The hippopotamus belongs to the family Hippopotamidae, which consists of only two species, namely the Common Hippopotamus (Hippopotamus amphibious), which we will be discussing below, and the Pygmy Hippopotamus (Choeropsis liberiensis).
The name Hippopotamus is derived from the ancient Greek word hippopotamus, which was a name given to a large, barrel shaped animal that was seen in Africa. It is a combination of the words ‘hippos’ meaning horse, and ‘potamos’ meaning river.
It is mostly regarded as a herbivore, although there are records of this species feeding on meat, which is often as a result of a lack of suitable grass and other plant matter. Hippos are considered to be the third largest land mammal after elephants (Loxodonta africana) and the white rhinoceros (Ceratotherium simum).
They have large barrel-shaped bodies and short legs and a head with an enormously expanded muzzle, which is noticeably larger in males. They can weigh between 1,600 - 3,200kg, while females typically weigh around 1,400kg. The skin colour ranges from a brown to grey-purple with pink underparts. It is mostly naked and smooth except for short bristles on the head, back and tail. They have no scent or sweat glands, but mucous glands secrete a viscous red fluid that dries like lacquer and serves to protect the thin epidermis against water loss, sunburn and possibly even infection.
It is a species recognised by its large jaws and formidable teeth, with canines and lower middle incisors enlarged, again, especially in males. The incisors continue to grow and are also referred to as tusks. These may grow to lengths of 50cm and are kept sharp by honing against short upper canines. Hippos can live for around 40 years.
The hippopotamus is an African species and used to occur in suitable habitats everywhere south of the Sahara. Over the years it has become extinct or rare in areas that are very populated. In protected reserves and national parks, like the Kruger National Park, they can reliably be seen along the major rivers, dams, waterholes and may even be encountered out on land away from water during the cooler months, or early mornings before they have returned to their resting pool of water.
The two essential requirements is water deep enough to submerge in and nearby grassland. Because they don’t have sweat glands, a hippo out of water, in hot weather risks rapid dehydration and overheating. They therefore, spend most of their time during the day submerged in water, and typically only leave the safety of the water during overcast days when it is cooler, or at night. When hippos go underwater, they automatically fold back their ears into recesses and close their nostrils.
Mature hippos can stay under water for at least 5 minutes, but on average surface every 1 to 2 minutes. As they surface, their nostrils open wide, releasing the pent-up breath and ears spring erect.
Hippos rise to breathe even in their sleep. This is an involuntary act, just as breathing. Swimming hippos, in effect, gallop under water and may also walk on the bottom. Hippos have large muscular lips used for grazing and prefer short grass where they can consume around 40kg during a single night. They feed with intent, rapidly and noisily and may have a devastating effect on vegetation and soil. On land, they look clumsy but can gallop at speeds in excess of 30km/h.
Hippos are a gregarious species and enjoy contact while in the water, but are solitary when out of water, foraging. Only females with young and dependant offspring will graze together. Their sheer size and aggression allows them to graze on their own and not have to be in a group for safety. Herds typically number between 10 and 15 individuals, but range from 2 to 50 and, in some instances, as many as 150 in suitable large bodies of water. On average the density in lakes is 7 hippos/100m of shoreline and 33/100m in rivers. Numbers at a waterbody increase during the dry season, but disperse again during rains and as smaller streams and pans that dried up during the dry season fill up again.
The hippopotamus is a territorial animal and mature bulls will aggressively defend their territory. Although the dominant bull may successfully defend his territory for a number of years, variable climatic conditions which cause major changes in grouping patterns and density can cause territorial turnovers every few months.
Territorial bulls will usually tolerate bachelor males within their domain and even in cow herds, so long as they behave submissively and refrain from sexual activity. Lone hippo bulls may be either outcasts or territorial bulls without herds. Territorial bulls have frequent ritualised encounters. After approaching the common boundary, they stop and stare at each other, then turn tail, elevate their rumps and shower dung and urine over each other by rapidly flicking their tails from side to side. They then withdraw back into their territory.
Hippo dung middens are used for territorial marking and can be found along paths usually close to the water. There is still some speculation as to the territorial significance. Some believe these are purely used by the dominant bull, while others believe various passing hippos add their excrement, which may well assist in orientation and communication at night.
Bulls may also emerge during the day to defecate on rocks and/or islands in the water. Bull excrement is particularly smelly and interesting to other hippos. A juvenile may often be seen following a bull to a midden, intently smelling or licking his anal area, and then spends minutes nosing and even eating his excrement. While in water hippos advertise their presence by honking and grunting loudly.
The bulls often using the vocalisation as a form of establishing territory. Bulls may also be seen ‘yawning’ as a threat display – hereby showing off their formidable tusks.
