Hippopotamus

The Latin word is derived from the Ancient Greek (), from () and () , together meaning . In English, the usual plural is "hippopotamuses". ==Taxonomy and origins==

Classification The common hippopotamus and the pygmy hippopotamus are the only living members of the family Hippopotamidae. Some taxonomists place hippos and anthracotheres in the superfamily Anthracotheroidea. Hippopotamidae are classified along with other even-toed ungulates in the order Artiodactyla. • H. a. amphibius – (the nominate subspecies) ranges from Gambia east to Ethiopia and then south to Mozambique and historically ranged as far north as Egypt; its skull is distinguished by a moderately reduced preorbital region, a bulging dorsal surface, elongated mandibular symphysis and larger chewing teeth. • H. a. kiboko – found in Kenya and Somalia; was noted to be smaller and more lightly coloured than other hippos with wider nostrils, somewhat longer snout and more rounded and relatively raised orbits with the space between them being incurved. • H. a. capensis – found in Zambia and South Africa; distinguished by wider orbits. • H. a. tschadensis – ranges between Chad and Niger; featured a slightly shorter but broader face, and pronounced, forward-facing orbits. • H. a. constrictus – ranges from the southern Democratic Republic of Congo to Angola and Namibia; skull characterised by a thicker preorbital region, shorter snout, flatter dorsal surface, reduced mandibular symphysis and smaller chewing teeth. The suggested subspecies above were never widely used or validated by field biologists; the described morphological differences were small enough that they could have resulted from simple variation in nonrepresentative samples. A study examining mitochondrial DNA from skin biopsies taken from 13 sampling locations found "low, but significant, genetic differentiation" among H. a. amphibius, H. a. capensis, and H. a. kiboko. Neither H. a. tschadensis nor H. a. constrictus have been tested. Evolution Until 1909, naturalists classified hippos together with pigs based on molar patterns. Several lines of evidence, first from blood proteins, then from molecular systematics, and the fossil record, show their closest living relatives are cetaceans (whales, dolphins, and porpoises). magnum'' from the Oligocene of Europe The most recent theory of the origins of Hippopotamidae suggests hippos and whales shared a common semiaquatic ancestor that branched off from other artiodactyls around . One branch would evolve into cetaceans, possibly beginning about , with the protowhale Pakicetus and other early whale ancestors collectively known as Archaeoceti. This group eventually underwent aquatic adaptation into the completely aquatic cetaceans. These groups lived across Eurasia and Africa. The discovery of Epirigenys in East Africa, which was likely a descent of Asian anthracotheres and a sister taxon to Hippopotamidae, suggests that hippo ancestors entered Africa from Asia around . An early hippopotamid is the genus Kenyapotamus, which lived in Africa from 15 to . The oldest records of the genus Hippopotamus date to the Pliocene (5.3–2.6 million years ago). Extinct species Three species of Malagasy hippopotamus became extinct during the Holocene on Madagascar, the last of them within the past 1,000 years. The Malagasy hippos were smaller than the modern hippo, likely a result of the process of insular dwarfism. Fossil evidence indicates many Malagasy hippos were hunted by humans, a factor in their eventual extinction. Hippopotamus gorgops from the Early Pleistocene to the early Middle Pleistocene of Africa and West Asia grew considerably larger than the living hippopotamus, with an estimated body mass of over . Hippopotamus antiquus ranged throughout Europe, extending as far north as Britain during the Early and Middle Pleistocene epochs, before being replaced by the modern H. amphibius in Europe during the latter part of the Middle Pleistocene. The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands, including Crete (Hippopotamus creutzburgi), Cyprus (the Cyprus dwarf hippopotamus, Hippopotamus minor), Malta (Hippopotamus melitensis), and Sicily (Hippopotamus pentlandi). Of these, the Cyprus dwarf hippo survived until the end of the Pleistocene or early Holocene. Evidence from the archaeological site Aetokremnos continues to cause debate on whether or not the species was driven to extinction or even encountered by humans. ==Characteristics==

, showing the large canines and incisors used for fighting The hippopotamus is a megaherbivore and is the third-largest land mammal after elephants and some rhinoceros species. The mean adult weight is around for bulls and for cows. Exceptionally large males have been recorded reaching . Male hippos appear to continue growing throughout their lives, while females reach maximum weight at around age 25. It is long, including a tail of about in length and tall at the shoulder, with males and females ranging and tall at the shoulder respectively. Hippos have barrel-shaped bodies with short tails and legs, and an hourglass-shaped skull with a long snout. Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden. The toes are webbed and the pelvis rests at an angle of 45 degrees. The hippo's jaw is powered by huge masseter and digastric muscles, and the hinge is located far back enough so that they can open their mouths at 100–110 degrees. On the lower jaw, the incisors and canines grow continuously, the former reaching , while the latter can grow to up to . The lower canines are sharpened through contact with the smaller upper canines. The canines and incisors are used mainly for combat instead of feeding, Hippos rely on their flattened, horny lips to grasp and pull grasses which are then passed to the molars, This natural sunscreen cannot prevent the animal's skin from cracking if it stays out of water too long. The testes of the males do not fully descend and a scrotum is not present. In addition, the penis retracts into the body when not erect. The genitals of the female hippos are unusual in that the vagina is ridged and the vulval vestibule has two large, protruding diverticula. Both of these have an unknown function. until her death in 2012 at the age of 61. Two hippos share the record for the oldest hippo ever recorded at 65 years. Bertha, a female Hippo, who lived in the Manila Zoo in the Philippines since it first opened in 1959 until her death in July 2017, and male Hippo Lu, from the Ellie Schiller Homosassa Springs Wildlife State Park, who was born at the San Diego Zoo on January 26th, 1960, and died at Homosassa, where he died in June 2025, also at the age of 65.{{Cite web |last= |date=2025-06-08 |title=Lu, Citrus County's celebrity hippo, dies at 65 |url=https://www.chronicleonline.com/news/local/lu-citrus-county-s-celebrity-hippo-dies-at-65/article_38cbe57c-5def-53ff-a563-d589cdd235d5.html |access-date=2025-06-09 |website=Chronicle Online ==Distribution and status==

Hippopotamus amphibius arrived in Europe around 560–460,000 years ago, during the Middle Pleistocene. The distribution of Hippopotamus amphibius in Europe during the Pleistocene was largely confined to Southern Europe, including the Iberian Peninsula, Italy (southwards to Sicily), Greece, and probably Herzegovina, but extended into northwestern Europe, including northern France, Great Britain (as far north as Stockton-on-Tees Analysis of ancient DNA indicates that Late Pleistocene European hippopotamuses are closely related to and nested within the genetic diversity of living African hippopotamuses. The youngest records of the species in Europe are from the Late Pleistocene of Greece, and the Rhine Graben of southwest Germany, dating to around 40–30,000 years ago. and probable remains from the Rub' al Khali desert in southern Saudi Arabia. Remains are also known from Shanidar Cave in northern Iraq, suggested to be Late Pleistocene in age. Archaeological evidence exists of its presence in the Levant, dating to less than 3,000 years ago. H. amphibius was also formerly present in the Maghreb in northern Algeria and Morocco during the Middle-Late Pleistocene, with H. amphibius remains in the region historically assigned to the species "H. icosiensis". In the African Humid Period during the early Holocene, around 10-4,000 years ago, the range of hippopotamuses extended across the Sahara (which at that time formed an extensive savannah crossed with rivers and lakes, leading it to be dubbed the "Green Sahara"), as indicated by finds of hippopotamus remains and rock art depicting them. For much of the historical period, the hippopotamus was present in the Egyptian part of the Nile from the Sudan border to the Nile Delta, but their distribution appears to have fragmented from the Ptolemaic and Roman periods onwards, especially during the early modern period, due to persecution by humans, with hippos having becoming rare in the Egyptian Nile by 1600, by which time they were only found in the eastern delta near Damietta and the southern Nubian part of the Egyptian Nile near the Sudan border, where some records suggest they persisted into the early 19th century (though at least some of these animals may have been swept in from Sudan). Reports of the slaughter of the last hippo in Natal in modern South Africa were made at the end of the 19th century. Hippos are