Scientific Name Hippopotamus amphibius
Conservation Status Vulnerable
The bulky barrel like body of the river hippo is covered by a purplish, brown hide. This has almost no hair on it and is 15cm (6in) thick. The underside and around the eyes, ears and cheeks are pink. Their legs are short in comparison to their body. Their feet are adapted for swimming as they have four webbed toes on each. Their eyes, ears and nostrils are situated on top of their head so they can remain out of the water while the rest of the body is submerged. These close over when the hippo submerges.
Hippos fight using their 50cm long canines which are housed in their large mouth.
Adult male hippos reach between 1,500 and 1,800kg (3,300 and 4,000lb). Females are smaller only reaching between 1,300 and 1,500kg (2,900 and 3,300lb). Males continue growing their entire life while females stop around 25.
From the head to the base of the tail river hippos measure between 2.7 and 3.5m (9-11.5ft). Their tail adds 56cm (22in) to their length. At the shoulder they can stand up to 1.6m (5.2ft).
An average river hippo will live for 36 years. The oldest living hippo though was able to reach 61 years of age.
River hippos are herbivores. They feed upon the plants which grow near their water home with grasses forming a large part of their diet.
At night hippos may travel up to 5km to reach their grazing area. They mark a path out with dung to lead the way.
Hippos do not need their large canine teeth to eat. Instead their strong lips will clip the grass and then their cheek teeth grind them up. Only 40kg of food needs to be consumed by the hippo each night as they spend most of their day floating in the water. They occasionally come into conflict with humans when they invade their rice crops.
Africa is the native home of the river hippo. They are native to Angola, Benin, Botswana, Burkina Faso, Burundi, Cameroon, the Central African Republic, Chad, The Democratic Republic of the Congo, Cote d’Ivoire, Equatorial Guinea, Ethiopia, Gabon, Gambia, Guniea, Guniea-Bissau, Kenya, Liberia, Malawi, Mali, Mozambique, Namibia, Niger, Nigeria, Rwanda, Sengal, Somalia, South Africa, Sudan, Swaziland, Tanzania, United Republics of Togo, Uganda, Zambia and Zimbabwe.
Their preferred habitat is estuaries and the lower sections of rivers. They have recently been found in reservoirs. These areas need to have grassland nearby where they can forage. On occasion they will enter rainforest areas if they have a large river running through them. During the rainy season they may wander from their home river.
Habitat loss due to agriculture has led to a decline in hippo numbers.
Only about 10% of the male hippos reproduce. These are the ones which control territory. Breeding peaks during the dry season. Both species mate in the water. Females are fully submerged only raising their head for air periodically. During this process the male will make a wheeze-honk sound.
Gestation last 227-240 days (approximately 8 months). After this a 25-55kg (55-121lb) baby is born. On a rare occasion twins are born.
The infant is adapted to suckling in the water. Whenever they are nursing their ears will automatically fold over and the nostrils will close.
Infants can remain underwater for up to 2 minutes but they will surface every 30 seconds on average. Calves will remain in the water when mum goes to forage. Suckling continues for up to a year. New research suggests that this may last longer in poor environmental conditions.
When they are resting the calf may sit on the back of the mother.
By 1 month old the calf is trying grazing and by 5 months they are spending a large amount of their time grazing. At 6-8 months of age the infants are weaned.
Sexual maturity occurs in captivity at 3-4years old while in the wild males mature at 6-13 years old and 7-15 years old for females. Young bulls do not have large amounts of reproductive success.
Once they are mature young males move off and become more independent. They will find a bank which they can patrol and attract females to join them.
Due to infanticide by adult and juvenile males a number of calves do not make it to this age. Females will attempt to defend the calf by running in sidewards at the male. This is the opposite of another male who would attack head on and takes the male by surprise.
Predators of the river hippo include large cats such as lions, hyenas and crocodiles. Humans also prey upon hippos for their meat and teeth which are made from ivory. Since hunting of elephants was banned hippo deaths have increased dramatically.
Up to 18 hours of a hippos day is spent in the water allowing them to keep cool. When in the water their specific gravity means they can walk along the base of the river. This adaptation makes it difficult for them to swim. They are nocturnal species choosing to visit their foraging grounds at night.
A hippo herd consists of 10-20 animals. A dominant male leads the herd of females and their young. He will fiercely defend his portion of river bank against rival males. The dominant male may tolerate another male in the territory if it behaves well but this one is not permitted to breed with the others. When grazing they are solitary.
Hippos are cleaned by a number of fish. They will regularly visit cleaning stations where they open their mouth to allow the fish to clean their teeth.
Main vocalizations made by the river hippo include a “wheeze-honk” and a roar.
Hippos are said to be the most dangerous animals in Africa.
The name hippopotamus comes from the Greek word for horse which is hippos and the Greek word for potamos meaning water.
River hippos cannot sweat. Instead they secrete an oily pink substance which protects from sunburn and is also thought to have anti-bacterial properties which keeps wounds clean and protects from infection in the dirty water.
A bill was almost passed in 1910 that would have seen hippos released in the bayous of Louisiana. The aim was that they would eat invasive fish and then provide meat during a time when supplies were low.
Top – By Kabacchi (Hippopotamus – 04) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons
Middle – By Hans Stieglitz (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Bottom – By BS Thurner Hof (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons