Blue wildebeest

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Blue wildebeest
Male in the Ngorongoro Crater
Conservation status
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Mammalia
Order: Artiodactyla
Family: Bovidae
Subfamily: Alcelaphinae
Genus: Connochaetes
Species: C. taurinus
Binomial name
Connochaetes taurinus
(Burchell, 1823)
Subspecies

C. t. albojubatus (Thomas, 1912)
C. t. cooksoni (Blaine, 1914)
C. t. johnstoni (Sclater, 1896)
C. t. mearnsi (Heller, 1913)
C. t. taurinus (Burchell, 1823)

The blue wildebeest (Connochaetes taurinus), also called the common wildebeest, white-bearded wildebeest or bridled gnu, is a large antelope and one of the two species of wildebeest. It is placed in the genus Connochaetes and family Bovidae. It was first described by William John Burchell in 1823. It has a close taxonomic relationship with the black wildebeest. The blue wildebeest is known to have five subspecies. The blue wildebeest is typically between 170–240 cm (67–94 in) in head-and-body length. The average height is 115–145 cm (45–57 in). While males weigh up to 290 kg (640 lb), females weigh up to 260 kg (570 lb).

They range the open plains, bushveld, and dry woodlands of Southern and East Africa, living for more than 20 years. The male is highly territorial, using scent markings and other devices to protect his domain. The largest population is in the Serengeti, numbering over one million animals. They are a major prey item for lions, hyenas, and crocodiles.

Taxonomy and naming

The scientific name of the blue wildebeest is Connochaetes taurinus.[2] The generic name Connochaetes derives from the Greek words κόννος, kónnos, "beard", and χαίτη, khaítē, "flowing hair", "mane".[3] The specific name taurinus originates from the Greek word tauros, which means a bull or bullock. It means the same as the Latin taurus.[4] The common name "blue wildebeest" refers to a conspicuous silvery-blue sheen of the coat.[5] The name "gnu" originates from the Khoikhoi name for these animals, gnou.[6]

The blue wildebeest was first described by English naturalist William John Burchell in 1823.[7] It shares the genus Connochaetes with the black wildebeest (C. gnou), and is placed in the family Bovidae.[2] Though the blue and black wildebeest are currently in the same genus, earlier reports have placed the former in a separate genus of its own, Gorgon. In a study of the mitotic chromosomes and mtDNA, intended to understand more of the evolutionary relations of the two species, it was revealed that the two species had diverged about a million years back, which showed a close phylogenetic relationship between them.[8]

Subspecies

C. taurinus consists of five subspecies:[1][9][10]

  • C. t. albojubatus (Thomas, 1912; Eastern white-bearded wildebeest), found in the Gregory Rift Valley (south of the equator). The range extends from northern Tanzania to central Kenya.
  • C. t. cooksoni (Blaine, 1914; Cookson's wildebeest), whose range is restricted to the Luangwa Valley in Zambia. Sometimes they may wander into the plateau region of central Malawi.
  • C. t. johnstoni (Sclater, 1896; Nyassaland wildebeest), that occurs from Mozambique (north of Zambezi river) to east-central Tanzania. Now extinct in Malawi.
  • C. t. mearnsi (Heller, 1913; Western white-bearded wildebeest), found in northern Tanzania and southern Kenya, range extends from the west of the Gregory Rift Valley till the Lake Victoria at Speke Bay.
  • C. t. taurinus (Burchell, 1823; Blue wildebeest or brindled gnu; southern Africa), whose range extends from Namibia and South Africa to Mozambique (north of Orange river) and further from southwestern Zambia (south of Zambezi river) to southern Angola.

