Animal Wednesday #80

Today something barrel-shaped and big - meet Hippopotamus.

Hippopotamus

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 (3,010 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. Hippos measure 2.90 to 5.05 m (9.5 to 16.6 ft) long, 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, 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. 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.

Hippos have barrel-shaped bodies with short tails and legs, and an hourglass-shaped skull with a long muzzle. 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 pelvis rests at an angle of 45 degrees. Though they are bulky animals, hippos can gallop at 30 km/h (19 mph) on land, but they normally trot. They are incapable of jumping but do climb up steep banks.

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. Muscular closing valves exist in the nostrils while nictitating membranes cover the eyes. Despite being semiaquatic and having webbed feet, an adult hippo is not a particularly good swimmer, nor can it float. It is rarely found in deep water; when it is, the animal moves by porpoise-like leaps off the bottom. Adult hippos move at speeds of up to 8 km/h (5 mph) in water, typically resurfacing to breathe every three to five minutes. The young have to breathe every two to three minutes. The hippopotamus sleeps with both hemispheres of the brain resting, as in all land mammals. Despite this, it is able to sleep while submerged, intermittently surfacing to breathe seemingly without waking. They may be able to transition between different phases of sleep more quickly than other mammals.

Hippos differ from all other large land mammals in being semiaquatic, spending their days in lakes and rivers. They require habitat with enough water to submerge themselves in and which has plenty of grass nearby. When bodies of water feature firm, smooth, sloping beaches, larger numbers of hippos may congregate. Male hippos may also be found in very small numbers in rapid waters in rocky gorges. Hippos mostly live in freshwater habitats; however, populations in West Africa mostly inhabit estuarine waters and may even be found out at sea.

Hippos spend most the day in water to stay cool and hydrated. Just before night begins, they leave the water to feed on land. 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. A hippo will eat around 40 kg (88