hippopotamus

hippopotamus
Hippopotamus ( Hippopotamus amphibius )
Systematics
Subclass : Higher mammals (Eutheria) Superordinate : Laurasiatheria Order : Artiodactyla (Artiodactyla) Family : Hippos (Hippopotamidae) Genre : Hippopotamus Type : hippopotamus
Scientific name of the  genus
Hippopotamus
Linnaeus , 1758
Scientific name of the  species
Hippopotamus amphibius
Linnaeus , 1758

The hippopotamus ( Hippopotamus amphibius ), also known as the large hippopotamus , is a species of mammal belonging to the hippopotamus family and the cloven-hoofed order . It is now the only member of the genus Hippopotamus . After the elephants and some representatives of the rhinos and giraffes, it is one of the largest land-dwelling animals. Special features are the large, barrel-shaped and largely hairless body, the short limbs and the massive head with a wide mouth, in which the incisorsand especially the lower canines are enlarged. The ears, eyes and nostrils are placed very high on the head as an adaptation to a partially water-dwelling way of life. The distribution area of ​​the hippopotamus includes sub-Saharan Africa and is partly highly fragmented. The main habitats are open landscapes and forest areas, but they are largely lacking in the tropical rainforest . Originally, the hippopotamus also appeared along the Nile up to its mouth delta , which is where the common name hippopotamus comes from. Today it is extinct on the entire lower reaches of the Nile, stocks still exist on the White and Blue Nile .

The animals stay in water during the day. Their main activities begin at dusk or at night when they leave their resting places and go ashore to their grazing grounds. They are predominantly herbivores and feed on different types of grass , less often on aquatic plants and plundered crops . They may also consume carnal resources. The hippopotamus shows complex social behavior. There are various, but mostly unstable, group formations. Associations of female animals with their offspring, groups of male individuals and mixed associations are formed. Solitary males are often territorially bound and defend their mating privilege as long as they are in their territory . The communication is varied and consists of a repertoire of gestures , of which the wide open mouth is the best known, and vocalizations. Little research has been done into the latter. The animals use them both underwater and on land. The mating and the birth of the mostly single young take place exclusively in the water, as does the suckling. Around eight months pass between the sexual act and the birth of the female animal. Due to its group life and the long time it spends in the water, but also its feeding behavior, the hippopotamus has a great ecological influence on its immediate environment.

Representatives of the genus Hippopotamus probably appeared for the first time in the Lower Pliocene around 5 million years ago. The origin lies in Africa, where it has a rich fossil record with numerous species. In the course of its tribal history , it also reached the Middle East and Europe . The latter probably colonized the genus several times, since there are also remains of the actual hippopotamus in addition to individual, more original forms. The presence of the animals was largely limited to the warm periods of the Pleistocene . Dwarf forms emerged on some islands in the Mediterranean , and dwarfed hippos have also come down to us from Madagascar . Overall, the systematics of the fossil forms of hippopotamus is assessed as in need of revision.

The first scientific description of the hippopotamus as a species and genus took place in 1758. Previously, it was mainly mentioned in travel reports. An attitude in the modern western world is not documented before 1850. However, numerous reports by ancient scholars have come down to us, which at least up to the 6th century BC. Go back. In prehistoric times, the animals served as a source of food and raw materials. Numerous rock paintings in northern and southern Africa testify to its importance, especially since the end of the Pleistocene and Holocene . In ancient Egypt , the hippopotamus was worshiped in the form of the goddess Taweret . According to the belief of the time, the animal had caring and destructive powers. At this time, numerous statuettes were created that were placed in the graves of the deceased.

The hippopotamus population, an estimated 115,000 to 130,000 animals, is considered endangered. The main threats are habitat destruction and sometimes intensive hunting. There is also an intensive trade in the animals' teeth. The dependence of the hippopotamus on water also leads to conflicts with the local population. According to a widespread opinion, the hippopotamus is one of the most dangerous animals for humans, but there is no statistical basis for this. Outside the traditional range of the hippopotamus in Africa, there has been a population on the Río Magdalena in South America since the 1990s that emerged from abandoned animal husbandry.

features

Habitus

The broad head of a hippopotamus

Hippo in the Kruger National Park in South Africa

The hippopotamus is a large and heavy representative of the artifacts. Several studies have been carried out on individual populations . For example, over 190 animals from the Kruger National Park in South Africa had a head-trunk length of 259 to 350 cm, a shoulder height of 110 to 172 cm and a weight of 955 to 1999 kg. Male individuals are usually larger than females. The dimensions of the former are on average 312 cm, 150 cm and 1546 kg, the latter 299 cm, 144 cm and 1385 kg. In Uganda , according to measurements taken in the 1960s, the weight of males averaged 1536 kg with a maximum of 2065 kg, and that of females was 1386 kg and 1716 kg, respectively. Similar information is available for studies on around 440 animals in the Murchison Falls National Park in Uganda from the 1950s. Here male individuals had an average weight of 1475 kg and a maximum weight of 1895 kg, females of 1360 kg and 2018 kg. For several hundred animals from the Luangwa river basin in Zambia , which were examined in the 1970s, the shoulder height in males was 130 to 147 cm with a weight of 1027 to 1799 kg, in females 123 to 151 cm and 891 to 1565 respectively kg. The largest known individual, a bull, weighed 2660 kg. The body has a characteristic barrel-like shape with a trunk circumference of a good 300 cm, the limbs are short and strong. They each end in four toes protruding forward, which are equipped with wide hooves and connected with partially webbed feet. The tail is short and wide, its length is given as 40 to 56 cm. The head is massive and broad. As a typical adaptation to a semi-aquatic life, the ears, eyes and nostrils are very high on the head. Compared to the large head, the ears are very small. The nostrils can be closed by muscular valves. The body color varies between dark reddish brown on the back and flesh-colored on the underside, but it is individually very different. The apparently bare skin is covered by short hair, its density is 20 to 30 per 100 cm² on the back, it thins to about half on the sides, the hair is even sparse on the stomach. A thin fluff of hair is also formed on the sides of the head, lips and neck. Some bristle-like thick hairs can be found on the mouth and tail.

Features of the skull and teeth

Skull of a hippopotamus

The skull of the hippopotamus is large and massive. It becomes 63.5 to 77.0 cm long in males and 36.8 to 48.3 cm wide on the zygomatic arches . The skull is between 17.4 and 22.2 cm high. In female animals, the dimensions are somewhat smaller and are 57.7 to 69.0 cm, 32.7 to 41.1 cm and 16.7 and 20.2 cm, respectively. The entire front section of the skull with the rostrum is more extensive than the rear. The rostrum widens significantly towards the front, which is due to the tooth sockets of the canines . In turn, it constricts significantly at the level of the premolars . Behind it, the small, rounded brain skull stands out. The wide rostrum, the strong narrowing in the middle section and the somewhat wider rear part give the skull the shape of an hourglass when viewed from above . There are strong bony ribs on the upper skull, including the crest and the bulges above the eyes. The former is massive and rises due to the shape of the skull. When pygmy hippo ( Choeropsis liberiensis ), however, it is directed downward. The latter are caused by the high position of the orbit on bony bases. As a result, the upper edge of the eye socket is well above the forehead line, the distance can be up to 5.5 cm, while it is less in the pygmy hippopotamus. In addition, there is a prominent pit at the front edge of the orbit, which is one of the defining features of the genus Hippopotamus . Another important feature is that the frontal bone has no contact with the nasal bone , as a greatly enlarged tear bone is pushed in between. The widely protruding zygomatic arch serves as a starting point for massive masseter and temporalis muscles .

Chewing surface of the posterior teeth

The lower jaw is also extremely robust and, as a unique feature, heavier than the skull. Its length varies from 39.8 to 62.0 cm, its height below the second molar from 10.9 to 14.3 cm. The extremely far back position of the articular process, which articulates with the skull near the occiput, is striking. This enables the animals to have a wide mouth opening of up to 150 °. The angular process at the rear end of the lower jaw extends downwards like a hook. The bit consists of 36 to 40 teeth, and shows the following dental formula : . The inner pair of incisors is larger than the outer. In the upper row of teeth the incisors have a rounded cross-section, in the lower row a triangular cross-section. The canines have a tusk-like shape, the lower ones are larger and can reach a total length of 70 cm (of which 30 cm protrude from the gums), the largest tooth was registered in an animal from the Congo area with a total length of almost 164 cm. Its triangular outline points with the flat side to the rear and the pointed side to the front. A longitudinal, shallow groove is formed on the rear of the upper canine teeth. The inside of the lower canines is rubbed smooth by contact with the upper counterparts when the mouth is closed. The thick enamel of the canines folds into distinctive ripples that converge on the lower ones. Both incisors and canines have no roots and grow for a lifetime. The annual increase for the lower canines is around 28 to 30 mm in younger individuals and 13 to 14 mm in older individuals. The growth rate of the canines slows down with the age of 20 to 25 years, it is generally lower in females than in males, so that the canines are only half as heavy in the former as in the latter. The same goes for the incisors. The front teeth are not used for food intake, but serve "representative" purposes. The premolars usually have one cusp, the molars have two pairs of cusps, only the rearmost three. The front molars are parallel to each other or converge slightly. In general, the molars are very high crowned ( hypsodontal ), so that the height usually exceeds their width. The length of the molar row of the lower jaw ranges from 23.2 to 29.8 cm, that of the upper jaw from 21.3 to 27.8 cm. ${\displaystyle {\frac {2.1.3-4.3}{2.1.3-4.3}}}$

distribution

Previous distribution (vague)

Today's distribution

The hippopotamus is currently in Africa south of the Sahara before ( Sub-Saharan Africa ). The distribution area extends from Senegal and Gambia in the west east to Sudan and Ethiopia or Somalia and south to northern South Africa and Botswana . The animals inhabiting predominantly open grassland and Miombo -Waldgebiete which are connected in each case with water in the form of streams, rivers or lakes. Aside from large river areas, they do not occur in tropical rainforests . In West Africa , the hippopotamus can also be found on the lower reaches of rivers and sometimes penetrates into coastal waters . Individual stocks were reported in the 19th and 20th centuries from the island of Mafia around 17 km off the East African coast, which may survive to the present day. The animals reached the island via the mouth of the Rufiji . No evidence is available for the neighboring islands of Zanzibar and Pemba . The altitude distribution accordingly ranges from sea level up to 2000 m of the mountains. For the higher elevations, the occurrence of the hippopotamus in Ngorongoro in Tanzania is remarkable , for which the animals must have completed long stretches over dry landscapes and the ascent of the crater wall several hundred meters high. The same applies to the stocks in some lakes in the Hanang area of ​​Tanzania, which has since disappeared , and is one of the driest in the region.

In total, the hippopotamus is represented in 29 countries. The largest populations are found in southern and eastern Africa with around 60,000 and 50,000 individuals, respectively. Zambia with 40,000 to 45,000, Tanzania with up to 20,000 and Uganda with up to 10,000 individuals have the largest share . In western Africa, the species is rare and the population is divided into a number of smaller groups that comprise a total of around 7500 animals in 19 countries. In some regions, such as the Republic of the Congo or the Gambia, only a few dozen animals are suspected. In historical times the hippopotamus was also found in North Africa , mainly in the Nile Valley , where it was found around 1700 in the delta area and on the lower reaches. There it disappeared through hunting at the beginning of the 19th century. It was also wiped out in the Cape region in southern Africa. High population densities are known from the Queen Elizabeth National Park in Uganda and the Luangwa region of Zambia, with 28 to 42 individuals per square kilometer.

