The Black Rhinoceros

The Black Rhinoceros

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“Two tonnes of live body weight and a horn straight out of the age of the dinosaur, all carried by four sturdy pillar-like legs which can propel the colossus in a trot faster than a 100-metre sprinter: these are features of an animal which has often served as a symbol for primal power and fortitude.” (cf. Rettet die Nashörner e.V.)

Rhinoceroses have lived on the Earth for 60 million years. The most famous prehistoric species was the woolly rhino, which lived in Europe during the last Ice Age. It owed its name to its thick woolly fur. But of the 170 species which also lived in northern regions, including Europe, northern Asia and North America, only five still exist.

The oldest and smallest species of rhinoceros is the Sumatra rhinoceros from South-east Asia: the reclusive Javan rhinoceros lives in Vietnam and feeds primarily on fruit. The largest rhino in Asia is the Indian rhinoceros, famous for its thick, overlapping armour-like plates of skin. Two species have survived in Africa: the white rhino, also known as the square-lipped rhinoceros, which is the largest land mammal after the elephant, and the slightly smaller black (or hook-lipped) rhinoceros.

The Hook-Lipped or Black Rhinoceros (Diceros bicornis)
Afrikaans: Swartrenoster | English: Black Rhinoceros or Hook-Lipped Rhinoceros | French.: Rhinocéros noir | Swaheli: Faru

Etymology

Up until the early 19th century the black rhino was the only species of rhino from Africa known in Europe, and was called the “African rhinoceros”. The British naturalist William John Burchell (1782–1863) discovered the square-lipped (white) rhinoceros in South Africa in 1812, and named it Rhinoceros simus, without translating the name. In South Africa during the late 18th century, English hunters killed several specimens of this unfamiliar species, and called it “white”, which did not refer to the skin colour. The most common theory why they are called white is that there was a mistranslation of the Afrikaans word “wijd” or “wyd”, which means “wide” but is confusingly similar to “white”. The term “Black rhinoceros” was adopted for the hook-lipped rhino to complement this term. Another popular theory has it that the name describes the mostly dark mud in which the hook-lipped rhino likes to wallow. Because the mud in the square-lipped rhinoceros’ natural habitat is rich in chalk, these are consequently referred to as “white” rhinos. When clean, however, their colour is grey.

The terms “black” and “white” were first used to differentiate hook-lipped from square-lipped rhinoceroses in 1838.

General

The hook-lipped or black rhinoceros (Diceros bicornis) is a mammal of the rhinocerotidae family. Its closest relative is the square-lipped rhinoceros (Ceratotherium simum), from which it is most clearly differentiated by its finger-shaped pointed upper lip, from which it derives its name, which it uses to pluck leaves and twigs from trees.

It reaches a length of up to 3,5 metres and has a tail which can be as long as 70 cm. The height at the shoulder can be up to 1,6 metres and the weight can reach up to 1,4 tonnes (male) or 900 kg (female).

The most prominent feature of the hook-lipped rhino is its two horns, which are formed from keratin. The larger nasal horn, at the front, is on average 50 cm long, and in rare cases can be as long as 1 metre. The longest documented horn was 138 cm. The second horn is known as the frontal horn and is situated on the forehead. It is smaller, but can also grow as long as 50 cm. Bulls usually have chunky, thick horns, and cows typically have slenderer horns: as they grow older the frontal horn becomes much longer. Throughout the rhino’s life its horn will grow at a rate of 0,7 cm per month, but due to wear and tear and abrasion from undergrowth, tree trunks or stone, the effective growth during active periods is limited to 0,2 cm per month.

Distribution and Habitat

The hook-lipped rhino used to inhabit a much more extensive territory in sub-Saharan Africa than the square-lipped rhino. The hook-lipped rhinoceros now inhabits the transitional countryside between the arid savannah and the high forests of East and South Africa.
It is dependent on open water sources, where it can wallow in mud to protect itself from insects and cover up minor wounds. The mud baths also help in cooling: because rhinoceroses have no sweat glands, their large mass with its relatively limited surface area can quickly overheat. During dry spells they will also wallow in dust.
Although hook-lipped rhinos prefer dry bush country, the thorny savannah with its many woody groves and herbaceous vegetation, they can also be found in damp, misty mountain forests at altitudes of up to 3500 metres, in forested regions, on the savannah, and even in semi-deserts or sub-alpine heathlands, for example in the Namib or the Kaokoveld. The only region in which they are never seen is the hot, humid rainforest. In regions with a lot of vegetation and a rich supply of food there can be up to one rhino per square kilometre, whereas in semi-deserts like the Kunene region of Namibia there is only one rhino per 100 km².

Today, there are four recognised subspecies of hook-lipped rhinoceros which are very limited in their regional distribution. The Eastern subspecies (D. b. michaeli) now inhabits Kenya and Tanzania, whereas the South-western (D. b. bicornis) is largely confined to Namibia, although some individual animals wander into South Africa. The South-central African hook-lipped rhino (D. b. minor) is now the most common subspecies, and inhabits primarily South Africa, Zimbabwe, Swaziland and some areas of southern Tanzania. Some specimens from South Africa have been re-introduced to Zambia, Rwanda, Botswana and Malawi, after having become extinct in these regions. The Western subspecies (D. b. longipes) can only be found in Cameroon, and may, according to recent reports, now be extinct. The last sighting of this subspecies was in 1996.

