The Black Rhino is no more black, than the White Rhino is white. Alternative names such as the 'browse rhinoceros' and 'grass rhinoceros', or the 'hook-lipped rhinoceros' and 'square-lipped rhinoceros' have been used for black and white respectively. Described by Linnaeus in 1758 as the two-horned rhinoceros, (the only other known species being the Indian one horned), the Black Rhinoceros seems to have absorbed its misleading common name by contrast with the misnamed White Rhinoceros, when that species was discovered.
To this day there remains some uncertainty about whether the two species are different enough to be separated into two distinct genera. There is also disagreement over the number of subspecies of black rhino.
The black rhinoceros is separated from the white by its ecological requirements. As a browser, it is able to colonise areas of rugged hilly terrain where grass is scarce, at an altitude of up to 2 700 m (9 000 ft). It will avoid open grassland frequented by the white rhinoceros, and very dense vegetation, preferring the edges of wooded areas. Ideal black rhino habitat is adequate shrubs and young trees up to about 4 m high, including well developed woodland or thicket in which to shelter during the heat of the day. Originally its range covered the southern third of Africa, northwards between the east side of the Rift Valley and the east coast, as well as a band of open woodlands stretching from the Horn of Africa to the west coast, south of the Sahara.
As already mentioned, one of the major differences between the black and white rhinoceroses is the prehensile upper lip of the black rhinoceros: this is used to grasp twigs of the woody plants that they feed off. They also have a shorter head, longer neck, and smaller, rounded ears. The shape of the back is also slightly different, and the black rhino carries its head higher off the ground.
They manoeuvre food into their mouths with the aid of their prehensile upper lip, bite shoots off with their premolar teeth, and grind food with the massive molar teeth. Black rhino feed on an unusually wide variety of species, and they are flexible feeders, as they vary their diet according to availability.
Rhino appear heavy footed when walking, but are very agile when provoked, and can achieve impressive speeds. They can also spin around within their own length. Their sight is poor, but their senses of smell and hearing are acute.
The black rhino feeds on leaves and twigs from a wide variety of shrubs in the acacia woodland community. It will pick up fallen fruits from the ground as well as taking those it can reach from trees. In the Ngorongoro Crater, in Tanzania, black rhino have been known to pick up and eat wildebeest dung when browse was in short supply. Such behaviour might have satisfied the need for minerals and trace elements as well as the use of the sustenance remaining in the droppings.
The black rhino will range freely in the rainy season; during the dry season the rhino will stay within 5 km (3 miles) of permanent water. They require one drink a day and in especially arid conditions, they can dig for water, up to 50 cm (20 in) deep, using their forelegs to excavate the soil.
Like the elephant and the white rhino, black rhinos often take on the colour of the soil on which they live, as they wallow in mud and cover themselves with dust.
Unlike white rhinos, black rhinos tend to be solitary: the only stable bond is that formed between mother and calf, but even that is fairly temporary, lasting only until her next calf is born. Other associations, such as male-female associations or between a number of individuals of the same age, are very transitory. They are not strictly territorial (ie: they do not actively defend territories), but they do tend to remain with a specific home range, which may overlap with the home ranges of other members of the population. The size of their home ranges differ according to sex, age and the type of habitat, with immature animals usually occupying larger areas than adults. The only time they gather in groups is temporarily to wallow: five is the largest party usually seen together, though groups of as many as 13 have been recorded.
Although aggression between bulls is normal, they tend to actively avoid contact: sometimes serious fighting does occur, however, particularly over females in oestrus. Snorting and pawing are the prelude to a series of short charges, which will usually stop about 6 m (20 ft) short of impact. However, during a time of ecological stress in East Tsavo, before the drought in 1960/1, all the rhino were found to be wounded and some were killed in fights. This was evidently abnormal behavior produced by conditions of extreme hardship.
During the day they retire to the shade of thickets to sleep, either standing or lying with their legs curled under them. Black rhinos sometimes sleep lying flat on their sides; a position never adopted by the white rhino.
The black rhino seems to take a particular delight in crashing through cover; unlike the other animals of the bush in that it has no regular predators as an adult, it has no need to move stealthily. Like the white rhino the black rhino sprays urine and dung; it also leaves a scented trail consisting of flakes of mud and pieces of dead skin by rubbing against trees: this helps to communicate its presence, and possibly its identity, to the next rhinoceros who comes along.
Feeding in the morning and evening and sleeping in the heat of the day, the species has become largely nocturnal in most parts of its range. This is most likely the result of natural selection, which has eliminated the more diurnal individuals which were most likely to be shot. Wallowing plays an important part as it helps to lower body temperature, offers protection against biting insects when the mud dries, and helps with 'rhino sores', which are areas of cracked and often inflamed skin which occur most commonly in the hollow behind the elbows of the front legs.
