Background :: Black Rhino

Diceros Bicornis Bicornis - the Black Rhino of the Kunene region

Genus: DICEROS (Prehensile lipped rhino; black rhino)
Species: Diceros bicornis
Subspecies: Diceros bicornis bicornis

The first rhinoceros that was scientifically described by Carl Linnaeus in 1758 was the black rhinoceros, originating in the Cape. The desert rhino are regarded as part of the nominal form and thus retain the original name Diceros bicornis bicornis. This opinion is based on measurements of rhino skulls from the Kaokoveld, and the historical record of black rhino distribution. Rhino were distributed from the Cape up the escarpment zone to the Kunene. The original Cape rhino are known today only from records in literature, and from seven skulls held in various museums. The skulls are considerably larger than those of any other rhino, and the closest in size to them are the black rhino of the Kaokoveld. The desert rhino also appear to be slightly larger than, for example, those from Zululand. They have longer horns and the posterior horn is usually larger relative to the anterior horn, than it is in the rhino of Zululand or the Zambezi valley.

Namibia’s desert-adapted black rhino (Diceros bicornis bicornis) surviving in the Kunene Region (former Damaraland and Kaokoland) in the arid north-west of the country are the only rhino worldwide that have survived on communal land with no formal conservation status. They are also the largest free-ranging black rhino population anywhere in the world.

Due to the scarcity of resources in the arid Namib, these rhino are known to cover some 2,500 km² in search of food. They have very large home ranges, measuring 500 - 600 km². The dryness of the climate gives the skin of the rhino a smooth, glossy appearance. The footprints (spoor) are larger than other black rhino subspecies. These rhino have no lesions or visible parasites. Their mountaineering abilities are remarkable. They can climb high onto mountain ledges out of the heat of the valley, to catch the cool wind from the Atlantic or forage for succulents.

That these rhino can survive in areas with less than 100 mm mean annual rainfall is amazing. Normally rhino drink every night, yet in the Kunene, because they must move great distances in search of food, they may drink only every third or even fourth night. Yet Kunene’s black rhinos remain heavily dependant upon undisturbed access to permanent water sources. In the water-limited Kunene, this sometimes causes conflict between human and livestock water use since black rhino in the Kunene, like other black rhino populations across Africa, tend to avoid areas utilized by humans and their livestock.

The rhino feed on only an estimated 74 plant species of the 103 species that are available during the driest time of the year. Among the plants taken are several which contain very high levels of soluble tannins, which are normally regarded as a chemical defence mechanism by which plants avoid being eaten.

Euphorbia is one of the most highly favoured plant species consumed. The rhino feed extensively on Euphorbia virosa bushes, sometimes staying to feed on one large bush until it is totally eaten up. This can take days, with the rhino sometimes leaving the bush only to drink and then returning to the same bush to feed.

Euporbia damarana is often browsed by rhino, kudu, springbok and gemsbok for hours at a time. This plant is highly poisonous to humans and can cause blindness if the milk enters the eye. Extracts of Euphorbia species’ chemical contents are used in the medical profession to combat certain types of cancer.

The rhino show a distinct preference for certain other plants as well, such as Sterculia africana, which is often browsed down to a stump. Fortunately such plants recover quickly after rain and put out new shoots. The rhino also feed on Welwitschia mirabilis plants but sometimes just chew on the leaves and drop them.

An interesting observation over the accumulated 20 years of study is that the calf spends  to two to two-and-a-half years with the cow in a specific part of her home range before the calf is weaned . The calf becomes well orientated, learning the whereabouts of water, mountain succulents and other food sources. The cow weans the calf and then moves out of the area to another part of her home range to give birth to her new calf. The weaned calf may join up for a while later on but soon leaves and returns to the range which is familiar to it. This is where it stays unless something, such as the first rains, urges it to move right away from the area into new territory (usually in the direction of the rain).

Adult rhino kick their dung and spray urinate as a communication system while moving about their ranges, spreading their scent around and making dung middens along pathways near water holes.

The desert rhino have sometimes been observed in groups of six, but most times they are solitary. There is seldom fighting between bulls, but occasionally very aggressive bulls have been known to kill another bull. Cows have been observed to chase other cows with calves in overlapping home ranges.

Namibia’s desert black rhino add a dimension of awe and wonder to an environment that is singularly beautiful and that, if conserved and utilized sensibly, can add immeasurably to the richness of Namibia, and the attractions of its flourishing tourist industry. The desert-adapted black rhino population is currently one of very few populations in Africa that is on the increase. But this will only last while the current vigilance and anti-poaching effort is maintained.

Remarks:
This site is based on Hall-Martin, Walker, Bothma: Kaokoveld - The last wilderness, pages 29 - 30; Southern Book Publishers, Johannesburg 1988