The black wildebeest or white-tailed gnu (Connochaetes gnou) is one of the two closely related wildebeest species. It is a member of the genus Connochaetes and family Bovidae. It was first described in 1780 by Eberhard August Wilhelm von Zimmermann. The black wildebeest is typically between 170–220cm (67–87 in) in head-and-body length, and the average weight is 110–180 kg (240–400 lb). Males stand up to approximately 111–121 cm (44–48 in) at the shoulder, while the height of the females is 106–116 cm (42–46 in). The black wildebeest is characterised by its white, long, horse-like tail. It also has a dark brown to black coat and long, dark-coloured hair between its forelegs and under its belly.
The black wildebeest is a herbivore, and almost the whole diet consists of grasses. Water is an essential requirement. There are three distinct social groups: the female herds, the bachelor herds and the territorial bulls. They are fast runners, and communicate using a variety of visual and vocal communication. The primary breeding season for the black wildebeest is from February to April. A single calf is usually born after a gestational period of about eight and a half months. The calf remains with its mother until her next calf is born a year later. The black wildebeest inhabits open plains, grasslands and Karoo shrublands.
The natural populations of black wildebeest, endemic to the southern part of Africa, were almost completely exterminated in the 19th century, due to their reputation as pests and the value of their hides and meat. However, the species has been reintroduced widely from captive specimens, both in private areas and nature reserves throughout most of Lesotho, Swaziland, and South Africa. It has also been introduced outside its natural range in Namibia and Kenya.
The scientific name of the black wildebeest is Connochaetes gnou. The animal is placed in the genus Connochaetes and family Bovidae and was first described by the German zoologist, Eberhard August Wilhelm von Zimmermann in 1780. He based his description on an article written by natural philosopher Jean-Nicolas-Sébastien Allamand in 1776. The generic name Connochaetes derives from the Greek words κόννος, kónnos, "beard", and χαίτη, khaítē, "flowing hair", "mane". The specific name "gnou" originates from the Khoikhoi name for these animals, gnou. The common name "gnu" is also said to have originated from the Hottentot name T'gnu, which refers to the repeated calls of "ge-nu" by the bull in the mating season. The black wildebeest was first discovered in the northern part of South Africa in the 1800s.
The black wildebeest is currently included in the same genus as the blue wildebeest (Connochaetes taurinus). This has not always been the case and at one time the latter was placed under a separate genus of its own, Gorgon. The black wildebeest lineage seems to have diverged from the blue wildebeest in the mid to late Pleistocene, and became a distinct species around a million years ago. This evolution is quite recent on a geologic time scale.
Features necessary for defending a territory such as the horns and broad-based skull of the modern black wildebeest, have been found in their fossil ancestors. The earliest known fossil remains are in sedimentary rock in Cornelia in the Orange Free State and date back about eight hundred thousand years. Fossils have also been reported from the Vaal River deposits, though it is unclear whether or not they are as ancient as those found in Cornelia. Horns of the black wildebeest have been found in sand dunes near Hermanus in South Africa. This is far beyond the recorded range of the species and it has been suggested that these animals may have migrated to that region from the Karoo.
The black wildebeest is known to hybridise with its taxonomically close relative, the blue wildebeest. Male black wildebeest have been reported to mate with female blue wildebeest and vice versa. The differences in social behaviour and habitats have historically prevented interspecific hybridisation between the species, however hybridisation may occur when they are both confined within the same area. The resulting offspring is usually fertile. A study of these hybrid animals at Spioenkop Dam Nature Reserve in South Africa revealed that many had disadvantageous abnormalities relating to their teeth, horns and the wormian bones in the skull. Another study reported an increase in the size of the hybrid as compared to either of its parents. In some animals the auditory bullae are highly deformed and in others the radius and ulna are fused.
Black wildebeest are sexually dimorphic, with females being smaller in size and more slender than males. The head-and-body length is typically between 170 and 220 cm (67 and 87 in). Males reach approximately 111 to 121 cm (44 to 48 in) at the shoulder, while females reach 106 to 116 cm (42 to 46 in).[15] Males typically weigh 140 to 157 kg (309 to 346 lb) and females 110 to 122 kg (243 to 269 lb). A distinguishing feature in both sexes is the tail, which is long and similar to that of a horse. Its bright-white colour gives this animal the vernacular name of "white-tailed gnu", and also distinguishes it from the blue wildebeest, which has a black tail. The length of the tail ranges from 80 to 100 cm (31 to 39 in).
The black wildebeest has a dark brown or black coat which is slightly paler in summer and coarser and shaggier in the winter. Calves are born with shaggy, fawn-coloured fur. Males are darker than females. They have bushy and dark-tipped manes that, as in the blue wildebeest, stick up from the back of the neck. The hairs which compose this are white or cream-coloured with dark tips. On its muzzle and under its jaw it has black bristly hair. It also has long, dark-coloured hair between its forelegs and under its belly. Other physical features include a thick neck, a plain back, and rather small and beady eyes.
Both sexes have strong horns that curve forward, resembling hooks and are up to 78 cm (31 in) long. The horns have a broad base in mature males, and are flattened to form a protective shield. In females, the horns are both shorter and narrower. They become fully developed in females in the third year, while it is not before the age of four or five that horns are fully grown in males. The black wildebeest normally has 13 thoracic vertebrae, though specimens with 14 have been reported, and this species shows a tendency for the thoracic region to become elongated. There are scent glands that secrete a glutinous substance in front of the eyes, under the hair tufts and on the forefeet. Females have two nipples. Apart from the difference in the appearance of the tail, the two species of wildebeest also differ in size and colour, with the black being smaller and darker than the blue.
The black wildebeest can maintain its body temperature within a small range in spite of large fluctuations in external temperatures. It shows well-developed orientation behaviour towards solar radiation which helps it thrive in hot, and often shadeless, habitats. The erythrocyte count is high at birth and increases till the age of two to three months, while in contrast, the leucocyte count is low at birth and falls throughout the animal's life. The neutrophil count is high at all ages. The haematocrit and haemoglobin content decreases till twenty to thirty days after birth. There is a peak in the content of all these haemological parameters at the age of two to three months, after which the readings gradually decline, reaching their lowest values in the oldest individuals. The presence of fast-twitch fibres and the ability of the muscles to use large amounts of oxygen help explain the rapid running speed of the black wildebeest and its high resistance to fatigue. Individuals may live for about twenty years.