Way of life

Territorial and social behavior

Adjustments and Physiology

The nose, eyes and ears are very high on the head and can thus be kept above the waterline

Hippo with injured skin in Ngorongoro in Tanzania

Hippos spend most of the day in the water, while sunbathing on the sandbank is partly used for thermoregulation

The hippopotamus lives semi-aquatic and is well adapted to this milieu. The beneficial features for this include the nose, eyes and ears positioned very high on the head so that the animals can hold them above the waterline while swimming. When diving, a reflex closes the slit-like nostrils and ears, and the breathing rate is then around six puffs per minute. The short limbs are to be regarded as a functional modification, as are the compact and partly compacted bones, the pith tubes of which are filled with cancellous material. The more massive front legs carry the greater part of the body weight, which among other things benefits the locomotion in the water. However, the hippopotamus also lacks some typical characteristics such as a streamlined shape, and fore and hind legs only show limited swimming properties, for example in the form of the partially webbed feet.

The epidermis of the skin is very thin, sometimes only around 1 mm like on the back. Due to numerous nerves , it shows a high level of sensitivity. It can be very easily injured by branches and twigs from bushes, but it heals quite quickly. In addition, it breaks quickly when dry on land and must therefore be kept moist. The dermis, on the other hand, is very thick. It reaches 60 mm on the back and sides, and becomes thinner on the head, neck and stomach. Overall, the skin weighs around 270 kg, which is around 18% of the body weight of an individual, and covers an area of ​​10 m².

There are no sweat glands , but special subdermal skin glands secrete an alkaline liquid with a pH value of 8.5 to 10.5, which protects the animals from dehydration. These excretory organs are distributed in a dense network of one gland per square centimeter over the body surface, have a lenticular outline and each have two glandular canals. The initially colorless liquid turns reddish in color within a few minutes and then brownish later. This liquid contains two non- benzoid , aromatic pigments , a red one called hipposudoric acid and an orange colored one called norhipposudoric acid. Both act as sun protection by absorbing UV rays , as well as antibiotic against various pathogens. The reddish shimmer used to lead to the assumption that the hippopotamus was sweating blood.

Another function of the secretion concerns thermoregulation , which takes place mainly through the skin. It takes place via the evaporation of water, which is very intense compared to other mammals in the hippopotamus, especially when the skin is wet and covered with the glandular fluids. The body temperature is around 36 ° C and fluctuates very little on land. As a rule, the animals avoid heat stress and therefore spend the day in the water. However, this also includes various types of sunbathing, which can vary in length depending on the season and the ambient temperature.

Activity rhythm

The hippopotamus is largely crepuscular and nocturnal. It spends practically the whole day sleeping or resting in or near water, which can take more than twelve hours. Preferred water depths for the resting places range from 1.3 to 1.5 m. Larger activities in the water unfold in the late afternoon and early evening between 4:00 p.m. and 7:00 p.m. At dusk, the animals go ashore and migrate to their pastures. Food intake takes up to six hours. The rhythm is largely dependent on the weather and the time of year, as the animals stay longer outside of the waters under more humid conditions and sometimes rest in their pastures or visit them several times. For animals from the Boye wetlands near Jimma in Ethiopia, the activity was found to be 51.2% rest, 34.2% migration, 19.6% feeding and 3.7% mating. On average, bulls rest longer than cows, who invest more time in migration and nutrition.

Social organization and use of space

Dense hippos on the Luangwa in Zambia

Extensive studies on the social structure of the hippopotamus took place in the Queen Elizabeth National Park in Uganda, in the Masai Mara in Kenya or in the Okavango Delta in Botswana. The social behavior of the hippopotamus is variable. According to studies in the Masai Mara, 8% of a 2800-headed population consisted of bulls, 36% of cows and 56% of young animals, here almost half each were almost full-grown individuals and half were newborns. The hippopotamus appears solitary or several individuals join together to form a group, the average size of which in the Masai Mara is around a dozen animals. There are different forms of group formation, on the one hand those made up of female animals with their offspring, on the other hand bachelor groups with male individuals. However, the boundaries are not clearly defined, as representatives of the opposite sex can often be in the respective groups. None of the associations is stable, they are rather loose associations of animals in favored places. Depending on the attractiveness of the area, they can include up to 200 individuals. In rainy seasons, existing groups often split up, so that fewer animals can be found in a group than in dry seasons. The only lasting relationship is that between the mother and her offspring, which lasts for several years.

Solitary bulls usually establish their own territory , their social organization is based on territoriality. The territories often include the shorelines of rivers and lakes. You can stretch over 50 and 100 m like on the Ishasha River or 250 to 500 m like on Lake Edward , both in Queen Elizabeth National Park. The boundaries shift over the year, as there is a dependency on the population density of a region. In addition, natural factors such as changes in the flow of water in a river or the course of the lake shore as a result of droughts, rainfall or flooding play a role. Often times, an individual claims their territory over a long period of time. Individual observations were made over four and a half to twelve years, in some cases it is assumed that a single animal occupies its territory during its entire life. The boundaries of a territory include one or more action spaces of group living individuals. Territories and areas of action are not identical. In the Ruaha National Park in Tanzania, larger, almost fully grown young animals use far more extensive action areas that are three times the size of the territories of dominant bulls. The hikes of more than 4 km required for this are probably undertaken in order to avoid intra-species conflicts, especially during the dry seasons, when the individual groups move closer together.

Pile of dung from a hippopotamus in Tsavo West National Park in Kenya

The claim to a territory is expressed through the presence of the male animal, its dominance behavior and through defecation . The droppings that a bull spreads by wagging its tail piles up into larger mounds with an area of ​​several square meters. However, these hills do not mark the actual boundaries of the territory, but rather serve as points of orientation. They also do not prevent foreign bulls from entering a territory; sometimes they stimulate another individual to deposit their feces there as well. Neighboring bulls defecate partially ritualized in the water at the same time and look at or in the opposite direction with their heads raised high and ears pointing forward, which means dominance in each case.

Two fighting hippos

Like other hippos, a bull goes inland to forage at night and thus leaves its territory. If a bull crosses its own territorial boundaries, it loses its dominant position and gains the status of a subordinate animal in relation to the owner of the other territory. In general, however, the hippopotamus is peaceful towards all conspecifics, which also includes bulls, provided that they recognize the dominant animal's prerogative to procreate. Sometimes bachelor groups with an individual size of up to 100 animals can also stay in the territory of a territorial bull. A denser crowding of the animals at individual water points, as is often the case in the dry season, can lead to increased aggression , which is directed against every gender and every age group, but usually involves little physical effort . Fights between neighboring animals are ritualized and carried out frontally. They are partly associated with splashing water, which is supposed to indicate a limit. Real fights, on the other hand, take place in a side position. Each animal then tries to hit the opposite side with the help of its large canine teeth. Despite the overall thick skin, this can lead to serious injuries or even death.

The pastures, which are mainly visited at night, are sometimes several kilometers away from the traditional water points. Unlike the bulls' territories, the feeding grounds are not monopolized. They are therefore shared and not subject to any defense. The walk to the pastures and the feeding take place individually or in mother-young animal groups. With the exception of the latter, there is hardly any social interaction, so that each individual eats for himself. In the Masai Mara, the animals move up to 1,350 m from their watering place, in the Kruger National Park in South Africa the distance can be up to 4.5 km. The distances are mostly dependent on the productivity of a landscape.

Locomotion and communication

Hippos underwater

Although the hippopotamus spends much of its life in the water, it is not a good swimmer. Mostly it runs along the bottom of a body of water or lets itself be carried by the water; the mode of locomotion is sometimes referred to as "swimming running". The hippopotamus uses a kind of gallop with relatively extended jumping phases that last longer than the contact phases with the ground. With each jump, an animal covers between 1.0 and 2.4 m. The speeds achieved are between 0.2 and 0.6 m per second. Dives can last up to 30 minutes. On land, on the other hand, the hippopotamus moves forward at low speeds in a kind of pass walk, in which mostly three feet touch the ground at the same time and thus stabilize the massive body. A bipedal phase occurs only in a short sequence. Higher speeds are achieved by trotting with a diagonal leg movement. Maximum speeds when escaping or attacking are around 30 kilometers per hour. As a result, the hippopotamus is relatively agile despite its massive build.

The open mouth of a hippopotamus

The internal communication of the hippopotamus is diverse. Above all, this includes body language and gestures. Dominant bulls can often be recognized by protruding ears, cows and subordinate animals by those that are laid back. The domineering behavior is associated with a raised head and a curved back, which expresses greater massiveness. The open mouth is one of the most famous gestures. The head is thrown back so that the forehead line is at right angles to the back. Dominant animals hold this gesture for up to eight seconds. However, the open mouth is practiced by almost all members of a group, including the young, and takes place to a greater extent in the evening before going ashore. Perhaps this behavior is an expression of excitement. When attacked, the animals only partially open their mouths. Submissive behavior is shown by a bowed head, wagging tail, and lip smacking. It begins on land at a distance of around 100 m from the opponent, sometimes subordinate animals crawl the last few meters and then sniff the genital region of the territorial bull. In the water, nose contacts play a role, sometimes the subordinate individual remains in the environment of the dominant animal for hours. Sometimes defecation also occurs , although the meaning is not clear here.

Little information is available about the voices of the hippopotamus. It is most often noticeable at the time of the strongest activity in the water, which takes place in the late afternoon. It is rarely seen on land. As a semi-aquatic animal, the hippopotamus is able to communicate with conspecifics both on land and under water by means of vocalization. Communication that takes place over both media at the same time usually encounters difficulties as sound waves break at the boundaries . Only around 4% of all vocalizations come exclusively through the air. In contrast, the hippopotamus produces almost two thirds of its vocalizations under water. They are difficult to perceive on the surface and hardly need any air for their modulation.

The function of the tones is not clear in all cases. Wine sounds that are short-lived and sometimes combined with individual clicks may be associated with aggressors. On the other hand, croaks are emitted when there is general alertness or attention, or serve as contact calls, for example in cloudy water. They consist of a series of around half a dozen pulses, each of which usually lasts 2 milliseconds and reaches frequencies from 600 to 1800  Hz , and a maximum of 9000 Hz. The pitch can stay the same or change, which may express variable motivations. During social interactions, click sounds are emitted, which can be very varied and take place in both broadband and narrowband areas . These are also made up of several pulses that are shorter than the croaks. Broadband clicks occur in frequencies of up to 7800 Hz, while narrowband clicks rarely exceed 2000 Hz.

Almost a third of the sounds made by the hippopotamus are amphibious and therefore spread through the water and the air. For this form of communication, the animals are in a half-submerged position with their eyes and nostrils above, their mouths and throats under water. The air required for this is forced through the nose for above water communication by means of the throat , for underwater communication the larynx activates the skin and fatty tissue of the throat. In the completely submerged position, the sound modulations are partially connected to a rising air bubble. The airborne sounds are perceived by means of the ears, while the water-borne sounds are perceived through the bone conduction of the lower jaw. The sound waves propagate at different speeds due to the varying density of the media and have a very different range. In the air they are slower with lower maximum frequencies (around 210 Hz), in water they are faster and with higher maximum frequencies (over 2000 Hz). In addition, the sound pressure in the water is higher, but the higher density of the moist medium leads to a lower intensity of the sounds.