The infrastructure of female herds remains to be explained. Although herd composition may remain fairly consistent for several months at a time, there appears to be no close ties between cows. Each female looking out for what’s best for herself and her offspring. Maternal bonds with daughters persist to the sub-adult stage.
Breeding in hippos is not strictly seasonal but most conceptions probably occur in the dry season, with most births peaking during the rainy season. They have a gestation period of 8 months and calve at 2-year intervals and only conceive for the first time at around 9 years of age. Bulls questing for mating opportunities may wander through basking nursery herds sniffing for receptive cows.
Bulls risk being mobbed should the cows become disturbed. To avoid this, the bull moves carefully and at the first sign of trouble lies down in a display of submission that is unusual for dominant males. Once an estrous female is located, courtship displays lead to the water where the two may clash jaws before the bull forces the cow into submission to initiate copulation.
During this time the females head is often forced underwater, and when she raises it to breathe, the bull may snap at her. Prior to calving, the cow will isolate herself and only rejoin the herd after about two weeks. Calves weigh on average between 22 and 55kg at birth and are adapted to nursing underwater. When suckling out of water, the typical underwater flattening of ears and closing of nostrils still occurs. By 1 month of age, calves may start grazing a little and in more earnest by 5 months, being weaned from the mother by 8 months.
Expectant and new mothers tend to be savagely protective, keeping other hippos at a distance and length, jaw snapping and moaning may be observed between a mother and a soliciting bull. The bond between a mother and calf is close. The mother licks, nuzzles and scrapes the calf with her lower incisors and calves reciprocate.
At times small calves may be left in creches guarded by one or a few hippos while their mothers are away grazing. When the young accompany the mother on land, any tendency to stray will be swiftly punished by nudging, sideswiping, or even biting the calf. Calves left in creches often engage in play-fights and chasing games.
The sheer size of a hippo will make any predator think twice before trying to attack. Adult hippos are typically only preyed on by lions (Panthera leo) and usually only when they are far enough from water to warrant an attack.
Hippos will retreat to water when in danger and defend itself with its formidable jaws, if prevented from doing so in any way. Even if a hippo is surrounded by lions, its strength can still allow it to run towards the safety of water with lions hanging on. Calves are an easier target and may become a target for hyenas (Crocuta crocuta). While in water, hippo calves are in danger from attacks by crocodiles, if they venture away from the mother.
For centuries, people and hippos have lived side by side, both being dependant on water. Through large parts of Africa, rural villages can be found all along the major rivers. The people using the river for fishing, washing and a means of transport to another area.
Hippos are as dependant on these rivers and it is therefore no surprise that humans and hippos would clash at some point. Territorial bulls and cows with young are very aggressive and will not hesitate to attack anyone who dares to venture too close. For the most part humans have learned to live side by side with hippos, but regular accidental interactions often lead to human deaths.
Few situations can be as dangerous as coming between a hippo and water. Hippos retreat to water for safety and often villagers use these same hippo paths to go down to the river to wash. These confrontations seldom turn out in favour of the person involved. Besides villagers relying on these waterways, canoeing on rivers such as the Zambezi River and in places like the Okavango Delta - a major tourism attraction, also means more chance of hippo and human interactions.
It’s for this reason that the hippopotamus is largely regarded as the animal responsible for more human deaths than any other dangerous animal in Africa. In fact some would go as far as to say that hippos kill more people than all of the Big 5 (lion, leopard, elephant, buffalo and rhino) put together.
There is an amusing tale of hippos and how they live and it goes like this…
When hippos were created, they were made with all the leftovers. Hippo wasn’t happy about how he looked and complained to their Creator. He was embarrassed at his big fat body and wanted to live in the water where he could hide from the mocking of the other animals.
The Creator however refused and told hippo that he could not be trusted to live in water with his big mouth and that hippo would eat all the fish. Hippo denied that he would do that and, in response, promised to only spend the day in the water and by night, he would leave the water so that the other animals would not see him. He also promised to only graze on grass. The Creator was still not sure hippo could be trusted and refused.
After days of moaning and begging, the Creator finally agreed to let hippo have his way. A condition however, was that everyday upon leaving the water, hippo would have to scatter his dung to prove that he had only eaten grass and that there were no fish bones. To this day hippos still live in water, coming out at night to graze and scatter their dung.
Be sure to look out for this animal when on your next Kruger Park safari. This is one of the best places to see the hippopotamus and it can be found in all the larger rivers and permanent dams throughout the park.
You may even be fortunate enough to see a hippo out of water during the early hours of the morning before it returns to the water. Camps such as Lower Sabie, Berg en Dal, Olifants, Mopani and Shingwedzi are reliable camps to not only see but also hear hippos.
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