Blue wildebeest
The blue wildebeest, also called the common wildebeest, white-bearded gnu or brindled gnu, is a large antelope and one of the two species of wildebeest. It is placed in the genus Connochaetes and family Bovidae, and has a close taxonomic relationship with the black wildebeest. The blue wildebeest is known to have five subspecies. This broad-shouldered antelope has a muscular, front-heavy appearance, with a distinctive, robust muzzle. Young blue wildebeest are born tawny brown, and begin to take on their adult coloration at the age of 2 months. The adults' hues range from a deep slate or bluish-gray to light gray or even grayish-brown. Both sexes possess a pair of large curved horns.
The blue wildebeest is an herbivore, feeding primarily on short grasses. It forms herds which move about in loose aggregations, the animals being fast runners and extremely wary. The mating season begins at the end of the rainy season and a single calf is usually born after a gestational period of about 8.5 months. The calf remains with its mother for 8 months, after which it joins a juvenile herd. Blue wildebeest are found in short-grass plains bordering bush-covered acacia savannas in southern and eastern Africa, thriving in areas that are neither too wet nor too arid. Three African populations of blue wildebeest take part in a long-distance migration, timed to coincide with the annual pattern of rainfall and grass growth on the short-grass plains where they can find the nutrient-rich forage necessary for lactation and calf growth.
The blue wildebeest is native to Angola, Botswana, Eswatini, Kenya, Mozambique, South Africa, Tanzania, Zambia, and Zimbabwe. Today, it is extinct in Malawi, but has been successfully reintroduced in Namibia. The southern limit of the blue wildebeest range is the Orange River, while the western limit is bounded by Lake Victoria and Mount Kenya. The blue wildebeest is widespread and is being introduced into private game farms, reserves, and conservancies. The International Union for Conservation of Nature and Natural Resources rates the blue wildebeest as being of least concern. The population has been estimated to be around 1.5 million, and the population trend is stable.
Taxonomy and naming
The blue wildebeest was first described in 1823 by English naturalist William John Burchell, who gave it the scientific name Connochaetes taurinus. It shares the genus Connochaetes with the black wildebeest, and is placed in the family Bovidae, ruminant animals with cloven hooves. The generic name Connochaetes derives from the Greek words κόννος, kónnos, "beard", and χαίτη, khaítē, "flowing hair", "mane". The specific name taurinus originates from the Greek word tauros, which means a bull or bullock. The common name "blue wildebeest" refers to the conspicuous, silvery-blue sheen of the coat, while the alternative name "gnu" originates from the name for these animals used by the Khoikhoi people, a native pastoralist people of southwestern Africa.Though the blue and black wildebeest are currently classified in the same genus, the former was previously placed in a separate genus, Gorgon. In a study of the mitotic chromosomes and mtDNA, which was undertaken to understand more of the evolutionary relationships between the two species, the two were found to have a close phylogenetic relationship and had diverged about a million years ago.
Subspecies
C. taurinus has five subspecies:- C. t. taurinus — the blue wildebeest, common wildebeest, or brindled gnu occurs in Southern Africa from Namibia and South Africa to north of the Orange River in Mozambique and south of the Zambezi River in southwestern Zambia to southern Angola.
- C. t. johnstoni — the Nyassaland wildebeest occurs from north of the Zambezi River to east-central Tanzania. It is now extinct in Malawi.
- C. t. albojubatus — the eastern white-bearded wildebeest occurs in the Gregory Rift Valley, and from northern Tanzania to central Kenya.
- C. t. mearnsi — the western white-bearded wildebeest, occurs in northern Tanzania and southern Kenya. Its range extends from the west of the Gregory Rift Valley to Speke Bay on Lake Victoria.
- C. t. cooksoni — Cookson's wildebeest is restricted to the Luangwa Valley in Zambia and wanders sometimes into the plateau region of central Malawi.
Hybrids
The blue wildebeest is known to hybridise with the black wildebeest. The differences in social behaviour and habitats have historically prevented interspecific hybridisation, but it may occur when both species are confined within the same area, and the offspring are usually fertile. A study of these hybrid animals at Spioenkop Dam Nature Reserve in South Africa revealed that many had congenital abnormalities relating to their teeth, horns, and the Wormian bones of the skull. Another study reported an increase in the size of the hybrid as compared to either of its parents. In some hybrid animals, the auditory bullae are highly deformed, and in others, the radius and ulna are fused.Genetics and evolution
The diploid number of chromosomes in the blue wildebeest is 58. Chromosomes were studied in a male and a female wildebeest. In the female, all except a pair of very large submetacentric chromosomes were found to be acrocentric. Metaphases were studied in the male's chromosomes, and very large submetacentric chromosomes were found there as well, similar to those in the female both in size and morphology. The rest were acrocentric. The X chromosome is a large acrocentric, while the Y chromosome is a minute one.This species of wildebeest seems to have evolved around 2.5 million years ago. The black wildebeest is believed to have diverged from the blue wildebeest to become a distinct species around 1 million years ago, in the Middle to Late Pleistocene. Fossil evidence suggests that blue wildebeest were quite common in the Cradle of Humankind in the past. Apart from eastern Africa, fossils are commonly found in Elandsfontein, Cornelia, and Florisbad.