Hybrids

The blue wildebeest is known to hybridise with its taxonomically close relative, the black wildebeest. Male black wildebeest have been reported to mate with female blue wildebeest and vice versa.[11] 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.[12] 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.[13]

Genetics and evolution

The diploid number of chromosomes in the blue wildebeest is 58.[14] 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. Other chromosomes were acrocentric. The X chromosome is a large acrocentric and the Y chromosome a minute one.[15][16]

This species of wildebeest seems to have evolved around 2.5 million years ago.[17] The black wildebeest is believed to have diverged from it to become a distinct species around a million years ago, in the mid to late Pleistocene.[18] Fossil evidence suggests that the blue wildebeest were quite common in the Cradle of Humankind in the past. Apart from east Africa, fossils are commonly found in Elandsfontein, Cornelia and Florisbad.[17]

Description

A close view of the blue wildebeest

The blue wildebeest is typically between 170–240 cm (67–94 in) in head-and-body length. The average height is 115–145 cm (45–57 in).[19] While males weigh up to 290 kg (640 lb), females weigh up to 260 kg (570 lb).[20] A characteristic feature is the long, black tail, which is around 60–100 cm (24–39 in) in length.[19] The blue wildebeest exhibits sexual dimorphism, with the males having a larger and darker appearance in comparision to the females. All features and markings of this species are bilaterally symmetrical for both sexes.[21] The average life span in the wild is 20 years.[22]

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 colouration at the age of two months. The adults' hues actually vary from a deep slate or bluish gray all the way to light gray or even grayish-brown. The dorsal coat and flanks are slightly lighter in hue than the ventral hide and underparts. Dark brown vertical stripes mark the area between the neck and the back of the ribcage.[23] The manes of both sexes appear long, stiff, thick and jet black, a colour assumed by the tail and face as well.[21]

Both sexes possess two large horns, which are shaped like parentheses. These extend outward to the side and then curve up and inward. In the males, the horns can be 83 cm (33 in) long, while horns of the females are 30–40 cm (12–16 in).[19] Despite of being an antelope, the blue wildebeest displays various bovine characteristics. For instance, the horns resemble those of the female African buffalo.[19] Further, the heavy build and disproportionately large forequarters give it a bovine appearance.[22][24]

In terms of skull length, the smallest subspecies of the blue wildebeest is C. t. mearnsi. The longest nasals are found in C. t. johnstoni, and the shortest in C. t. mearnsi females. The beard is creamy white in C. t. mearnsi and C. t. albojubatus, whereas it is black in C. t. taurinus and C. t. johnstoni.[16]

Diseases and parasites

In a study, blue wildebeest were found to be hosts of 13 nematodes, one trematode, larvae of five oestrid flies, three species of lice, seven ixodid tick species, one mite and nymphae of a pentastomid. Of these, most were seasonally prevalent.[25] Parasites like Trichostrongylus deflexus have been found to be prevalent in the wildebeest.[26] Blue wildebeest are resistant to infestations by several ticks.[27] The herpesvirus was first isolated from the blue wildebeest in 1960 by veterinary scientist Walter Plowright.[28] Generally, the larvae of Gedoelstica and Oestrus occur in the nasal passages and pneumatic cavities of the blue wildebeest, and can even enter the brain. While rinderpest is probably the most fatal disease for the wildebeest, they can also be affected by Anthrax, sarcoptic mange, hoof gangrene.[24]

Behaviour

The Serengeti herds are purely migratory and abandon the usual plains after the rainy season has ended to seek higher grasses in wetter areas. Grasslands bordering alkaline lakes or pans are particularly choice dry-season (winter) habitats.[29] Herds may be mixed gender with a dominant male, female only, or bachelor only. Blue wildebeest often graze together with other species such as plains zebras, for purposes of mutual protection. Zebras in particular are beneficial, since they mow down highly vegetated areas, leaving the wildebeests to eat the newly exposed and more nutritious short grasses, which they prefer. A blue wildebeest can attain maximum a speed of 65 to 80 kilometres per hour (40 to 50 mph).[30]

Territoriality

Blue wildebeest are unusually territorial; adult males occupy their territories for a month or for the entire year. The physical size of territories ranges from one to two hectares. The bulls mark territory boundaries with dung heaps, preorbital gland secretions, hoof scent glands and pawing of the earth. When competing over territory, males grunt quite loudly, make a thrusting motion with their horns, and perform other displays of aggression.

