HIPPOPOTAMUS
Scientific Classification
Class: Mammalia
(Mammals)
Order: Artiodactyla
Family: Hippopotamidae
Genus: Hippopotamus
Species: amphibious
Quick Facts
Life span: Median life expectancy is 36 years
Gestation: 8 months
Number of young at birth: 1
Age of maturity: Females 5 to 6 years; males average 7 years
Size: 10.8
to 16.5 feet (3.3 to 5 meters) long
Size: Up
to 5.2 feet (1.6 meters) tall at shoulders
Weight: Females
average 3,000 pounds (1,400 kilograms); males are 3,500 to 9,920 pounds (1,600
to 4,500 kilograms)
Conservation
Status
The
common hippopotamus (Hippopotamus amphibius), or hippo,
is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in
the family Hippopotamidae,
the other being the pygmy hippopotamus (Choeropsis
liberiensis orHexaprotodon liberiensis). The name comes from
the ancient Greek for "river horse"
(ἱπποπόταμος). After the elephant andrhinoceros,
the common hippopotamus is the third-largest type of land mammal and the
heaviest extant artiodactyl.
Common
hippos are recognizable by their barrel-shaped torsos, wide-opening mouths
revealing large canine tusks, nearly hairless bodies, columnar-like legs and
large size; adults average 1,500 kg (3,300 lb) and 1,300 kg
(2,900 lb) for males and females respectively, making them the largest
species of land mammal after the 3 species of elephants and
the white and Indian
rhinoceros. Despite its stocky shape and short legs, it is capable
of running 30 km/h (19 mph) over short distances. The hippopotamus is
a highly aggressive and unpredictable animal and is ranked among the most
dangerous animals in Africa. Nevertheless, they are still threatened by habitat
loss and poaching for their meat and ivory canine teeth.
The
common hippopotamus is semiaquatic, inhabiting rivers, lakes and mangrove swamps,
where territorial bulls preside over a stretch of river and groups of five to
30 females and young. During the day, they remain cool by staying in the water
or mud; reproduction and childbirth both occur in water. They emerge at dusk to
graze on grasses. While hippopotamuses rest near each other in the water,
grazing is a solitary activity and hippos are not territorial on land.
Classification
A pygmy hippopotamus (Choeropsis liberiensis).
The
hippopotamus is the type genus of the family Hippopotamidae.
The pygmy hippopotamus belongs to a different
genus in Hippopotamidae, either Choeropsis orHexaprotodon. Hippopotamidae
are sometimes known as hippopotamids. Sometimes, the subfamily Hippopotaminae
is used. Further, some taxonomists group hippopotamuses and anthracotheres in
the superfamily Anthracotheroidea. Hippopotamidae are classified along
with other even-toed ungulates in the order Artiodactyla.
Other artiodactyls include camels, cattle, deer and pigs, although hippopotamuses are not closely related to these
groups.
Five
subspecies of hippos have been described based on morphological differences in their
skulls and geographical differences:
- H. a. amphibius – (the nominate subspecies) which stretched
from Egypt,
where they are now extinct, south up the Nile
River toTanzania and Mozambique
- H. a. kiboko – in Kenya in
the African Great Lakes region, and
in Somalia in
the Horn of Africa. Broader nasals and more
hollowed interorbital region
- H. a. capensis – from Zambia to South
Africa, most flattened skull of the subspecies
- H. a. tschadensis – throughout Western Africa to, as the name
suggests, Chad,
slightly shorter and wider face, with prominent orbits
- H. a. constrictus – in Angola,
the southern Democratic Republic of Congo and Namibia,
named for its deeper preorbital constriction
The
suggested subspecies 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. Genetic
analyses have tested the existence of three of these putative subspecies. A
study examining mitochondrial DNA from skin biopsies taken
from 13 sampling locations, considered genetic diversity and structure among
hippo populations across the continent. The authors 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 has been tested.
Extinct species
Choeropsis madagascariensisskeleton with a modern hippopotamus skull.
Three
species of Malagasy hippopotamus became extinct
during the Holocene on Madagascar,
one of them within the past 1,000 years. The Malagasy hippos were smaller than
the modern hippopotamus, likely through the process of insular
dwarfism. Fossil
evidence indicates many Malagasy hippos were hunted by humans, a likely factor
in their eventual extinction. Two species of hippopotamus, the European hippopotamus (H. antiquus)
and H. gorgops, ranged throughout
continental Europe and the British Isles. Both species became extinct before
the last glaciation.
Behavior
A hippo out of water
just after sunrise
With the exception of eating, most of hippopotamuses' lives – from
childbirth, fighting with other hippos, to reproduction – occurs in the water.
Hippos leave the water at dusk and travel inland, sometimes up to 10 km
(6 mi), to graze on short
grasses, their main source of food. They spend four to five hours grazing and
can consume 68 kg (150 lb) of grass each night. Like almost any herbivore, they
consume other plants if presented with them, but their diet in nature consists
almost entirely of grass, with only minimal consumption of aquatic plants. Hippos are born with sterile intestines, and
require bacteria obtained from their mothers' feces to digest vegetation. Hippos have (rarely) been filmed
eating carrion,
usually close to the water. There are other reports of meat-eating, and even cannibalism and predation.
The stomach anatomy of a hippo is not suited to carnivory, and meat-eating is
likely caused by aberrant behavior or nutritional stress.
Hippo defecation createsallochthonous deposits of organic matter along the
river beds. These deposits have an unclear ecological function. 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, both by keeping the land
clear of vegetation and depressing the ground. Over prolonged periods, hippos
can divert the paths of swamps and channels.
Adult
hippos move at speeds 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
process of surfacing and breathing is automatic. A hippo sleeping underwater
rises and breathes without waking. A hippo closes its nostrils when it
submerges into the water. As with
fish and turtles on a coral reef, hippos occasionally visit cleaning stations and signal, by opening their mouths
wide, their readiness for being cleaned of parasites by certain species of
fishes. This is an example of mutualism in
which the hippo benefits from the cleaning, while the fish receive food.
- When agitated, a hippo can charge at up to 14 miles per hour (30 kilometers per hour) on land.
- The hippo is similar in size to the white rhinoceros.
- Hippos can store two days' worth of grass in their stomachs and can go up to three weeks without eating.
- An adult hippo can hold its breath underwater for up to 30 minutes.
- In African rivers, hippos look like floating islands, with birds fishing from their backs.
- Turtles and even baby crocodiles have been seen sunning themselves on hippos.
- A group of hippos is sometimes called a bloat, pod, or siege.
- Hippos have stiff whiskers above the upper lip and some fuzziness around their ears and on their tail.
- Several fish species in Africa can keep busy feeding on the food remnants and dead skin cells found on the hippo’s skin.
- Hippos are much faster than they appear, reaching speeds of 20 mph (32 kph) on land and also moving quickly in the water.
- Hippos vocalize on both land and in the water and are the only mammals that make amphibious calls.
Source:
http://animals.nationalgeographic.com/animals/mammals/hippopotamus/
