The White Rhinoceros
The white rhinoceros or square-lipped rhinoceros (Ceratotherium simum) is one of the five species of rhinoceros that exist. It has a wide mouth used for grazing and is the most social of all rhino species. The white rhinoceros consists of two subspecies: the southern white rhinoceros, with an estimated 17,460 wild-living animals at the end of 2007 (IUCN 2008), and the much rarer northern white rhinoceros. The northern subspecies has very few remaining, with seven confirmed individuals left (including those in captivity).
There are two subspecies of white rhinos; the southern white rhinoceros (Ceratotherium simum simum) and the northern white rhinoceros.
- Southern white rhinoceros – As of 31 December 2007, there were an estimated 17,480 southern white rhino in the wild (IUCN 2008), making them the most abundant subspecies of rhino in the world. South Africa is the stronghold for this subspecies (93.0%), conserving 16,255 individuals in the wild in 2007 (IUCN 2008). There are smaller reintroduced populations within the historical range of the species in Namibia, Botswana, Zimbabwe and Swaziland, while a small population survives in Mozambique. Populations have also been introduced outside of the former range of the species to Kenya, Uganda and Zambia. Wild-caught southern whites will readily breed in captivity given appropriate amounts of space and food, as well as the presence of other female rhinos of breeding age. For instance, 91 calves have been born at the San Diego Zoo Safari Park since 1972. However, for reasons that are not currently understood, the rate of reproduction is extremely low among captive-born southern white females.
- Northern white rhinoceros – The northern white rhinoceros, or northern square-lipped rhinoceros (Ceratotherium simum cottoni) is considered Critically Endangered or Extinct in the Wild. Formerly found in several countries in East and Central Africa south of the Sahara, this subspecies is a grazer in grasslands and savanna woodlands. In the world, there are currently only three rhinos of this subspecies left in captivity and four have been returned to a conservancy in Kenya. Initially, six northern white rhinoceros lived in the Dvůr Králové Zoo in the Czech Republic. Four of the six rhinos (which are also the only reproductive animals of this subspecies) were transported to Ol Pejeta Conservancy in Kenya, Africa, where scientists hope they will successfully breed and save this subspecies from extinction. One of two remaining in the Czech Republic died in late May 2011. The two other rhinos presently live at the San Diego Zoo's Safari Park in California. Following the phylogenetic species concept, recent research has suggested the northern white rhinoceros may be an altogether different species, rather than a subspecies of white rhinoceros, in which case the correct scientific name for the former is Ceratotherium cottoni. Distinct morphological and genetic differences suggest the two proposed species have been separated for at least a million years.
The white rhinoceros is the largest of the five species of rhinoceros and the world's largest land mammal after the three species of elephant. It has a massive body and large head, a short neck and broad chest. The head and body length is 3.7 to 4 m (12 to 13 ft) in males and 3.4 to 3.65 m (11 to 12.0 ft) in females, with the tail adding another 70 cm (28 in) and the shoulder height is 1.7 to 1.85 m (5 ft 7 in to 6 ft 0.8 in) in the male and 1.6 to 1.77 m (5 ft 3 in to 5 ft 10 in) in the female. Weight in this animal typically ranges from 1,360 to 3,630 kg (3,000 to 8,000 lb). The male, averaging 2,300 kg (5,100 lb) is heavier than the female, at an average of 1,700 kg (3,700 lb). The largest recorded white rhinoceros was about 4,500 kg (9,900 lb). On its snout it has two horn-like growths, one behind the other. These are made of solid keratin, in which they differ from the horns of bovids (cattle and their relatives), which are keratin with a bony core, and deer antlers, which are solid bone. The front horn is larger and averages 90 cm (35 in) in length, reaching as much as 150 cm (59 in). The white rhinoceros also has a noticeable hump on the back of its neck. Each of the four stumpy feet has three toes. The color of the body ranges from yellowish brown to slate grey. Its only hair is the ear fringes and tail bristles. White rhinos have a distinctive broad, straight mouth which is used for grazing. Its ears can move independently to pick up sounds but it depends most of all on smell. The olfactory passages which are responsible for smell are larger than their entire brain. The white rhinoceros has the widest set nostrils of any land based animal.
White rhinoceroses are found in grassland and savannah habitat. Herbivore grazers that eat grass, preferring the shortest grains, the white rhinoceros is one of the largest pure grazers. It drinks twice a day if water is available, but if conditions are dry it can live four or five days without water. It spends about half of the day eating, one third resting, and the rest of the day doing various other things. White rhinoceroses, like all species of rhinoceros, love wallowing in mudholes to cool down.
White rhinoceroses produce sounds which include a panting contact call, grunts and snorts during courtship, squeals of distress, and deep bellows or growls when threatened. Threat displays (in males mostly) include wiping its horn on the ground and a head-low posture with ears back, combined with snarl threats and shrieking if attacked. The white rhinoceros is quick and agile and can run 50 km/h (31 mph).
White rhinoceroses live in crashes or herds of up to 14 animals (usually mostly female). Sub-adult males will congregate, often in association with an adult female. Most adult bulls are solitary. Dominant bulls mark their territory with excrement and urine. The dung is laid in well defined piles. It may have 20 to 30 of these piles to alert passing rhinoceroses that it is his territory. Another way of marking their territory is wiping their horns on bushes or the ground and scrapes with its feet before urine spraying. They do this around 10 times an hour while patrolling territory. The same ritual as urine marking except without spraying is also commonly used. The territorial male will scrape-mark every 30 m (98 ft) or so around its territory boundary. Subordinate males do not mark territory. The most serious fights break out over mating rights to do with a female. Female territory is overlapped extensively and they do not defend it.
Females reach sexual maturity at 6–7 years of age while males reach sexual maturity between 10–12 years of age. Courtship is often a difficult affair. The male stays beyond the point where the female acts aggressively and will give out a call when approaching her. The male chases and or blocks the way of the female while squealing or wailing loudly if the female tries to leave his territory. When ready to mate the female curls its tail and gets into a stiff stance during the half hour copulation. Breeding pairs stay together between 5–20 days before they part their separate ways. Gestation occurs around 16–18 months. A single calf is born and usually weighs between 40 and 65 kg (88 and 140 lb). Calves are unsteady for their first 2 to 3 days of life. When threatened the baby will run in front of the mother, who is very protective of her calf and will fight for it vigorously. Weaning starts at 2 months, but the calf may continue suckling for over 12 months. The birth interval for the white rhino is between 2 and 3 years. Before giving birth the mother will chase off her current calf. White rhinos can live to be up to 40–50 years old. Adult white rhinos have no natural predators (other than man) due to their size, and even young rhinos are rarely attacked due to the mother's presence or preyed on due to their tough skin.
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