The South-western black rhinoceros (Diceros bicornis occidentalis) is a subspecies of the Black rhinoceros. This subspecies is often mistaken for either the extinct Southern black rhinoceros (D. b. bicornis) or the southeastern subspecies (D. b. minor). However, the populations in the arid areas of northern Namibia and southwestern Angola represent a separate subspecies.
The South-western black rhinoceros, like all Black rhinoceros subspecies, has a distinct prehensile lip and is a browser. Its appearance is similar to other subspecies; the most important difference to them is a relatively broad head behind the eyes and minor features in the dentition.
South-western black rhinoceroses are found in southwestern Africa (northern Namibia and southern Angola, introduced to South Africa). They also are most adapted to arid habitats and live in arid savanna and desert climates.
Little is known about the behavior of this subspecies. In general, Black rhinos are usually solitary and sedentary creatures. They tend to live in the same area throughout their lives. They are not very territorial and often intersect other rhino territories. Males typically live alone before mating. Female rhinos, on the other hand, form small groups together with their young. The territories of these groups often overlap. In addition, females occasionally form temporary social units. Members of these groups travel and feed together. Black rhinos are most active in the morning and evening when they travel, feed, and drink. During the midday hours, they typically exhibit less activity. When feeling danger, they curl their tail and flee to escape the threat while emitting various snorting sounds. When the danger has passed, these curious animals start exploring the source of the threat. During the dry season of hot days, Black rhinos can often be seen taking mud baths, which help them to cool off. They get the required nutrients from salt licks of the area, to which they take occasional trips.
Black rhinos are herbivores (folivores, graminivores, frugivores, lignivores). They eat leafy plants, twigs, branches, shoots, thorny wood bushes, small trees, legumes, fruit, and grass.
Generally, Black rhinos are polygynous, which means that one male gets an exclusive right to mate with multiple females. Black rhinos breed year-round. However, they do have peak periods of breeding, which differ among populations, depending on geographical location. A single baby is born after 15 months of gestation. The mother keeps the calf hidden, until the latter is one week old, after which the baby comes out. During the following period, the mother and the calf communicate through special calls, which help them to find each other. The mother emits a panting sound, which is responded to by the squeal of the calf. By about one month old, the young rhino has learned to browse independently. At 4-5 months old, it begins to drink water. Black rhinos are weaned by 1.5 years old, although they become completely independent only after 4 years old. The age of reproductive maturity is 5-7 years old in females and 7-8 years old in males.
Historically, this subspecies once roamed in Angola and Namibia, but their current range has decreased. The stronghold of the species now occurs primarily in Namibia. One to four specimens have been reported from Angola and others were introduced to South Africa. Poaching due to increasing horn prices is considered the main threat to the population.
According to the IUCN Red List, the total population size of the South-western black rhinoceros in 2017 was estimated to be 2,188 individuals or 1,334 mature individuals. Currently, this subspecies is classified as Near Threatened (NT) on the IUCN Red List, but its numbers today are increasing.