Amphibious sounds are mostly used by animals when they are disturbed, for example during a fight or when lions are present , which are a danger to young animals. In addition to the aforementioned croak, click and cry, hippos can also make screams and variable growls, grunts and snorts, including a flutter of the nose. Usually the dominant bull calls first. The group responds to this signal and thereby stimulates neighboring collections. Through the air, the answers can span multiple territories up to a distance of 2 miles. As a rule, the neighboring groups remain involved under water, so that the greatest spread is around 500 m.

nutrition

Grazing hippo in Chobe National Park in Botswana

The hippo is a herbivore. It mainly ingests grasses . In studies in the Boye wetlands in Ethiopia, 26 species could be identified, among which Eriochloa with a share of almost 12%, cattails and barnyardgrass with over 9% and dog tooth grasses with over 8% are among the favored plants. In the Masai Mara, around a dozen types of grass are recorded as food for the hippopotamus. These include Themada , Sporobolus and Andropogon as well as love grasses . In the Queen Elizabeth National Park, over 30 different types of grass have been identified that are consumed by the animals. Dog tooth grasses are of particular importance, but genera such as Chloris , Heteropogon , Sporobolus and Themada are also represented with a high proportion. Occasionally the hippopotamus will eat individual herbaceous plants such as members of the genus Alternanthera . This also applies to fruits such as those from the liver sausage tree . Sometimes the animals also eat various aquatic plants, including water lettuce . Something similar was observed in southern Africa, where water lilies , balms and spawning herbs belong to the food spectrum. So far, only a few studies on the diet of the hippopotamus are available from central and western Africa. In Loango National Park in Gabon, nine plants were in field trials, a total notice of where the sweet grass Paspalmum with 81% had the highest share, followed by Axonopus and Stenotaphrum . Individual butterflies and aquatic plants such as pennywort are also documented. With around nine preferred plants in the W National Park in Niger , the number is similarly low. Day flowers , chicken millets and rice dominate here . Animals regularly look for arable land with rice, maize or teff , and sometimes also banana plantations , thereby looting crops . Isotope studies on individuals from different regions of Africa largely agree with the observations. According to this, a large part of the diet consists of C ₄ plants , in regions with closed vegetation such as in central Africa, higher amounts of C ₃ plants are added. In addition, according to the data, the composition can fluctuate regionally and seasonally with a high proportion of C ₄ plants in the dry periods of the year and with a mixed diet of C ₃ and C ₄ plants in the humid areas. According to individual reports, the hippopotamus occasionally eats the carrion and meat of animals that it has killed itself, including its own conspecifics. Although it has seldom been observed, it is basically able to digest meat.

In general, the hippopotamus is an opportunistic herbivore that prefers individual plants, but consumes them without pre-selecting certain vegetative parts. The large, thick-lipped mouth and the special lower jaw suspension prevent fine selection of the food. That is why the animals look for areas with frequent occurrences of their favorite plants and then empty larger areas. The amount of plants consumed is higher the further away the pasture is from the water point. Overall, the feeding strategy of the hippopotamus differs from that of other large herbivores, such as elephants or rhinos , which search for food for a long time and wander far and wide, with the restriction to a certain part of the day and distance from the traditional areas of activity and territories . Usually the grass is pressed between the lips and torn off with a movement of the head. The incisors and canines have no function in feeding, but the former are sometimes used for digging. Food is usually consumed at night and can take several hours. If the plant quality is poor, the hippopotamus will also eat during the day. An animal consumes between 20 and 45 kg of food per day. In relation to dry matter, this corresponds to 0.9 to 1.3% of body weight. The stomach holds an average of 34.9 kg in males and 37.4 kg in females, making up 12.8 and 15.2% of body weight, respectively. The hippopotamus has a four-chambered stomach that is convergent to that of ruminants . This has two blind bags in which the food is broken down by microorganisms. But they won't chew again. The passage time of the food is relatively long, which enables an efficient utilization of the rather nutrient-poor grasses.

Reproduction

Group of hippos with young animals in the Kruger National Park

Mother with young animal

Mating occurs throughout the year. It takes place in the water, while the female is submerged most of the time and only comes to the surface to breathe. Up to six copulations can take place per night. Sometimes, after successful mating, the cow will visit two or more territories for further mating activities. The gestation period is around 227 to 240 days. At least in some regions, a seasonality in reproduction can be seen. In Uganda, for example, most births occur in October and April, the year with the most rain. In South Africa , too , the vast majority of young animals are born in the humid months of October to March. Something similar was observed in Zambia .

Shortly before giving birth, the mother-to-be separates from the group. The birth takes place in shallow water, in case of disturbances the cow seeks deeper water. Usually a single young is born, twins are rare. Newborns weigh between 25 and 55 kg and can walk immediately after birth and push themselves off the water bed to the surface. Suckling takes place in the water, and the offspring activates the mother's mammary glands with their tongue. Presumably, the mother injects part of the breast milk into the boy's mouth through muscle contraction, similar to what is known in whales . The mother animal is very caring. It lets the offspring ride on their backs in deeper water and defends them vehemently against predators and conspecifics. This happens particularly aggressively in the first ten days. During this time, the mother hardly consumes any food. Only then does it begin to feed on the river bank during the day while the young rests nearby. After several weeks, mother and young hike together at night to the more distant pastures. The young stays hidden in the bushes while the mother grazes. The young animals consume their first solid food when they are around six to eight weeks old. The offspring are weaned after around six to eight months, sometimes even after twelve months. The growth phase is initially the same for both sexes, from around 24 years of age it slows down in female animals, while male individuals can increase in size throughout their life.

The sexual maturity occurs in males with seven to eight years, determined by the size of the testicles , but that can sperm production already use two years. In female animals, due to the size of the follicles , the period is usually around seven years, but individual individuals already achieved this at three years of age. The first reproduction usually takes place much later. In the Kruger National Park it was determined when it was around eleven years of age, and in Uganda and Zambia sometimes not until the age of 20. The differences are probably due to the population density and the quality of the food supply. Animals in captivity can sometimes reproduce as young as a little over two years old. Male animals are sexually active throughout their lives.

The birth interval is around two to three years. The sexual cycle lasts about 50 days, with oestrus lasting two to three days . The sex ratio at birth is 1: 1. There is evidence that cows are sexually mature again shortly after birth (postpartum oestrus), as around 25% of the females examined were both pregnant and lactating. The birth of a new boy does not break the existing connection with the older offspring. Some females have been observed with up to three cubs of different ages. In the marching order, the youngest animal follows the mother directly, the oldest forms the end. In some cases it comes to infanticide of young animals by bulls. Under certain circumstances, this happens when a dominant animal takes over a new territory and thus wants to guarantee its reproductive success, similar to what is known with lions. On the other hand, killing of young animals has often been observed in the dry season, so that external stress could also be an important factor. This puts young animals at risk up to an age of 50 days. After individual observations, the mother animals spend several hours with a dead boy, defend it against predators and bring it ashore. The hippopotamus is one of the few ungulates that show this behavior. Wild hippos live to be 30 to 40 years old. Animals in captivity can reach over 50 years, the highest known age of an animal was 61 years.

Predators, commensals and parasites

Hippo and Nile crocodile in the Serengeti National Park in Tanzania

A fully grown hippopotamus has few natural enemies; occasionally lions prey on an adult, but these sporadic actions have no effect on the local population. Young animals occasionally fall prey to hyenas or lions. As a rule, dams defend their offspring very aggressively. The Nile crocodile is also capable of killing young animals and possibly also adult individuals. In a shared body of water, groups of hippos usually do not tolerate crocodiles in the immediate vicinity of 2 m. On the other hand, crocodiles avoid hippos and dive in the immediate vicinity. According to observations on the round in Zimbabwe, hippos also drive crocodiles away from their sunbaths. Exceptions are the larger specimens from 3.5 m in length, which in turn were avoided by the hippos. As a rule, however, groups of hippos dominate those of crocodiles.

The hippopotamus often appears in association with different species of birds . The maggot chopper are known for this, especially the yellow-billed maggot chopper can be found in close proximity to the animals. According to studies from 2018, it could be detected in 11.3% of all observations. The would also cattle egret , the wattled starling , the piapia and the African Jacana to name. While the maggot chopper mainly benefit from the parasitic infestation of their host animals, the frequent occurrence of the cattle egret is probably due to the overlap of the commonly used habitats near the water. In the water, carp fish, such as members of the Labeo genus, take on the role of maggot chopper and eat algae from the hippo's skin.

There are numerous parasites in the hippopotamus. Significant external parasites are mainly found in ticks such as Cosmiomma . A specialty is the flatworm Oculotrema , which attaches itself to the eyes. Sometimes two dozen individuals can parasitize on one eye and up to three dozen on a hippopotamus, and different generations occur on one host animal. Paired leeches and the genus Fasciola , for example , are known to be internal parasites ; both belong to the flukes and infect the blood and the liver, respectively. Roundworms are represented by Toxocara , Stephanofilaria , Cobboldina and Hippopotamenema , among others . The hippopotamus is also prone to rinderpest and anthrax . An outbreak of anthrax in 1987 in Zambia killed over 4,000 animals, and another in 2004 in Uganda killed 300 individuals. Other disease-causing microorganisms are coccidia such as Eimeria , bacteria such as Brucella or Salmonella, and flagellates such as trypanosomes .

Ecological impact

As a large herbivore, the hippopotamus exerts a lasting influence on its immediate environment. It competes for food with some other grass-eating mammals, which can lead to ecological interactions. In Queen Elizabeth National Park, waterbuck numbers decrease when the hippopotamus is numerous and increase again when the hippopotamus population decreases. The animals often graze on short-stemmed grasses, promoting grass species that they prefer to eat but are avoided by waterbuck. By preferring shorter grasses and grazing them in abundance, a typical, spatially narrowly delimited "hippo lawn" is created. In connection with overgrassing and trampling over the area, rainfall sometimes leads to massive erosion , especially on the banks of the rivers. This also applies to the paths that are created by the hippopotamus' repeated hikes, the so-called "Hippo Trails". These sometimes cut up to 1 m into the subsoil of the river and lake banks or are gorge-like on steeper slopes. Often these are used by other, smaller animals. In the Okavango Delta, but also in the Ngorongoro , new water veins are sometimes being created in this way.

The grazing activity of the hippopotamus and other large herbivores such as elephants and rhinos can lead to a sharp decline in local vegetation with a correspondingly dense population, which results in erosion. Artificially keeping the landscapes open reduces the forest vegetation and promotes the grasses preferred by the hippopotamus. However, if the populations collapse, there may be a feedback effect. This was observed in Queen Elizabeth National Park, where, triggered by civil unrest and the associated more intensive hunting, a large part of the resident large mammals disappeared between 1960 and 2000. This caused a greater expansion of forest and bush communities. The hippos who remained locally no longer had enough grass available, which is why they increasingly switched to herbaceous plants. In the course of this process, their share in the amount of food increased from less than 20% in the 1960s to up to 45% in the 1980s and 1990s.

