Blesbok (Damaliscus pygargus phillipsi)

Blesbok

Damaliscus pygargus phillipsi (Pallas, 1767)

Photo: Deon Furstenburg

Afrikaans:Blesbok
German:Blessbock
French:Blesbok
isiZulu:Inoni
isiXhosa:Ilinga
Sesotho:Nônê, Nônô
Tswana:Nônê, Nônô
Shona:Noni

IUCN Conservation Status:

Lower Risk, conservation dependent (LR/cd)

In the past, hundreds of thousands of blesbok roamed the South African highveld covering the plains from horizon to horizon. However, there was confusion over their identification and a century passed before they were separated from their cousin the bontebok. The Bontebokvlakte recorded near Cathcart in the Eastern Cape, for example, refers to blesbok and not to bontebok as the latter were never found there. The difference between the two sub-species was first recorded in the journals of the Cape colonists during their expeditions into the interior of the country.
The division of the of the two species took place in historical times when a group of blesbok was separated from the rest by a sudden, unfavourable climate change and became isolated in an area south of the Cape folded mountains. Here they specialised to survive in the conditions of a single habitat in the area, and became the bontebok.

Taxonomy

Classification

Class:MAMMALIA
Supercohort:LAURASIATHERIA
Cohort:FERUNGULATA
Superorder:CETARTIODACTYLA
Order:RUMINANTIA
Suborder:PECORA
Superfamily:Bovoidea
Family:Bovidae
Subfamily:Antilopinae
Tribe:Alcelaphini
Genus:Damaliscus
Species:pygargus

 

The genus Damaliscus has two species namely:

  • Damaliscus pygargus, formerly known as D. dorcas, with two sub-species
  •  D.p.phillipsi the blesbok
  •  D.p.pygargus the bontebok
  •  Damaliscus lunatus with the subspecies
  •  D.l. lunatus the tsessebe of southern Africa
  •  D.l. tiang the tiang of the eastern regions of the Sahel
  •  D.l. topi the topi of East Africa
  •  D.l. jimela the nyamera of the lakes area of the Rift Valley in eastern Africa
  •  D.l. korrigum the korrigum of West Africa.

Blesbok are endemic to southern Africa with a distribution restricted to the south of the Zambezi River. Two important colour variants of blesbok have been selectively bred by private game farmers for the commercial market namely the white-blesbok and the yellow-blesbok. These variants are not genetically different from the blesbok and thus are not new sub-species. They breed successfully with each other and the blesbok, as well as with the bontebok sub-species. The blesbok and bontebok sub-species also interbreed freely. All of the hybrid offspring are fertile and reproduce a second and third generation which causes a significant threat to the genetic purity of both sub-species. Several populations of privately owned blesbok and bontebok have already, due to serious hybridization, been deregistered by authorities as they are not suitable for trading.

Description

A medium sized plains antelope with shoulders that is higher than the hind quarters, resulting in a sloping back. This is the typical body profile of the Alcelaphinae, the hartebeest family. The popular name blesbok refers to the distinct white blaze on the forehead and muzzle. The remainder of the coat usually varies from a light to dark brown but lacks the dark plum like shading that distinguishes the bontebok. The saddle and the rear of the buttocks are a dull yellow-brown. The underside of the body and parts of the lower legs are a dirty white.

Comparison To Man

Trophy

Both genders bear well-developed lyre-shaped horns that bend backwards from the skull and then turn outwards away from the body until the tips point upwards or slightly forward. The horns are heavily grooved for 85-90% of their length and have smooth tips. The horns of adult rams are thicker at the base and lighter in colour than those of the ewes. In rams the horn base thickens with age until they almost meet, but remain separated by a gap of 2-3 cm with ewes. The adult horn length varies from 38-50 cm, the maximum documented trophy record being 52.39 cm.

