disappear, there could be enormous impacts on the environment. The hippopotamus helps to maintain pathways in swamps, which leads to new channel systems. The areas they graze also tend to be more nutritious, and birds are known to coexist with hippos, eating insects off their bodies.