Frequent dumping of feces and urine into the water can also change its chemical composition. This has an impact on the fish community , which benefits from the input of nutrients. The carp fish genus Labeo feeds not only on algae on the skin of the hippopotamus, but also on its falling excrement . This also has a positive effect on the populations of various species of cichlids ( e.g. Oreochromis , Sarotherodon and Tilapia ). Especially in the dry season when the water level is low and the hippo density is high, there is sometimes a strong oversaturation and lack of oxygen . This then often results in a decline in local fish and insect fauna in terms of both total numbers and diversity. This has been observed in the Ruaha National Park and in the Masai Mara, among others. The high demand for plants and the defecation in the water also mean that the hippopotamus makes a major contribution to the silicon cycle. The animals bring around 400 kg of silicon into the Mara River every day, which is around three quarters of the total. Silicon is important for numerous diatoms in the tropical lakes of Africa, which on the one hand represent important carbon stores and oxygen producers , on the other hand also form the basis of the food chain .

Systematics

Internal organization of the hippopotamus according to Hassanin et al. 2012  Cetancodonta     Hippopotamidae     Hippopotamus    Hippopotamus amphibius      Choeropsis      Cetacea

The pygmy hippo ( Choeropsis liberiensis ) today as the closest relative of the hippo

The hippopotamus is a kind of the genus hippopotamus and the family of the hippopotamus (Hippopotamidae). Within the genus, the species is currently the only recognized representative, which makes it monotypical . To the family, the genus is still only rezent Choeropsis counted, which the pygmy hippo ( Choeropsis liberiensis contains). Depending on the opinion, a division into two recent species is also possible for Choeropsis . Outwardly, the hippos are characterized by their plump, cylindrical body with short legs and their large head with strongly developed incisors and canines . The two genera Hippopotamus and Choeropsis can be differentiated , in addition to the general body size differences, among other things on the basis of the structure of the front dentition. The former has four incisors each in the upper and lower teeth ( tetraprotodont ), the latter six ( hexaprotodont ). The family of hippos is traditionally in the order of the cloven- classified (Artiodactyla). Molecular genetic and biochemical studies as well as fossil finds have led to the realization that the whales (Cetacea) are the closest living relatives of the hippos. From a cladistic point of view, the ungulates and whales thus form a common lineage, which is summarized as Cetartiodactyla . The closer family group of whales and hippos accordingly bears the name Cetancodonta (sometimes also Whippomorpha). According to the genetic data, the hippos and whales separated around 54 million years ago, at the beginning of the Lower Eocene . A greater diversification of the hippos did not begin before the Upper Miocene around 8 million years ago. The origin of the hippopotamus is not entirely clear; they first appeared in fossil form in the Lower Miocene. The large time gap between the separation from the whales and the appearance of the hippopotamus allows for several interpretations. A derivation of the group from the Anthracotheriidae , an extinct community of hippopotamus-like cloven-hoofed animals from the Eocene to the Pliocene of Africa and Eurasia is often favored . Other authors, however, prefer an ancestry from the Palaeochoeridae , pig-like animals that occurred in Eurasia from the Eocene to the Miocene.

Several subspecies of the hippopotamus are distinguished, their exact number is unknown. According to Hans Klingel , published in 2013 in the Mammals of Africa collection , there are a total of five:

• H. a. amphibius Linnaeus , 1758; Nominate form , from Gambia eastwards to Sudan and Ethiopia as well as southwards over the north of the Democratic Republic of the Congo , Tanzania to Mozambique ; probably also in the Nile valley , though extinct there; on the skull the constriction in front of the eyes is relatively moderate, long symphysis of the lower jaw and large molars
• H. a. capensis Desmoulins , 1825; Zambia to South Africa ; Skull flatter than in H. a. chadensis , so that it is wider than high at the orbits
• H. a. constrictus Miller , 1910; southern Democratic Republic of the Congo, Angola and Namibia ; Skull lighter than in the nominate form and deep constriction in front of the orbit; Rostrum less broad, symphysis short and molars smaller
• H. a. kiboko Heller , 1914; Kenya and Somalia ; Skull with broad nasal bones and slight constriction in front of the orbit, orbit more rounded than in H. a. capensis and more prominent than in H. a. constrictus
• H. a. chadensis Schwarz , 1914; Chad and Nigeria ; comparable to the nominate form, but with more prominent orbit, compared to H. a. capensis shorter and wider rostrum and more forward-facing orbits

On the other hand, Rebecca Lewison distinguishes between three subspecies in the second volume of the standard work Handbook of the Mammals of the World in 2011 :

• H. a. amphibius Linnaeus , 1758
• H. a. capensis Desmoulins , 1825
• H. a. kiboko Heller , 1914

In this case, H. a. chadensis a synonym for H. a. amphibius and H. a. constrictus to H. a. capensis . Don E. Wilson and DeeAnn M. Reeder made a similar arrangement in 2005.

Internal organization of the hippopotamus according to Pandolfi et al. 2020  Hippopotamidae     Hippopotamus    Hippopotamus Lemerlei      Hippopotamus guldbergi      Hippopotamus pentlandi      Hippopotamus amphibius      Hippopotamus antiquus      Hippopotamus gorgops      Hippopotamus afarensis      Hexaprotodon      Archaeopotamus      Saotherium      Choeropsis

In addition to the recent hippopotamus, various extinct species are listed within the genus Hippopotamus . These were originally not limited to Africa, but also occurred in western Eurasia and Madagascar :

• African forms:

• aff. Hippopotamus aethiopicus Coryndon & Coppens , 1975
• aff. Hippopotamus afarensis ( Gèze , 1985)
• aff. Hippopotamus coryndonae Gèze , 1985
• aff. Hippopotamus dulu ( Boisserie , 2004)
• aff. Hippopotamus karumensis Coryndon , 1977
• aff. Hippopotamus protamphibius Arambourg , 1944
• Hippopotamus gorgops Dietrich , 1926 ( Hippopotamus behemoth Faure , 1986?)
• Hippopotamus kaisensis Hopwood , 1926
• Hippopotamus sirensis Pomel , 1896

• Eurasian forms

• Hippopotamus antiquus Desmarest , 1822 ( Hippopotamus georgicus Vekua , 1976?) (Mainland)
• Hippopotamus creutzburgi Boekschoten & Sondaar , 1966 (Crete)
• Hippopotamus melitensis Major , 1902 (Malta)
• Hippopotamus minor Desmarest , 1822 (Cyprus)
• Hippopotamus pentlandi Meyer , 1832 (Sicily, Malta)
• Hippopotamus tiberinus Mazza , 1991 (mainland)

• Malagasy forms:

• Hippopotamus guldbergi Fovet, Faure & Guérin , 2011 ( Hippopotamus madagascariensis Guldberg , 1883)
• Hippopotamus laloumena Faure & Guérin , 1990
• Hippopotamus lemerlei Grandidier , 1868

Most of the African forms (aff. H. aethiopicus , aff. H. coryndonae , aff. H. karumensis , aff. H. protamphibius ) were originally referred to the genus Hexaprotodon , aff. H. afarensis, in turn, was part of the independent genus Trilobophorus . A phylogenetic study from 2005 by Jean-Renaud Boisserie limited Hexaprotodon largely to the Asian hippopotamus and saw the African representatives more closely related to the actual hippopotamus. However, the exact taxonomic position for several forms has not yet been established. This also applies to the Cypriot hippopotamus H. minor , which is mostly considered to belong to the genus Phanourios . However, other authors classify Phanourios as a direct descendant of hippopotamus .

Various forms and sometimes used names from Eurasia must be viewed as synonyms. In the younger forms, H. incognitus (Europe) is to be equated with H. amphibius . Among the older representatives, H. major (Europe) is considered identical to H. antiquus , which is probably also to be assumed for H. georgicus (Caucasus). Some scientists believe this also applies to H. tiberinus (Europe). For the African hippos there is the possibility that H. sirensis (North Africa) and H. gorgops (East Africa) are only variations of one species and that the latter would then have to merge into the former according to the priority rule. Most scientists also consider this for H. behemoth from the Middle East. It is also often assumed that the African H. gorgops is the predecessor of the Eurasian H. antiquus , and both show clear similarities. Thus, both could be understood as con- specific, with which the entire species name would fall on H. antiquus . However, so far no African forms have been adopted north of the Taurus - Zagros mountain range. In principle, scientists are calling for a comprehensive revision of the Eurasian and African hippos.

For the Mediterranean hippos, H. minutus is a partial synonym for H. melitensis . The Malagasy hippopotamus H. madagascariensis was originally introduced by Gustav Adolf Guldberg , but the type specimen largely corresponds to H. lemerlei . A skeleton presented in 1902 by Charles Immanuel Forsyth Major also under H. madagascariensis differs significantly. As a consequence, H. madagascariensis was synonymous with H. lumerlei in 2011 and H. guldbergi was proposed as a replacement name for Major's skeleton. The renaming is not fully recognized.

Tribal history

Development in Africa

The genus Hippopotamus probably appeared in Africa as early as the Lower Pliocene . Almost all of the early finds came to light in the northeast and eastern parts of the continent . For most of the early forms, direct assignment is currently still problematic. Their close relationship with hippopotamus is expressed, however, by the sometimes more expansive lower jaw, in which the tooth sockets of the canines clearly protrude, which is less reminiscent of other early groups such as the Hexaprotodon and Archaeopotamus . This affects, among other things, the skull and lower jaw of aff. Hippopotamus dulu from the Sagantole Formation in the Awash area in the Afar Triangle in Ethiopia , which is one of the earliest remains with an age of 5.2 to 4.9 million years. Overall, it still shows clear reminiscences of more primitive representatives such as archaeopotamus , for example in the structure of the mandibular symphysis. From the same region, but from the Hadar formation , which was 3.4 to 2.3 million years old, a little younger , aff. Hippopotamus afarensis and aff. Hippopotamus coryndonae described. Skull remains were available for both of them. Hippopotamus afarensis had a massive rostrum that resembled that of today's hippopotamus, while aff. Hippopotamus coryndonae was significantly smaller. In this characteristic the form was similar to aff. Hippopotamus protamphibius . In contrast to aff. Hippopotamus coryndonae and also to the other two previously mentioned species, which each had six incisors in the upper and lower dentition and were therefore hexaprotodont, were characterized by affection. Hippopotamus protamphibius, like today's hippopotamus, has only four incisors, so it belonged to the tetraprotodont type. However, this feature appears to be in aff. Hippopotamus protamphibius was more likely to have been variable, as some skulls also have six incisors each. The shape has been passed down from numerous finds from the Omo valley in southwestern Ethiopia. There it is distributed over several rock units, from the Mursi to the Usno to the Shungura Formation , and thus has a temporal range of around 4.0 to 1.9 million years. The Shungura formation alone yielded over 8,000 hippo remains. The abundant found material enables insights into the way of life. This showed that, apparently controlled by climatic changes, around 2.8 million years ago there was a change from more foliage to more grassy food. Further finds have been documented from the important Koobi Fora formation from Lake Turkana in northern Kenya , which is between 2.0 and 1.4 million years old. From individual sites on Lake Turkana, aff. Hippopotamus karumensis and aff. Hippopotamus aethiopicus introduced two more forms, both of which are considered tetraprotodont . However, the former species sometimes only had two incisors in the lower jaw. It is an overall large representative, similar to today's hippopotamus. The latter form turned out to be rather small with a size comparable to the recent pygmy hippopotamus .

