104-405: The hippopotamus ( Hippopotamus amphibius ) ( / ˌ h ɪ p ə ˈ p ɒ t ə m ə s / ; pl. : hippopotamuses ; often shortened to hippo ( pl. : hippos ), further qualified as the common hippopotamus , Nile hippopotamus , or river hippopotamus , is a large semiaquatic mammal native to sub-Saharan Africa . It is one of only two extant species in the family Hippopotamidae ,
208-415: A pinna and hair . Whales have an elongated head, especially baleen whales , due to the wide overhanging jaw. Bowhead whale plates can be 9 metres (30 ft) long. Their nostril(s) make up the blowhole , with one in toothed whales and two in baleen whales. The nostrils are located on top of the head above the eyes so that the rest of the body can remain submerged while surfacing for air. The back of
312-429: A US$ 73 million exhibit to house three adult hippos, featuring a 250,000 L (55,000 imp gal; 66,000 US gal) tank. Modern hippo enclosures also have a complex filtration system for the animal's waste, an underwater viewing area for the visitors, and glass that may be up to 9 cm (3.5 in) thick and capable of holding water under pressures of 31 kPa (4.5 psi). In Egyptian mythology ,
416-621: A ballerina hippo dancing to the opera La Gioconda . The film Hugo the Hippo is set in Tanzania and involves the title character trying to escape being slaughtered with the help of local children. The Madagascar films feature a hippo named Gloria . Hippos even inspired a popular board game, Hungry Hungry Hippos . Semiaquatic In biology , being semi-aquatic refers to various macro organisms that live regularly in both aquatic and terrestrial environments . When referring to animals ,
520-601: A factor in the ability to produce sounds used in echolocation. Mysticeti, who don't have the ability to echolocate, possess general symmetry of the skull and facial region, while Odontoceti display a nasofacial asymmetry that is linked to their echolocating abilities. Differences in the level of asymmetry also seem to correlate with differences in the types of sounds produced. Mysticeti have exceptionally thin, wide basilar membranes in their cochleae without stiffening agents, making their ears adapted for processing low to infrasonic frequencies. The initial karyotype includes
624-609: 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 4,000 kg (8,800 lb). Hippopotamus antiquus ranged throughout Europe, extending as far north as Britain during
728-450: A great distance across South Africa . The hippo is considered to be extremely aggressive and has frequently been reported charging and attacking boats. Small boats can easily be capsized by hippos and passengers can be injured or killed by the animals, or drown in the water. 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
832-418: 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
936-439: A large melon and multiple, asymmetric air bags. River dolphins , unlike most other cetaceans, can turn their head 90°. Most other cetaceans have fused neck vertebrae and are unable to turn their head at all. The baleen of baleen whales consists of long, fibrous strands of keratin. Located in place of the teeth, it has the appearance of a huge fringe and is used to sieve the water for plankton and krill. Sperm whales have
1040-580: A latitudinal basis to move between seasonal habitats. For example, the gray whale migrates 10,000 miles (16,000 km) round trip. The journey begins at winter birthing grounds in warm lagoons along Baja California, and traverses 5,000–7,000 miles (8,000–11,300 km) of coastline to summer feeding grounds in the Bering, Chuckchi and Beaufort seas off the coast of Alaska. Conscious breathing cetaceans sleep but cannot afford to be unconscious for long, because they may drown. While knowledge of sleep in wild cetaceans
1144-513: A long snout. Their skeletal structures are graviportal , adapted to carrying their enormous weight, and their dense bones and low centre of gravity allows them to sink and move along the bottom of the water. 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. Though chubby-looking, hippos have little fat. The eyes, ears, and nostrils of hippos are placed high on
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#17328698913371248-850: A marked population expansion during or after the Pleistocene , 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 . The species is included in Appendix II of the Convention on International Trade in Endangered Species (CITES) meaning international export/import (including in parts and derivatives) requires CITES documentation to be obtained and presented to border authorities. As of 2017,
1352-537: A set of chromosomes from 2n = 44. They have four pairs of telocentric chromosomes (whose centromeres sit at one of the telomeres ), two to four pairs of subtelocentric and one or two large pairs of submetacentric chromosomes. The remaining chromosomes are metacentric—the centromere is approximately in the middle—and are rather small. All cetaceans have chromosomes 2n = 44, except the sperm whales and pygmy sperm whales , which have 2n = 42. Cetaceans are found in many aquatic habitats. While many marine species, such as