still found in the rivers and lakes of the northern Democratic Republic of the Congo, Uganda, Tanzania, and Kenya, north through to Ethiopia, Somalia, and Sudan, west to The Gambia, and south to South Africa. As of 2017, the IUCN Red List drawn up by the International Union for Conservation of Nature (IUCN) lists the species as vulnerable, with a stable population estimated between 115,000 and 130,000 animals. By 2005, the population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid-1970s. The poachers are believed to be Mai-Mai rebels, underpaid Congolese soldiers, and local militia groups. Reasons for poaching include the belief hippos are harmful to society, as well as financial gain. The sale of hippo meat is illegal, but black-market sales are difficult for Virunga National Park officers to track. Hippo meat is highly valued in some areas of central Africa and the teeth may be used as a replacement for elephant ivory. A population of hippos exists in Colombia, descended from captive individuals that escaped from Pablo Escobar's estate after his death in 1993. Their numbers grew to 100 by the 2020s and ecologists believe the population should be eradicated, as they are breeding rapidly and are an increasing menace to humans and the environment. Attempts to control them include sterilisation and culling. ==Behaviour and ecology==

Hippos are semiaquatic and require enough water to immerse in, while being close to grass. They are incapable of jumping but can walk up steep banks. Because of their size and their habit of taking the same paths to feed, hippos can have a significant impact on the land across which they walk, keeping the land clear of vegetation and depressing the ground. Over prolonged periods, hippos can divert the paths of swamps and channels. By defecating in the water, the animals also appear to pass on microbes from their gut, affecting the biogeochemical cycle. On occasion, hippos have been filmed eating carrion, usually near the water. There are other reports of meat-eating and even cannibalism and predation. Hippos' stomach anatomy lacks adaptions to carnivory, and meat-eating is likely caused by lack of nutrients or represents an abnormal behaviour. Hippo pods fluctuate but can contain over 100 hippos. Although they lie close together, adults develop almost no social bonds. Males establish territories in water but not land, and these may range in lakes and in rivers. Territories are abandoned when the water dries up. The bull has breeding access to all the cows in his territory. Younger bachelors are allowed to stay as long as they defer to him. A younger male may challenge the old bull for control of the territory. Within the pods, the hippos tend to segregate by sex and status. Bachelor males lounge near other bachelors, females with other females, and the territorial male is on his own. When hippos emerge from the water to graze, they do so individually. When threatened or alarmed, they produce exhalations, They have the unique ability to hold their heads partially above the water and send out a cry that travels through both water and air; individuals respond both above and below water. Reproduction Cows reach sexual maturity at five to six years of age and have a gestation period of eight months. A study of endocrine systems revealed cows may begin puberty at as early as three or four years. Bulls reach maturity at around 7.5 years. Both conceptions and births are highest during the wet season. Male hippos always have mobile spermatozoa and can breed year-round. Calves may be temporarily kept in nurseries, guarded by one or more adults, and will play amongst themselves. Calves no longer need to suckle when they are a year old. Lions occasionally prey on adults at Gorongosa National Park and calves are sometimes taken at Virunga. Crocodiles are frequent targets of hippo aggression, probably because they often inhabit the same riparian habitats; crocodiles may be either aggressively displaced or killed by hippos, although they will avoid crocodiles larger than . In turn, very large Nile crocodiles have been observed preying occasionally on calves, "half-grown" hippos, and possibly also adult female hippos. Groups of crocodiles have also been observed finishing off still-living male hippos that were previously injured in mating battles with other males. Hippos occasionally visit cleaning stations in order to be cleaned of parasites by certain species of fishes. They signal their readiness for this service by opening their mouths wide. This is an example of mutualism, in which the hippo benefits from the cleaning while the fish receive food. Hippo defecation creates allochthonous deposits of organic matter along the river beds. These deposits have an unclear ecological function. A 2015 study concluded hippo dung provides nutrients from terrestrial material for fish and aquatic invertebrates, while a 2018 study found that their dung can be toxic to aquatic life in large quantities, due to absorption of dissolved oxygen in water bodies. The parasitic monogenean flatworm Oculotrema hippopotami infests hippopotamus eyes, mainly the nictitating membrane. It is the only monogenean species (which normally live on fish) documented to live on a mammal. ==Relationship with humans==

