The waterbuck (Kobus ellipsiprymnus) is a large antelope found widely in sub-Saharan Africa. It is 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. 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 thirty individuals. These groups are either nursery herds with females and their offspring or bachelor herds. Males start showing territorial behaviour from the age of five years, but are most dominant from 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
thumb|left|Common waterbuck in Botswana
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, 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. 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.
- K. e. ellipsiprymnus (ellipsen waterbuck, common or ringed waterbuck) group: Found in the Webi Shebeli river valley in southeastern Ethiopia; the Juba and Webi Shebeli river valleys in Somalia; essentially east of the Rift Valley in Kenya and Tanzania; east of the Rift Valley in the middle Zambezi and Luangwa valleys in Zambia; Malawi; Mozambique; east of the Kwando River in the Caprivi Strip of Namibia; eastern and northern Botswana; Zimbabwe; and eastern and northern Transvaal in South Africa. Its distribution slightly overlaps that of the typical defassa along the Rift Valley in Kenya and Tanzania, and that of the Crawshay defassa in the Rift Valley in Zambia.
:Includes the following four subspecies:
:* K. e. ellipsiprymnus <small>Ogilby, 1833</small> (southern Africa)
:* K. e. kondensis <small>Matschie, 1911</small> (including K. e. lipuwa, K. e. kulu) (southern Tanzania)
:* K. e. pallidus <small>Matschie, 1911</small> (Webi Shebeli drainage in Ethiopia, and Juba and Webi Shebeli drainages in Somalia)
:* K. e. thikae <small>Matschie, 1910</small> (including K. e. kuru and K. e. canescens) (southern and eastern Kenya and northeastern Tanzania)
- K. e. defassa (defassa waterbuck) group: Found mostly west of the Gregory Rift, ranging from Ethiopia west to Senegal and south to Zambia.
:Includes the following subspecies:
:*Angolan defassa waterbuck (K. e. penricei) <small>W. Rothschild, 1895</small> Can be found in Southern Gabon, southern Congo (Brazzaville), Angola, southwestern Congo (Kinshasa), and marginally in Namibia along the Okavango River.
:*Crawshay defassa waterbuck or Rhodesian defassa waterbuck (K. e. crawshayi) <small>P. L. Sclater, 1894</small> (including K. e. uwendensis, K. e. frommiand K. e. münzneri) Can be found in Zambia, from the upper Zambezi River eastward to the Muchinga escarpment (which is a southern extension of the Great Rift Valley). Also in adjoining parts of Katanga Province in Congo (Kinshasa).
:*East African defassa waterbuck
::* K. e. adolfi-friderici <small>Matschie, 1906</small> (including K. e. fulvifrons, K. e. nzoiae and K. e. raineyi) (northeastern Tanzania west of the Rift Wall, and north into Kenya)
::* K. e. defassa <small>Rüppell, 1835</small> (including K. e. matschiei and K. e. hawashensis) (central and southern Ethiopia)
::* K. e. harnieri <small>Murie, 1867</small> (including K. e. avellanifrons, K. e. ugandae, K. e. dianae, K. e. ladoensis, K. e. cottoni, K. e. breviceps, K. e. albertensis and K. e. griseotinctus) (northeastern Congo [Kinshasa], Sudan, western Ethiopia, Uganda, western Kenya, Rwanda, Burundi and northwestern Tanzania)
::* K. e. tjäderi <small>Lönnberg, 1907</small> (including K. e. angusticeps and K. e. powelli) (Laikipia Plateau in Kenya)
:* Sing-sing waterbuck
::* K. e. annectens <small>Schwarz, 1913</small> (including K. e. schubotzi) (C.A.R.)
::* K. e. tschadensis <small>Schwarz, 1913</small> (Chad)
::* K. e. unctuosus <small>Laurillard, 1842</small> (including K. e. togoensis) (Cameroon west to Senegal)
<gallery mode="packed" heights="130px">
Waterbuck (Kobus ellipsiprymnus ellipsiprymnus) female head.jpg|Female K. e. ellipsiprymnus, Zimbabwe
Ugandan defassa waterbuck (Kobus ellipsiprymnus defassa) juvenile male.jpg|Juvenile male K. e. defassa<br />Queen Elizabeth National Park, Uganda
Ugandan defassa waterbuck (Kobus ellipsiprymnus defassa) juvenile female.jpg|Juvenile female K. e. defassa<br />Queen Elizabeth National Park, Uganda
Sing-sing waterbuck (Kobus ellipsiprymnus unctuosus).jpg|Male K. e. unctuosus<br />Senegal
Sing-sing waterbuck (Kobus ellipsiprymnus unctuosus) head.jpg|Male K. e. unctuosus<br />Senegal
Common waterbuck, Namibia.jpg|Male K. e. ellipsiprymnus<br />Namibia
</gallery>
Description
The waterbuck is the largest amongst the six species of Kobus. Males reach approximately at the shoulder, while females reach . The waterbuck is one of the heaviest antelopes. A newborn typically weighs , and growth in weight is faster in males than in females. The tail is long. Though apparently thick, the hair is sparse on the coat. The hair on the neck is, however, long and shaggy. When sexually excited, the skin of the waterbuck secretes a greasy substance with the odour of musk (sebum), giving it the name "greasy kob". This secretion also assists in water-proofing the body when the animal dives into water.