1456-725: A specific body of water. The southern right whale dolphin and the hourglass dolphin live only in the Southern Ocean . The narwhal and the beluga live only in the Arctic Ocean. Sowerby's beaked whale and the Clymene dolphin exist only in the Atlantic and the Pacific white-sided dolphin and the northern straight dolphin live only in the North Pacific. Cosmopolitan species may be found in
1560-426: A terrestrial mammal breathing out on a cold day, a small cloud of 'steam' appears. This is called the 'spout' and varies across species in shape, angle and height. Species can be identified at a distance using this characteristic. The structure of the respiratory and circulatory systems is of particular importance for the life of marine mammals . The oxygen balance is effective. Each breath can replace up to 90% of
1664-431: 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 3–5 km (1.9–3.1 mi) per night, eating around 40 kg (88 lb) of grass. By dawn, they are back in
1768-654: Is bicornuate . Cetacean eyes are set on the sides rather than the front of the head. This means only species with pointed 'beaks' (such as dolphins) have good binocular vision forward and downward. Tear glands secrete greasy tears, which protect the eyes from the salt in the water. The lens is almost spherical, which is most efficient at focusing the minimal light that reaches deep water. Odontocetes have little to no ability to taste or smell, while mysticetes are believed to have some ability to smell because of their reduced, but functional olfactory system . Cetaceans are known to possess excellent hearing. At least one species,
1872-809: Is Lu the Hippo, from the Ellie Schiller Homosassa Springs Wildlife State Park . As of 2024, he is 64 years old. 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 ),
1976-447: 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 carnivorous diet. They propel themselves through the water with powerful up-and-down movement of their tail which ends in a paddle-like fluke, using their flipper-shaped forelimbs to maneuver. While
2080-606: 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
2184-521: Is around 1,480 kg (3,260 lb) for bulls and 1,365 kg (3,009 lb) for cows. Exceptionally large males have been recorded reaching 2,660 kg (5,860 lb). Male hippos appear to continue growing throughout their lives, while females reach maximum weight at around age 25. It is 2.90 to 5.05 m (9 ft 6 in to 16 ft 7 in) long, including a tail of about 35 to 56 cm (14 to 22 in) in length and 1.30 to 1.65 m (4 ft 3 in to 5 ft 5 in) tall at
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#17328698913372288-566: Is attributed to the disruptions caused by the Second Congo War . 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. 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
2392-411: Is capable of running 30 km/h (19 mph) over short distances. Hippos inhabit rivers, lakes, and mangrove swamps. Territorial bulls each preside over a stretch of water and a group of five to thirty cows and calves. Mating 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
2496-468: Is common among small mammals such as rodents). Calves no longer need to suckle when they are a year old. Hippos coexist alongside a variety of large predators in their habitats. Nile crocodiles , lions , and spotted hyenas 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
2600-515: Is considered to be functionally extinct due to human activity. The two parvorders, baleen whales (Mysticeti) and toothed whales (Odontoceti), are thought to have diverged around thirty-four million years ago. Baleen whales have bristles made of keratin instead of teeth . The bristles filter krill and other small invertebrates from seawater. Grey whales feed on bottom-dwelling mollusks. Rorqual family (balaenopterids) use throat pleats to expand their mouths to take in food and sieve out
2704-804: Is generally rare. 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. 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
2808-430: Is home to elongated spindle neurons that, prior to 2019, were known only in hominids . In humans, these cells are thought to be involved in social conduct, emotions, judgment and theory of mind. Cetacean spindle neurons are found in areas of the brain homologous to where they are found in humans, suggesting they perform a similar function. The cetacean skeleton is largely made up of cortical bone , which stabilizes
2912-479: 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
3016-433: Is limited, toothed cetaceans in captivity have been recorded to exhibit unihemispheric slow-wave sleep (USWS), which means they sleep with one side of their brain at a time, so that they may swim, breathe consciously and avoid both predators and social contact during their period of rest. A 2008 study found that sperm whales sleep in vertical postures just under the surface in passive shallow 'drift-dives', generally during
3120-402: 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 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
