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The hippopotamus (''Hippopotamus amphibius;'' ; : hippopotamuses), often shortened to hippo (: hippos), further qualified as the common hippopotamus, Nile hippopotamus and river hippopotamus, is a large
semiaquatic In biology, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
native to
sub-Saharan Africa Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the list of sovereign states and ...
. It is one of only two
extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
in the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Hippopotamidae Hippopotamidae is a family of stout, naked-skinned, and semiaquatic artiodactyl mammals, possessing three-chambered stomachs and walking on four toes on each foot. While they resemble pigs physiologically, their closest living relatives are th ...
, the other being the
pygmy hippopotamus The pygmy hippopotamus or pygmy hippo (''Choeropsis liberiensis'') is a small Hippopotamidae, hippopotamid which is native to the forests and swamps of West Africa, primarily in Liberia, with small populations in Sierra Leone, Guinea, and Ivory Co ...
(''Choeropsis liberiensis'' or ''Hexaprotodon liberiensis''). Its name comes from the
ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...
for "river horse" (). After
elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...
s and
rhinoceros A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...
es, the hippopotamus is the next
largest land mammal The following is a list of largest mammals by family. Tenrecs and allies (Afrosoricida) *The largest of these insectivorous mammals is the giant otter shrew (''Potamogale velox''), native to Central Africa. This species can weigh up to and m ...
. It is also the largest extant land
artiodactyl Artiodactyls are placental mammals belonging to the order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other t ...
. Despite their physical resemblance to
pig The pig (''Sus domesticus''), also called swine (: swine) or hog, is an omnivorous, domesticated, even-toed, hoofed mammal. It is named the domestic pig when distinguishing it from other members of the genus '' Sus''. Some authorities cons ...
s and other terrestrial even-toed ungulates, the closest living relatives of the hippopotamids are
cetacea Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...
ns (
whale Whales are a widely distributed and diverse group of fully Aquatic animal, aquatic placental mammal, placental marine mammals. As an informal and Colloquialism, colloquial grouping, they correspond to large members of the infraorder Cetacea ...
s,
dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...
s,
porpoise Porpoises () are small Oceanic dolphin, dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and Beluga whale, belugas than to the Oceanic dolphi ...
s, etc.), from which they diverged about 55 million years ago. Hippos are recognisable for their barrel-shaped torsos, wide-opening mouths with large canine tusks, nearly hairless bodies, pillar-like legs, and large size: adults average for bulls (males) and for cows (females). Hippos inhabit rivers, lakes, and
mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...
swamps.
Territorial A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...
bulls each preside over a stretch of water and a group of five to thirty cows and calves.
Mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. '' Copulation'' is the union of the sex organs of two sexually repr ...
and birth both occur in the water. During the day, hippos remain cool by staying in water or mud, emerging at dusk to graze on grasses. While hippos rest near each other in the water, grazing is a solitary activity and hippos typically do not display territorial behaviour on land. Hippos are among the most dangerous animals in the world due to their aggressive and unpredictable nature. They are threatened by
habitat loss Habitat destruction (also termed habitat loss or habitat reduction) occurs when a natural habitat is no longer able to support its native species. The organisms once living there have either moved elsewhere, or are dead, leading to a decrease ...
and
poaching Poaching is the illegal hunting or capturing of wild animals, usually associated with land use rights. Poaching was once performed by impoverished peasants for subsistence purposes and to supplement meager diets. It was set against the huntin ...
for their meat and
ivory Ivory is a hard, white material from the tusks (traditionally from elephants) and Tooth, teeth of animals, that consists mainly of dentine, one of the physical structures of teeth and tusks. The chemical structure of the teeth and tusks of mamm ...
(canine teeth).


Etymology

The
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
word is derived from the ancient
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
(), from () and () , together meaning . In English, the
plural In many languages, a plural (sometimes list of glossing abbreviations, abbreviated as pl., pl, , or ), is one of the values of the grammatical number, grammatical category of number. The plural of a noun typically denotes a quantity greater than ...
is "hippopotamuses".


