Hippos are the third largest land mammal species on Earth, after elephants and white rhinos. The closest relatives of the hippopotamus are ...the whales and dolphins.2-3 million years ago, there were numerous species of hippopotamus, including outside mainland Africa in Europe (UK included), Asia (plus Sri Lanka), and Madagascar.Hippopotamus gorgops, which inhabited deeper waters than the current species, lived 120,000 years ago in the UK. 10,000 years ago, in Cyprus, Crete, Malta and Sicily lived dwarf species of hippopotamus. They were exterminated by humans. 1,000 years ago disappeared from Madagascar Hippopotamus lemerlei, a dwarf species, perhaps due to clime fluctuations and human hunting.
Only elephants are bigger than hippopotamuses: adult males can be 3 tonnes, and exceptionally 4.5 tonnes, heavy.
The hippo's proportions reflect its sedentary, amphibious existence. Its plump and bulky body is set on short, stumpy legs, with each foot having four toes. Although webbed, the toes splay enough to distribute the weight evenly over each toe and therefore adequately support the hippo on land.
With very thick skin, especially over the back and rump, the grayish-brown body is almost completely hairless, with only a few bristles around the mouth and the tip of the tail. The hippo has neither sweat nor sebaceous glands but does have unique glands that produce a viscous red fluid, leading to the myth that hippos "sweat blood." The hippo relies on water or mud to keep it cool, and the red fluid may have a similar function, but it is often produced in copious amounts when the animal is excited.
Hippos live in herds of 10 to 30. The dominant male can mate will all the females in the herd. If challenged, a male hippopotamus will fight using its long canine tusks. These teeth can grow a foot long.
The female Hippos give birth to a baby calf one at a time within a time span of two to three years. Before and after giving birth, the expecting mother isolates herself for a time period of 10 to 44 days along with the baby. The mother then nurses the baby for 12 months, stays by it in the early years and protects it. Just like other mammals the female Hippos feed their babies with their own milk, but one thing that differentiates the Hippo’s milk with others’ is its color.
A hippopotamus is born underwater. The mother helps her baby to the surface to breathe. Hippos bear single young. Calves weigh 55 to 120 pounds and nurse underwater. Mother hippos protect them from lions, leopards, crocodiles and male hippos. Sometimes calves will rest on their mother’s back.
Two hippo species are found in Africa. The large hippo, found in East Africa, occurs south of the Sahara. This social, group-living mammal is so numerous in some areas that "cropping" schemes are used to control populations that have become larger than the habitat can sustain. The other, much smaller (440 to 605 pounds) species of hippo is the pygmy hippopotamus (Choeropsis liberiensis). Limited to very restricted ranges in West Africa, it is a shy, solitary forest dweller, and now rare.
Amazingly agile for their bulk, hippos are good climbers and often traverse rather steep banks each night to graze on grass. They exit and enter the water at the same spots and graze for four to five hours each night in loop patterns, covering one or two miles, with extended forays up to five miles. Their modest appetites are due to their sedentary life, which does not require high outputs of energy.
Hippos mature at an average age of 7 (males) to 9 (females) years and have a life expectancy of about 45 years. On top they are brownish gray and underneath pinkish. Hippos have good sight, sense of smell, and hearing.