Territories are advertised by actions of the bull, as well as physical marking.[5] Body language used by the territorial male includes standing in an erect posture, profuse ground pawing and horning, frequent defecation, rolling on his back, and bellowing the sound "ga-noo".[5] To attract the opposite sex at the beginning of courtship, the male (and less frequently the female) will rub its preorbital gland on a tree, and then proceed with a destructive horning of said tree. This behaviour is not only effective in enticing a mate, but also provides more grassland for future wildebeest generations by removing brush.

Reproduction

Blue wildebeest fighting for dominance

Males exhibit rivalry when staking out territory and when competing for females. In the actual clashes between males, they face off resting on bent front knees, exchanging horn thrusts for brief periods. Elaborate individual displays are made in the rivalry and courtship process, where males bellow, snort and dig their horns into the soil. The mating process is thought to begin at the first full moon at the end of the rainy season. Once territory is established, the male attempts to lure or corral the female into his domain.[31] A female may mate with several different males, visiting several different territories.[31] Most mating occurs during a three- to four-week period at the end of the rainy season (March to April), when this species is at its maximum vigour.[31]

The female reaches sexual maturity at age three, and the male at age four; however, it is more typically age five when the male has developed sufficient strength and experience to defend territory. Generally, fewer than half of the adult males create territories in a given year. In the Serengeti, population densities are very high, up to 270 territorial bulls may occupy one square kilometer. The total volume of noise created during the Serengeti rutting season is "indescribable" in its amplitude and variety of snorting, bellowing and fighting.[29] When the dry season is well underway, usually sometime in August, territories are no longer defended.

The gestation period is about 8.5 months. Female wildebeest give birth in the middle of a herd rather than alone,[31] and typically in the middle of the day, in order to give some time for the newborn to practice walking before the predators become active again after sunset. Calves are able to stand within seven minutes and run with the herd in less than two hours from birth. These precocial features are warranted, since the calves are vulnerable to predators. To escape predation, calves remain close to their mothers for a significant time, and may suckle for up to one year. In large herds, 80% of wildebeest offspring survive the first month, compared to a 50% survival rate within small herds.

Distribution and habitat

Distribution of the subspecies:
  C. t. taurinus
  C. t. cooksoni
  C. t. johnstoni
  C. t. albojubatus
  C. t. mearnsi

Blue wildebeest are found in open and bush-covered savanna in south and east Africa, thriving in areas that are neither too wet nor too arid. They can be found in places that vary from overgrazed areas with dense bush to open woodland floodplains. Wildebeest prefer the bushveld and grasslands of the southern savanna. The terrestrial biome designations for these preferred habitats are savanna, grassland, open forest and scrub forest.

Large herds numbering into the thousands may be observed on the Tanzanian Serengeti equatorial plain, and in Zambia in Liuwa Plain National Park, in their annual migration. Smaller herds of about 30 are found in northern Botswana, Zimbabwe,[32] and the South African locations of Waterberg, Kruger National Park, and Mala Mala. Some herds can be found almost to the southern tip of South Africa.

Blue wildebeest can tolerate arid regions, as long as a potable water supply is available. Since all wildebeests require a long drink every day or two, they must have water within about 15 to 25 km distance. Their blunt muzzles are best equipped for biting short green grasses,[5] since a wide incisor row prevents more selective feeding. Short grasses of this type are usually only found on alkaline or volcanic soils. Blue wildebeest are locally the favored prey for lions, spotted hyenas, and mature Nile crocodiles. The latter, giant reptiles, stalk them at river crossings and explosively grab them by their faces, dragging them into the water to drown. Lionesses usually attack them by ambush and then bite down onto their throats or sometimes snouts until they are suffocated. Hyenas usually kill wildebeest by repeatedly biting to the sides, ultimately causing death by shock and blood loss. The young also fall prey to cheetahs, leopards, and wild dogs, the last sometimes also take adults in if in a large pack.