Taxonomy and origins


Classification

The modern hippopotamus and the
pygmy hippopotamus The pygmy hippopotamus or pygmy hippo (''Choeropsis liberiensis'') is a small Hippopotamidae, hippopotamid which is native to the forests and swamps of West Africa, primarily in Liberia, with small populations in Sierra Leone, Guinea, and Ivory Co ...
are the only living members of the family Hippopotamidae. Some taxonomists place hippos and
anthracotheres Anthracotheriidae is a paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales. The oldest genus, '' Elomeryx'', first appeared during the middle Eocene in Asia. They thrived in Africa and Eura ...
in the superfamily Anthracotheroidea. Hippopotamidae are classified along with other
even-toed ungulates Artiodactyls are placental mammals belonging to the order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other t ...
in the
order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...
Artiodactyla Artiodactyls are placental mammals belonging to the order (biology), order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof ...
. Five subspecies of hippos have been described based on morphological differences in their skulls as well as differences in geographical range: *''H. a. amphibius'' – (the nominate subspecies) ranges from
Gambia The Gambia, officially the Republic of The Gambia, is a country in West Africa. Geographically, The Gambia is the List of African countries by area, smallest country in continental Africa; it is surrounded by Senegal on all sides except for ...
east to
Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
and then south to
Mozambique Mozambique, officially the Republic of Mozambique, is a country located in Southeast Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west, and Eswatini and South Afr ...
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 In human anatomy, the facial skeleton of the skull the external surface of the mandible is marked in the median line by a faint ridge, indicating the mandibular symphysis (Latin: ''symphysis menti'') or line of junction where the two lateral ha ...
and larger chewing teeth. *''H. a. kiboko'' – found in
Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...
and
Somalia Somalia, officially the Federal Republic of Somalia, is the easternmost country in continental Africa. The country is located in the Horn of Africa and is bordered by Ethiopia to the west, Djibouti to the northwest, Kenya to the southwest, th ...
; was noted to be smaller and more lightly coloured than other hippos with wider nostrils, somewhat longer snout and more rounded and relatively raised
orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...
s with the space between them being incurved. *''H. a. capensis'' – found in
Zambia Zambia, officially the Republic of Zambia, is a landlocked country at the crossroads of Central Africa, Central, Southern Africa, Southern and East Africa. It is typically referred to being in South-Central Africa or Southern Africa. It is bor ...
and
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
; distinguished by wider orbits. *''H. a. tschadensis'' – ranges between
Chad Chad, officially the Republic of Chad, is a landlocked country at the crossroads of North Africa, North and Central Africa. It is bordered by Libya to Chad–Libya border, the north, Sudan to Chad–Sudan border, the east, the Central Afric ...
and
Niger Niger, officially the Republic of the Niger, is a landlocked country in West Africa. It is a unitary state Geography of Niger#Political geography, bordered by Libya to the Libya–Niger border, north-east, Chad to the Chad–Niger border, east ...
; featured a slightly shorter but broader face, and pronounced, forward-facing orbits. *''H. a. constrictus'' – ranged from the southern
Democratic Republic of Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...
to
Angola Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...
and
Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...
; 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 Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...
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 Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is cal ...
classified hippos together with pigs based on molar patterns. Several lines of evidence, first from blood proteins, then from
molecular systematics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
,
DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
and the
fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
, show their closest living relatives are
cetacean Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...
s (
whale Whales are a widely distributed and diverse group of fully Aquatic animal, aquatic placental mammal, placental marine mammals. As an informal and Colloquialism, colloquial grouping, they correspond to large members of the infraorder Cetacea ...
s,
dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...
s, and
porpoise Porpoises () are small Oceanic dolphin, dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and Beluga whale, belugas than to the Oceanic dolphi ...
s). The common ancestor of hippos and whales branched off from
Ruminantia Ruminants are herbivorous grazing or browsing artiodactyls belonging to the suborder Ruminantia that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, principa ...
and the rest of the even-toed ungulates; the cetacean and hippo lineages split soon afterwards. 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 . This hypothesised ancestral group likely split into two branches again around . One branch would evolve into cetaceans, possibly beginning about , with the protowhale ''
Pakicetus ''Pakicetus'' (meaning 'whale from Pakistan') is an extinct genus of amphibious cetacean of the family Pakicetidae, which was endemic to the Indian Subcontinent during the Ypresian (early Eocene) period, about 50 million years ago. It was a w ...
'' and other early whale ancestors collectively known as
Archaeoceti Archaeoceti ("ancient whales"), or Zeuglodontes in older literature, is an obsolete paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene (). Representing the earliest cetacean radiation, they include th ...
. This group eventually underwent aquatic adaptation into the completely aquatic
cetacea Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...
ns. The other branch became the
anthracotheres Anthracotheriidae is a paraphyletic family of extinct, hippopotamus-like artiodactyl ungulates related to hippopotamuses and whales. The oldest genus, '' Elomeryx'', first appeared during the middle Eocene in Asia. They thrived in Africa and Eura ...
, a large family of four-legged beasts, the earliest of which in the late
Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
would have resembled skinny hippos with comparatively smaller, narrower heads. All branches of the anthracotheres, except that which evolved into
Hippopotamidae Hippopotamidae is a family of stout, naked-skinned, and semiaquatic artiodactyl mammals, possessing three-chambered stomachs and walking on four toes on each foot. While they resemble pigs physiologically, their closest living relatives are th ...
, became extinct during the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...
species: from '' Anthracotherium'' and '' Elomeryx'' to the
Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...
species ''
Merycopotamus ''Merycopotamus'' is an extinct genus of Asian anthracothere that appeared during the Middle Miocene, and died out in the Late Pliocene. At the height of the genus' influence, species ranged throughout South Asia and South East Asia (Indonesia ...
'' and ''
Libycosaurus ''Libycosaurus'' ("Lizard of Libya") was one of the last anthracothere genera. It lived from the Middle to the Late Miocene, and ranged throughout Central and Northern Africa, and in Uganda Uganda, officially the Republic of Uganda, ...
'' and finally the very latest anthracotheres in the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...
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 . Hippopotamid species would spread across Africa and Eurasia, including the modern pygmy hippo. From 7.5 to , a possible ancestor to the modern hippo, '' Archaeopotamus'', lived in Africa and the Middle East. The oldest records of the genus ''
Hippopotamus The hippopotamus (''Hippopotamus amphibius;'' ; : hippopotamuses), often shortened to hippo (: hippos), further qualified as the common hippopotamus, Nile hippopotamus and river hippopotamus, is a large semiaquatic mammal native to sub-Sahar ...
'' date to the
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Middle Pleistocene The Chibanian, more widely known as the Middle Pleistocene (its previous informal name), is an Age (geology), age in the international geologic timescale or a Stage (stratigraphy), stage in chronostratigraphy, being a division of the Pleistocen ...
, though there are possible
Early Pleistocene The Early Pleistocene is an unofficial epoch (geology), sub-epoch in the international geologic timescale in chronostratigraphy, representing the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently esti ...
records.