3224-487: Is powered by huge masseter and digastric muscles which give them large, droopy cheeks. The jaw hinge allows the animal to open its mouth at almost 180°. A folded orbicularis oris muscle allows the hippo to attain an extreme gape without tearing any tissue. On the lower jaw, the incisors and canines grow continuously, the former reaching 40 cm (16 in), while the latter can grow to up to 50 cm (20 in). The lower canines are sharpened through contact with
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3328-424: Is so well-adapted for both air and water that some blind specimens can survive. Some species, such as sperm whales, are well adapted for diving to great depths. Several species of toothed whales show sexual dimorphism , in which the males differ from the females, usually for purposes of sexual display or aggression. Cetacean bodies are generally similar to those of fish, which can be attributed to their lifestyle and
3432-759: Is swallowed whole. Teeth are shaped like cones (dolphins and sperm whales), spades ( porpoises ), pegs ( belugas ), tusks ( narwhals ) or variable (beaked whale males). Female beaked whales' teeth are hidden in the gums and are not visible, and most male beaked whales have only two short tusks. Narwhals have vestigial teeth other than their tusk, which is present on males and 15% of females and has millions of nerves to sense water temperature, pressure and salinity. A few toothed whales, such as some orcas , feed on mammals, such as pinnipeds and other whales. Toothed whales have well-developed senses – their eyesight and hearing are adapted for both air and water, and they have advanced sonar capabilities using their melon . Their hearing
3536-608: Is the genus Kenyapotamus , which lived in Africa from 15 to 9 million years ago . Hippopotamid species would spread across Africa and Eurasia, including the modern pygmy hippo. From 7.5 to 1.8 million years ago , a possible ancestor to the modern hippo, Archaeopotamus , lived in Africa and the Middle East. The oldest records of the genus Hippopotamus date to the Pliocene (5.3–2.6 million years ago). The oldest unambiguous records of
3640-700: 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 , in the US until her death in 2012 at the age of 61. The oldest hippo ever recorded was called Bertha; she had lived in the Manila Zoo in the Philippines since it first opened in 1959. When she died in 2017, her age was estimated to be 65. The oldest living hippopotamus in captivity
3744-412: Is vital for deep diving, since beyond a depth around 100 m (330 ft), the lung tissue is almost completely compressed by the water pressure. The stomach consists of three chambers. The first region is formed by a loose gland and a muscular forestomach (missing in beaked whales); this is followed by the main stomach and the pylorus . Both are equipped with glands to help digestion. A bowel adjoins
3848-455: The Amazon river dolphin . The collarbone is completely absent. Cetaceans have a cartilaginous fluke at the end of their tails that is used for propulsion. The fluke is set horizontally on the body and used with vertical movements, unlike fish and ichthyosaurs, which have vertical tails which move horizontally. Cetaceans have powerful hearts. Blood oxygen is distributed effectively throughout
3952-580: The Bouri Formation 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 near Djanet . The ancient Egyptians recognised the hippo as ferocious, and representations on the tombs of nobles show humans hunting them. The hippo was also known to the Greeks and Romans . The Greek historian Herodotus described
4056-550: 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,
4160-707: 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. The hippo population has declined most dramatically in the Democratic Republic of the Congo. By 2005, the population in Virunga National Park had dropped to 800 or 900 from around 29,000 in the mid-1970s. This decline
4264-532: The beaked whale family, several species of the porpoise family, orcas, pilot whales , eastern spinner dolphins and northern right whale dolphins show this characteristic. Males in these species developed external features absent in females that are advantageous in combat or display. For example, male sperm whales are up to 63% percent larger than females, and many beaked whales possess tusks used in competition among males. Hind legs are not present in cetaceans, nor are any other external body attachments such as
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4368-654: The blue whale , the humpback whale and the orca , have a distribution area that includes nearly the entire ocean, some species occur only locally or in broken populations. These include the vaquita , which inhabits a small part of the Gulf of California and Hector's dolphin , which lives in some coastal waters in New Zealand. Most river dolphin species live exclusively in fresh water. Many species inhabit specific latitudes, often in tropical or subtropical waters, such as Bryde's whale or Risso's dolphin . Others are found only in
4472-432: The fossil record , show their closest living relatives are cetaceans ( whales , dolphins , and porpoises ). The common ancestor of hippos and whales branched off from Ruminantia and the rest of the even-toed ungulates; the cetacean and hippo lineages split soon afterwards. Tylopoda Suina Ruminantia Hippopotamidae Cetacea The most recent theory of