Like all rhinoceroses, the hook-lipped rhino is a solitary creature. The dominant bulls in particular maintain a clear territory by moving around alone, while cows can occupy overlapping territories. This territorial loyalty also means that if the rhinos in one specific area are exterminated then there is no migration to inhabit these abandoned territories: there is no movement to occupy more hospitable habitats, even in the face of inimical environmental conditions. The hook-lipped rhino marks its territory by urinating on bushes and rocks: bulls do this much more frequently than cows. They leave dung on the borders of their territories and either drag it out to form long border markers or make mounds of droppings. The more dominant the bull, the larger the mound of droppings.

They wander very long distances within their large territories, which, depending on their availability of water and food, can cover anything from 6 to 40 km², as they cover 10 to 25 km between watering holes and feeding grounds. The paths they wander are regularly used, and tend to be 45cm wide. These paths do not strictly follow topographical features like the paths used by elephants, and can in places ascend very steep gradients.

Diet

Hook-lipped rhinoceroses feed on plants. Their diet consists of twigs, leaves and the bark of trees and bushes, but also thorns. The upper lip of the hook-lipped rhino is prehensile and is used like a finger to strip their food from plants and trees. This method leaves a typical bite pattern which is different from other herbivores in that it leaves a straight, regular mark. The various strains of acacia comprise a good third of the diet: depending on the landscape and climate, however, there are up to 100 plant types on which rhinoceroses feed. The most important are tamboti (Spirostachys africana), capers (Capparis) and hibiscus. Grasses are browsed mainly in search of herbs, and rhinoceroses only eat quantities of grass when other food is scarce.

Hook-lipped rhinoceroses usually drink water on a daily basis, and prefer standing water: during dry spells they use their feet to dig fresh water sources. In very arid regions, such as the semi-deserts, they supplement their water intake in part through the consumption of water-rich plants. They can get by for days without water, but during longer drought seasons they will die.

Senses and Movement

The hook-lipped rhinoceros has a broad range of vocalisations. It can grunt, growl and also make quiet, short pig-like squeals: most frequent, however, is a snorting snuffle, repeated three or four times, which it makes when anxious or shortly before an attack. A loud yip or whistle is used to express pain or suffering, as well as by calves to get their mothers’ attention: the same sound is also used by bulls to cows when in search of a mate. Mothers use a sighing sound to call their calves, and this sound is also used to indicate pleasurable expectation.

Hook-lipped rhinoceroses are typically active in the evenings and at night. They can be observed particularly well at dawn or in the evening when they are searching for water or food. During the day they usually rest or sleep in the shade of trees, or they wallow in mud. They also like to wallow or roll around in the dust.

Despite their enormous bulk, hook-lipped rhinos are extremely mobile and agile – they can spin around on the spot, for example. The most frequently observed gait is a swift walk or trot. If they are disturbed or alarmed they can react extremely quickly and try to locate the source of the disturbance: this can be difficult because hook-lipped rhinos, like all rhinoceroses, have very poor vision and can only see up to about 30 metres. They can only identify movements at much closer ranges, but to compensate for this they have a well-developed sense of hearing and smell. They will typically run in a threatening manner, with head and tail raised, in the direction of the disturbance. When fleeing they adopt a lively trot, and when attacking they can gallop at full speed. An aggressive or enraged hook-lipped rhinoceros can reach speeds of over 50 km/h. When charging the rhinoceros lowers its head so that the horns can be used as weapons and can change direction very quickly, as well as being able to trample obstacles such as bushes.

Reproduction

The calf stays by its mother for a long time, and it is not uncommon to encounter a cow with two calves, one baby and one adolescent.

Male and female hook-lipped rhinoceroses only pair up for a few days during the mating season. During this time it is possible to find groups of up to five animals. They do not, however, form herds. There is no fixed mating season, but most pairs mate in the rainy season (October to December). During this period the bulls are extremely aggressive towards each other and older adolescent bulls: they often fight, sometimes even to the death.

Bulls achieve sexual maturity at the age of four to six, and cows at three to four: they give birth to their first calves at the age of seven or eight, followed by others every two or three years, depending on the age and nutritional condition of the individual animal. Gestation lasts for 15 months on occasion however it can stretch to 18 months. The mother will seek out remote, usually bushy areas where she can give birth. Any older sibling calves are chased away and are occasionally taken care of by other cows. The newborn calf weighs 25 to 40kg at birth, is about half a metre tall and, three hours after the birth, can already run. Calves are suckled for two years and stay with the mother after this period, who will continue to protect her calves against all potential dangers. In its early years the calves are concealed in tall bushes, and the mother will only leave their side in order to find water. Up to eight months after the birth, the mother will allow the older calves to return. Male calves leave their mothers after six or seven years. Hook-lipped rhinoceroses have a life expectancy of up to 45 years: bulls often die younger due to aggressive fighting, and cows often live longer.

Danger to People

Hook-lipped rhinoceroses are notably more aggressive than their relatives, the square-lipped rhinoceros, but the threat posed by rhinoceroses is often wildly exaggerated. A person approaching a rhinoceros is first perceived by smell, and the rhinoceros will then usually flee. It is only if the wind is blowing in the wrong direction and the rhinoceros is surprised that it will attack. Rhinoceroses’ behaviour is largely unpredictable, and it can often happen that apparently friendly animals will suddenly attack. If the person being attacked runs away, the rhinoceros will sometimes abandon the chase. If it does decide to pursue however, it can use its horn to fling a person into the air, thereby causing serious injuries.

Text Sources: Wikipedia, WWF, Website IUCN (International Union for Conservation of Nature), www.naturlexikon.com, www.traffic.org, www.cites.org