Facts about Hippopotamus

Hippos are characterized by a massive body structure, thick undulating skin almost devoid of hair, and a thick layer of subcutaneous fatty tissue. They lead an amphibious lifestyle and can stay underwater for long periods. Hippos are classified with other families of even-toed ungulates, including camels, cattle, cervids, and pigs. Nevertheless, hippos are not closely related to these animals.

Until 1985, naturalists grouped hippos with domestic pigs by suggesting the structure of their teeth. However, data obtained from the study of blood proteins, molecular phylogeny (path of ancestral development, origin, and evolutionary changes), DNA, and fossils indicate that their closest living relatives are cetaceans - whales, porpoises, dolphins, and others. The common ancestor of whales and hippos separated from other even-toed ungulates about 60 million years ago.

Because of their size, it is difficult to weigh such an individual in the wild. Based on estimates, it is assumed that the average weight of adult males is 1,500-1,800 kg. Although females are smaller than males, their average weight is 1,300-1,500 kg. Older males can weigh even more than 3,000 kg. Hippos reach their maximum body weight at the end of their lives. Females reach their maximum body weight at about 25 years of age.

Their head can weigh up to 225 kg. Hippos can open their mouths to a width of about 1 meter, and the length of their teeth reaches a maximum of 30 cm.

They mostly stay in the water during the daytime, showing activity after dusk and at night. Then they come ashore and nibble grass in meadows near the water (they also feed on aquatic plants). Moreover, they can venture up to 8 km inland in search of food. On land, despite their gigantic size, they can run faster than humans. Their speed ranges from 30 to even 50 km/h, but only over short distances, up to a few hundred meters.

Their trunk is barrel-shaped and hairless. Bristles are present only on the muzzle and tail. The legs are short, and the head is large. Although their skeleton is adapted to carry the significant weight of the animal, the water in which they live reduces their weight by the body's buoyancy. Eyes, ears and nostrils are placed high on the skull vault, allowing these animals to become almost completely submerged in the water and mud of tropical rivers. While submerged, the animals cool down, which protects them from sunburn. Hippos are also characterized by long tusks (about 30 cm long) and four toes connected by an amniotic membrane.

It is protected from the sun by a secreted substance that is natural sunscreen. This secretion, neither blood nor sweat, is initially colorless; after a few minutes, it becomes reddish-orange and eventually brown. It is made up of two pigments (red and orange), which are acidic solid chemical compounds, and the red pigment has additional bacteriostatic properties and is probably an antibiotic. Light absorption from both pigments has a maximum in the ultraviolet band, which protects hippos from excessive heat. Because of the color of the secretions, hippos are said to "sweat blood."

One of the world's oldest hippos, the 55-year-old "Hippolyte", died in 2016 at the Silesian Zoological Garden, Poland. He stayed with one partner, "Hamba", for 45 years. Together they lived to see 14 offspring. Unfortunately, Hamba passed away in 2011. The oldest known hippo living at the Mesker Park Zoo in Evansville, Indiana, was called "Donna" and lived for 61 years. The oldest ever recorded hippo was "Bertha", who lived for approximately 65 years in the Manilla Zoo, Philippines.

They spend up to 16 hours a day in it - as a way to cool off. They live mainly in freshwater habitats, but populations in West Africa mainly inhabit estuarine waters and can even be found in the sea. They are not the most skillful swimmers - they swim at a speed of 8 km/h. Adults are also unable to float but only stand in the shallows. On the other hand, juveniles can stay afloat and often swim by making movements with their hind legs. They surface to take a breath every four to six minutes. The young can close their nostrils while submerged. The process of surfacing and breathing is automatic to the point where hippos surface without waking up, even while sleeping underwater.

Females reach sexual maturity at 5-6 years and males at 7.5 years. Copulation of the pair occurs in the water. Pregnancy lasts for eight months. Hippos are one of the few mammals that are born underwater. Cubs are born with a weight of 25 to 45 kg and an average length of about 127 cm. Usually, only one cub is born, although twin pregnancies do occur. Breastfeeding also happens in the water.