Habitat requirement

Preferred habitat is higher altitude grassland plains found in the central and eastern regions of South Africa at an annual rainfall of 400-1 200 mm. Blesbok are dependent on surface water and must drink daily or at least every second day. Arid environments lacking surface water, karroid veld without a grass stratum, thickets, forests, dense bushveld, closed woodland and tall grass stands are unsuitable. Open woodland and savannah are marginal.

The most important habitat features are:

  •     sufficient short-grass veld (0.5-15 cm) with a mixture of both sweet and sour grass species
  •     a wide range of scattered dicot forbs
  •     sandy soils
  •     daily drinking water

Distribution

Blesbok are well adapted to mountain plateaux’s with a mixed short grass stratum and a high rainfall. In the warmer subtropical savannahs, an abundance of trees providing shade is essential. Although blesbok can survive on sourveld, these habitats are marginal and result in a reduced performance. Steep slopes and rocky surfaces are avoided. Blesbok has been successfully introduced into marginal habitats across the major part of South Africa, the central regions of Zimbabwe and the north-central areas of Namibia. These areas include fynbos, coastal plains, open bushveld and semi-Kalahari habitats.

Feeding & Nutrition

Blesbok are predominantly diurnal. They become less active during the cold winter months when many hours are spend lying, either in the sun or in the shade of trees. It is a highly selective grazer of exclusively short grasses, smaller than 6 cm, that are grazed down to 0.5 cm above ground. Sweet-grass species are preferred although they adapt well to mixedveld where sour-grass species constitute up to 65% of the grass layer. Overall, the diet consists of 95% grass and 5% dicot forbs and browse. The young summer growth on burnt veld and cultivated lands are preferred and they will travel long distances to reach it. Moribund grass that has not been grazed for longer than a year, as well as grass tufts from a previous season’s growth is avoided. The species composition of the diet changes markedly between seasons. In winter, blesbok roam and feed across the entire home range but in spring and early summer vast numbers concentrate on burnt veld.

Photo: Deon Furstenburg

Social structure

Blesbok are social animals that live in groups of varying sizes.

The structure of a population consists of:

  • family groups of 20-120 with sub-adult females of all ages, young males of 1-2 years and post-mature ewes
  • harem groups of 4-25 socially mature ewes >2.5 years and their lambs of 10-18 months, and sometimes associated with a territorial ram
  • bachelor groups of sub-adult rams, 2-4 years, and occasionally one or two adult rams, >4 years.
  • adult ram groups of 20-120 with non-territorial adult rams, 4-8 years, and post-mature rams >8 years
  • solitary territorial rams, 4-8 years

In some populations, especially on smaller game farms, there are less distinctive differences between bachelor and adult ram groups and both categories can be united into a single group. The same applies to family and harem groups on smaller land units with spatial restrictions. Bodily contact between individuals is rare and family bonding poor. They groom themselves by rubbing the body with the muzzle or horns or by nibbling the skin with the incisors. After 12-18 months the sub-adult females leave to join a family group and after 10-12 months the young males leave to join a bachelor group. The stability and size of home ranges depends mainly on the food source. Sporadically migrations occur when food sources become depleted. During the rutting and mating season adult rams display aggressive, territorial behaviour. Some remain in or around their territories long after the mating season but only because the habitat in the area is optimal. During these times, territories are not defended. During moist, summer months, aggregations of up to 650 animals frequently form.

Information Table

 

Blesbok information table
Characteristic
Ram
Ewe
Adult body weight
kg
70-80
60-70
Adult shoulder height
cm
95-105
95-105
Expected longevity
years
10-12
9-11
Age of sexual maturity
months 28
28-30
Age of social adulthood (1st mating)
years
3.1-4
2.5
Gestation
days