In the transition from the Pliocene to the Pleistocene around 2.5 million years ago, unique members of the genus Hippopotamus appeared for the first time , which, in addition to the massive lower jaw, stand out as a typical characteristic associated with the genus with their ribbed lower canines. From the Kaiso lineup in Uganda was Hippopotamus kaisensis reported by the present including a skull. Overall, the shape has only been little studied and there are sometimes problems of delimitation from the actual hippopotamus. This is shown, among other things, by finds from the Lusso Beds on the Upper Semliki in the Central African Rift of Uganda. The numerous tooth finds are very similar to those of today's hippopotamus and could thus indicate a very early appearance of the species as early as around 2.3 million. However, there is also an overlap with Hippopotamus gorgops . This very large animal, which clearly surpassed the recent representatives, has come down to us from numerous sources. Probably the earliest remains came to light at Lake Turkana and are around 2.5 million years old. By far the most important location is also for the early human development important Olduvai Gorge in northern Tanzania . There the species is documented in the Old and Middle Pleistocene over a period of 1.9 to 0.6 million years ago. It occurs relatively often there, in addition to countless bones, some well-preserved skeletons and rarely fossilized footsteps have been found, the latter form a kind of "hippo trail". Based on the bone finds from the Olduvai Gorge, a striking change in the structure of the skull of Hippopotamus gorgops can be traced. While the earliest representatives were still similar to today's hippopotamus, later forms developed into extreme specialists in relation to the amphibious way of life. The muzzle lengthened significantly, which also stretched the diastema between the second and third premolars of the lower jaw. The posterior skull, on the other hand, became shorter and the crest of the occiput shifted upwards, as did the skull in general. Furthermore, there was an additional postponement of the eye socket, which looked so extremely periscope-like and where the scientific species name comes from (from Greek γοργός ( gorgos ) for "terrible" and ὤψ ( ops ) for "face" or "countenance"). Hippopotamus gorgops achieved a wide distribution in eastern Africa and has been found at sites such as Olorgesailie in Kenya or Buia in Eritrea . The latter produced numerous fragments of teeth from around 1 million years ago. It is also probably the first member of the genus Hippopotamus to reach southern Africa. Finds include an approximately 69 cm long skull from Cornelia in the South African province of Free State . It dates to the Middle Pleistocene. Hippopotamus sirensis appeared in North Africa as early as the early Pleistocene . The large form is documented there from various sites, including Tighénif (Ternifine) in Algeria and Thomas Quarry in Morocco , both of which are important because of their finds of Homo erectus . Hippopotamus sirensis was found in large numbers in the then humid landscapes.

Apart from the already mentioned problematic finds from the Semliki, a partial skeleton from Gafalo in the Gobaad plain of Djibouti is currently the oldest evidence of the actual hippopotamus, which can thus be clearly identified in the Old Pleistocene around 1.6 million years ago. The carcass of Hippopotamus amphibius was found there together with the skeleton of the elephant representative Palaeoloxodon recki . Other early finds came to light in the upper sections of the Shungura Formation in the Omo Valley. Their age is around 1.38 million years. The finds from Nariokotome on western Lake Turkana are of a comparable age. An upper jaw from Asbole in the Awash Valley already belongs to the early Middle Pleistocene. Also from the region, around 700,000 year old footsteps have been described in Gombore, some of which are sunk 30 cm into the once muddy subsoil and sometimes still show the four toes. Other noteworthy fossil remains are distributed among the sites Lainyamok, Isenya and Kapthurin , all of them Kenya. In southern Africa, Hippopotamus amphibius is represented in Elandsfontein with more than 200 bone fragments from around a dozen individuals . The site is located in the southwest of South Africa and has a Middle Pleistocene time position.

Near Eastern finds

Fossil finds of Hippopotamus amphibius from Khall Amayshan, Saudi Arabia

Representatives of the genus Hippopotamus emigrated from Africa several times. The migration route probably took place via the Levant . From here, extensive fossil material has been documented, including from 'Ubeidiya in Israel , which dates back to around 1.4 million years. The allocation of the finds is not entirely clear, as they can be addressed either as Hippopotamus gorgops , Hippopotamus antiquus or as the local form Hippopotamus behemoth . A little later, hippos also appear in Latamne in Syria . The age data are inconsistent here, as both an old and a middle Pleistocene position come into question. In the Middle Pleistocene, Hippopotamus amphibius also reached the region, which may already have been present in Gesher Benot Ya'aqov in Israel. The site dates from 700,000 to 500,000 years ago. Determining the find material often proves difficult because it is largely highly fragmented. The species remained here until the Holocene and colonized the river valleys, possibly with an interruption during the cooler sections of the last glacial period . The hippopotamus spread from the Levant to the Arabian Peninsula , as evidenced by a large collection of finds from Khall Amayshan in the Nefud in Saudi Arabia . During the last warm period a good 110,000 years ago, there were individual lakes with a rich fauna. Another eastward expansion of the hippopotamus did not take place. This was possibly prevented by the fact that a comparable ecological niche was already occupied by representatives of the genus Hexaprotodon in southern and eastern Asia .

Europe and the islands of the Mediterranean

Skeletal reconstruction of Hippopotamus antiquus

Skeletal reconstruction of Hippopotamus tiberinus

In Europe, hippos have been recorded at least since the Old Pleistocene; the early forms are mostly assigned to Hippopotamus antiquus . One of the earliest finds with an upper incisor comes from the Coste San Giacomo site, southeast of Rome in central Italy . The site is believed to be around 2 million years old. Other old references were found in Spain, France and Greece, in the former with a row of teeth from Venta Micena near Granada around 1.6 million years old . Several partial skeletons from Untermaßfeld in Thuringia , which may have been washed ashore in a catastrophic river flood a good 1.07 million years ago, are of great importance . Of a total of more than 320 bone remnants, which belong to about 20 individuals, more than half were found to belong to young animals. Other important finds are from Collecurti halfway between Rome and Florence , again Italy. These, too, came to light in river deposits and are made up of around 400 bone elements from around a dozen individuals. Their geological age is almost the same as that of the Untermaßfeld hippos. The fossil remains from Het Gat are a specialty, as they were fished from the bottom of the North Sea roughly in the middle between the Netherlands and England. To the east, the form presumably penetrated into the Caucasus region, as again remains from the approximately 700,000 year old Georgian site of Akhalkalaki . Hippopotamus antiquus was a formidable animal, probably the largest hippopotamus to appear in Europe. The length dimensions of its individual skeletal elements are mostly 106 to 126% larger than the values ​​of the more recent animals. Based on the findings from Untermaßfeld and Collecurti, a weight of 2100 to 3200 kg can be inferred, other data range up to 4200 kg, which is roughly double that of today's hippopotamus. Towards the end of the Old Pleistocene , Hippopotamus tiberinus can still be detected. Its remains are much more sparse, however, the form is documented among other things from La Maglianella in Italy and possibly from Mosbach in Germany. Both forms may have a closer connection to the African hippopotamus gorgops , which is shown, among other things, by individual skull features. The skull turns out to be slimmer and longer compared to the actual hippopotamus and the eye sockets are more prominent.

Both the last appearance of the earlier European hippos and the first appearance of the classic hippopotamus amphibius in Europe can hardly be determined at the moment. The species was originally reported from the early Middle Pleistocene . As a single evidence, some tooth finds from Isernia la Pineta in the Molise region in central Italy were considered, but these are now classified as Hippopotamus antiquus . One of the most recent occurrences of Hippopotamus tiberinus can be found in the late Middle Pleistocene Castel di Guido, again in central Italy. Hippopotamus amphibius has a fairly frequent presence during the Eem warm period around 126,000 to 115,000 years ago. Important in this context are some sites in the Rhineland where the species appeared together with the European forest elephant and the water buffalo . Evidence to the extreme north was unearthed at Barrington in Cambridgeshire , from where extensive material from Hippopotamus amphibius is known. Individual teeth and vertebral remains also come from the banks of the Severn near Gloucester in Gloucestershire , both sites are in England . The individuals found in Barrington, with an estimated body weight of up to 3000 kg, almost regained the proportions of Hippopotamus antiquus . The settlement of the Central and Western European areas far north of the Alps during the last warm period requires individual ecological conditions. It is possible that the climate at that time was influenced by the maritime sector , with warm summers and, above all, mild, less frosty winters. As a result, the species is also missing in the more continental areas of Central and Eastern Europe and withdrew from these northern refuges at the end of the Eem warm period. In southern Europe, for example on the Balkan , Apennine and Iberian peninsulas , Hippopotamus amphibius probably persisted until the early Vistula glaciation . One example is the Grotta Romanelli near Lecce in southern Italy.

Skeletal reconstruction of hippopotamus minor

In the course of their fossil history in Europe, the hippos reached various islands in the Mediterranean , which applies to both Hippopotamus antiquus and Hippopotamus amphibius . There each time dwarfed forms emerged. The earliest finds in research history include those in Sicily and Malta . A distinction is made here as a rule with Hippopotamus pentlandi and Hippopotamus melitensis, two species that differ from one another in terms of their body size. The larger form, which weighed around 1100 kg, is provided by Hippopotamus pentlandi and was present on both islands. It belongs to the late Middle and early Young Pleistocene. There are numerous sites in Sicily in particular, such as Messina in the northeast or San Vito lo Capo in the northwest. Hippopotamus melitensis, on the other hand, is largely only occupied by Malta and forms the smaller form with an average weight of around 900 kg. At individual sites such as the Gamar Dalam , it occurs together with Hippopotamus pentlandi . Their exact geological time is often poorly understood. Both species may represent different stages of island dwarfing, which has progressed further in the latter due to the smaller island area and stronger endemism . However, due to the skull morphology, they are traced back to Hippopotamus amphibius as the original form. Finds of hippos also came to light on Crete as early as the middle of the 19th century. A larger part comes from the eastern island area, such as the Lasithi plateau or the Karoumes bay near Sitia . Further fossil remains could also be recovered from Akrotiri on the northwest coast. They are largely related to an Old to Middle Pleistocene, which is expressed, among other things, by the findings of Kritimys . It is a small representative of the hippopotamus, which was named Hippopotamus creutzburgi in 1966 . The origin of this form was discussed for a long time, today Hippopotamus antiquus is mostly considered an ancestor. Compared to these, Hippopotamus creutzburgi was clearly dwarfed with a weight of almost 400 kg. The smallest member of the Mediterranean hippopotamus is known from Cyprus and is led under the scientific name Hippopotamus minor . The animals were only reconstructed to weigh around 132 kg. The shape experienced the strongest impressions in the structure of the skull. The crest is no longer formed, and the posterior premolars are missing. The clear deviations from the mainland representatives also lead to a reference to a separate genus under the name Phanourios . In addition, the phylogenetic derivation is made more difficult, so that the direct ancestor could not yet be determined. Several dozen sites are known to exist on the island, including caves and abrises as well as open-air sites . One of the most important can be found in the south on the Akrotiri peninsula , where more than 218,000 hippopotamus remains of more than 500 individuals are documented in the collapsed Aetokremnos cave . They represent more than 90% of all faunistic finds. The immense accumulation of hippopotamus remains , the lack of larger predators on the island and original radiocarbon measurements , which gave the finds an age of around 11,800 years ago and thus a position at the end of the Pleistocene, led to the view that early human settlers were responsible . However, due to the lack of evidence of human manipulation, this view was viewed critically. More recent dates indicate that the lowest strata with the highest number of hippos was around 12,500 years ago. They are thus outside the time of the first appearance of humans on Cyprus, which means that the bone collections are probably to be assessed as natural.