Extinct species

Three species of
Malagasy hippopotamus Several species of Malagasy hippopotamus (also known as Malagasy pygmy hippopotamus or Madagascan pygmy hippopotamus) lived on the island of Madagascar but are now believed to be extinct. The animals were very similar to the extant hippopotamus ...
became extinct during the
Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
on
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
, 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 Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands. This natural process is disti ...
. Fossil evidence indicates many Malagasy hippos were hunted by humans, a factor in their eventual extinction. Isolated individual Malagasy hippos may have survived in remote pockets; in 1976, villagers described a living animal called the ''kilopilopitsofy'', which may have been a Malagasy hippo. '' 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 .van der Made J, Sahnouni M & Boulaghraief K. 2017
''Hippopotamus gorgops'' from El Kherba (Algeria) and the context of its biogeography
In Proceedings of the II Meeting of African Prehistory: Burgos 15–16 April 2015, Sahnouni M, Semaw S, Rios Garaizar J (eds). CENIEH: Burgos; 135–169.
''
Hippopotamus antiquus ''Hippopotamus antiquus'' is an extinct species of the genus ''Hippopotamus'' that ranged across Europe during the Early and Middle Pleistocene. It was considerably larger than the living hippopotamus (''Hippopotamus amphibius''). Description ...
'' ranged throughout Europe, extending as far north as Britain during the Early and
Middle Pleistocene The Chibanian, more widely known as the Middle Pleistocene (its previous informal name), is an Age (geology), age in the international geologic timescale or a Stage (stratigraphy), stage in chronostratigraphy, being a division of the Pleistocen ...
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 Crete ( ; , Modern Greek, Modern: , Ancient Greek, Ancient: ) is the largest and most populous of the Greek islands, the List of islands by area, 88th largest island in the world and the List of islands in the Mediterranean#By area, fifth la ...
(''
Hippopotamus creutzburgi ''Hippopotamus creutzburgi'', the Cretan dwarf hippopotamus, is an extinct species of hippopotamus from the island of Crete. It lived on the island from the Early Pleistocene to early Middle Pleistocene, and probably descended from '' Hippopot ...
''),
Cyprus Cyprus (), officially the Republic of Cyprus, is an island country in the eastern Mediterranean Sea. Situated in West Asia, its cultural identity and geopolitical orientation are overwhelmingly Southeast European. Cyprus is the List of isl ...
(the Cyprus dwarf hippopotamus, ''Hippopotamus minor''),
Malta Malta, officially the Republic of Malta, is an island country in Southern Europe located in the Mediterranean Sea, between Sicily and North Africa. It consists of an archipelago south of Italy, east of Tunisia, and north of Libya. The two ...
(''
Hippopotamus melitensis ''Hippopotamus melitensis'' is an extinct hippopotamus from Malta. It lived during Middle-Late Pleistocene. It probably descended from '' Hippopotamus pentlandi'' from Sicily, which in turn probably descended from the common hippopotamus (''H ...
''), and
Sicily Sicily (Italian language, Italian and ), officially the Sicilian Region (), is an island in the central Mediterranean Sea, south of the Italian Peninsula in continental Europe and is one of the 20 regions of Italy, regions of Italy. With 4. ...
(''
Hippopotamus pentlandi ''Hippopotamus pentlandi'' is an extinct species of hippopotamus from Sicily, known from the late Middle Pleistocene to early Late Pleistocene. It is the largest of the insular dwarf hippos known from the Pleistocene of the Mediterranean, "at m ...
''). Of these, the Cyprus dwarf hippo survived until the end of the Pleistocene or early Holocene. Evidence from the archaeological site
Aetokremnos Aetokremnos is a rock shelter near Limassol on the southern coast of Cyprus. It is widely considered to host some of the oldest evidence of human habitation of Cyprus, dating to around 12,000 years ago. It is situated on a steep cliff site c. abo ...
continues to cause debate on whether or not the species was driven to extinction or even encountered by humans.


Characteristics

The hippopotamus is a
megaherbivore Megaherbivores (Greek :wiktionary:μέγας, μέγας megas "large" and Latin ''herbivora'' "herbivore") are large herbivores that can exceed in weight. The earliest herbivores to reach such sizes like the Pareiasauria, pareiasaurs appeare ...
and is the third largest land mammal after
elephant Elephants are the largest living land animals. Three living species are currently recognised: the African bush elephant ('' Loxodonta africana''), the African forest elephant (''L. cyclotis''), and the Asian elephant ('' Elephas maximus ...
s and some
rhinoceros A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...
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. The species has a typical head–body length of and an average standing height of at the shoulder. Hippos have barrel-shaped bodies with short tails and legs, and an hourglass-shaped skull with a long snout. Their skeletal structures are graviportal, adapted to carrying their enormous weight, and their dense bones and low
centre of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weighted relative position of the distributed mass sums to zero. For a ...
allows them to sink and move along the bottom of the water. Hippopotamuses have small legs (relative to other
megafauna In zoology, megafauna (from Ancient Greek, Greek μέγας ''megas'' "large" and Neo-Latin ''fauna'' "animal life") are large animals. The precise definition of the term varies widely, though a common threshold is approximately , this lower en ...
) because the water in which they live reduces the weight burden. The toes are webbed and the
pelvis The pelvis (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...
rests at an angle of 45 degrees. Though chubby-looking, hippos have little fat. The eyes, ears, and nostrils of hippos are placed high on the roof of their skulls. This allows these organs to remain above the surface while the rest of the body is submerged. The nostrils and ears can close when underwater while
nictitating membrane The nictitating membrane (from Latin '' nictare'', to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision. Most ...
s cover the eyes. The
vocal fold In humans, the vocal cords, also known as vocal folds, are folds of throat tissues that are key in creating sounds through Speech, vocalization. The length of the vocal cords affects the pitch of voice, similar to a violin string. Open when brea ...
s of the hippo are more horizontally positioned, much like baleen whales. Underneath are throat tissues, where vibrations are transmitted to produce underwater calls. The hippo's jaw powered by huge
masseter In anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the ...
and
digastric muscle The digastric muscle (also digastricus) (named ''digastric'' as it has two 'bellies') is a bilaterally paired suprahyoid muscle located under the jaw. Its posterior belly is attached to the mastoid notch of temporal bone, and its anterior belly ...
s, and the hinge is located far back enough so that they can open their mouths at 100–110 degrees. Extensions at the back of the jaw create more surface area for muscle attachment, which gives them large, droopy cheeks This allows them to achieve their gape without tearing any tissue. On the lower jaw, the
incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...
s 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, and the jaws are too rigid for side to side motion, making them less efficient for chewing. Hippos rely on their flattened, horny lips to grasp and pull grasses which are then passed to the
molars The molars or molar teeth are large, flat tooth, teeth at the back of the mouth. They are more developed in mammal, mammals. They are used primarily to comminution, grind food during mastication, chewing. The name ''molar'' derives from Latin, '' ...
, which have complex enamel folds on their chewing surface. The hippo is considered to be a
pseudoruminant Pseudoruminant is a classification of animals based on their digestive tract differing from the ruminants. Hippopotamidae, Hippopotami and camels are ungulate mammals with a three-chambered stomach (ruminants have a four-chambered stomach) while Eq ...
; it has a complex three-chambered stomach, but does not "chew
cud Cud is a portion of food that returns from a ruminant's stomach to the mouth to be chewed for the second time. More precisely, it is a bolus of semi-degraded food regurgitated from the reticulorumen of a ruminant. Cud is produced during the phy ...
". Hippo skin is thick across much of its body with little hair. The animal is mostly purplish-grey or blue-black, but brownish-pink on the underside and around the eyes and ears. Their skin secretes a natural, red-coloured
sunscreen Sunscreen, also known as sunblock, sun lotion or sun cream, is a photoprotection, photoprotective topical product for the Human skin, skin that helps protect against sunburn and prevent skin cancer. Sunscreens come as lotions, sprays, gels, fo ...
substance that is sometimes referred to as "blood sweat" but is neither blood nor sweat. This secretion is initially colourless and turns red-orange within minutes, eventually becoming brown. Two highly acidic pigments have been identified in the secretions; one red hipposudoric acid and one orange norhipposudoric acid, which inhibit the growth of disease-causing bacteria and their light-absorption profile peaks in the
ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
range, creating a sunscreen effect. Regardless of diet, all hippos secrete these pigments so food does not appear to be their source; rather, they may be synthesised from precursors such as the
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...
tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is ...
. 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 The vulval vestibule (also known as the vulvar vestibule or vestibule of vagina) is the part of the vulva between the labia minora. At the innermost part are the vaginal introitus and urinary meatus. The Bartholin's and Skene's glands each ha ...
has two large, protruding
diverticula In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false. In medicine, t ...
. Both of these have an unknown function. A hippo's lifespan is typically 40 to 50 years. Donna the Hippo was one of the oldest living hippos in captivity. She lived at the Mesker Park Zoo in
Evansville, Indiana Evansville is a city in Vanderburgh County, Indiana, United States, and its county seat. With a population of 118,414 at the 2020 United States census, 2020 census, it is Indiana's List of cities in Indiana, third-most populous city after India ...
, in the US until her death in 2012 at the age of 61. Two hippos share the record for the oldest hippo ever recorded at 65 yeras. Bertha, a female Hippo, who lived in the
Manila Zoo The Manila Zoo, formally known as the Manila Zoological and Botanical Garden, is a zoo located in Malate, Manila, Malate, Manila, Philippines. First opened on July 25, 1959, it was recently renovated and reopened on November 21, 2022. History ...
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. Two other notably long-lived hippos were the female Tanga (1934-1995) at the
Hellabrunn Zoo Hellabrunn Zoo () is a 40 hectare (99 acre) zoological garden in the Bavarian capital of Munich. The zoo is situated on the right bank of the river Isar, in the southern part of Munich near the quarter of Thalkirchen. A high ratio of enclosures ...
in
Munich, Germany Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...
and male Blackie at the Cleveland Metroparks Zoo (1953-2014). Currently, the oldest hippo in captivity is believed to be Mae Mali at the Khao Kheow Open Zoo in Thailand, who will turn 60 in September 2025.