Conservation

The Serengeti boasts over one million blue wildebeests, but southern Africa's large herds have diminished over the last several centuries under pressure from hunting, cattle ranching and habitat intrusion stemming from overpopulation of humans. In southern Africa, some efforts are being made to enhance grasslands and repair damage of cattle grazing and excessive fencing. These activities are particularly evident in the Waterberg Biosphere, where invasive brush (induced by excess cattle grazing) is being extirpated and many fences are coming down to promote wildlife migration.[33] While the species status is considered secure as a whole, there is concern for smaller herds in the southern Africa habitats which have already become marginalized.

References

  1. ↑ 1.0 1.1 IUCN SSC Antelope Specialist Group (2008). "Connochaetes taurinus". IUCN Red List of Threatened Species. Version 2010.2. International Union for Conservation of Nature. Retrieved 28 August 2010.  Database entry includes a brief justification of why this species is of least concern.
  2. ↑ 2.0 2.1 Grubb, P. (2005). "Order Artiodactyla". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 676. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  3. ↑ Benirschke, K. "Wildebeest, Gnu". Comparative Placentation. Retrieved 14 January 2014. 
  4. ↑ "Taurus". Encyclopaedia Britannica. Merriam-Webster. 
  5. ↑ 5.0 5.1 5.2 5.3 Estes, R. (1991). The Behavior Guide to African Mammals, Including Hoofed Mammals, Carnivores, Primates. Los Angeles, The University of California Press. pp. 150–156, ISBN 0520080858
  6. ↑ "Gnu". Merriam-Webster. Retrieved 14 January 2014. 
  7. ↑ Pickering, J. (October 1997). "William J. Burchell's South African mammal collection, 1810–1815". Archives of Natural History 24 (3): 311–26. doi:10.3366/anh.1997.24.3.311. ISSN 0260-9541. 
  8. ↑ Corbet, S.W.; Robinson, T.J. (1991). "Genetic divergence in South African Wildebeest: comparative cytogenetics and analysis of mitochondrial DNA". The Journal of Heredity 82 (6): 447–52. PMID 1795096. 
  9. ↑ "Zambezian and Mopane woodlands". Terrestrial Ecoregions. World Wildlife Fund. Retrieved 2006-06-29. 
  10. ↑ "Connochaetes taurinus". ITIS. Retrieved 22 January 2014. 
  11. ↑ Grobler, J.P.; Rushworth, I.; Brink, J.S.; Bloomer, P.; Kotze, A.; Reilly, B.; Vrahimis, S. (5 August 2011). "Management of hybridization in an endemic species: decision making in the face of imperfect information in the case of the black wildebeest—Connochaetes gnou". European Journal of Wildlife Research 57 (5): 997–1006. doi:10.1007/s10344-011-0567-1. ISSN 1439-0574. 
  12. ↑ Ackermann, R. R.; Brink, J. S.; Vrahimis, S.; De Klerk, B. (29 October 2010). "Hybrid wildebeest (Artiodactyla: Bovidae) provide further evidence for shared signatures of admixture in mammalian crania". South African Journal of Science 106 (11/12): 1–4. doi:10.4102/sajs.v106i11/12.423. 
  13. ↑ De Klerk, B. (2008). An osteological documentation of hybrid wildebeest and its bearing on black wildebeest (Connochaetes gnou) evolution (Doctoral dissertation). 
  14. ↑ Skinner, J. D.; Chimimba, C. T. (2005). The Mammals of the Southern African Subregion (3rd ed.). Cambridge: Cambridge University Press. pp. 645–8. ISBN 978-0-521-84418-5. 