Hippos of Madagascar

Skull of Hippopotamus Lemerlei

In addition to the various islands of the Mediterranean, the hippopotamus also reached Madagascar , which is at least 400 km east of Africa. Several dwarf forms also developed there. When the species first set foot on the island is unclear. The oldest finds so far are from the Belobaka cave in the northwest of the island and are around 20,600 years old, so they come from the high phase of the Last Cold Age . It is only a matter of individual teeth and foot bones of a young animal. However, these early representatives were not yet dwarfed, but came close to the original African form in terms of size. They are assigned to the species Hippopotamus laloumena . The species was described using a lower jaw from Mananjary on the east coast, which may only be 2500 years old. In addition to this form, with Hippopotamus lemerlei and Hippopotamus guldbergi , two other species belong to the Malagasy hippopotamus , which were significantly smaller and with a weight of about 374 and 393 kg respectively corresponded to today's pygmy hippopotamus . Both Malagasy forms differ in the position of the eye socket relative to the skull line, the thickening of the socket edges and in their limb proportions. The former has raised orbits with thickened margins, while the latter has a longer shin and a shorter femur . The variations are probably an expression of a different way of life. The earliest evidence of Hippopotamus guldbergi comes from the area around Tsaramody in the Sambaina Basin in the central highlands of Madagascar. With an age of 17,600 years ago, it dates to the end of the last glacial period. Several parts of the musculoskeletal system were found. Hippopotamus lemerlei is documented with a skull from the Ihazofotsy River in the south-central highlands of the Isalo Mountains from the beginning of the Holocene around 11,000 years ago. Both species were found together in several places and thus probably had a partly sympatric appearance. These common occurrences include Ampoza and Taolambiby in southwest Madagascar and Belo Sur Mer on the west coast. The age of the sites ranges from 1220 to 2713 years ago. Some of the hippopotamus bones found have marks, some of which are interpreted as cutting marks caused by humans. The view is not fully accepted because on the one hand there are similarities to gnawing traces of predators, on the other hand some absolute age data lie outside the earliest settlement of the island, which in a traditional view of the period around 500 BC. Is set. The most recent finds of hippos that have been directly dated include those of Itampolo on the southwest coast, which are around 1,000 years old. It is possible, however, that individual residual populations survived until contact with the Europeans in the 16th and 17th centuries or beyond, which individual mentions and folkloric elements suggest.

Spread of the hippos and the consequences of island dwarfing

The investigations into the locomotion of the hippopotamus and its limited swimming abilities in deeper water raised the question of how the animals could have reached the islands that might have been distant. The focus was primarily on islands such as Cyprus, Crete and Madagascar, which in the course of the recent geological past were not connected to the mainland during the lows of the seas in the course of the various cold phases of the Pleistocene. According to Paul PA Mazza , the hippopotamus could only reach distant islands via potential land bridges or in shallow water during periods of maximum freezing. However, these circumstances did not exist in the case of the three islands mentioned in the Pliocene and Pleistocene. Alexandra van der Geer and colleagues therefore state that there are different propagation scenarios. More or less random events could also take hold here, such as catastrophic events such as tsunamis or floods, whereby groups of hippos got into the sea. Surf currents or drifting plants could also play a role , albeit to a lesser extent. The special texture of the hippo's skin and the slow metabolism help the animals to survive such extreme situations. In addition, the buoyancy in the salty sea water compensates for the heavy bone structure. This is probably also the reason why the hippopotamus occurs today on Central Island in Lake Turkana . The island is about 9 km from the mainland and is surrounded by 50 m deep, but very salty water. In addition, young animals are much better swimmers than adult individuals and thus increase the chances of the group continuing to exist as such. Ultimately, other large mammals such as elephants also managed to reach distant islands.

The settlement of different islands led to the island dwarfing of the individual forms. This generally resulted in a slimming of the skeleton and shortening of the facial skull, which in turn led to changes in the structure of the teeth. This process may have a different background on the smaller Mediterranean islands than on the much larger Madagascar. Due to its size, Madagascar has numerous different habitats . Possibly the animals were therefore subject to various evolutionary constraints and developed the comparatively great diversity. Hippopotamus guldbergi shows significantly fewer adaptations to a semi-aquatic way of life than Hippopotamus lemerlei and was probably more terrestrially active. However, even on the Mediterranean islands, different forms of life developed compared to the actual hippopotamus. Part of this is due to the mostly stony subsoil and probably also to the noticeably drier climate. Some dwarf forms of the hippopotamus developed long phalanges and lost the wide hooves. They therefore moved more strongly than tiptoe , similar to goats . The animals were able to open up the rocky habitats and walk along steep slopes and on cliffs. They also used caves as a shelter or possibly as a resource for mineral-rich waters. Another noticeable change concerns the size of the brain , which did not decrease in proportion to the body size. Today's hippopotamus has a brain volume of 800 to 955 cm³. For the Malagasy pygmy hippopotamus this was reconstructed at 305 to 485 cm³, which corresponds to the range of variation for the pygmy hippopotamus. Hippopotamus minor, the smallest dwarfed hippopotamus, had a brain of 218 cm³. The encephalization quotient rose from 0.41 in today's hippopotamus to 0.58 in hippopotamus minor . In general, the hippopotamus has a very small brain compared to other ungulates. The trend towards a relative increase in brain size has also been proven in dwarf elephants.

Research history

Mentions in ancient historical literature

Individual ancient authors devoted themselves to the hippopotamus very early on. The oldest description comes from Hekataios of Miletus from the 6th century BC. He stated that the animal had split hooves, but resembled the horse in tail, mane and voice. This was adopted by numerous later scholars, including Herodotus , who wrote in his histories in the 5th century BC. Chr. Wrote:

“The hippos are considered sacred in the Papremis district, but not in the rest of Egypt. The hippopotamus looks like this: it has four feet, split claws, a blunt nose, a mane like a horse, protruding teeth, a horse's tail and voice, and is as big as a very large ox. The skin is so thick that you can turn the dried skin into lance shafts. "

- Herodotus, Historien II, chap. 71

Aristotle also reported on the hippopotamus and noted in his Historia animalium from the 4th century BC. The similarity of the internal organs with those of donkeys and horses, with the tail, however, it was more like pigs. Other authors such as Zenobios and Aelian emphasized the dangerousness and violence of animals. In the Naturalis historia , Pliny the Elder gives an exact picture of the way of life of the hippopotamus in the first century AD, although he took over parts of Herodotus. However, he already mentioned the characteristic red skin excretions. Furthermore, it can be seen from his work that around at least 58 BC A hippopotamus was used in a Roman arena. In the period that followed, various Roman rulers had hippos brought to Rome to allow them to appear at games, such as Nero and Antoninus Pius . According to Cassius Dio, Commodus alone is said to have defeated six hippos. But as early as the 4th century Themistios had to sum up that the hippopotamus had been exterminated in Lower Egypt because it destroyed plantings, but the disappearance of the animals had negative effects on the Games in Rome. Ammianus Marcellinus made a similar statement in roughly the same period, who also stated that the animals were to be found further south with the Blemmyans in Nubia .

Early modern times and first description

Historical illustration of a hippopotamus with a crocodile by Pierre Belon , 1553

Preparation of a hippopotamus known as Ippopotamo di Boboli in the Florentine Museum La Specola

One of the oldest descriptions of the hippopotamus in the western world was made by the French naturalist Pierre Belon in 1553, in which he devoted several pages to the animal. In it he also presented several images, including one showing the hippopotamus fighting with a crocodile. Belon's treatise is part of his travelogues, which were based on his expeditions through the island world of the Mediterranean , the Middle East and Egypt in 1547 and 1549. In 1598, Christoph Harant von Polschitz and Weseritz also went to the region and wrote down his experiences, which only appeared in German a good 80 years later. His remarks on the hippopotamus are heavily influenced by the ancient authors. At the turn of the 16th to the 17th century, the Italian doctor Federico Zerenghi reported on his ventures to Upper Egypt, on which, according to his own statements, he had killed two hippos and brought their skins back to his homeland. His publication was published in 1603 with a representation of the hippopotamus. The skins were later stuffed in Venice. The resulting preparations, however, contain some anatomical deviations, for example in the area of ​​the head and feet, the latter given an appearance that is more reminiscent of dog paws. One of the two preparations probably ended up in the La Specola Museum in Florence , where it is exhibited under the name Ippopotamo di Boboli . The name comes from the fact that allegedly at the turn of the 17th to the 18th century under Cosimo III. a hippopotamus roamed free in the Boboli Gardens , but there is no record of it. The whereabouts of the second preparation is currently unclear. In the further course of the 17th and 18th centuries, several explorers of southern Africa also mention the hippopotamus, including Étienne de Flacourt , the governor of Madagascar , in his travelogues from 1658. Johann Schreyer , who lived in southern Africa from 1668 to 1674 traveled, describes in 1681 the amphibious way of life of the animals and their nocturnal migrations from the resting places by the water to the pastures, but he describes them as "sea cows". Expressed a similar little later Simon van der Stel , the first Governor of the Cape Province , where the 1685-1686 Namaqualand in South West Africa in search of copper deposits explored and the river Verlorevlei , his Zeekoejen-valey ( "Sea Cow Valley"), Sighted hippos.

Historical depiction of a hippopotamus by Fabio Colonna , 1603

The painting “The Hippo Hunt” by Peter Paul Rubens , 1615

Fetus of a hippopotamus, historical illustration after Georges-Louis Leclerc de Buffon , 1764

In addition to these explorers, the scholars of Europe also dealt with the hippopotamus at an early age, but hardly saw a living specimen. In 1606, the Italian naturalist Fabio Colonna published a longer section on the hippopotamus in his Ekphrasis , to which he also contributed an illustration. As with Belon before, this seems a bit unrealistic in terms of body, head and foot design. Colonna had largely adopted his information on the animal from Pliny the Elder. However, he also mentioned Zerenghi, so it is believed that his image of the hippopotamus was influenced by one of the doctor's stuffed hides. Colonna's portrait of the hippopotamus would have a strong influence on the image of the animal in Europe in the period that followed. This can also be seen in part in the painting “The Hippopotamus Hunt” by Peter Paul Rubens , which was created in 1615 and shows the hippopotamus with a similar head and foot design. In addition, there were also significant modifications that gave the animal a more equine to cattle-like appearance. Georges-Louis Leclerc de Buffon wrote by far the most precise and comprehensive treatise of that time on the hippopotamus in 1764. It appeared in the twelfth volume of his work Histoire naturelle, générale et particulière, edited together with Louis Jean-Marie Daubenton . Buffon had not seen any living animals either, but in addition to the previously published articles by Belon, Zerenghi, Colonna and others, which he extensively cited and critically assessed, he also had a fetus , several skulls and foot bones available for his work. These were in the Cabinet du roi , the natural history cabinet of the French king and later the Muséum national d'histoire naturelle in Paris. In his work, he dedicates a copper engraving to the fetus with a full-grown animal in the background, which is a copy of Colonna's animal and appears in Buffon très-défectueuse ("extremely flawed"). His detailed descriptions not only accurately introduce the fetus, but also explain the internal organs and the umbilical cord . The same applies to the skulls and foot bones in words and pictures.

