Black Rhinoceros

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Lore & Background

The species was first named Rhinoceros bicornis by Carl Linnaeus in the 10th edition of his Systema naturae in 1758. The name means 'double-horned rhinoceros'. There is some confusion about what exactly Linnaeus conceived under this name as this species was probably based upon the skull of a single-horned Indian rhinoceros (Rhinoceros unicornis), with a second horn artificially added by the collector. Such a skull is known to have existed and Linnaeus even mentioned India as origin of this species. However he also referred to reports from early travellers about a double-horned rhino in Africa and when it emerged that there is only one, single-horned species of rhino in India, Rhinoceros bicornis was used to refer to the African rhinos (the white rhino only became recognised in 1812). In 1911 this was formally fixed and the Cape of Good Hope officially declared the type locality of the species.

In Their Own Story

The modern white rhinoceros was initially thought to be descended from Ceratotherium praecox, a species from approximately seven million years ago with remains found at Langebaanweg near Cape Town. However, a 2005 review of African fossil rhinos by Denis Geraads proposed that while the Langebaanweg species belongs to the genus Ceratotherium, it is not C. praecox. Geraads argued that the type specimen of C. praecox exhibits closer affinities with the black rhinoceros (Diceros bicornis) and should therefore be classified as Diceros praecox. It had been suggested by Turner (2004) that the modern white rhino's elongated skull—compared to that attributed to C. praecox—evolved to facilitate grazing on shorter grasses as Africa experienced long-term drying conditions. If C. praecox is indeed Diceros praecox, its shorter skull could instead indicate a browse diet. Further complicating this interpretation, carbon isotope analysis of teeth from fossils assigned to Ceratotherium at Makapansgat, South Africa, indicated that these animals incorporated over 30% browse into their diet, unlike the exclusively grass-eating modern Ceratotherium simum. Based on these considerations, Geraads (2005) proposed an alternative lineage for the white rhino: Ceratotherium neumayri → Ceratotherium mauritanicum → C. simum, with the Langebaanweg rhinos considered an as-yet-unnamed Ceratotherium species, and black rhinos descending from C. neumayri via Diceros praecox. An alternative evolutionary scenario was proposed by Hernesniemi et al. (2011). This model posits Ceratotherium efficax (now considered synonymous with C. mauritanicum) from the Late Pliocene of Ethiopia and Early Pleistocene of Tanzania as the earliest African Ceratotherium. This species is then proposed to have diversified into C. mauritanicum in northern Africa, C. germanoafricanum in East Africa (both now extinct), and the extant C. simum. C. germanoafricanum is noted as being very similar to C. simum and has often been regarded as a fossil and ancestral subspecies of the latter. The 2011 study also casts doubt on the Miocene species Ceratotherium neumayri from southern Europe being ancestral to African species. It is likely that the common ancestor of both black and white rhinos was a mixed feeder, with the two lineages subsequently specializing in browsing and grazing, respectively. The oldest definitive fossil record of Ceratotherium simum dates to the mid-Early Pleistocene, around 1.8 million years ago, at Olduvai Gorge in Tanzania.

Reader's Guide

An adult black rhinoceros stands 1.32–1.8 m (4.3–5.9 ft) high at the shoulder and is 2.8–3.75 m (9.2–12.3 ft) in length. An adult typically weighs from 800 to 1,400 kg (1,800 to 3,100 lb), however unusually large male specimens have been reported at up to 2.9 t (3.2 short tons). The cows are smaller than the bulls. Two horns on the skull are made of keratin with the larger front horn typically 50 cm (1.6 ft) long, exceptionally up to 135.9 cm (4.5 ft). The longest known black rhinoceros horn measured nearly 1.5 m (4.9 ft) in length. Sometimes a third, smaller horn may develop. These horns are used for defense, intimidation, and digging up roots and breaking branches during feeding. The black rhino is smaller than the white rhino and close in size to the Javan rhino of Indonesia. It has a pointed and prehensile upper lip, which it uses to grasp leaves and twigs when feeding, whereas the white rhinoceros has square lips used for eating grass. The black rhinoceros can also be distinguished from the white rhinoceros by its size, smaller skull, and ears; and by the position of the head, which is held higher than the white rhinoceros, since the black rhinoceros is a browser and not a grazer. Their thick-layered skin helps to protect black rhinos from thorns and sharp grasses. Their skin harbors external parasites, such as mites and ticks, which may be eaten by oxpeckers and egrets.

Did You Know?

• The word 'white' in the name 'white rhinoceros' is often said to be a misinterpretation of the Afrikaans word 'wyd' meaning wide, referring to its square upper lip, as opposed to the pointed or hooked lip of the black rh
• The black rhinoceros is the only extant species of the genus Diceros.
• Three subspecies of black rhinoceros have been declared extinct: the southern black rhinoceros (D. b. bicornis), the north-eastern black rhinoceros (D. b. brucii), and the western black rhinoceros (D. b. longipes).
• The western black rhinoceros was declared extinct by the IUCN in 2011.