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, and Greece, but extended into northwestern Europe, including Great Britain (as far north as
North Yorkshire North Yorkshire is a Ceremonial counties of England, ceremonial county in Northern England.The Unitary authorities of England, unitary authority areas of City of York, York and North Yorkshire (district), North Yorkshire are in Yorkshire and t ...
), the Netherlands, and western Germany during
interglacial An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age. The current Holocene i ...
periods, such as the
Last Interglacial The Last Interglacial, also known as the Eemian, was the interglacial period which began about 130,000 years ago at the end of the Penultimate Glacial Period and ended about 115,000 years ago at the beginning of the Last Glacial Period. It cor ...
(130–115,000 years ago). The youngest records of the species in Europe are from the Late Pleistocene of Greece, dating to around 40–30,000 years ago. Archaeological evidence exists of its presence in the
Levant The Levant ( ) is the subregion that borders the Eastern Mediterranean, Eastern Mediterranean sea to the west, and forms the core of West Asia and the political term, Middle East, ''Middle East''. In its narrowest sense, which is in use toda ...
, dating to less than 3,000 years ago. The species was common in
Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...
's
Nile The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...
region during antiquity, but it has since been driven out. According to
Pliny the Elder Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...
, in his time, the best location in Egypt for capturing this animal was in the Saite nome;
English translation
the animal could still be found along the
Damietta Damietta ( ' ) is a harbor, port city and the capital of the Damietta Governorate in Egypt. It is located at the Damietta branch, an eastern distributary of the Nile Delta, from the Mediterranean Sea, and about north of Cairo. It was a Cath ...
branch of the Nile after the Arab Conquest in 639. Reports of the slaughter of the last hippo in
Natal Province The Province of Natal (), commonly called Natal, was a province of South Africa from May 1910 until May 1994. Its capital was Pietermaritzburg. During this period rural areas inhabited by the black African population of Natal were organised int ...
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 The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...
,
Uganda Uganda, officially the Republic of Uganda, is a landlocked country in East Africa. It is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the ...
,
Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...
, and
Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...
, north through to
Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
,
Somalia Somalia, officially the Federal Republic of Somalia, is the easternmost country in continental Africa. The country is located in the Horn of Africa and is bordered by Ethiopia to the west, Djibouti to the northwest, Kenya to the southwest, th ...
, and
Sudan Sudan, officially the Republic of the Sudan, is a country in Northeast Africa. It borders the Central African Republic to the southwest, Chad to the west, Libya to the northwest, Egypt to the north, the Red Sea to the east, Eritrea and Ethiopi ...
, west to
The Gambia The Gambia, officially the Republic of The Gambia, is a country in West Africa. Geographically, The Gambia is the List of African countries by area, smallest country in continental Africa; it is surrounded by Senegal on all sides except for ...
, and south to
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
. Genetic evidence suggests common hippos in Africa experienced a marked population expansion during or after the
Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
, attributed to an increase in water bodies at the end of the era. These findings have important conservation implications, as hippo populations across the continent are currently threatened by loss of access to fresh water. Hippos are also subject to unregulated hunting and
poaching Poaching is the illegal hunting or capturing of wild animals, usually associated with land use rights. Poaching was once performed by impoverished peasants for subsistence purposes and to supplement meager diets. It was set against the huntin ...
. The species is included in Appendix II of the
Convention on International Trade in Endangered Species Convention may refer to: * Convention (norm), a custom or tradition, a standard of presentation or conduct ** Treaty, an agreement in international law ** Convention (political norm), uncodified legal or political tradition * Convention (meeting ...
(CITES) meaning international export/import (including in parts and derivatives) requires CITES documentation to be obtained and presented to border authorities. As of 2017, the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...
drawn up by the
International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the stat ...
(IUCN) lists the species as vulnerable, with a stable population estimated between 115,000 and 130,000 animals. The hippo population has declined most dramatically in the Democratic Republic of the Congo. By 2005, the population in
Virunga National Park Virunga National Park is a national park in the Albertine Rift Valley in the eastern part of the Democratic Republic of the Congo. It was created in 1925. In elevation, it ranges from in the Semliki River valley to in the Rwenzori Mountains. ...
had dropped to 800 or 900 from around 29,000 in the mid-1970s. This decline is attributed to the disruptions caused by the
Second Congo War The Second Congo War, also known as Africa's World War or the Great War of Africa, was a major conflict that began on 2 August 1998, in the Democratic Republic of the Congo, just over a year after the First Congo War. The war initially erupted ...
. The poachers are believed to be
Mai-Mai The term Mai-Mai or Mayi-Mayi refers to any kind of community-based militia group active in the Democratic Republic of the Congo (DRC) that is formed to defend local communities and territory against other armed groups. Most were formed to resis ...
rebels, underpaid Congolese soldiers, and local militia groups. Reasons for poaching include the belief hippos are harmful to society, as well as financial gain. As of 2016, the Virunga hippo population appears to have increased again, possibly due to better protection from park rangers, who have worked with local fishermen. 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 Pablo Emilio Escobar Gaviria (; ; 1 December 19492 December 1993) was a Colombian drug lord, narcoterrorist, and politician who was the founder and leader of the Medellín Cartel. Dubbed the "King of Cocaine", Escobar was one of the wealthie ...
'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 Culling is the process of segregating organisms from a group according to desired or undesired characteristics. In animal breeding, it is removing or segregating animals from a breeding stock based on a specific trait. This is done to exagge ...
.


Behaviour and ecology

Hippos are
semiaquatic In biology, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...
and require enough water to immerse in, while being close to grass. They mostly live in freshwater habitat, but can be found in
estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...
. They prefer relatively still waters with gently sloping shores, though male hippos may also be found in very small numbers in more
rapid Rapid(s) or RAPID may refer to: Hydrological features * Rapids, sections of a river with turbulent water flow * Rapid Creek (Iowa River tributary), Iowa, United States * Rapid Creek (South Dakota), United States, namesake of Rapid City Sport ...
waters with rocky slopes. Like most herbivores, hippos will consume a variety of plants if presented with them in captivity, but their diet in nature consists almost entirely of grass, with only minimal consumption of aquatic plants. Hippos spend most of the day in water to stay cool and hydrated. Just before night begins, they leave the water to forage on land. A hippo will travel per night, eating around of grass. By dawn, they are back in the water. Despite being semiaquatic, an adult hippo is not a particularly good swimmer, nor can it float. It rarely enters deep water; when it does, the animal moves by bouncing off the bottom. An adult hippo surfaces every four to six minutes, while young need to breathe every two to three minutes. Hippos move on land by
trot The trot is a two-beat diagonal horse gait where the diagonal pairs of legs move forward at the same time with a moment of suspension between each beat. It has a wide variation in possible speeds, but averages about . A very slow trot is som ...
ting, and limb movements do not change between speeds. They can reach an airborne stage (a stage when all limb are off the ground) when they move fast enough. Hippos are reported to reach but this has not been confirmed. They are incapable of jumping but can walk up steep banks. The hippopotamus sleeps with both hemispheres of the brain resting, as in all land mammals, and usually sleeps on land or in water with the nostrils exposed. Despite this, it may be capable of sleeping while submerged, intermittently surfacing to breathe without waking. They appear to transition between different phases of sleep more quickly than other mammals. 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 A biogeochemical cycle, or more generally a cycle of matter, is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cyc ...
. On occasion, hippos have been filmed eating
carrion Carrion (), also known as a carcass, is the decaying flesh of dead animals. Overview Carrion is an important food source for large carnivores and omnivores in most ecosystems. Examples of carrion-eaters (or scavengers) include crows, vultures ...
, usually near the water. There are other reports of meat-eating and even
cannibalism Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is also well document ...
and
predation Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
. Hippos' stomach anatomy lacks adaptions to carnivory and meat-eating is likely caused by lack of nutrients or just an abnormal behaviour.