), Middle Kingdom of Egypt, 1961–1878 BC Cut marks on bones of H. amphibius found at Bolomor Cave, a site in Spain preserving fossils dating from 230,000 to 120,000 years ago, provides evidence for Neanderthal butchery of hippopotamuses. The earliest evidence of modern human interaction with hippos comes from butchery cut marks on hippo bones found at the Bouri Formation and dated to around 160,000 years ago. 4,000–5,000 year old art showing hippos being hunted have been found in the Tassili n'Ajjer Mountains of the central Sahara near Djanet. The hippo was also known to the Greeks and Romans. The Greek historian Herodotus described the hippo in The Histories (written circa 440 BC) and the Roman naturalist Pliny the Elder wrote about the hippo in his encyclopedia Naturalis Historia (written circa 77 AD). The Yoruba people called the hippo erinmi, which means "elephant of the water". Some individual hippos have achieved international fame. Huberta became a celebrity during the Great Depression for trekking a great distance across South Africa. Hippos can easily capsize small boats and injure or kill passengers. In one 2014 case in Niger, a boat was capsized by a hippo and 13 people were killed. Hippos will often raid farm crops if the opportunity arises, and humans may come into conflict with them on these occasions. These encounters can be fatal to either humans or hippos. According to the Ptolemaic historian Manetho, the pharaoh Menes was carried off and then killed by a hippopotamus. In zoos lounging at the London Zoo in 1852 Hippos have long been popular zoo animals. The first record of hippos taken into captivity for display is dated to 3500 BC in Hierakonpolis, Egypt. The first zoo hippo in modern history was Obaysch, who arrived at the London Zoo on 25 May 1850, where he attracted up to 10,000 visitors a day and inspired a popular song, the "Hippopotamus Polka". Hippos generally breed well in captivity; birth rates are lower than in the wild, but this can be attributed to zoos' desire to limit births, since hippos are relatively expensive to maintain. Starting in 2015, the Cincinnati Zoo built a US$73 million exhibit to house three adult hippos, featuring a tank. Modern hippo enclosures also have a complex filtration system for waste, an underwater viewing area for the visitors, and glass that may be up to thick and capable of holding water under pressures of . The Ijaw people of the Niger Delta wore masks of aquatic animals like the hippo when practising their water spirit cults, and hippo ivory was used in the divination rituals of the Yoruba. Hippo masks were also used in Nyau funerary rituals of the Chewa of Southern Africa. The Behemoth from the Book of Job, 40:15–24 is thought to be based on the hippo. Hippos have been the subjects of various African folktales. According to a San story, when the Creator assigned each animal its place in nature, the hippos wanted to live in the water, but were refused out of fear they might eat all the fish. After begging and pleading, the hippos were finally allowed to live in the water on the condition they would eat grass instead of fish, and fling their dung so it can be inspected for fish bones. In a Ndebele tale, the hippo originally had long, beautiful hair, but it was set on fire by a jealous hare and the hippo had to jump into a nearby pool. The hippo lost most of his hair and was too embarrassed to leave the water. Hippopotamuses were rarely depicted in European art during the Renaissance and Baroque periods, due to less access to specimens by Europeans. One notable exception is Peter Paul Rubens' The Hippopotamus and Crocodile Hunt (1615–1616). Hippos even inspired a popular board game, Hungry Hungry Hippos. Among the most famous poems about the hippo is "The Hippopotamus" by T. S. Eliot, where he uses a hippo to represent the Catholic Church. Hippos are mentioned in the novelty Christmas song "I Want a Hippopotamus for Christmas" that became a hit for child star Gayla Peevey in 1953. They also featured in the popular "The Hippopotamous Song" by Flanders and Swann. ==See also==