Waterbuck (Kobus ellipsiprymnus)

Waterbuck

Kobus ellipsiprymnus (Ogilby, 1833)

Waterbuck

Photo: Doug Lee

Afrikaans:Waterbok
German:Wasserbock
French: 
Cobe ā croissant
Swahili: Kuru
isiNdebele:Isidumuka
isiZulu:Iphiva
seSotho:Phitlwa
seTswana: Tumoga
Shona:Dhumukwa
Shangaan:Phiva
Nama:!! Gampiris

                                                                                           
Worldwide confusion exists over the waterbuck’s name.  It is frequently and incorrectly used to refer to the lechwe and the sitatunga, two species that are considered aquatic in their behaviour.  The waterbuck, however, is not aquatic but terrestrial and is usually found in close vicinity to water rich environments.  Waterbuck have a reputation for smelly and unpalatable meat.  This is due to a musky oil secreted by glands found primarily in the skin of the flanks which forms a waterproof layer around the hair and protects the skin when the waterbuck enters water.  Many incidents have been reported where crocodile and lion have avoided preying on waterbuck because of their unpleasant smell.

IUCN Conservation Status:
Common or Ellipsen waterbuck = Least Concern (LC)
Southern waterbuck = Lower Risk, Conservation dependent (LR/Cd)
Defassa waterbuck = Near Threatened (NT)

The present total population numbers are estimated at 105 000 Common waterbuck and 95 000 Defassa waterbuck.  The population numbers are declining.

Taxonomy

Classification                                                                  

Class:Mammalia
Supercohort:LAURASIATHERIA
Cohort:FERUNGULATA
Superorder:CETARTIODACTYLA
Order:RUMINANTIA
Superfamily:Bovoidea
Family:Bovidae
Subfamily:Reduncinae
Tribe:Reduncini
Genus:
Kobus
Species:
ellipsiprymnus


The subfamily includes three genera namely Pelea the grey rhebuck, Redunca the reed bucks and Kobus with the genera


•    Kobus kob the kob of central and West Africa
•    K. leche the lechwe of southern-central Africa
•    K. megaceros the Nile lechwe of Sudan
•    K. vardonii the puku of southern-central Africa
•    K. ellipsiprymnus the Common or Ellipsen waterbuck of eastern and southern Africa with a diploid chromosome number of 2n = 50-52
•    K.e. ellipsiprymnus the Southern waterbuck
•    K.e. kondensis the Tanzanian waterbuck
•    K.e. thikae the Eastern waterbuck
•    K.e. pallidus the Somalian waterbuck
•    K. defassa the Defassa waterbuck of central and West Africa with a diploid chromosome number of 2n = 53-54
•    K.d. defassa the Typical Defassa waterbuck of the Nile Basin
•    K.d. ugandae the Ugandan Defassa waterbuck
•    K.d. crawshayi Crawshy’s Defassa waterbuck of Zambia
•    K.d. penricei the Angolan Defassa waterbuck
•    K.d. unctuosus the Sing-sing Defassa waterbuck of the Sahel

Description

The two species K. ellipsiprymnus and K. defassa are similar in build with a strong bone structure and a skin covered with long greyish-brown hair 4-7 cm in length.  The marking on the rump, the eyebrows, the line around the muzzle and the patch on the throat are white.  The white marking on the rump of the Defassa waterbuck is a solid patch while the other waterbuck have a distinctive, 4 cm thick white ring.  The colour of the pelage varies between locations and sub-species.  The Typical Defassa waterbuck is a rich reddish brown, the Ugandan Defassa a pale grey with short hair, Crawshy’s Defassa a dark grey, the Angolan Defassa a blackish-brown with red speckles and the Sing-sing Defassa has a light sandy-brown back with dark brown flanks and a white underside.  The Ellipsen waterbuck sub-species are greyish-brown.

