WATERBUCK

Facts

The Waterbuck is the largest amongst the six species of Kobus. It is a sexually dimorphic antelope, with the males nearly 7% taller than females and around 8% longer. The head-and-body length is typically 177–235 cm (70–93 in) and the typical height is 120–136 cm (47–54 in). Males reach approximately 127 cm (50 in) at the shoulder, while females reach 119 cm (47 in). The Waterbuck is one of the heaviest antelopes. A newborn typically weighs 13.6 kg (30 lb), and growth in weight is faster in males than in females. Males typically weigh 198–262 kg (437–578 lb) and females 161–214 kg (355–472 lb). The tail is 22–45 cm (8.7–17.7 in) long.

The Waterbuck has a robust build. The shaggy coat is reddish brown to grey, and becomes progressively darker with age. Males are darker than females. 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, giving it the name “Greasy Kob”. The odour of this is so unpleasant that it repels predators. This secretion also assists in water-proofing the body when the animal dives into water. The facial features include a white muzzle and light eyebrows and lighter insides of the ears. A cream-coloured patch (called “bib”) is on the throat. Waterbuck are characterised by a long neck and short, strong, black legs. Females have two nipples. Preorbital glands, foot glands, and inguinal glands are absent.

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.

The long, spiral horns curve backward, then forward. Found only on males, the horns range from 55 to 99 cm (22 to 39 in) in length. To some extent, the length of the horns is related to the bull’s age. A rudimentary horn in the form of a bone lump may be found on the skulls of females.

Waterbuck are rather sedentary in nature, though some migration may occur with the onset of monsoon. A gregarious animal, the Waterbuck may form herds consisting of six to 30 individuals. The various groups are the nursery herds, bachelor herds and territorial males. Herd size increases in summer, whereas groups fragment in the winter months, probably under the influence of food availability. 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. Females have home ranges stretching over 200–600 hectares (0.77–2.32 sq mi; 490–1,480 acres). A few females may form spinster herds. Though females are seldom aggressive, minor tension may arise in herds.

Males start showing territorial behaviour from the age of 5 years, but are most dominant from 6 to 9 years. Territorial males hold territories 4–146 hectares (0.015–0.564 sq mi; 9.9–360.8 acres) in size. Males are inclined to remain settled in their territories, though over time they may leave inferior territories for more spacious ones. Marking of territories includes no elaborate rituals; dung and urine are occasionally dropped. After the age of ten years, males lose their territorial nature and are replaced by a younger bull, following which they recede to a small and unprotected area. There is another social group, that of the satellite males, which are mature bulls as yet without their own territories, who exploit resources, particularly mating opportunities, even in the presence of the dominant bull. The territorial male may allow a few satellite males into his territory, and they may contribute to its defence. However, gradually they may deprive the actual owner of his territory and seize the area for themselves. In a study in the Lake Nakuru National Park, only 7 percent of the adult males held territories, and only half of the territorial males tolerated one or more satellite males.

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. Fights, which may last up to thirty minutes, involve threat displays typical of bovids accompanied by snorting. Fights may even become so violent that one of the opponents meets its death due to severe abdominal or thoracic wounds. A silent animal, the Waterbuck makes use of flehmen response for visual communication and alarm snorts for vocal communication. Waterbuck often enter water to escape from predators which include Lion, Spotted Hyena, Leopard, Cheetah, African Wild Dog and Nile Crocodile (Leopard and Hyena prey on juveniles). However, it has been observed that the Waterbuck does not particularly like being in water. Waterbuck may run into cover when alarmed, and males often attack predators.

The Waterbuck exhibits great dependence on water. It cannot 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, the Waterbuck ranges farther into the woodlands while maintaining its proximity to water. With grasses constituting a substantial 70 to 95 percent of the diet, the Waterbuck is predominantly a grazer frequenting grasslands. Reeds and rushes like Typha and Phragmites may also be preferred.

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.

Waterbuck are slower than other antelope in terms of the rate of maturity. While males become sexually mature at the age of six years, females reach maturity within two to three years. Females may conceive by the age of two-and-a-half years, and remain reproductive for another ten years. In equatorial regions, breeding takes place throughout the year, and births are at their peak in the rainy season. However, breeding is seasonal in the Sudan (south of Sahara), with the mating season lasting four months. The season extends for even longer periods in some areas of southern Africa. Oestrus lasts for a day or less.

The gestational period lasts for seven to eight months, followed by the birth of a single calf. Twins are rare. Pregnant females isolate themselves in thickets as parturition approaches. Newborn calves can stand on their feet within a half-hour of birth. The mother eats the afterbirth. She communicates with the calf by bleating or snorting. Calves are kept hidden from two to three weeks up to two months. At about three to four weeks, the calf begins following its mother, who signals it to do so by raising her tail. Though bereft of horns, mothers will fiercely defend their offspring from predators. Calves are weaned at eight months, following which time they join groups of calves of their own age. Young females remain with their mothers in nursery herds, or may also join bachelor herds. The Waterbuck lives to 18 years in the wild and 30 years in captivity.