The waterbuck (Kobus ellipsiprymnus) is a large antelope found widely in sub-Saharan Africa. It is placed in the genus Kobus of the family Bovidae. It was first described by Irish naturalist William Ogilby in 1833. Its 13 subspecies are grouped under two varieties: the common or ellipsiprymnus waterbuck and the defassa waterbuck. The head-and-body length is typically between and the typical height is between . In this sexually dimorphic antelope, males are taller and heavier than females. Males reach roughly at the shoulder, while females reach . Males typically weigh and females . Their coat colour varies from brown to grey. The long, spiral horns, present only on males, curve backward, then forward, and are long.
Waterbucks are rather sedentary in nature. As gregarious animals, they may form herds consisting of six to 30 individuals. These groups are either nursery herds with females and their offspring or bachelor herds. Males start showing territorial behaviour from the age of 5 years, but are most dominant from the six to nine. The waterbuck cannot tolerate dehydration in hot weather, and thus inhabits areas close to sources of water. Predominantly a grazer, the waterbuck is mostly found on grassland. In equatorial regions, breeding takes place throughout the year, but births are at their peak in the rainy season. The gestational period lasts 7–8 months, followed by the birth of a single calf.
Waterbucks inhabit scrub and savanna areas along rivers, lakes, and valleys. Due to their requirement for grasslands and water, waterbucks have a sparse ecotone distribution. The IUCN lists the waterbuck as being of least concern. More specifically, the common waterbuck is listed as of least concern. while the defassa waterbuck is near threatened. The population trend for both is downwards, especially that of the defassa, with large populations being eliminated from certain habitats because of poaching and human disturbance.
Taxonomy and etymology
The scientific name of the waterbuck is Kobus ellipsiprymnus. The waterbuck is one of the six species of the genus Kobus in the family Bovidae. It was first described by Irish naturalist William Ogilby in 1833. The generic name Kobus is a Neo-Latin word, originating from an African name, koba. The specific name ellipsiprymnus refers to the white, elliptical ring on the rump, from the Greek (ellipse) and (, hind part). The animal acquired the vernacular name "waterbuck" due to its heavy dependence on water as compared to other antelopes and its ability to enter into water for defence.
The type specimen of the waterbuck was collected by South African hunter-explorer Andrew Steedman in 1832. This specimen was named Antilope ellipsiprymnus by Ogilby in 1833. This species was transferred to the genus Kobus in 1840, becoming K. ellipsiprymnus. It is usually known as the common waterbuck. In 1835, German naturalist Eduard Rüppell collected another specimen, which differed from Steedman's specimen in having a prominent white ring on its rump. Considering it a separate species, Rüppell gave it the Amharic name "defassa" waterbuck and scientific name Antilope defassa. Modern taxonomists, however, consider the common waterbuck and the defassa waterbuck a single species, K. ellipsiprymnus, given the large number of instances of hybridisation between the two. Interbreeding between the two takes place in the Nairobi National Park owing to extensive overlapping of habitats. Though both groups occur in Zambia as well, their ranges are separated by relief features or by the Muchinga escarpment.
Evolution
Not many fossils of the waterbuck have been found. Fossils were scarce in the Cradle of Humankind, occurring only in a few pockets of the Swartkrans. On the basis of Valerius Geist's theories about the relation of social evolution and dispersal in ungulates during the Pleistocene, the ancestral home of the waterbuck is considered to be the eastern coast of Africa, with the Horn of Africa to the north and the East African Rift Valley to the west.
Subspecies
On the basis of coat colour, 37 subspecies of the waterbucks had been initially recognised. They were classified into two groups: the ellipsiprymnus waterbuck group and the defassa waterbuck group. Owing to the large number of variations in the coat colour in the defassa waterbuck group, as many as 29 subspecies were included in it; the ellipsiprymnus waterbuck group consisted of eight subspecies. In 1971, however, the number of subspecies was reduced to 13 (4 for the ellipsenprymnus waterbuck group and 9 for the defassa waterbuck group). The subspecies are listed below, along with notes about the former subspecies which were recombined into a single subspecies: