The river horse

Probably one of the oddest looking and most intimidating animals in Africa is the hippopotamus (literally translated, river horse).  Hippos are uniquely amphibious, spending most of their day in the water but their nights on land foraging.

Basking hippos, Kruger Park, South Africa

Although occasionally, hippos come out for a sunbath on land.  Their skin may be six inches thick but is still subject to sunburn.  Unlike elephants that throw dirt on their wet skin to protect it, hippos secrete an oily substance from their skin that reflects ultra-violet light, a “hippo sunscreen”.

Hippos foraging at sunset, Chobe national park, Botswana

Out on land just at sunset, the nightly grazing on grasses begins. Hippos might travel 6-10 miles to find enough grass to sustain them for one day.  But surprisingly, this 1.5-2 ton animal eats just 80-100 lbs of food per day, because it has a multi-chambered stomach (like cows) which increases its digestive efficiency.

Despite their short, stubby legs, flat, webbed feet, and rotund girth, hippos can move quickly on land, up to 20 mph (30 kph), at least for short distances, so it would be a mistake to try to outrun one.  Their bulky weight is supported in water of course, where they seem much more “graceful”.

A pod of hippos

Eyes, ears, and nostrils are displaced to the top of a hippo’s head, so they can keep tabs on their environment while floating (well, actually while standing on the bottom).

A pod of hippos

Usually one bull hippo controls a stretch of river or lake area in which dozens of females, calves, and bachelor males hang out in social groups.

Hippos are aggressive, especially when they feel threatened, and their great bulk and quick movements mean humans should maintains respectful distance.  But sometimes, a hippo surfaces for air closer than is comfortable, requiring a speedy retreat.

Hippo in Okavango delta

Fortunately, not an aggressive one, it left our little boat alone.

Hippo yawn, or threat display

But this one may be warning us away, or it could just be a bored yawn.  Those projecting lower canine teeth can grow to 1.5 foot length in big bulls, and do serious damage even to thick-skinned hippos.

Hippo yawn, or threat display

No, this looks more like a threat display, with head raised above the water, and jaws open almost 180 degrees. It kind of reminds me of the Animal on the Pez candy dispenser.  The only reason to open its mouth this wide must be to intimidate or do physical damage to another hippo.  Sort of a “my teeth are bigger than yours” contest…

Small front incisors are used to cut the grass, rear molars are useful grind it before passing the food into the chambered stomach.  Unlike cows, hippos don’t regurgitate the mix and chew their cud.  Projecting canines are used as weapons.

But the most amazing thing to me about hippos is that they are not at all related to the other, diverse, grazing ungulates of the African savanna! nor are they at all related to horses (despite being called the river horse).  Instead, there is clear genetic evidence that their closest relatives are the whales, dolphins, and porpoises.  The common ancestor of hippos and whales branched off well before grazing animals like antelope and horses appeared in the fossil record.

12 thoughts on “The river horse

  1. Hi Sue, Very nice photos of the hippos! I know you have a good telephoto lens so you didn’t have to get too close to them. Most of what you wrote I was familiar with, but I had no idea that they are most closely related to whales, dolphins, and porpoises! That is so interesting. I think I will have to investigate that a bit more. When I get back to the Cities, I will let you know as I would love to hear firsthand from you and Steve about your Africa trip. Shannon

  2. Fascinating facts and wonderful photos,Sue. Your reminder about the origin of the animal’s name and the comment about its speed makes me conjure up images in my mind of a hippodrome with racing hippos rather than horses. Yikes!

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