Social life

It is challenging to study the interaction of bulls and cows because hippos are not
sexually dimorphic Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...
, so cows and young bulls are almost indistinguishable in the field. Hippo pods fluctuate but can contain over 100 hippos. Although they lie close together, adults develop almost no social bonds. Males establish
territories A territory is an area of land, sea, or space, belonging or connected to a particular country, person, or animal. In international politics, a territory is usually a geographic area which has not been granted the powers of self-government, ...
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. Hippos engage in "muck-spreading" which involves defecating while spinning their tails to distribute the faeces over a greater area. Muck-spreading occurs both on land and in water and its function is not well understood. It is unlikely to serve a territorial function, as the animals only establish territories in the water. They may be used as trails between the water and grazing areas. "Yawning" serves as a threat display. When fighting, bulls use their incisors to block each other's attacks and their large canines as offensive weapons. When hippos become over-populated or a habitat shrinks, bulls sometimes attempt
infanticide Infanticide (or infant homicide) is the intentional killing of infants or offspring. Infanticide was a widespread practice throughout human history that was mainly used to dispose of unwanted children, its main purpose being the prevention of re ...
, but this behaviour is not common under normal conditions. The most common hippo vocalisation is the "wheeze honk", which can travel over long distances in air. This call starts as a high-pitched squeal followed by a deeper, resonant call. The animals can recognise the calls of other individuals. Hippos are more likely to react to the wheeze honks of strangers than to those they are more familiar with. When threatened or alarmed, they produce exhalations, and fighting bulls will bellow loudly. Hippos are recorded to produce clicks underwater which may have echolocative properties. 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 In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once i ...
of eight months. A study of
endocrine system The endocrine system is a messenger system in an organism comprising feedback loops of hormones that are released by internal glands directly into the circulatory system and that target and regulate distant Organ (biology), organs. In vertebrat ...
s 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 The wet season (sometimes called the rainy season or monsoon season) is the time of year when most of a region's average annual rainfall occurs. Generally, the season lasts at least one month. The term ''green season'' is also sometimes used a ...
. Male hippos always have mobile
spermatozoa A spermatozoon (; also spelled spermatozoön; : spermatozoa; ) is a motile sperm cell (biology), cell produced by male animals relying on internal fertilization. A spermatozoon is a moving form of the ploidy, haploid cell (biology), cell that is ...
and can breed year-round. After becoming pregnant, a female hippo will typically not begin ovulation again for 17 months. Hippos mate in the water, with the cow remaining under the surface, her head emerging periodically to draw breath. Cows give birth in seclusion and return within 10 to 14 days. Calves are born on land or shallow water weighing on average and at an average length of around . The female lies on her side when nursing, which can occur underwater or on land. The young are carried on their mothers' backs in deep water. Mother hippos are very protective of their young, not allowing others to get too close. One cow was recorded protecting a calf's carcass after it had died. Calves may be temporarily kept in nurseries, guarded by one or more adults, and will play amongst themselves. Like many other large mammals, hippos are described as
K-strategists In ecology, selection theory relates to the selection of combinations of traits in an organism that trade off between quantity and quality of offspring. The focus on either an increased quantity of offspring at the expense of reduced individual ...
, in this case typically producing just one large, well-developed infant every couple of years (rather than many small, poorly developed young several times per year, as is common among small mammals such as rodents). Calves no longer need to suckle when they are a year old.


Interspecies interactions

Hippos coexist alongside a variety of large predators in their habitats.
Nile crocodile The Nile crocodile (''Crocodylus niloticus'') is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed in sub-Saharan Africa, occurring mostly in the eastern, southern, and ce ...
s,
lion The lion (''Panthera leo'') is a large Felidae, cat of the genus ''Panthera'', native to Sub-Saharan Africa and India. It has a muscular, broad-chested body (biology), body; a short, rounded head; round ears; and a dark, hairy tuft at the ...
s, and
spotted hyena The spotted hyena (''Crocuta crocuta''), also known as the laughing hyena, is a hyena species, currently classed as the sole extant member of the genus ''Crocuta'', native to sub-Saharan Africa. It is listed as being of least concern by the IUC ...
s are known to prey on young hippos. Beyond these, adult hippos are not usually preyed upon by other animals due to their aggression and size. Cases where large lion prides have successfully preyed on adult hippos have been reported, but it is generally rare. Lions occasionally prey on adults at
Gorongosa National Park Gorongosa National Park is at the southern end of the Great African Rift Valley in the heart of central Mozambique, Southeast Africa. The more than park comprises the valley floor and parts of surrounding plateaus. Rivers originating on nearby ...
and calves are sometimes taken at Virunga.
Crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large, semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term "crocodile" is sometimes used more loosely to include ...
s are frequent targets of hippo aggression, probably because they often inhabit the same
riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...
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 River ecosystems are flowing waters that drain the landscape, and include the biotic (living) interactions amongst plants, animals and micro-organisms, as well as abiotic (nonliving) physical and chemical interactions of its many parts.Angelier ...
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
monogenea Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they ...
n
flatworm Platyhelminthes (from the Greek language, Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a Phylum (biology), phylum of relatively simple bilaterian, Segmentation (biology), ...
'' 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.