4576-404: The melon as a head buckle. This is filled with air sacs and fat that aid in buoyancy and biosonar . The sperm whale has a particularly pronounced melon; this is called the spermaceti organ and contains the eponymous spermaceti , hence the name "sperm whale". Even the long tusk of the narwhal is a vice-formed tooth. In many toothed whales, the depression in their skull is due to the formation of
4680-404: The sperm whale , and the poorly understood beaked whales ) and the filter feeding Mysticeti or baleen whales (which includes species like the blue whale , the humpback whale and the bowhead whale ). Despite their highly modified bodies and carnivorous lifestyle, genetic and fossil evidence places cetaceans as nested within even-toed ungulates , most closely related to hippopotamus within
4784-433: The tucuxi or Guiana dolphin, is able to use electroreception to sense prey. The external ear has lost the pinna (visible ear), but still retains a narrow ear canal . The three small bones or ossicles that transmit sound within each ear are dense and compact , and differently shaped from those of land mammals. The semicircular canals are much smaller relative to body size than in other mammals. A bony structure of
4888-749: The wet season . Male hippos always have mobile spermatozoa 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 50 kg (110 lb) and at an average length of around 127 cm (50 in). 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
4992-452: 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. The hippopotamus is a megaherbivore and is exceeded in size among land animals only by elephants and some rhinoceros species. The mean adult weight
5096-965: The Elder , in his time, the best location in Egypt for capturing this animal was in the Saite nome ; the animal could still be found along the Damietta branch of the Nile after the Arab Conquest in 639. Reports of the slaughter of the last hippo in Natal Province 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 . Genetic evidence suggests common hippos in Africa experienced
5200-743: The Netherlands, and western Germany during interglacial periods, such as the Last Interglacial (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 , dating to less than 3,000 years ago. The species was common in Egypt 's Nile region during antiquity , but it has since been driven out. According to Pliny
5304-665: The Pacific, Atlantic and Indian Oceans. However, northern and southern populations become genetically separated over time. In some species, this separation leads eventually to a divergence of the species, such as produced the southern right whale , North Pacific right whale and North Atlantic right whale . Migratory species' reproductive sites often lie in the tropics and their feeding grounds in polar regions. Thirty-two species are found in European waters, including twenty-five toothed and seven baleen species. Many species of whales migrate on
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#17328698913375408-661: The Yoruba. Hippo masks were also used in Nyau funerary rituals of the Chewa of Southern Africa. According to Robert Baden-Powell , Zulu warriors referred to hippos in war chants. 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,
5512-402: The amount of brain mass available for cognitive tasks. Allometric analysis of the relationship between mammalian brain mass (weight) and body mass for different species of mammals shows that larger species generally have larger brains. However, this increase is not fully proportional. Typically the brain mass only increases in proportion to somewhere between the two-thirds power (or the square of
5616-522: The animal in the water. For this reason, the usual terrestrial compact bones, which are finely woven cancellous bone , are replaced with lighter and more elastic material. In many places, bone elements are replaced by cartilage and even fat, thereby improving their hydrostatic qualities. The ear and the muzzle contain a bone shape that is exclusive to cetaceans with a high density, resembling porcelain . This conducts sound better than other bones, thus aiding biosonar . The number of vertebrae that make up
5720-411: 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. A hippo's lifespan
5824-439: The body wall. The stable lumbar and tail include the other vertebrae. Below the caudal vertebrae is the chevron bone . The front limbs are paddle-shaped with shortened arms and elongated finger bones, to support movement. They are connected by cartilage. The second and third fingers display a proliferation of the finger members, a so-called hyperphalangy. The shoulder joint is the only functional joint in all cetaceans except for
5928-416: The body. They are warm-blooded, i.e., they hold a nearly constant body temperature. Cetaceans have lungs, meaning they breathe air. An individual can last without a breath from a few minutes to over two hours depending on the species. Cetacea are deliberate breathers who must be awake to inhale and exhale. When stale air, warmed from the lungs, is exhaled, it condenses as it meets colder external air. As with