225-235
1st lamb born at
years

3.5
Lambing interval
months

12
Post maturity age (last mating)
years
7-8
8
Rutting season
Mar-May
Lambing season

Nov-Jan
Weaning age months
3-4
Gender ratio: Natural (all ages)
1
1
Gender ratio: Production (all ages)
1
4
Mating ratio: Natural (adults)
1
1.8
Mating ratio: Production (adults)
1
8
Re-establishment: Absolute minimum number needed
3
2
Re-establishment: Smallest viable population size
3
5
Spatial Behaviour: home range
ha
250
250
Spatial Behaviour: territory range
ha
2.5
None
Large stock grazing unit (adult):
Dietary ratio (Grass):
LSU
0.23 per animal
(95% of diet)
0.22 per animal
(95% of diet)
Browsing unit (adult):
Dietary ratio: (browse):
BU
0.56 per animal
(5% of diet)
0.54 per animal
(5% of diet)
Maximum stocking load
167 animals per 1000 ha (at 450-550 mm annual rainfall)
Minimum habitat Size Required
ha
200
Annual population growth
18-55% (mean 30%)
Optimal annual rainfall
400-800mm
Optimal vegetation structure:
Grass height:
Woody canopy cover:

0.5-15 cm
0-35%

Bibliography

  1. Du Plessis, SF, 1969. The past and present geographical distribution of the Perrisodactyla and Artiodactyla in Southern Africa. M.Sc. Thesis, University of Pretoria.
  2. Du Plessis, SS, 1968. Ecology of blesbok on the Van Riebeeck Nature Reserve, Pretoria, with special reference to productivity. D.Sc. Thesis, University of Pretoria.
  3. Du Plessis, SS, 1989. Blesbok. Wild & Jag 4(6).
  4. Furstenburg, D 2004. Blesbok. Wild & Jag 10(5).
  5. Furstenburg, D, 1970-2008. Personal field notes (unpublished). IEA (Institute of Applied Ecology), 1998. Damaliscus pygargus. In African Mammals Databank - A Databank for the Conservation and Management of the African Mammals Vol 1 & 2. European Commission Directorate, Bruxelles: http://gorilla.bio.uniroma1.it/amd/
  6. IUCN, 2006. IUCN Red list of Threatened Species, Gland, Switzerland: http://www.iucnredlist.org
  7. Kingdon, J, 1997. The Kingdon Field Guide to African Mammals. Princeton University Press, Princeton.
  8. Kingdon, J, 1979. East African Mammals, Vol. IIID, Bovids: An atlas of evolution in Africa. Academic Press, London.
  9. Lynch, CD, 1971. A behavioural study of blesbok Damaliscus dorcas philipsi with special reference to territoriality. M.Sc. Thesis, University of Pretoria.
  10. Marais, AL, 1988. Factors affecting synchronized breeding in blesbok and impala. Ph.D. Thesis, University of Pretoria.
  11. Novellie, PA, 1975. Comparative social behaviour of springbok and blesbok on the Jack Scott Nature Reserve, Transvaal. M.Sc. Thesis, University of Pretoria.
  12. Nowak, RM, 1991. Walker's Mammals of the World 5th edn. The Johns Hopkins University Press, Baltimore.
  13. Skead, CJ, 1987. Historical Mammal incidence in the Cape, Vol 1 & 2, Government Printer, Cape Town. Skinner, JD & Chimba, CT, 2005. The Mammals of the Southern African Subregion, 3rd edn. Cambridge University Press.
  14. Walther, F. R. 1990. Hartebeests. In Grzimek's Encyclopedia of Mammals. Edited by S. P. Parker. New York: McGraw-Hill. Volume 5.
  15. Ward, R, 2006. Rowland Ward’s Records of Big Game, 27tth edn. Rowland Ward Publications. Watson, JP, Skinner, JD, Erasmus, BH & Dott, HM, 1991. Age determination from skull growth in blesbok. S. Afr. J. Wildl. Res. 21(1):6-14.
  16. Wikipedia Encyclopedia, 2008. Damaliscus. http://en.wikipedia.org
  17. Wilson, D E & Reeder, DM, 1993. Mammal Species of the World: A Taxonomic and Geographic Reference. 2nd edn., Smithsonian Institution Press, Washington. http://nmnhwww.si.edu/msw/

 

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