Hippos and humans

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 Neanderthals ( ; ''Homo neanderthalensis'' or sometimes ''H. sapiens neanderthalensis'') are an extinction, extinct group of archaic humans who inhabited Europe and Western and Central Asia during the Middle Pleistocene, Middle to Late Plei ...
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 The Bouri Formation is a sequence of sedimentary deposits that is the source of australopithecine and Homo (that is, hominin) fossils, Artifact (archaeology), artifacts, and bones of large mammals with cut marks from butchery with tools by earl ...
and dated to around 160,000 years ago. 4,000–5,000 year art showing hippos being hunted have been found in the Tassili n'Ajjer Mountains of the central
Sahara The Sahara (, ) is a desert spanning across North Africa. With an area of , it is the largest hot desert in the world and the list of deserts by area, third-largest desert overall, smaller only than the deserts of Antarctica and the northern Ar ...
near Djanet. The
ancient Egypt Ancient Egypt () was a cradle of civilization concentrated along the lower reaches of the Nile River in Northeast Africa. It emerged from prehistoric Egypt around 3150BC (according to conventional Egyptian chronology), when Upper and Lower E ...
ians recognised the hippo as ferocious, and representations on the tombs of nobles show humans hunting them. The hippo was also known to the
Greeks Greeks or Hellenes (; , ) are an ethnic group and nation native to Greece, Greek Cypriots, Cyprus, Greeks in Albania, southern Albania, Greeks in Turkey#History, Anatolia, parts of Greeks in Italy, Italy and Egyptian Greeks, Egypt, and to a l ...
and Romans. The Greek historian
Herodotus Herodotus (; BC) was a Greek historian and geographer from the Greek city of Halicarnassus (now Bodrum, Turkey), under Persian control in the 5th century BC, and a later citizen of Thurii in modern Calabria, Italy. He wrote the '' Histori ...
described the hippo in '' The Histories'' (written ''
circa Circa is a Latin word meaning "around, approximately". Circa or CIRCA may also refer to: * CIRCA (art platform), in London * Circa (band), a progressive rock supergroup * Circa (company), an American skateboard footwear company * Circa (contempora ...
'' 440 BC) and the Roman naturalist
Pliny the Elder Gaius Plinius Secundus (AD 23/24 79), known in English as Pliny the Elder ( ), was a Roman Empire, Roman author, Natural history, naturalist, and naval and army commander of the early Roman Empire, and a friend of the Roman emperor, emperor Vesp ...
wrote about the hippo in his encyclopedia ''
Naturalis Historia The ''Natural History'' () is a Latin work by Pliny the Elder. The largest single work to have survived from the Roman Empire to the modern day, the ''Natural History'' compiles information gleaned from other ancient authors. Despite the work' ...
'' (written ''circa'' 77 AD). The
Yoruba people The Yoruba people ( ; , , ) are a West African ethnic group who inhabit parts of Nigeria, Benin, and Togo, which are collectively referred to as Yorubaland. The Yoruba constitute more than 50 million people in Africa, are over a million outsid ...
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 South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
.


Attacks on humans

The hippo is considered to be extremely aggressive and has frequently been reported charging and attacking boats. Hippos can easily capsize small boats and injure or kill passengers. In one 2014 case in
Niger Niger, officially the Republic of the Niger, is a landlocked country in West Africa. It is a unitary state Geography of Niger#Political geography, bordered by Libya to the Libya–Niger border, north-east, Chad to the Chad–Niger border, east ...
, 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 Ptolemaic is the adjective formed from the name Ptolemy, and may refer to: Pertaining to the Ptolemaic dynasty *Ptolemaic dynasty, the Macedonian Greek dynasty that ruled Egypt founded in 305 BC by Ptolemy I Soter *Ptolemaic Kingdom Pertaining t ...
historian
Manetho Manetho (; ''Manéthōn'', ''gen''.: Μανέθωνος, ''fl''. 290–260 BCE) was an Egyptian priest of the Ptolemaic Kingdom who lived in the early third century BCE, at the very beginning of the Hellenistic period. Little is certain about his ...
, the
pharaoh Pharaoh (, ; Egyptian language, Egyptian: ''wikt:pr ꜥꜣ, pr ꜥꜣ''; Meroitic language, Meroitic: 𐦲𐦤𐦧, ; Biblical Hebrew: ''Parʿō'') was the title of the monarch of ancient Egypt from the First Dynasty of Egypt, First Dynasty ( ...
Menes Menes ( ; ; , probably pronounced *; and Μήν) was a pharaoh of the Early Dynastic Period of ancient Egypt, credited by classical tradition with having united Upper and Lower Egypt, and as the founder of the First Dynasty. The identity of M ...
was carried off and then killed by a hippopotamus.


In zoos

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 London Zoo, previously known as ZSL London Zoo or London Zoological Gardens and sometimes called Regent's Park Zoo, is the world's oldest scientific zoo. It was opened in London on 27 April 1828 and was originally intended to be used as a colle ...
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 The Cincinnati Zoo & Botanical Garden is the second oldest zoo in the United States, founded in 1873 and officially opening in 1875. It is located in the Avondale neighborhood of Cincinnati, Ohio. It originally began with in the middle of the ...
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 .