Apart from puffing and snorting, the black rhino has few vocalisations whose function may be guessed at. The sounds made by black rhino are not as varied as those made by the white. Mother and calf communicate with a variety of squeals and when in a panic, the calf will produce a loud and penetrating squeal which will bring the males within a kilometer to investigate. Fighting adults grunt and scream at each other and upon approaching a waterhole already occupied by wallowers, they puff and gasp as a warning of their presence, in order to avoid conflict.
The most frequent signals used by the black rhinoceros are based on scent. Urine spraying is very common and bushes, clumps of grass, tree stumps and conspicuous stones are all marked regularly. Females spray when they are in oestrus but their spraying is undirected.
Use of dung as a means of signaling, is similar in both species of rhinoceros. Black rhino use communal dung heaps beside their regular tracks through the bush and, in places frequented by black and white rhino, the heaps are used by both species. The male will defaecate, stand in the faeces with his hind feet and then scrape them on his back legs so as to leave an imprint of his identity for a considerable distance on his trail. This serves very much the same purpose as urine spraying, for the benefit of later passers by.
Scenting the area in both ways provides passers by with a constantly updated record of the population present as well as the sexual condition of the females.
Black rhinos breed at any time of year. When a cow is in oestrus the bull approaches carefully, and they then spar with their front horns or nudge each other with the sides of their heads. Although most females respond violently to the male's first approaches, and she may attack him occassionally, no serious or vicious fighting takes place during courtship. In a recognisable group, it was found that one cow was courted, if not mounted, by three different bulls in eleven days. Mating lasts for 20 to 35 minutes at a time, several times a day. The first successful captive birth recorded dates back to 1941, in Brookfield Zoo, Chicago.
Gestation is between
446 and 548 days: the average seems to be 460 days or about 15 months.
Females breed only every two to five years because of the time required
to rear the calf. The newborn calf weighs between
Unlike the white rhinoceros, black rhino calves walk behing their mothers. As they grow older they have to lie down to suckle: they usually suckle for about a year. The mother and calf communicate with each other via vocalizations, and the mother will defend her calf vigourously, even from lions. Calves are rejected by their mothers when they are between 2 and 4 years of age, either when the mother is pregnant, or immediately after the birth of her new calf.
Black rhino are usually fully grown at about seven years of age and they reach sexual maturity at about six. Their life expectancy is not accurately known, but black rhino are said to live for up to 40 years; this figure has been estimated by some to be closer to 50 or 60 years .
"Rhino sores" are skin lesions caused by a filaria parasite - in visiting communal dung heaps along their trails, the rhinoceros pass the infection around the population: almost every individual has been infected by a small filariform worm called Stephanofilaria dinniki. The five other species of this genus of worm are all parasites of cattle: the intermediate host is a biting fly which breeds in dung. The sores are inflamed, often septic, patches of skin as much as 20 cm (8 in) in diameter.
Ticks, (over 20 species have been identified feeding on black rhino, some of them specific to rhino, while others are parasites on elephant too), provide a regular food supply for oxpeckers, a bird related to starlings. The birds not only remove the parasites; they also cause the rhinoceros some discomfort by sticking their sharp beaks into ears and nostrils and pecking at any open wounds or sores. Internally, the black rhino suffers bot-flies, whose larvae lives in the stomach, as well as several species of tapeworm.
With regard to predators, the black rhino has few. Lions have been known to cause fatalities amongst adults and they will take a calf if they are able to separate it from its mother, but the mothers defensive behaviour ensures that this event is infrequent. A far more serious threat is the spotted hyaena, which preys on rhino calves. Although lions and spotted hyaenas do attack fully grown rhinoceroses, the rhinos usually emerge the victor. There are several accounts of elephant killing rhino and although bull elephant will tolerate them, the female elephant simply cannot stand their presence: rhinos will normally give way to elephants, although aggressive encounters between elephant, rhinos and buffaloes have been witnessed at waterholes during drought conditions. Adult rhino exhibit no fear of the larger predators, and usually ignore other mammals.
The chief factor which makes the black rhino more dangerous than the white, is its habitat. It is more likely to be taken by surprise in thick bush than the white rhino in open grassland, and is able to charge at up to 50 km (30 miles) per hour, and attack and obliterate any identified object with its horn. People on foot in the bush are extremely vulnerable and many cars have been severely damaged by startled animals. In addition to habitat differences, the black rhino is known to be more wary, more temperamental, and more aggressive than the white rhino.
The greatest enemy of the black rhinoceros is mankind. Because its favoured habitat is fertile and well watered, it has come into conflict with humans long before the arrival of Europeans in Africa. Its uncertain behaviour made it an alarming neighbour to cattle-herders and its feeding habits did not coincide well with crop farmers. The demand for land for settlement is increasing and with it the call for control or the elimination of all rhinoceroses. The black rhino is endangered, but increased protection and anti-poaching measured have saved it from extinction. A total of 185 black rhinoceroses have been translocated from KwaZulu-Natal reserves.