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The hippopotamus is a chunky animal with a wide body and short legs. They can weigh up to two tons and big males often more than that. An average weight might be about 3300 pounds (about 1500 kilograms). They are chunky; have short legs, a short neck, a big head, with a cylindrical body and an arched back. One of the in-the-field characteristics of hippo country are the neat little trails they use to get from the water to the grazing areas. The chubby body and short legs means that they cannot step their own toes or cross their legs, nor can they trample a wide swath as they walk. The left legs make a narrow trail and the right legs make a separate narrow trail. For a big animal they seem to walk delicately through the bush. The two lane trails are obvious once you know what to look for.
They also make exit trails from the water where they spend the day. They leave the river via the same path each evening and break down the sandy edges of the river bank. These sloping trails to and from the water are what the migrating wildebeest and zebras use when crossing rivers. They descend along the hippo paths and hopefully they find another path, on the far side, that offers them an escape from the river (and the hungry crocodiles that just wait for the migration). The migratory beasts don’t plan well and sometimes get stuck against the far bank; sometimes with dire consequences.
Hippos are quite dangerous especially in the dark. They travel long distances from the water and they can panic if they feel separated from the water. Most people are hit by the large and heavy head of the hippo or are trampled as the hippo bolts for the water. It is an unpredictable animal, and very widespread, making it one of the most dangerous animals on the continent.
Hippos have an even number of toes; four on each foot. That is important as grazing animals, most land mammals, are divided into two groups – those with an even number of toes and those with an odd number of toes. The even-toed are the Artiodactyla and the odd-toed are the Perissodactyla. The latter group, odd-toed, contains the horses, rhinoceroses, and tapirs who balance on their hoof-covered, third digit. The former group, even-toed, contains the hippo, deer, goats, camels, pigs, bison, giraffe, antelope, and llamas and they walk on their third and fourth toes, often fused. This divergence in hand/foot structure goes back about 53 million years when the even-toed animals first appear in the fossil record. By the way, the word ungulate isn’t really a good taxonomical word; it usually refers to hoofed animals although it is often used to refer to the cud-chewing animals. And further by the way; a hoof is merely a modified toenail.
Like elephants, hippos are declining rapidly because of poaching. The large teeth are sought after for carving and for a wrongly presumed to have a medicinal value. Loss of wetlands and grazing habitat (mostly to farming) also is having an impact.
The hippo’s nearest evolutionary relative is an aquatic or semi-aquatic creature from which evolved the cetaceans and the hippos. The shared relative existed about 60 million years ago and the splitting of the ancestor into the two groups (whales and hippos) happened about 54 million years ago. You might Google Pakicetus to get a look at one of the earliest forms that is in the whale/dolphin/porpoise (cetacean) line. The hippo’s evolutionary relationship with cetaceans has been solidified with blood protein analysis and even more recent DNA work.