Cultural significance

In
Egyptian mythology Egyptian mythology is the collection of myths from ancient Egypt, which describe the actions of the Egyptian pantheon, Egyptian gods as a means of understanding the world around them. The beliefs that these myths express are an important part ...
, the god
Set Set, The Set, SET or SETS may refer to: Science, technology, and mathematics Mathematics *Set (mathematics), a collection of elements *Category of sets, the category whose objects and morphisms are sets and total functions, respectively Electro ...
takes the form of a red hippopotamus and fights
Horus Horus (), also known as Heru, Har, Her, or Hor () in Egyptian language, Ancient Egyptian, is one of the most significant ancient Egyptian deities who served many functions, most notably as the god of kingship, healing, protection, the sun, and t ...
for control of the land, but is defeated. The goddess
Tawaret In Ancient Egyptian religion, Taweret (, also spelled Taurt, Tuat, Tuart, Ta-weret, Tawaret, Twert and Taueret, and in , Thoeris, Taouris and Toeris) is the protective goddess of childbirth and fertility. The name "Taweret" means "she who is grea ...
is depicted as a pregnant woman with a hippo head, representing fierce maternal love. The
Ijaw people The Ijaw people, also known as the Izon people, are an ethnic group found in the Niger Delta region in Nigeria, with primary Population, population clusters in Bayelsa State, Bayelsa, Delta State, Delta, and Rivers State, Rivers. They also have ...
of the
Niger Delta The Niger Delta is the delta of the Niger River sitting directly on the Gulf of Guinea on the Atlantic Ocean in Nigeria. It is located within nine coastal southern Nigerian states, which include: all six states from the South South geopolitic ...
wore masks of aquatic animals like the hippo when practising their
water spirit A water spirit is a kind of supernatural being found in the folklore of many cultures: African Some water spirits in traditional African religion include: * Mami Wata is a transcultural pantheon of water spirits and deities of the African ...
cults, and hippo ivory was used in the
divination Divination () is the attempt to gain insight into a question or situation by way of an occultic ritual or practice. Using various methods throughout history, diviners ascertain their interpretations of how a should proceed by reading signs, ...
rituals of the Yoruba. Hippo masks were also used in Nyau funerary rituals of the
Chewa Chewa may refer to: *the Chewa people *the Chewa language Chewa ( ; also known as Nyanja ) is a Bantu languages, Bantu language spoken in Malawi and a recognised minority in Zambia and Mozambique. The noun class prefix ''chi-'' is used for lang ...
of Southern Africa. According to
Robert Baden-Powell Lieutenant-General Robert Stephenson Smyth Baden-Powell, 1st Baron Baden-Powell, ( ; 22 February 1857 – 8 January 1941) was a British Army officer, writer, founder of The Boy Scouts Association and its first Chief Scout, and founder, with ...
, Zulu warriors referred to hippos in war chants. The
Behemoth Behemoth (; , ''bəhēmōṯ'') is a beast from the biblical Book of Job, and is a form of the primeval chaos-monster created by God at the beginning of creation. Metaphorically, the name has come to be used for any extremely large or powerful ...
from the
Book of Job The Book of Job (), or simply Job, is a book found in the Ketuvim ("Writings") section of the Hebrew Bible and the first of the Poetic Books in the Old Testament of the Christian Bible. The language of the Book of Job, combining post-Babylonia ...
, 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 The Renaissance ( , ) is a Periodization, period of history and a European cultural movement covering the 15th and 16th centuries. It marked the transition from the Middle Ages to modernity and was characterized by an effort to revive and sur ...
and
Baroque The Baroque ( , , ) is a Western Style (visual arts), style of Baroque architecture, architecture, Baroque music, music, Baroque dance, dance, Baroque painting, painting, Baroque sculpture, sculpture, poetry, and other arts that flourished from ...
periods, due to less access to specimens by Europeans. One notable exception is
Peter Paul Rubens Sir Peter Paul Rubens ( ; ; 28 June 1577 – 30 May 1640) was a Flemish painting, Flemish artist and diplomat. He is considered the most influential artist of the Flemish Baroque painting, Flemish Baroque tradition. Rubens' highly charged comp ...
' '' The Hippopotamus and Crocodile Hunt'' (1615–1616). Ever since Obaysch inspired the "Hippopotamus Polka", hippos have been popular animals in
Western culture Western culture, also known as Western civilization, European civilization, Occidental culture, Western society, or simply the West, refers to the Cultural heritage, internally diverse culture of the Western world. The term "Western" encompas ...
for their rotund appearance, which many consider comical. The
Disney The Walt Disney Company, commonly referred to as simply Disney, is an American multinational mass media and entertainment industry, entertainment conglomerate (company), conglomerate headquartered at the Walt Disney Studios (Burbank), Walt Di ...
film '' Fantasia'' featured a ballerina hippo dancing to the opera '' La Gioconda''. The film ''
Hugo the Hippo ''Hugo the Hippo'' () is a 1975 animated film produced by the Pannónia Filmstúdió of Hungary and co-produced in the United States by Brut Productions, a division of French perfume company Faberge. It was released in Hungary in 1975 and in th ...
'' is set in Tanzania and involves the title character trying to escape being slaughtered with the help of local children. The ''
Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
'' films feature a hippo named Gloria. Hippos even inspired a popular board game,
Hungry Hungry Hippos Hungry Hungry Hippos (or Hungry Hippos in some UK editions) is a tabletop game made for 2–4 players, produced by Hasbro, under the brand of its subsidiary, Milton Bradley. The idea for the game was published in 1967 by toy inventor Fred Kroll ...
. Among the most famous poems about the hippo is "The Hippopotamus" by
T. S. Eliot Thomas Stearns Eliot (26 September 18884 January 1965) was a poet, essayist and playwright.Bush, Ronald. "T. S. Eliot's Life and Career", in John A Garraty and Mark C. Carnes (eds), ''American National Biography''. New York: Oxford University ...
, where he uses a hippo to represent the Catholic Church. Hippos are mentioned in the novelty Christmas song "
I Want a Hippopotamus for Christmas "I Want a Hippopotamus for Christmas" is a Christmas novelty song written by John Rox (1907–1957) and performed by 10-year-old Gayla Peevey in 1953. The song peaked at number 24 on ''Billboard (magazine), Billboard'' magazine's pop chart in De ...
" that became a hit for child star
Gayla Peevey Gayla Rienette Peevey (born March 8, 1943) is a former singer and child star from Oklahoma City, Oklahoma. She is best known for her recording of " I Want a Hippopotamus for Christmas" ( Columbia 4-40106, 1953). Peevey recorded the novelty song w ...
in 1953. They also featured in the popular "The Hippopotamous Song" by
Flanders and Swann Flanders and Swann were a British comedy duo and musicians. Michael Flanders (1922–1975) was a lyricist, actor, and singer. He collaborated with Donald Swann (1923–1994), a composer and pianist, in writing and performing comedy music, comic ...
.


See also

* American Hippo bill - 1910 bill that proposed the introduction of hippos into Louisiana * List of individual hippos


References


External links

* * * {{Authority control Mammals of Africa Fauna of Sub-Saharan Africa Herbivorous mammals Vulnerable animals Vulnerable biota of Africa Mammals described in 1758 Articles containing video clips Taxa named by Carl Linnaeus Semiaquatic mammals