  15. ↑ Wallace, C. (1978). "Chromosome analysis in the Kruger National Park: The chromosomes of the blue wildebeest Connochaetes taurinus". Koedoe 21 (1): 195–6. doi:10.4102/koedoe.v21i1.974. 
  16. ↑ 16.0 16.1 Groves, C.; Grubbs, P. (2011). Ungulate Taxonomy. JHU Press. ISBN 978-1-4214-0329-8. 
  17. ↑ 17.0 17.1 Hilton-Barber, B.; Berger, L. R. (2004). Field Guide to the Cradle of Humankind : Sterkfontein, Swartkrans, Kromdraai & Environs World Heritage Site (2nd revised ed.). Cape Town: Struik. pp. 162–3. ISBN 177-0070-656. 
  18. ↑ Bassi, J. (2013). Pilot in the Wild: Flights of Conservation and Survival. South Africa: Jacana Media. pp. 116–8. ISBN 978-1-4314-0871-9. 
  19. ↑ 19.0 19.1 19.2 19.3 Huffman, B. "Connochaetes taurinus : Brindled gnu, Blue wildebeest". Ultimate Ungulate. Retrieved 22 January 2014. 
  20. ↑ "Blue wildebeest". Wildscreen. ARKive. Retrieved 22 January 2014. 
  21. ↑ 21.0 21.1 Geraci, G. "Connochaetes taurinus : Blue wildebeest". University of Michigan Museum of Zoology. Animal Diversity Web. Retrieved 22 January 2014. 
  22. ↑ 22.0 22.1 "Wildebeest (""Connochaetes taurinus)". National Geographic. Retrieved 22 January 2014. 
  23. ↑ Stuart, C.; Stuart, T. (2001). Field Guide to Mammals of Southern Africa (3rd ed.). Cape Town: Struik. p. 204. ISBN 1-86872-537-5. 
  24. ↑ 24.0 24.1 Kingdon, Jonathan (1989). East African Mammals : An Atlas of Evolution in Africa (Vol. 3, Part D:Bovids ed.). London: Academic Press. pp. 525–38. ISBN 022-6437-256. 
  25. ↑ Horak, I G; De Vos, V; Brown, M R (1983). "Parasites of domestic and wild animals in South Africa. XVI. Helminth and arthropod parasites of blue and black wildebeest (Connochaetes taurinus and Connochaetes gnou).". The Onderstepoort journal of veterinary research 50 (4): 243–55. PMID 6676686. 
  26. ↑ Van Wyk, I.C.; Boomker, J. (24 February 2011). "Parasites of South African wildlife. XVIV. The prevalence of helminths in some common antelopes, warthogs and a bushpig in the Limpopo province, South Africa". Onderstepoort Journal of Veterinary Research 78 (1): 308. doi:10.4102/ojvr.v78i1.308. PMID 23327219. 
  27. ↑ Horak, I G; Golezardy, H.; Uys, A.C. (2006). "The host status of African buffaloes, Syncerus caffer, for Rhipicephalus (Boophilus) decoloratus". Onderstepoort Journal of Veterinary Research 73 (3). doi:10.4102/ojvr.v73i3.145. PMID 17058441. 
  28. ↑ O.A., Ryder; Byrd, M.L. (1984). One Medicine: A Tribute to Kurt Benirschke, Director Center for Reproduction of Endangered Species Zoological Society of San Diego and Professor of Pathology and Reproductive Medicine University of California San Diego from his Students and Colleagues. Berlin, Heidelberg: Springer. pp. 296–308. ISBN 978-3-642-61749-2. 
  29. ↑ 29.0 29.1 Estes, Richard D. (1999) The Safari Companion, Chelsea Green Publishing Company, Vermont, ISBN 0-7974-1159-3
  30. ↑ Top Ten Fastest Mammals. Top10land.com. Retrieved on 2013-10-16.
  31. ↑ 31.0 31.1 31.2 31.3 Moss, C. (1975). Portraits in the Wild, Boston, Houghton Mifflin Company.
  32. ↑ Unwin, Mike (2003) Southern African Wildlife, Globe Pequot Press, USA, ISBN 1841620602
  33. ↑ Hogan, C.M.; Cooke, Mark L. and Murray, Helen (May 22, 2006) The Waterberg Biosphere, Lumina Technologies for Ant Africa Enterprises, Limpopo Province, South Africa

External links

External identifiers for Connochaetes taurinus
GBIF 2441105
ITIS 625079
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