They spend four to five hours a day eating and can consume up to 68 kg of food at a time. They feed mainly on grasses, sometimes on aquatic plants, and in the absence of preferred food, on other plants. There are also cases of scavenging and carnivorous behavior, predation and cannibalism, although hippos' stomachs are not adapted to digest meat. These are unnatural behaviors, perhaps caused by a lack of proper food. However, the authors of the Mammal Review journal claim that carnivorousness is natural for hippos. According to them, a meaty diet is typical for this group of animals, as their closest relatives - cetaceans - are carnivorous.

Studying the interactions of hippos is difficult because they lack sexual dimorphism - males and females are virtually indistinguishable. Although they stay close, they do not form social bonds. In the water, the dominant males defend a section of the river about 250 meters long, with about ten females per section. The largest herd consists of about 100 individuals. Copulation laws define these territories. In the herd, there is segregation by sex - they group themselves according to sex. When feeding, they do not manifest territorial instincts.

Their sounds are reminiscent of a pig's quack, although they can also roar. Their voice can be heard during the day since they do not speak at night.

They allow cattle egrets to sit on their backs since they rid their skin of parasites and insects that plague them.

They show aggression towards crocodiles living in the same water bodies, especially when young hippos are around. Attacks on humans also occur, although there are no reliable statistics. It is reported that about 500 people are killed yearly in clashes with hippos. However, this information travels from village to village without verifying the true causes of death. It is also rare for hippos to kill each other. When males clash, the fight ends with one recognizing the superiority of its opponent. It also happens that males try to kill the offspring or females try to kill a male in defense of the young - this happens only when food is scarce or the area occupied by the herd is shrinking.

They urinate backward and vigorously curl their tails during defecation to spread their excrement as far as possible.

The first images of these animals were cave paintings in the mountains of the central Sahara. One of them depicts the moment when humans hunt a hippopotamus. In Egypt, these animals were considered threatening to humans until females' protectiveness over their offspring was noticed. Since then, the goddess Taweret, protector of pregnancy and childbirth, was depicted as a female with a hippopotamus head.

In 2006, hippos were classified as a species at risk of extinction in the IUCN Red List of Threatened Species, with a population estimated at around 125,000 individuals. The primary threat to hippos is that they are cut off from freshwater reservoirs. However, humans also kill animals for their meat, fat, skin and upper tusks.

They are most often found in the oases, lakes and rivers of Sudan, Somalia, Kenya and Uganda, as well as Ghana, Gambia, Botswana, South Africa, Zambia and Zimbabwe. During the last glaciation, hippos also lived in North Africa and Europe, as they adapted to living in cold climates as long as they had unfrozen bodies of water at their disposal. However, they were exterminated by humans.

The animals were brought to Escobar's private zoo at the Hacienda Napoles ranch in the 1980s. Initially, the herd consisted of three females and one male. After Escobar died in 1993, the exotic animals from his private zoo were moved elsewhere, but the hippos remained. Since it was not easy to find transportation for such massive animals, they have lived undisturbed ever since. Because of the connotation of their former owner's profession, Colombia's hippos are called "Cocaine hippos".

Each season, their number in the Magdalena River basin grows more and more. Since residents of Medellin and the surrounding area have already become accustomed to their proximity, Cocaine hippos have become a local tourist attraction. The authorities do not consider the presence of hippos a problem. However, in the future, when their population grows to 400-500 animals, they could threaten the survival of other animals that forage in the same places.

Their population has almost doubled since 2012.

According to studies, hippopotamus droppings change oxygen levels in water bodies, negatively affecting aquatic organisms and humans. In addition, the animals destroy crops and are sometimes aggressive - a 45-year-old man was seriously injured after a "cocaine hippo" attack.

Enrique Zerda Ordonez, a National University of Colombia biologist, believes that neutering these animals would be an appropriate solution. However, it would be a challenging undertaking, given their size.