Carl von Linné

In 1758, before Buffon began his comprehensive elaborations on the hippopotamus, Linnaeus presented the first scientific description of both genus and species in the 10th edition of his work Systema Naturae , which is important for binomial nomenclature . He named the structure of the dentition as characteristic of the genus Hippopotamus . In this, he identified Belon's 1553 treatise as his main source. With habitat in Nilo et bambolo Africae et ad ostia fluviorum Asiae , Linnaeus indicated the Nile , Senegal and the estuaries of Asia as a type area. Oldfield Thomas restricted this to the Nile in 1911. In addition to the hippopotamus, Linnaeus also led the lowland tapir ( Tapirus terrestris ) within the genus Hippopotamus . He differentiated both forms on the basis of the number of toes, but they are not closely related to each other.

In the 19th century, extinct hippos were introduced scientifically for the first time. Georges Cuvier described several forms from Europe in 1804 without naming them scientifically. He distinguished between individual size variants, including a large one, which was available through fossil finds from Tuscany and the vicinity of Paris, and a small one with remains of unknown origin, but for which Cuvier assumed a Mediterranean origin due to the rock breccia in which they were stored. Based on Cuvier's work, Anselme Gaëtan Desmarest then assigned various scientific names in 1822. Of these, with Hippopotamus antiquus for the large form and with Hippopotamus minor for the smaller two representatives are recognized to this day. Only ten years later, Hermann von Meyer followed suit with the description of Hippopotamus pentlandi based on numerous bone remains from a cave near Palermo , Sicily . It would then again take around three and a half decades until Alfred Grandidier presented the remains of extinct hippos from Madagascar in 1868 with Hippopotamus lemerlei .

etymology

The name hippopotamus for the hippopotamus is a loan translation and Latinized form of the Greek word ἱπποπόταμος ( hippopótamos ), which is composed of the parts ἵππος ( hippos ) for "horse" and ποταμός ( potamos ) for "river". It has been used since ancient times . It can be found among others in Herodotus in the 5th century BC. BC, who at that time still stated ἵππος ποτάμιος ( hippos potamios ), which means something like "horse from the river". They also used Nikandros from colophon in the 2nd century BC. Chr. And Strabo at the turn of the times. The specific epithet amphibius is also of Greek origin ( ἀμφίβιος ) and refers to the amphibious way of life in water and on land. This has already been pointed out by individual authors of antiquity, such as Pliny the Elder.

Hippopotamus and human

Influences in human history and culture

Prehistoric use

Shoulder blade of a hippopotamus with cut marks from Gombore, Ethiopia, around 700,000 years old

Relations between humans and the hippopotamus began as early as the Old Pleistocene . They mainly consist of human use of the animal carcasses. It is uncertain whether the hippopotamus, as a large and dangerous creature, was also hunted at this point in time. The oldest references to the use of the animals can be found in cut marks on bones or in broken or broken skeletal elements. Such anthropogenic impacts have already been observed in the lower layers of the Olduvai Gorge ( FLK site ) in Tanzania and in Koobi Fora in Kenya, as well as in El Kherba in Algeria, they are each between 1.8 and 1.5 million years old old and are therefore in an old Paleolithic context. As a rule, these are individual finds that indicate an occasional use of the hippopotamus remains. This persists in the following time, so that the hippopotamus represents a regular, albeit rare, element of the human supply of food and raw materials. Here, too, there are examples from Olduvai ( BK site and SHK site ), as well as from Buia in Eritrea. The hippopotamus does not appear in significant numbers at any of these sites related to human remains. Some of the body parts that were separated from humans were later used by predators , as documented by a shoulder blade from Gombore in Ethiopia. A special feature with regard to the use of hippopotamus remains as raw material is an approximately 12.8 cm long hand ax made from a thigh bone from the 1.4 million year old Konso site , also in Ethiopia. In Europe, too, the hippopotamus can occasionally be found in connection with archaeological sites, for example in Marathousa on the Peloponnese in Greece , although here too there are usually individual finds.

The hippopotamus has a significantly higher proportion at some sites in the Affad Basin on the central reaches of the Nile in Sudan, which belong to the end of the Young Pleistocene around 15,000 years ago and go back to people of the late Middle Paleolithic . Among other things, a bone concentration of more than 180 skeletal elements of the hippopotamus was found, which corresponds to a good 19% of the determinable fauna material. However, no direct manipulation can be detected on any of the bones. With the subsequent settling down of humans, various Neolithic cultures emerged. Especially in the Nile Valley, the teeth of the hippopotamus, among other things, were used to manufacture various objects. Mention should be made in this context of the cemetery of Kadruka at the level of the third cataract of the Nile. A cosmetic container made from a canine, called a bucrania (actually a decorative element made from a cattle horn ), was found in a grave . The site belongs to the early to middle Neolithic of the 5th millennium BC. Another example is the cemetery of Kadero, northeast of Khartoum , which is also in the Neolithic context and has about the same age . In some of the more than 240 graves, various objects were found made from the canine teeth of the hippopotamus. But other parts of the body also found their way into human material culture. In addition to several vessels, bracelets and clam shells, Kadero's grave 244 also contained individual long, narrow objects with dimensions of around 5 × 30 cm. According to traces of use, they are probably scrap instruments made from the ribs of a hippopotamus. What is remarkable about Kadero is that the hippopotamus finds are often associated with burials of men or children and are sometimes very richly furnished. Some researchers therefore suspect that at that time the hunt for the animals was reserved for a certain group of people.

Outside of Africa, in the Neolithic and Chalcolithic times, the teeth of the hippopotamus were also processed by humans in the Levant . It is possible that the denser structure and the clearer white coloring are the main reasons for using hippopotamus ivory over elephant ivory, for example. Something similar can be said about the Aegean region . There ivory was used to manufacture seals , inlays or plaques or coverings, which, since the raw materials had to be imported, mostly represent luxury items. This lasted until at least the Mycenaean period . Although the tusks of the elephants were mainly used here, individual objects also consist of hippopotamus teeth. The Middle East and the Nile Valley in North Africa come into consideration as places of origin for the hippopotamus teeth, possibly with a transport across the Mediterranean . This suggests, among other things, the ship from Uluburun , which sank in front of today's Kaş in southeastern Turkey around 3400 years ago and was examined in the 1980s. In addition to numerous valuable objects made of gold, bronze and glass, as well as various ceramic shapes, it also contained elephant tusks and the teeth of hippos.

Artistic representations

In addition to the use of the hippopotamus as a food and raw material resource in prehistoric times, it also found its way into the performing arts. Thousands of years old rock paintings, such as those found in the Tassili n'Ajjer Mountains in Algeria , testify to this . The mountain range, which is protected by the 80,000 km² Tassili-n'Ajjer National Park, contains an estimated 15,000 individual images, some of which are also dedicated to the hippopotamus. A picture of a young animal can be found in the Oued Djerat gorge in the north of the mountains. The Big Hippo site in the Oued Afar around 20 km south of the Oued Djerat is of great importance , where 22 images of the hippopotamus alone have been discovered, the largest of which is 4.62 m long. The representations are kept quite simple and show the outline of the animals including the characteristic head with snout, eyes and ears without revealing any further details. As a rule, individual individuals are shown, in some cases several. A scenic depiction, on the other hand, shows a hippopotamus standing opposite an archer. Some of the images in Tassili-n'Ajjer depicting wild animals such as the hippopotamus, but also giraffes, elephants, rhinos and others were probably made in the early phase of rock art in the region, when the climatic conditions were even more humid. The rock art phase is known locally as the “big game fauna phase” and dates between 12,000 and 6,000 years ago. As the landscapes dried up, the large animals disappeared. The pictorial representations therefore increasingly switched to farm animals, which is why we also speak of the “pastoral phase” here. Other rock carvings of hippos are documented from the Messak Settafet in Libya , for example in Wadi Taleschout with 15 individual depictions alone. Apart from the North African rock art, portraits of hippos in the southern part of the continent can also be mentioned on various occasions. An outstanding example are those of the Matopo Mountains , which are enclosed by the Matobo National Park in western Zimbabwe . In addition, images from Mashonaland in the north of the state are known. In the latter area, for example, a depiction shows two animals with people moving around them, possibly performing a kind of rain dance and thus lending meaning to the hippopotamus' affinity for water.

Faience sculpture of a hippopotamus from the New Kingdom of Egypt , around 1500 to 1300 BC Chr.

Due to its presence on the Nile, the hippopotamus was also known in ancient Egypt . A wide variety of objects with a hippopotamus shape are already known from the Badari and Naqada cultures of the predynastic period . They had varying functions and included vessels, pendants or figurines. Ivory, chrysoprase and the like were used as materials . Several of these objects were found in graves, such as the large burial area at Mostagedda . In some cases the objects are very clearly recognizable as a hippopotamus, sometimes only the head is shown, in others they appear more abstract. The meaning of the objects is not clear, but they may have been in a magical context. In the Old Kingdom , Pepi II was depicted hunting hippos on a relief in his mortuary temple in Saqqara . Here harpooned the Pharaoh the animal in a scene in another it is transported on a sled. According to popular belief, hunting in the Old Kingdom was not to be understood as a sport, but symbolized the victory of order, visualized by the ruler, over chaos, represented by the wild animal. Depictions of hippos in the Middle and New Kingdom were much more intimate . Not only that the hunt for the animals was illustrated on scarabs and private seal amulets , also numerous small figurines made of faience emerged during this time , around 50 to 60 such figurines are documented from the Middle Kingdom alone. Often they were buried as gifts. Possibly they replaced the temple reliefs here equally and then had a comparable function. Depictions of hippos were possibly also connected to the Egyptian goddess Taweret , who, as the mistress of the household, was responsible for protecting pregnant women and who, as a hybrid creature, carried the head of a hippopotamus, sometimes the body is also designed like a hippopotamus. It gained greater importance in the New Kingdom, previously its position was taken by other goddesses, some of whom were associated with the hippopotamus, such as Ipet and Reret . In the ancient Egyptian belief, however, the hippopotamus not only possessed protective properties, as it also developed destructive powers in the company of Seth , the god of doom and chaos and Tawaret's consort. However, it was largely only given the latter attributes in the New Kingdom with the ostracism of Seth.

Other cultural references

According to some scientists, the goddess Tawaret or her older incarnations were the godfathers of the " Minoan Genius ", a type of demonic creature that was found during the Middle Minoan period in the second millennium BC. BC and was of importance in religious festivals and ceremonies. In the initial phase, the "Minoan Genius" was still very similar to its Egyptian counterpart, had a hippopotamus or lion-like head and had the body of a pregnant woman. In later times, however, its external attributes changed, it became more lion-like with a male body up to an insectoid appearance. In this modification it then also reached the Greek mainland. The way in which this mythical figure was spread has not yet been clarified. While some scholars see a direct origin from Egypt, others favor a detour via the Levant, where similar figures appear at the same time. Apart from the transfer of mythical figures, remains of pygmy hippopotamuses have been found in some ancient sites in the Mediterranean. Unlike the pygmy elephants , some of which were associated with the Cyclopes of Greek mythology , there is no equivalent for the pygmy hippopotamus. More recently, the bones were thought to be the remains of dragons or saints and were ground into powder for medicinal purposes.