The common waterbuck and the defassa waterbuck are remarkably different in their physical appearances. Measurements indicate greater tail length in the latter, whereas the common waterbuck stands taller than the defassa waterbuck. However, the principal differentiation between the two types is the white ring of hair surrounding the tail on the rump, which is a hollow circle in the common waterbuck, but covered with white hair in the defassa waterbuck. As soon as young males start developing horns (at around seven to nine months of age), they are chased out of the herd by territorial bulls. These males then form bachelor herds and may roam in female home ranges. Though females are seldom aggressive, minor tension may arise in herds.
Territorial males may use several kinds of display. In one type of display, the white patch on the throat and between the eyes is clearly revealed, and other displays can demonstrate the thickness of the neck. These activities frighten trespassers. Lowering of the head and the body depict submission before the territorial male, who stands erect. Waterbuck may run into cover when alarmed, and males often attack predators. because they produce volatiles which act as repellents. Waterbuck odor volatiles are under testing and development as repellents to protect livestock. However ticks may introduce parasitic protozoa such as Theileria parva, Anaplasma marginale, and Baberia bigemina; 27 species of ixodid ticks have been found on waterbucks - a healthy waterbuck may carry over 4000 ticks in their larval or nymphal stages, the most common among them being Amblyomma cohaerens and Rhipicephalus tricuspis. Internal parasites found in waterbuck include tapeworms, liver flukes, stomach flukes, and several helminths.
Diet
thumbnail|The waterbuck is predominantly a grazer.
The waterbuck exhibits great dependence on water. It can not tolerate dehydration in hot weather, and thus inhabits areas close to sources of water. However, it has been observed that unlike the other members of its genus (such as the kob and puku), the waterbuck ranges farther into the woodlands while maintaining its proximity to water.
Though the defassa waterbuck was found to have a much greater requirement for protein than the African buffalo and the Beisa oryx, the waterbuck was found to spend much less time on browsing (eating leaves, small shoots, and fruits) in comparison to the other grazers. In the dry season, about 32% of the 24-hour day was spent in browsing, whereas no time was spent on it during the wet season. The choice of grasses varies with location rather than availability; for instance, in western Uganda, while Sporobolus pyramidalis was favoured in some places, Themeda triandra was the main choice elsewhere. The common waterbuck and the defassa waterbuck in the same area may differ in their choices; while the former preferred Heteropogon contortus and Cynodon dactylon, the latter showed less preference for these grasses. while the defassa waterbuck is near threatened (NT). The population trend for both the common and defassa waterbuck is decreasing, especially that of the latter, with large populations being eliminated from their habitats due to poaching and human settlement. Their own sedentary nature too is responsible for this to some extent. Numbers have fallen in Queen Elizabeth National Park, Murchison Falls National Park, Akagera National Park, Lake Nakuru National Park, and Comoé National Park.
Over 60 percent of the defassa waterbuck populations thrive in protected areas, most notably in Niokolo-Koba, Comoe, Mole,Gorongosa National Park, Bui, Pendjari, Manovo-Gounda St. Floris, Moukalaba-Doudou, Garamba, Virunga, Omo, Mago, Murchison Falls, Serengeti, and Katavi, Kafue and Queen Elizabeth National Parks, the national parks and hunting zones of North Province (Cameroon), Ugalla River Forest Reserve, Nazinga Game Ranch, Rukwa Valley, Awash Valley, Murule and Arly-Singou. The common waterbuck occurs in Tsavo, Tarangire, Mikumi, Kruger and Lake Nakuru National Parks, Laikipia, Kajiado, Luangwa Valley, Selous and Hluhluwe-Umfolozi game reserves and private lands in South Africa.