6032-403: The brain folds around the insula and expands more laterally than in terrestrial mammals. As a result, the cetacean prefrontal cortex (compared to that in humans) rather than frontal is laterally positioned. Brain size was previously considered a major indicator of intelligence . Since most of the brain is used for maintaining bodily functions, greater ratios of brain to body mass may increase
6136-543: The clade Whippomorpha . Cetaceans have been extensively hunted for their meat, blubber and oil by commercial operations. Although the International Whaling Commission has agreed on putting a halt to commercial whaling, whale hunting is still going on, either under IWC quotas to assist the subsistence of Arctic native people or in the name of scientific research, although a large spectrum of non-lethal methods are now available to study marine mammals in
6240-483: The closest living relatives of the hippopotamids are cetaceans ( whales , dolphins , porpoises , 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 1,500 kg (3,300 lb) for bulls (males) and 1,300 kg (2,900 lb) for cows (females). Despite its stocky shape and short legs, it
6344-422: The completely aquatic cetaceans . The other branch became the anthracotheres , a large family of four-legged beasts, the earliest of which in the late Eocene would have resembled skinny hippos with comparatively smaller, narrower heads. All branches of the anthracotheres, except that which evolved into Hippopotamidae , became extinct during the Pliocene , leaving no descendants. A rough evolutionary lineage of
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#17328698913376448-542: The cube root) and the three-quarters power (or the cube of the fourth root) of the body mass. m brain ∝ ( m body ) where k is between two-thirds and three-quarters. Thus if Species B is twice the size of Species A, its brain size will typically be somewhere between 60% and 70% higher. Comparison of a particular animal's brain size with the expected brain size based on such an analysis provides an encephalization quotient that can be used as an indication of animal intelligence. The neocortex of many cetaceans
6552-607: 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. Until 1909, naturalists classified hippos together with pigs based on molar patterns. Several lines of evidence, first from blood proteins, then from molecular systematics , DNA and
6656-530: The fin are for stabilization and steering in the water. The male genitals and the mammary glands of females are sunken into the body. The male genitals are attached to a vestigial pelvis . The body is wrapped in a thick layer of fat, known as blubber . This provides thermal insulation and gives cetaceans their smooth, streamlined body shape. In larger species, it can reach a thickness up to one-half meter (1.6 feet). Sexual dimorphism evolved in many toothed whales. Sperm whales, narwhals , many members of
6760-456: The god Set takes the form of a red hippopotamus and fights Horus for control of the land, but is defeated. The goddess Tawaret is depicted as a pregnant woman with a hippo head, representing fierce maternal love. 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
6864-601: The ground) when they move fast enough. Hippos are reported to reach 30 km/h (19 mph) 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
6968-403: The group's members. For example, the blue whale reaches a maximum confirmed length of 29.9 meters (98 feet) and a weight of 173 tonnes (190 short tons), making it the largest animal ever known to have existed. There are approximately 89 living species split into two parvorders : Odontoceti or toothed whales (containing porpoises , dolphins , other predatory whales like the beluga and
7072-405: The habitat conditions. Their body is well-adapted to their habitat, although they share essential characteristics with other higher mammals ( Eutheria ). They have a streamlined shape, and their forelimbs are flippers . Almost all have a dorsal fin on their backs, but this can take on many forms, depending on the species. A few species, such as the beluga whale , lack them. Both the flipper and
7176-629: The hippo can thus be traced from Eocene and Oligocene species: from Anthracotherium and Elomeryx to the Miocene species Merycopotamus and Libycosaurus and finally the very latest anthracotheres in the Pliocene . 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 35 million years ago . An early hippopotamid
7280-674: 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). Ever since Obaysch inspired the "Hippopotamus Polka", hippos have been popular animals in Western culture for their rotund appearance, which many consider comical. The Disney film Fantasia featured
7384-562: 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
7488-404: 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
7592-434: The largest brain mass of any animal on Earth, averaging 8,000 cm (490 in ) and 7.8 kg (17 lb) in mature males. The brain to body mass ratio in some odontocetes, such as belugas and narwhals, is second only to humans. In some whales, however, it is less than half that of humans: 0.9% versus 2.1%. In cetaceans, evolution in the water has caused changes to the head that have modified brain shape such that
7696-422: The majority of cetaceans live in marine environments, a small number reside solely in brackish water or fresh water . Having a cosmopolitan distribution , they can be found in some rivers and all of Earth's oceans, and many species inhabit vast ranges where they migrate with the changing of the seasons. Cetaceans are famous for their high intelligence , complex social behaviour, and the enormous size of some of
7800-463: The middle and inner ear, the auditory bulla , is composed of two compact and dense bones (the periotic and tympanic). It is housed in a cavity in the middle ear; in the Odontoceti (apart from in the physeterids , this cavity is filled with dense foam and completely surrounds the bulla, which is connected to the skull only by ligaments. This may isolate the ear from sounds transmitted through the bones of
7904-547: The modern H. amphibius date to the Middle Pleistocene , though there are possible Early Pleistocene records. 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, a likely result of the process of insular dwarfism . Fossil evidence indicates many Malagasy hippos were hunted by humans,
8008-490: The nictitating membrane. It is the only monogenean species (which normally live on fish) documented to live on a mammal. 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
8112-565: 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. 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
8216-528: The origins of Hippopotamidae suggests hippos and whales shared a common semiaquatic ancestor that branched off from other artiodactyls around 60 million years ago . This hypothesised ancestral group likely split into two branches again around 54 million years ago . One branch would evolve into cetaceans , possibly beginning about 52 million years ago , with the protowhale Pakicetus and other early whale ancestors collectively known as Archaeoceti . This group eventually underwent aquatic adaptation into
8320-404: The other being the pygmy hippopotamus ( Choeropsis liberiensis or Hexaprotodon liberiensis ). Its name comes from the ancient Greek for "river horse" ( ἱπποπόταμος ). After elephants and rhinoceroses , the hippopotamus is the next largest land mammal . It is also the largest extant land artiodactyl . Despite their physical resemblance to pigs and other terrestrial even-toed ungulates,
8424-562: 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 . Hippos are semiaquatic and require enough water to immerse in, while being close to grass. They mostly live in freshwater habitat, but can be found in estuaries . They prefer relatively still waters with gently sloping shores, though male hippos may also be found in very small numbers in more rapid waters with rocky slopes. Like most herbivores, hippos will consume
8528-599: The river ' . In English, the plural is "hippopotamuses". The modern 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 . Five subspecies of hippos have been described based on morphological differences in their skulls as well as differences in geographical range: The suggested subspecies above were never widely used or validated by field biologists;
8632-414: 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 membranes cover the eyes. The vocal folds 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
8736-430: 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
8840-454: 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 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 tyrosine . This natural sunscreen cannot prevent
8944-476: The shoulder, with males and females ranging 1.40 to 1.65 m (4 ft 7 in to 5 ft 5 in) and 1.30 to 1.45 m (4 ft 3 in to 4 ft 9 in) tall at the shoulder respectively. The species has a typical head–body length of 3.3–3.45 m (10.8–11.3 ft) and an average standing height of 1.4 m (4 ft 7 in) at the shoulder. Hippos have barrel-shaped bodies with short tails and legs, and an hourglass-shaped skull with
9048-426: The skull is significantly shortened and deformed. By shifting the nostrils to the top of the head, the nasal passages extend perpendicularly through the skull. The teeth or baleen in the upper jaw sit exclusively on the maxilla . The braincase is concentrated through the nasal passage to the front and is correspondingly higher, with individual cranial bones that overlap. In toothed whales, connective tissue exists in
9152-908: The skull, something that also happens in bats . Cetaceans use sound to communicate , using groans, moans, whistles, clicks or the 'singing' of the humpback whale. Odontoceti are generally capable of echolocation . They can discern the size, shape, surface characteristics, distance and movement of an object. They can search for, chase and catch fast-swimming prey in total darkness. Most Odontoceti can distinguish between prey and nonprey (such as humans or boats); captive Odontoceti can be trained to distinguish between, for example, balls of different sizes or shapes. Echolocation clicks also contain characteristic details unique to each animal, which may suggest that toothed whales can discern between their own click and that of others. While differences in ear structure associated with echolocating abilities are found amongst Cetacea, cranial asymmetry has also been found to be
9256-424: 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 ground by the molars . The hippo is considered to be a pseudoruminant ; it has a complex three-chambered stomach, but does not "chew cud ". Hippo skin is 6 cm (2.4 in) thick across much of its body with little hair. The animal
9360-457: The spine varies by species, ranging from forty to ninety-three. The cervical spine , found in all mammals, consists of seven vertebrae which, however, are reduced or fused. This fusion provides stability during swimming at the expense of mobility. The fins are carried by the thoracic vertebrae , ranging from nine to seventeen individual vertebrae. The sternum is cartilaginous. The last two to three pairs of ribs are not connected and hang freely in
9464-500: The stomachs, whose individual sections can only be distinguished histologically . The liver is large and separate from the gall bladder . The kidneys are long and flattened. The salt concentration in cetacean blood is lower than that in seawater, requiring kidneys to excrete salt. This allows the animals to drink seawater. The urinary bladder is proportionally smaller in cetaceans than in land mammals. The testes are located internally, without an external scrotum . The uterus
9568-867: The term describes those that actively spend part of their daily time in water (in which case they can also be called amphibious ), or land animals that have spent at least one life stages (e.g. as eggs or larvae ) in aquatic environments. When referring to plants , the term describes land plants whose roots have adapted well to tolerate regular, prolonged submersion in water, as well as emergent and (occasionally) floating-leaved aquatic plants that are only partially immersed in water. Examples of semi-aquatic animals and plants are given below. Semi aquatic animals include: Semi aquatic plants include: Cetacean ( see text for families) Cetacea ( / s ɪ ˈ t eɪ ʃ ə / ; from Latin cetus ' whale ', from Ancient Greek κῆτος ( kêtos ) ' huge fish , sea monster ')
9672-427: The total lung volume. For land mammals, in comparison, this value is usually about 15%. During inhalation, about twice as much oxygen is absorbed by the lung tissue as in a land mammal. As with all mammals, the oxygen is stored in the blood and the lungs, but in cetaceans, it is also stored in various tissues, mainly in the muscles. The muscle pigment, myoglobin , provides an effective bond. This additional oxygen storage
9776-464: 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. 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
9880-459: 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 , 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
9984-423: 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
10088-407: 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
10192-537: 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 and poaching for their meat and ivory (canine teeth). The Latin word hippopotamus is derived from the ancient Greek ἱπποπόταμος ( hippopótamos ), from ἵππος ( híppos ) ' horse ' and ποταμός ( potamós ) ' river ' , together meaning ' horse of
10296-451: 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 trotting , and limb movements do not change between speeds. They can reach an airborne stage (a stage when all limb are off
10400-695: The water. Balaenids ( right whales and bowhead whales ) have massive heads that can make up 40% of their body mass. Most mysticetes prefer the food-rich colder waters of the Northern and Southern Hemispheres, migrating to the Equator to give birth. During this process, they are capable of fasting for several months, relying on their fat reserves. The parvorder of Odontocetes – the toothed whales – include sperm whales, beaked whales, orcas, dolphins and porpoises. Generally their teeth have evolved to catch fish, squid or other marine invertebrates , not for chewing them, so prey
10504-724: 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 just an abnormal behaviour. It is challenging to study the interaction of bulls and cows because hippos are not sexually dimorphic , 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 in water but not land, and these may range 250–500 m (820–1,640 ft) in lakes and 50–100 m (160–330 ft) in rivers. Territories are abandoned when
10608-407: The wild. Cetaceans also face severe environmental hazards from underwater noise pollution , entanglement in abandoned ropes and nets, collisions with ships, plastic and heavy metals build-up, to accelerating climate change , but how much they are affected varies widely from species to species, from minimally in the case of the southern bottlenose whale to the baiji (Chinese river dolphin) which
10712-512: 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
10816-411: 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 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
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