Description
The blue wildebeest exhibits sexual dimorphism, with males being larger and darker than females. The blue wildebeest is typically in head-and-body length. The average height of the species is. Males typically weigh and females weigh. A characteristic feature is the long, black tail, which is around in length. All features and markings of this species are bilaterally symmetrical for both sexes. The average life span is 20 years in captivity. The oldest known captive individual lived for 24.3 years. The age that blue wildebeest live to in the wild is debatable.Blue wildebeest have one of the most efficient locomotor muscles in terms of energy used for mechanical work and wasted as heat, with 62.6% of energy being converted into movement and the remainder in heat. They can travel up to in 5 days without drinking water, with average temperatures of in peak times of the day.
Colouration
This broad-shouldered antelope has a muscular, front-heavy appearance, with a distinctive robust muzzle. Young are born tawny brown, and begin to take on their adult coloration at the age of 2 months. The adults' hues range from a deep slate or bluish-gray to light gray or even grayish-brown. The back and flanks are slightly lighter than the ventral surface and underparts. Dark brown, vertical stripes mark the area between the neck and the back of the ribcage, thus giving it the name "brindled gnu". The manes of both sexes appear long, stiff, thick, and jet black, the same colour as the tail and face. While the manes of the western and eastern white-bearded wildebeest are lank, those of the Nyassaland wildebeest and common wildebeest stick up. Scent glands, which secrete a clear oil, are present in the forefeet and are larger in males than females.In terms of skull length, the smallest subspecies of the blue wildebeest is the western white-bearded wildebeest. It is also the darkest subspecies; the eastern white-bearded wildebeest is the lightest race. Both subspecies possess a creamy white beard, whereas the beard is black in both the Nyassaland wildebeest and the common wildebeest. The longest muzzles are found in the Nyassaland wildebeest, and the shortest in female western white-bearded wildebeest.
Horns
Both sexes possess a pair of large horns, which are shaped like parentheses. These extend outward to the side, and then curve upward and inward. In the males, the horns can be long, while the horns of the females are long. Despite being an antelope, the blue wildebeest possesses various bovine characteristics. For instance, the horns resemble those of the female African buffalo. Furthermore, the heavy build and disproportionately large forequarters give it a bovine appearance.Interdigital glands
The blue wildebeest only has interdigital glands in its fore legs. Analysis of chemical constituents from a free ranging animal in Zimbabwe showed this gland contains cyclohexanecarboxylic acid, phenol, 2-phenylethanol, methyl cyclohexanecarboxylate, and six short-chain carboxylic acids.Ecology and behavior
The blue wildebeest is mostly active during the morning and the late afternoon, with the hottest hours of the day being spent in rest. These extremely agile and wary animals can run at speeds up to, waving their tails and tossing their heads. An analysis of the activity of blue wildebeest at the Serengeti National Park showed that the animals devoted over half of their total time to rest, 33% to grazing, 12% to moving about, and a little to social interactions. However, variations existed among different age and sex groups.The wildebeest usually rest close to others of their kind and move about in loose aggregations. Males form bachelor herds, and these can be distinguished from juvenile groups by the lower amount of activity and the spacing between the animals. Around 90% of the male calves join the bachelor herds before the next mating season. Bulls become territorial at the age of four or five years, and become very noisy and active. The bulls tolerate being close to each other and of plain can accommodate 270 bulls. Most territories are of a temporary nature and fewer than half of the male population hold permanent territories. In general, blue wildebeest rest in groups of a few to thousands at night, with a minimum distance of between individuals. They are a major prey item for lions, cheetahs, leopards, African wild dogs, hyenas, and Nile crocodiles.
Female calves will stay with their mothers and other related females of the herd throughout their lives. Female individuals in a herd are from a wide range of ages, from yearlings to the oldest cow. During the wet season, the females generally lead the herd towards nutritious areas of grasses and areas where predators can be avoided. This is to ensure that newborn calves have the highest chance of survival as well as gaining the most nutritious milk.
Bulls mark the boundaries of their territories with heaps of dung, secretions from their scent glands, and certain behaviors. Body language used by a territorial male includes standing with an erect posture, profuse ground pawing, and horning, frequent defecation, rolling and bellowing, and the sound "ga-noo" being produced. When competing over territory, males grunt loudly, paw the ground, make thrusting motion with their horns, and perform other displays of aggression.