page_title: Hippopotamus
section_title: Reproduction
hierarchical_section_title: Hippopotamus / Behaviour and life history / Reproduction
caption_attribution_description: English: A hippo fetus from the collection of the Napier Natural History Museum in Thiruvananthapuram.
context_page_description: The hippopotamus, also called the hippo, common hippopotamus or river hippopotamus, is a large, mostly herbivorous, semiaquatic mammal and ungulate native to sub-Saharan Africa. It is one of only two extant species in the family Hippopotamidae, the other being the pygmy hippopotamus. The name comes from the ancient Greek for "river horse". After the elephant and rhinoceros, both of which are found in Africa, the hippopotamus is the third-largest type of land mammal and the heaviest extant artiodactyl. Despite their physical resemblance to pigs and other terrestrial even-toed ungulates, the closest living relatives of the Hippopotamidae are cetaceans from which they diverged about 55 million years ago.
  Hippos are recognisable by their barrel-shaped torsos, wide-opening mouths revealing large canine tusks, nearly hairless bodies, columnar legs and large size; adults average 1,500 kg for males and 1,300 kg for females. Despite its stocky shape and short legs, it is capable of running 30 km/h over short distances.
  Hippos inhabit rivers, lakes, and mangrove swamps, where territorial males preside over a stretch of river and groups of five to thirty females and young hippos.
context_section_description: Female hippos reach sexual maturity at five to six years and have a gestation period of eight months. A study of endocrine systems revealed that female hippos may begin puberty as early as three or four years. Males reach maturity at around 7.5 years. A study of hippo reproductive behaviour in Uganda showed that peak conceptions occurred during the end of the wet season in the summer, and peak births occurred toward the beginning of the wet season in late winter. This is because of the female's oestrous cycle; as with most large mammals, male hippo spermatozoa is active year-round. Studies of hippos in Zambia and South Africa also showed evidence of births occurring at the start of the wet season. After becoming pregnant, a female hippo will typically not begin ovulation again for 17 months.
  Mating occurs in the water, with the female submerged for most of the encounter, her head emerging periodically to draw breath. Female hippos isolate themselves to give birth and return within 10–14 days. Calves are born underwater at a weight between 25 and 50 kg (55 and 110 lb) and an average length of around 127 cm (4.17 ft), and must swim to the surface to take their first breaths. A mother typically gives birth to only one calf, although twins also occur. The young often rest on their mothers' backs when the water is too deep for them, and they swim under water to suckle. They suckle on land when the mother leaves the water.
  Mother hippos are very protective of their young and may keep others at a distance. However, calves are occasionally left in nurseries which are guarded by one or a few adults. Calves in nurseries engage in playfights. Weaning starts between six and eight months after birth, and most calves are fully weaned after a year. 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 is common among small mammals such as rodents).
caption: Preserved hippopotamus fetus
exif: {"Image Make": "Canon", "Image Model": "Canon EOS 600D", "Image Orientation": "Horizontal (normal)", "Image Software": "darktable 1.4.2", "Image DateTime": "2016:01:21 23:30:23", "Image Artist": "", "Image Rating": "1", "Image Tag 0x4749": "20", "Image Copyright": "", "Image ExifOffset": "224", "Image DateTimeOriginal": "2016:01:14 08:43:13", "EXIF ExposureTime": "1/50", "EXIF FNumber": "9/2", "EXIF ExposureProgram": "Unidentified", "EXIF ISOSpeedRatings": "2500", "EXIF SensitivityType": "Recommended Exposure Index", "EXIF RecommendedExposureIndex": "2500", "EXIF ExifVersion": "0230", "EXIF DateTimeOriginal": "2016:01:14 08:43:13", "EXIF DateTimeDigitized": "2016:01:14 08:43:13", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "45/8", "EXIF ApertureValue": "35/8", "EXIF ExposureBiasValue": "0", "EXIF MeteringMode": "Pattern", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "36", "EXIF SubSecTime": "40", "EXIF SubSecTimeOriginal": "40", "EXIF SubSecTimeDigitized": "40", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "4854", "EXIF ExifImageLength": "3349", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "45650", "EXIF FocalPlaneXResolution": "1036800/181", "EXIF FocalPlaneYResolution": "691200/119", "EXIF FocalPlaneResolutionUnit": "2", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF SceneCaptureType": "Standard", "EXIF CameraOwnerName": "", "EXIF BodySerialNumber": "353077046803", "EXIF LensSpecification": "[18, 55, 0/0, 0/0]", "EXIF LensModel": "EF-S18-55mm f/3.5-5.6 III", "EXIF LensSerialNumber": "00001b9856"}