Diceros bicornis (Linnaeus, 1758)

Don E. Wilson & Russell A. Mittermeier, 2011, Rhinocerotidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 144-181 : 177-178

2.

Black Rhinoceros

Diceros bicornis

French: Rhinocéros noir / German: Spitzmaulnashorn / Spanish: Rinoceronte negro

Other common names: Hook-lipped Rhinoceros

Taxonomy. Rhinoceros bicornis Linnaeus, 1758 ,

South Africa.

Four subspecies recognized.

Subspecies and Distribution.

D.b.bicornisLinnaeus,1758—Namibia,W&SESouthAfrica.

D.b.longipesZukowsky,1949—historicallyinNigeria,Cameroon,Chad,Sudan,andCentralAfricanRepublic(couldbeextinct).

D. b. michaeli Zukowsky, 1965 — Kenya, Rwanda (could be extinct by now), and N Tanzania; historically also in Sudan, Ethiopia, and Uganda.

D. b. minor Drummond, 1876 — C Tanzania, Zambia, Zimbabwe, Malawi, Botswana, and Mozambique (possibly extinct), to N and CE South Africa. Especially vague range map for conservation reasons.

Descriptive notes. Head-body 300-380 cm, tail 25-35 cm, shoulder height 140-170 cm; weight 800-1300 kg. The Black Rhino is the third largest among living rhinoceros species. Adult males and females are similar in size; there is little dimorphism. Black Rhinos have two horns; the anterior horn can reach 130 cm in some individuals. The posterior horn is usually much smaller, 2-55 cm, but in some individuals, even the smaller posterior horn is longer than the average horn of any of the Asian species. The base of the Black Rhino’s horn is rounded, unlike the White Rhinoceros’s (Ceratotheritum stmum), which is squarer in shape. Like the Greater One-horned ( Rhinoceros unicornis ), Javan ( R. sondaicus ), and Sumatran ( Dicerorhinus sumatrensis ) Rhinoceroses, the Black Rhino has a prehensile upper lip that aids in grasping foliage from shrubs. It has a more hollow back in silhouette than the White Rhino, and its ears are more rounded and trumpet-shaped, with the tip in the center of the ear pointing upwards (the White Rhino’s ear tip points sideways).

Habitat. Black Rhinos can be found in many habitats in Africa. They occur primarily in mesic wooded savanna, but can be found in wetter montane forest in Kenya, wetter dune forest in eastern South Africa, and semi-desert in Kunene, Namibia. However, they are not found in rainforests, perhaps in part because of their inability to thermoregulate in hot, humid conditions and the paucity of food in the subcanopy of such forests. Historically, the species had a wider habitat range than the White Rhino, occurring throughout much of sub-Saharan Africa. The species seems almost preadapted to disperse or to recolonize lost range, because it can feed in a variety of habitats and can survive up to five days without drinking. Rhino densities and carrying capacity have been shown to vary widely overits range. Carrying capacity is particularly dependent on the amount of suitable food. Densities can vary widely, from 0-01 ind/km? in poorly vegetated desert plains to peak levels of around 1-5 ind/km?. The carrying capacity in most areas is in the range of 0-1-0-4 ind/km?®. Savannas are dynamic, and changes in woody vegetation result in fluctuations in the carrying capacity of an area. Competition from other browsers can affect the Black Rhino’s use of habitat. The three Asian species are good swimmers and are never found far from water, but Black Rhinos are poor swimmers. They and White Rhinos can drownif they lose their footing.

Food and Feeding. This large herbivore eats more than 200 species of browse plants in its wide range of habitats. However, rhinos are highly selective, and specific size classes of a limited number of species make up the bulk of their diet. Of particular interest, they favor plants from genera such as Euphorbia , which are highly toxic to other herbivorous mammals. One ofthe favorite browse plants, a dietary staple in north-western Namibia, is the endemic E. damariana, a plant that burns the skin of humans. The rhino detoxifies the noxious compoundsin its large cecum. Another Euphorbiaceae, Spurostachys africana, is the species contributing the most to the Black Rhino’s woody diet in Hluhluwe-Umfolozi Game Reserve, South Africa. Black Rhinos also particularly like small Acacia spp., especially plants less than 1 m in height. As these plants grow taller, habitat suitability declines. Black Rhinos also ingest fruit, and like the three Asian species, can be important seed dispersers in some parts of their range for certain fleshy-fruited plants. They also eat some herbaceous plants, especially legumes.

Breeding. This species is essentially solitary. Males and females aggregate solely for breeding. Courtship,as in other rhino species,is quite violent. Mating can occur in any time of the year, and as in the Greater One-horned Rhino, shows no seasonal pattern. One exception might be for the south-western subspecies, where births may aggregate in the end of the rainy season when forage is most abundant. Reproductive data are similar to other species: gestation around 15-16 months, intercalf interval of 2-4 years (often depending on range conditions and population density relative to an area’s carrying capacity), and age atfirst reproduction around seven years. Conception rates improve with increases in rainfall. As in other species of rhinos, weaning takes place at around two years of age. Calves generally leave their mothers at around 3-5 years of age, but a female calf may remain with its mother after a new calf is born. Predation by Spotted Hyenas (Crocuta crocuta) and Lions (Panthera leo) on young calves occasionally occurs, and perhaps the oldersister’s remaining with the mother provides added defence against predators, although this has yetto be fully investigated.

Activity patterns. Black Rhinos feed in the morning and evening hours. During the hottest part of the day, they remain largely inactive, sleeping, resting, and, where available, wallowing in mud. Most observations of rhinos drinking at waterholes in daylight have been past midday and into the late afternoon. Peak times for drinking are at night.

Movements, Home range and Social organization. Black Rhinos are essentially solitary other than when breeding or occasionally when foraging. Studies of social organization reveal a range of behaviors relating to their use of space, from near-territorial to overlapping home ranges. As with other large herbivores, defending a widely distributed food source, such as browse,is difficult and may happen more where food resources are limited and widely spaced, and where females congregate. Differences in forage availability greatly influence home range size. Home ranges can be as large as 140 km? or much smaller, on the order of home ranges of the Greater One-horned Rhinos (2-3 km?) where good quality browse and water are especially plentiful. Home ranges are 1 km? in Addo Elephant National Park, South Africa, and 50 km? in the arid parts of Namibia.

Status and Conservation. CITES Appendix I. Classified as Critically Endangered on The IUCN Red Last, but the West African subspecies, longipes, was considered possibly extinct, minor and michael: are classified as Criticially Endangered, and bicornis is classified as Vulnerable. The subspecies minor is the most numerous of the three remaining subspecies, bicornis is almost as numerous as minor and has its stronghold in the arid lands of Namibia, and populations have been reestablished in western and southeastern South Africa. Kenya remains the stronghold of the East African subspecies michaeli, with increasing numbers in northern Tanzania and an out-of-range population in South Africa (which is being used to restock its former range). Numbers of these last three subspecies have been increasing.The Black Rhino has seen the most drastic decline of all rhino species because of relentless poaching and habitat loss. Before 1960, it was the most numerous of the five extant species and had the largest range. There may once have been as many as 850,000 Black Rhinos distributed across much of sub-Saharan and western Africa. Populations plummeted from about 100,000 in 1960 to around 65,000 in 1970 and to just under 15,000 only a decade later. The nadir forthis species occurred in the 1980s, when the total population may have dipped below 2400. Today, the speciesis largely restricted to parks and reserves where the rhinos can be better protected. Most of these areas are fenced. Some are small (less than 50,000 ha); others are very large (such as Greater Kruger National Park). Most of the unfenced areas where the rhinos occur are Intensive Protection Zones (IPZs), which were created to give them a higher level of protection. As with the White Rhino, most Black Rhino populations today have been created by translocating surplus animals from long-established populations and biologically managing populations for growth. Four range states, South Africa, Namibia, Zimbabwe, and Kenya conserve the bulk of Africa’s Black (95-7%) and White (98-:8%) Rhinos. Small but increasing numbers of Black Rhinos are found in Tanzania and Swaziland. Black Rhinos have also been reintroduced into Botswana and Malawi. By the start of 2008 the total population had reached 4200 individuals, and the current number may now be in the region of 4800. The decline in Black Rhino populations is largely a result of poaching to obtain the horn, long prized for dagger handles in Yemen and in other nations of the Persian Gulf region. Islamic leaders have declared that rhino horn should not be used for dagger handles, and this has helped to curb this dangerous consumption. The use of rhino horn in traditional Chinese medicine (predominantly as a fever reducer and not as an aphrodisiac) has also caused much poaching. Reports of new medical uses for rhino horn in Vietnam and increasing prices being paid for horn are a major cause for concern. Poaching of rhinos in Africa has been increasing in recent years and the growing involvement of organized crime syndicates is of great concern. In areas with both species, the Black Rhino tends to suffer lower levels of poaching, as the White Rhino spends more time in more open areas and is easier to find. As densities have built up in many populations in the major range states, surplus animals have become available for translocation. Namibia has successfully pioneered communal and private conservancies that look after rhinos on behalf ofthe state. Private custodians have also played an important role in Zimbabwe and Kenya. In South Africa, the private sector is playing an increasing role, although in that country many of the Black Rhinos are privately owned and can be bought and sold. In South Africa and Namibia, very limited sport hunting of a few specific individual surplus male Black Rhinos is enhancing the likelihood of meeting genetic and demographic goals (e.g. by removing a behaviorally dominant bull thatis infertile) and at the same time generating much needed revenue to help fund conservation efforts. Translocation offers the possibility of establishing populationsin state-run, private, and community-owned reserves. Increased protected areas available for Black Rhinos hold out hope for Black Rhino conservation. Countries, local communities, and individuals can receive substantial income from ecotourism, so the incentive exists to encourage people to protect, monitor, and manage these rare large mammals. In eastern South Africa, the Black Rhino Range Expansion Project, with partnerships between the state sector and private or community landowners, allows Black Rhino from source populations in state reserves to be used to found populations on land not necessarily traditionally involved in conservation. This strategy has created five new and viable Black Rhino populations on blocks of land capable of holding at least 50 rhinos, and has increased the land available to Black Rhinos in KwaZulu-Natal by 34%. The conceptis being adopted elsewhere in southern Africa. Rhinos can act as a flagship species because they require large areas, and when they are successfully protected, can be a catalyst for biodiversity conservation.

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Figures

1. White Rhinoceros (Ceratotherium simum), 2. Black Rhinoceros (Diceros bicornis), 3. Greater One-horned Rhinoceros (Rhinoceros unicornis), 4. Javan Rhinoceros (Rhinoceros sondaicus), 5. Sumatran Rhinoceros (Dicerorhinus sumatrensis)

Subspecies and Distribution. D.b.bicornisLinnaeus,1758—Namibia,W&SESouthAfrica. D.b.longipesZukowsky,1949—historicallyinNigeria,Cameroon,Chad,Sudan,andCentralAfricanRepublic(couldbeextinct). D. b. michaeli Zukowsky, 1965 — Kenya , Rwanda (could be extinct by now), and N Tanzania ; historically also in Sudan , Ethiopia , and Uganda . On following pages 3 Greater One-horned Rhmoceros ( Rhinoceros unıcomıs) 4 Javan Rhrnooeros (Flhmoceros sondarcusl 5 Sumatran Rhmoceros IDıceromınus sumatrenslsl D. b. minor Drummond, 1876 — C Tanzania , Zambia , Zimbabwe , Malawi , Botswana , and Mozambique (possibly extinct), to N and CE South Africa . Especially vague range map for conservation reasons.