Behemoth , a monster known from the Jewish community , is sometimes interpreted as a hippopotamus. In the book of Job there is a more detailed description of the Behemoth, which depicts him as a large and powerful being lying in the water or mud and devouring the river with its mouth open. It would also eat grass like a cow. The comparison of the behemoth with the hippopotamus is not shared in every case. Nevertheless, this had an influence on the naming of the animal in different languages: the hippopotamus is called бегемот ( transcribed Begemot or Behemot ) in Russian , Belarusian and Ukrainian , which is also used in the Kazakh , Azerbaijani and Tajik languages ( Баҳмут , Bachmut ) has found.

Medieval and early modern ivory trade

The use of ivory as a raw material, regardless of its origin, from elephants or hippopotamus, has been demonstrable in Africa since prehistoric times. The tradition was continued in later times. Especially from the 10th to 14th centuries under Muslim rule, there was brisk trade from West to North Africa, some of which also reached southern Europe. Important craft workshops were found in the Maghreb , for example . However, the Arab scholars of the time rarely made a distinction in the origin of the raw material, so that the hippopotamus is only rarely referred to. It is assumed that the cause is that they were familiar with the elephants but largely unknown to the hippopotamus. This also led to the confusion of animals, for example when Ibn Battūta traveled through Mali in the 14th century. However, a hoard discovered in Gao in Mali in 1993, which dates back to the 11th century and consists of at least 53 teeth that had been deposited in a pit, points to the great importance of hippopotamus ivory . The ivory trade took on larger dimensions during the European colonial era . For example, the Portuguese shipped elephant tusks from the Southeast African coast to India and traded them for spice . The discovery of a wreck from the 17th century off the coast of the Indian state of Goa , which contained a total of nine specimens , shows that there were also teeth of hippos among them .

A neozoon in South America

The only wild hippopotamus population outside of Africa exists in South America in lakes in the basin of the Río Magdalena in Colombia . In 1981 Pablo Escobar , leader of the Medellín cartel , imported four animals (three female and one male) from a zoo in the United States . At first they lived together with other species in the drug dealer's private zoo on the Hacienda Nápoles near Puerto Triunfo and around 13.5 km west of the Río Magdalena. With Escobar's death in 1993, most of the animals were distributed to zoos, but the hippos, which were difficult to transport, remained on site, where the Hacienda Nápoles gradually fell into disrepair. Thirteen years later, after the site had been converted into a tourist amusement park, 16 hippos were already living in the area, which consists of various marshlands and wetlands ( ciénagas ), artificial lakes and small rivers. As early as 2009, individual individuals were found in a region around 75 km further north. The following year a hippopotamus was first observed in the Río Magdalena and three years later in the Río Cocorná , a tributary. It is estimated that between 65 and 80 individuals lived in the region in 2020, with individual sightings up to 150 km from the place of origin. With a conservative assumption of a reproduction rate of 7 to 8%, which roughly corresponds to that of the hippopotamus in Africa, the population could grow to 400 to 800 individuals by 2050, under favorable circumstances with a growth rate of 11% - the animals have in South America no natural enemies and the death rate of the young animals is very low - even up to 5000. As in Africa, the animals ensure a considerable input of nutrients into their living waters by grazing on land and releasing their excretions in the water, which leads to a bloom of the phytoplankton and as a result also leads to a strong increase in zooplankton . In the opinion of some researchers, however, the effects are not very dramatic, since it is possibly a matter of the restoration of an original state that had prevailed until the megafauna became extinct at the end of the Pleistocene during the Quaternary extinction wave. Accordingly, the hippopotamus occupies the position in South America that at that time also semi-aquatic representatives of the extinct South American ungulates such as Trigonodops held in the ecosystem of South American rivers. On the other hand, two larger aquatic to semi-aquatic adapted mammals live in the region with the Caribbean manatee and the capybara , so that the hippopotamus creates additional competition for this . Other scientists therefore advocate extermination of the hippopotamus population, be it through sterilization or targeted killing.

Threat and protection

Depiction of the hippo hunt from 1876

Hippopotamus as food in what was then German East Africa

The IUCN classifies the hippopotamus in its entire population as "endangered" ( vulnerable ). According to estimates from 2016, there are around 115,000 to 130,000 animals worldwide. Earlier data for the total population of up to 148,000 individuals, which the IUCN published in 2008, are attributed to an overestimation of individual regional populations . Overall, the population of the hippopotamus proved to be relatively stable. However, regional and local fluctuations can occur. The number of animals in the Masai Mara along the Mara River and adjacent areas increased from 2330 individuals in 1984 to 4170 in 2006, which may be related to the favorable landscape conditions in the region. In other areas such as Gonarezhou National Park in Zimbabwe there was a decline in populations over a comparable period, partly triggered by periods of drought. In the area of ​​its occurrence, the hippopotamus is present in numerous protected areas, sometimes the species can also be found outside. However, in some parts it has also become extinct or very rare.

The loss of habitat is viewed as a major threat factor, which is often associated with the expansion of areas used for agriculture and livestock or water-regulating measures. The dependence of the hippopotamus on water leads to conflicts with the local population. In Kenya , almost 4,500 human-hippopotamus conflicts were registered between 1997 and 2008, which increased, among other things, during periods of major drought . In addition, the looting of fields by hippos has also been observed more frequently. In western and central Africa, the fragmentation of the hippopotamus populations into small units also plays a role, which are then often limited to individual, sometimes poorly managed reserves. Illegal hunting is another threat to the existence of the hippopotamus, which in the 1990s and early 2000s led, among other things, to severe falls in the population of hippos. On the one hand, the meat forms a food resource, for example in Burkina Faso , Burundi , the Ivory Coast or in South Sudan ; on the other hand, the ivory of the teeth is intensively traded. The latter can rise sharply, especially in countries with ongoing civil unrest or civil wars . The hippopotamus in the Democratic Republic of the Congo collapsed by 95% at the beginning of the 21st century as a result of eight years of unrest, while in Mozambique the population fell by around 70% between 1980 and 1992 during the civil war. The trade in hippopotamus ivory also increased massively with the ban on elephant ivory in 1989. Between 1991 and 1992 alone, around 27 t of hippopotamus canine teeth were traded in Uganda, compared to 12 t in the previous two years. A large part of the exchange takes place via Hong Kong , in 75% of the cases Uganda and Tanzania are the countries of origin. Sometimes, however, more hippopotamus teeth are imported into Hong Kong than officially exported from the countries of origin. According to studies by CITES , this affected a total of 14.2 t for the period from 1995 to 2013, which corresponds to around 2700 hippos or around 2% of the total population. As a result, in addition to the conservation of the landscape, the reduction of illegal hunting is of great importance for the protection of the hippopotamus.

In contrast to other large animals such as the elephant or the rhinoceros , the hippopotamus attracted attention relatively late in the western world. The first animal recently kept in a zoo was an individual called " Obaysch " who came to the London Zoo in 1850 and caused a real "hippomania". In other places, too, hippos later became popular zoo animals, for example " crumples " in the Berlin zoo. Today the species is relatively common in zoological facilities. In Germany alone there are more than half a dozen postures, with numerous additional ones being added across Europe and in the Middle East.

Danger to humans

Warning sign on the Zambezi

It is widely believed that the hippopotamus is one of the most dangerous large animals in Africa and that it causes more deaths than crocodiles or big cats , for example . Despite their sedate appearance, the animals can be very aggressive, especially mothers with young animals and distressed or wounded individuals. Many reports concern fishermen who came too close to or in groups of hippos in their boats and capsized, injured or killed in any attack. Dangerous situations can also arise on land at night when people get into groups of hippos on their way to their pastures. However, there are no statistics on the actual number and course of such encounters. The animals often tolerate groups of people up to a certain distance.

literature

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Individual evidence

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213. ↑ DN Castelblanco-Martínez, RA Moreno-Arias, JA Velasco, JW Moreno-Bernal, S. Restrepo, EA Noguera-Urbano, MP Baptiste, LM García-Loaiza and G. Jiménez: A hippo in the room: Predicting the persistence and dispersion of an invasive mega-vertebrate in Colombia, South America. Biological Conservation 253, 2021, p. 108923, doi: 10.1016 / j.biocon.2020.108923
214. ↑ Erustus M. Kanga, Joseph O. Ogutu, Han Olff and Peter Santema: Population trend and distribution of the Vulnerable common hippopotamus Hippopotamus amphibius in the Mara Region of Kenya. Oryx 45 (1), 2011, pp. 20-27, doi: 10.1017 / S0030605310000931
215. ↑ Patience Zisadza, Edson Gandiwa, Hugo van der Westhuizen, Elsabe van der Westhuizen and Vimbainashe Bodzo: Abundance, distribution and population trends of hippopotamus in Gonarezhou National Park, Zimbabwe. South African Journal of Wildlife Research 40 (2), 2010, pp. 149-157, doi: 10.3957 / 056.040.0206
216. ↑ Erustus M. Kanga, Joseph O. Ogutu, Hans-Peter Piepho and Han Olff: Human – hippo conflicts in Kenya during 1997–2008: vulnerability of a megaherbivore to anthropogenic land use changes. Journal of Land Use Science 7 (4), 2012, pp. 395-406, doi: 10.1080 / 1747423X.2011.590235
217. ↑ Alexandra Andersson and Luke Gibson: Missing teeth: Discordances in the trade of hippo ivory between Africa and Hong Kong. African Journal of Ecology 56 (1), 2017, pp. 235–243, doi: 10.1111 / aje.12441
218. ↑ Nina J. Root: Victorian England's Hippomania. Natural History 103, 1993, pp. 34-39
219. ↑ Zoo animal list ( [27] ), last accessed on October 12, 2020

Remarks

1. ↑ In some cases extreme values ​​of 509 cm and 4500 kg are given for head-torso length and weight, for example in Ronald M. Nowak in Walker's Mammals of the World. Johns Hopkins University Press, Baltimore 1999. Already in the first edition of 1964, the weight was estimated at 3 to 4.5 metric tons , which is far above the values ​​given in studies of different populations in the scientific literature. Especially in the 1950s and 1960s, weights were given variously in pounds (lb), for example in Bere 1959 in Oryx 5 (3), pp. 116-124 and Pienaar et al. 1966 in Koedoe 9 (1), pp. 1-15. In Pienaar et al. In 1966, adult hippos weighed between 3,000-over 4,000 lbs. (summed up for both sexes). The maximum stated here for an individual from Kruger National Park in South Africa of 4,412 lbs. leads to a weight of 1999 kg. In Bere 1959, the maximum figure for an animal from the Murchison Falls National Park in Uganda is 4.454 lb. converted 2018 kg. However, it is unclear whether there is a unit error in Walker's Mammals of the World .

Web links

Commons : Hippos  - Album with pictures, videos and audio files

Wiktionary: Hippopotamus  - explanations of meanings, word origins, synonyms, translations

Wiktionary: Hippopotamus  - explanations of meanings, word origins, synonyms, translations

• Hippopotamus amphibius in the endangered Red List species the IUCN 2017. Posted by: RL Lewison & J. Pluháček, 2016. Retrieved on 9 October 2020th
• Hippo on ultimateungulate.com (English)

This article was added to the list of excellent articles on April 25, 2021 in this version .