[Animals]hippopotamus - Description - life style

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The hippopotamus (/ˌhɪpəˈpɒtəməs/;[3] pl.: hippopotamuses or hippopotami), also shortened to hippo (pl.: hippos; Hippopotamus amphibius), 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, 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, 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 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 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). Etymology The Latin word hippopotamus is derived from the ancient Greek ἱπποπόταμος (hippopótamos), from ἵππος (híppos) 'horse' and ποταμός (potamós) 'river', together meaning 'horse of the river'.[4][5][6] In English, the plural is "hippopotamuses", but "hippopotami" is also used.[7] Taxonomy and origins Classification 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.[8]: 39–40 Detail of the head Five subspecies of hippos have been described based on morphological differences in their skulls as well as differences in geographical range:[8]: 3 [9][10][11] H. a. amphibius – (the nominate subspecies) ranges from Gambia east to Ethiopia and then south to Mozambique and historically ranged as far north as Egypt; its skull is distinguished by a moderately reduced preorbital region, a bulging dorsal surface, elongated mandibular symphysis and larger chewing teeth. H. a. kiboko – found in Kenya and Somalia; was noted to be smaller and more lightly coloured than other hippos with wider nostrils, somewhat longer snout and more rounded and relatively raised orbits with the space between them being incurved. H. a. capensis – found in Zambia and South Africa; distinguished by wider orbits. H. a. tschadensis – ranges between Chad and Niger; featured a slightly shorter but broader face, and pronounced, forward-facing orbits. H. a. constrictus – ranged from the southern Democratic Republic of Congo to Angola and Namibia; skull characterised by a thicker preorbital region, shorter snout, flatter dorsal surface, reduced mandibular symphysis and smaller chewing teeth. The suggested subspecies above were never widely used or validated by field biologists; the described morphological differences were small enough that they could have resulted from simple variation in nonrepresentative samples.[8]: 2  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.[10] Evolution Evolutionary relationships among hippo and Cetacea (whales, dolphins)[12]


Until 1909, naturalists classified hippos together with pigs based on molar patterns. Several lines of evidence, first from blood proteins, then from molecular systematics[13] and DNA[14][15] and the fossil record, show their closest living relatives are cetaceans (whales, dolphins, and porpoises).[16][17] 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.[14][17] Artiodactyla Tylopoda Artiofabula Suina Cetruminantia Ruminantia Whippomorpha Hippopotamidae Cetacea Anthracotherium magnum from the Oligocene of Europe The most recent theory of the origins of Hippopotamidae suggests hippos and whales shared a common semiaquatic ancestor that branched off from other artiodactyls around 60 million years ago.[14][16] This hypothesised ancestral group likely split into two branches again around 54 million years ago.[13] 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 the completely aquatic cetaceans.[17] 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.[16][17] A rough evolutionary lineage of 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.[18] 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.[19][20] An early hippopotamid is the genus Kenyapotamus, which lived in Africa from 15 to 9 million years ago.[18] 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.[21] The oldest records of the genus Hippopotamus date to the Pliocene (5.3-2.6 million years ago).[22] The oldest unambiguous records of the modern H. amphibius date to the Middle Pleistocene, though there are possible Early Pleistocene records.[23] Choeropsis madagascariensis skeleton with a modern hippopotamus skull Extinct species Three species of Malagasy hippopotamus became extinct during the Holocene on Madagascar, the last of them within the past 1,000 years. The Malagasy hippos were smaller than the modern hippo, a likely result of the process of insular dwarfism.[24] Fossil evidence indicates many Malagasy hippos were hunted by humans, a factor in their eventual extinction.[24] 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.[25] Hippopotamus gorgops from the Early Pleistocene-early Middle Pleistocene of Africa and West Asia grew considerably larger than the living hippopotamus, with an estimated body mass of over 4,000 kilograms (8,800 lb).[22][26][27] Hippopotamus antiquus ranged throughout Europe, extending as far north as Britain during the Early and Middle Pleistocene epochs, before being replaced by the modern H. amphibius in Europe during the latter part of the Middle Pleistocene.[28] The Pleistocene also saw a number of dwarf species evolve on several Mediterranean islands, including Crete (Hippopotamus creutzburgi), Cyprus (the Cyprus dwarf hippopotamus, Hippopotamus minor), Malta (Hippopotamus melitensis), and Sicily (Hippopotamus pentlandi). Of these, the Cyprus dwarf hippo survived until the end of the Pleistocene or early Holocene. Evidence from the archaeological site Aetokremnos continues to cause debate on whether or not the species was driven to extinction, or even encountered, by man.[29][30] Characteristics Hippo's skull, showing the large canines and incisors used for fighting The hippopotamus is a megaherbivore and is exceeded in size among land animals only by elephants and some rhinoceros species. The mean adult weight 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).[31] Male hippos appear to continue growing throughout their lives, while females reach maximum weight at around age 25.[32] Hippos measure 2.90 to 5.05 m (9.5 to 16.6 ft) long,[33] including a tail of about 35 to 56 cm (1.15 to 1.84 ft) in length and 1.30 to 1.65 m (4.3 to 5.4 ft) tall at the shoulder,[34][35] with males and females ranging 1.40 to 1.65 m (4.6 to 5.4 ft) and 1.30 to 1.45 m (4.3 to 4.8 ft) tall at the shoulder respectively.[35] 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 (4.6 ft) at the shoulder.[36] Hippos have barrel-shaped bodies with short tails and legs, and an hourglass-shaped skull with a long snout.[37][8]: 3, 19  Their skeletal structures are graviportal, adapted to carrying their enormous weight,[8]: 8  and their dense bones and low centre of gravity allows them to sink and move along the bottom of the water.[38] Hippopotamuses have small legs (relative to other megafauna) because the water in which they live reduces the weight burden.[39] The toes are webbed and the pelvis rests at an angle of 45 degrees.[8]: 3, 9  Though chubby-looking, hippos have little fat.[8]: 3  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.[40]: 259  The nostrils and ears can close when underwater while nictitating membranes cover the eyes.[8]: 4, 116  The vocal folds of the hippo are more horizontally positioned, much like cetaceans. Underneath are throat tissues, where vibrations are transmitted to produce underwater calls.[41] Characteristic "yawn" of a hippo The hippo's jaw is powered by huge masseter and digastric muscles which give them large, droopy cheeks.[40]: 259  The jaw hinge allows the animal to open its mouth at almost 180°.[8]: 17  A folded orbicularis oris muscle allows the hippo to attain an extreme gape without tearing any tissue.[42] On the lower jaw, the incisors and canines grow continuously, the former reaching 40 cm (1 ft 4 in), while the latter can grow to up to 50 cm (1 ft 8 in). The lower canines are sharpened through contact with the smaller upper canines.[37] 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.[40]: 259, 263  The hippo is considered to be a pseudoruminant; it has a complex three-chambered stomach, but does not "chew cud".[8]: 22 Completely submerged hippo (San Diego Zoo) Hippo skin is 6 cm (2 in) thick across much of its body with little hair.[37][40]: 260  The animal is mostly purplish-grey or blue-black, but brownish-pink on the underside and around the eyes and ears.[40]: 260  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 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.[43][44] 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.[44] This natural sunscreen cannot prevent the animal's skin from cracking if it stays out of water too long.[45] 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.[8]: 28–29 A hippo's lifespan is typically 40 to 50 years.[40]: 277  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[46][47] until her death in 2012 at the age of 61.[48] 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.[49] The oldest living hippopotamus in captivity is Lu the Hippo, from the Ellie Schiller Homosassa Springs Wildlife State Park. As of 2024, he is 64 years old.[50]



TS : https://en.wikipedia.org/wiki/Hippopotamus