The Nile lechwe, wasserbock or Mrs Gray's lechwe or waterbuck (Kobus megaceros) is a species of antelope in the genus Kobus in the family Bovidae. It was first described by Leopold Fitzinger in 1855. Nile lechwe stand 90–100 cm (35–39 in) at the shoulder and weigh from 70–80 kg (150–180 lb).
Nile lechwe are a herbivores, feeding on foliage, grasses, fruits, and twigs. They are gregarious, and form large, loose herds. They are found in floodplains in Southern Sudan and far southwestern Ethiopia.
Males are an average of 165 cm (65 in) long and 100–105 cm (39–41 in) tall at the shoulders, and weigh between 90 and 120 kg (200 and 260 lb), while females are an average of 135 cm (53 in) long, 80–85 cm (31–33 in) tall at the shoulders, and weigh 60–90 kg (130–200 lb). Nile lechwes live an average of 10 to 11.5 years, and most uncommonly 19 years.
Their coats are shaggy with the hair on the cheeks particularly long in both sexes, and males may have even longer hair on their necks. Nile lechwe exhibit extreme sexual dimorphism. Females are golden-brown (juveniles also have golden-brown coat, but the color changes to dark brown in young males when they reach two to three years of age) with white underbellies and no horns. Males are chocolate brown to russet with white 'hoods' over their shoulders and small white patches over their eyes.
They have long, ridge-structured horns which are vaguely 'S'-shaped in profile. The horns, 50–60 cm (20–24 in) long, are strongly ridged at their bases and are curved at the tips. Yearlings are usually infected by warble flies, which can also make them unhealthy.
Nile lechwe can visually signal and vocalize to communicate with each other. They rear high in the air in front of their opponents and turn their heads to the side while displaying. Females are quite loud, making a toad-like croaking when moving. When fighting, males duck their heads and use their horns to push against each other. If one male is significantly smaller than the other, he may move next to the larger male in a parallel position and push from there, which prevents the larger male from pushing with all his force. Known predators are humans, lions, crocodiles, Cape hunting dogs and leopards. They flee to water if disturbed, but females defend their offspring from smaller predators by direct attack, mainly kicking.
Nile lechwe are crepuscular, active in the early morning and late afternoon. They gather in herds of up to 50 females and one male or in smaller all-male herds. They divide themselves into three social groups: females and their new offspring, bachelor males, and mature males with territories. A males with territory sometimes allows a bachelor male into his territory to guard the region and not to copulate.
Nile lechwe feed on succulent grasses and water plants. Wild rice is thought to be a preferred food at the start of the flood season, while a larger proportion of swamp grasses are consumed when the waters recede. They have the special capability to wade in shallow waters and swim in deeper waters, and may feed on young leaves from trees and bushes, rearing up to reach this green vegetation. Nile lechwe are also found in marshy areas, where they eat aquatic plants.
Both sexes reach sexual maturity when they are two years old. Mating occurs throughout the year, but peaks between February and May. During mating season, young males bend their horns to the ground as if to poke the earth. Males fight in the water, their heads submerging in horn-to-horn combat, for dominance. These contests are usually short and violent. As in many other animals, the dominant male copulates with the female. A unique form of marking is seen with the start of mating. The male bends his head to the ground and urinates on his throat and cheek hair. He then rubs his dripping beard on the female's forehead and rump.
The gestation period is seven to 9 months long on average, after which a single calf is born. Infants weigh about 4.5 to 5.5 kg. Females experience estrus again about a month after producing young. After its birth, the calf is kept hidden in thick vegetation for two to three weeks, where the mother nurses it. It is weaned at five to six months, and a few months later is ready to be independent and join the herd.
Habitat and distribution
Nile lechwe usually live in swamplands where the water is 10–40 cm (3.9–15.7 in) deep, wetlands, coastal areas, grasslands, steppes, and high reed and cane thickets. These are mostly found in Sudan in the Sudd swamps, with smaller numbers in the Machar marshes near the Ethiopia border. According to one estimate, 30,000 to 40,000 Nile lechwe occur on both sides of the White Nile in the Sudd. In Ethiopia, the Nile lechwe occurs marginally in the southwest, in the Gambela National Park, but its population here is unstable due to human activities.
Uses and conservation
Nile lechwe may help reduce grass fires by trampling the grass when grazing, making a natural firewall. They are a highly prized trophy to hunters and may be traded for food or other resources. They were also traditionally hunted as a source of food. This endangered species (as of 2008) is gradually becoming rare due to excessive hunting and habitat loss. Still, conservation efforts are being made. According to the IUCN, in Sudan, the Nile lechwe occurs in three protected areas: Zeraf (however here the situation for wildlife is likely to worsen as a result of oil exploration and exploitation in the region), Fannyikang and Shambe, and in Ethiopia the species occurs in Gambela National Park. A special license is required to hunt these animals in Sudan. In Ethiopia, only six animals per year are allowed to be captured with a special license. Conservation efforts are also being made in the United States. White Oak Conservation in Yulee, Florida, for example, has kept a herd of Nile lechwe since the mid-1980s and has produced many calves. The success of the species at the center is partially attributed to its resemblance to their native habitat of moist lowlands.
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