Adult bulls are 20-25% heavier than adult cows.  Old bulls tend to become smelly as a result of the secretions of the subcutaneous oil glands. With a light breeze, experienced hunters claim they can smell them up to 500 m away.

Trophy

Horns are only carried by bulls, reach an adult length of 60-80 cm and are v-shaped and curve forward.  They have 18-38 prominent grooves across 60-70% of the length and smooth tips.  Rudimentary horn growths are sometimes found in cows.  The best trophy quality is generally found in outcast, post-mature, solitary bulls aged over ten years.  Horn buds appear at four months and the mature length is reached after five years.  The Rowland Ward minimal trophy standard is reached at an age of seven years. 

Waterbuck

Photo: Doug Lee

Habitat requirement

Waterbuck are mostly found in grassy savannah plains with open woodland or scattered bush clumps and are always within 1.8 km of the nearest permanent drinking water.  The Defassa waterbuck inhabits denser bush and savannah forests and is generally limited to areas with an annual rainfall of at least 750 mm, while the Ellipsen waterbuck inhabit drier regimes with a rainfall as little as 300 mm.  Both species occur from sea level to altitudes of 2 100 m.

Floodplains, riverine areas and marshes with scattered trees and shrubs generally provide an optimum habitat, as are broken bushveld thickets with a dense leaf canopy providing an abundance of shade, and a humid herbaceous stratum such as that of the Eastern Cape Valley Bushveld.  Ample shade for protection against the midday sun is essential but closed thickets with little space for movement are usually avoided.  Waterbuck are frequently encountered climbing small hills and ridges and the foothills of mountains near permanent water sources.  The grass layer must be dense, medium to tall (8-65 cm) sweet or mixedveld.  Overgrazed veld or veld with a plant structure that has been changed by other large animals is not suitable.  There are reports of waterbuck leaving habitats due to increased nyala competition.

Distribution

Waterbuck maps

Behaviour

Waterbuck are generally peaceful but can become highly aggressive when wounded, captured or under social stress when they do not hesitate to defend themselves.  When potential danger is detected they frequently retreat into water and submerge with only the nostrils above the surface.  Waterbuck are good swimmers and are capable of crossing flooded rivers.  They are known to swim to islands in lakes in order to graze.

They are mostly active in daylight during the early morning and late afternoon and move an average of 0.5-1km per day.  During the hot midday hours they rest by standing or lying in the shade of trees.

Comparison to man

Comparison to man

Feeding & Nutrition

Waterbuck are ruminants feeding almost exclusively on grass and forbs.  They consume both soft and roughage material of medium to tall grasses and are thus classed as semi-bulk feeders.  However, they prefer sweet grass species.  More roughage material is consumed during the dry winter months resulting in a decline of their condition, especially if animal densities are high.

The diet generally consists of 70-92% grass, 2-5% browse and a balance of forbs, herbs and fallen fruit.  Important grasses include Panicum maximum, Heteropogon contortis, Digitaria eriantha, Andropogon amplectens and Themeda triandra.  Reeds and water-grasses also form an important part of the diet.  In marginal habitats, feeding stress often causes high mortalities of young <1 year old.  Waterbuck tend to search for new habitats when there is insufficient fodder.  These movements cannot be regarded as migrations as they are isolated occurrences.

Waterbuck are highly dependent on water and drink two or more times a day, consuming an average of nine litres.  Most other antelope species drink once every 1-3 days.

Social structure

Waterbuck are semi-gregarious with small groups of 4-30 individuals.  The social structure consists of
 
•    mixed families of adult cows and calves with or without a dominant territorial bull
•    bachelor groups of sub-adult males aged between seven months and five years
•    groups of heifers aged 1–3 years
•    solitary, territorial bulls aged 6-10 years
•    solitary, nomadic post-mature bulls of >9 years

Group sizes vary with population density and season.  In moist summer periods herds tend to be larger, but split into smaller groups during the drier winter months when high quality fodder becomes scarce.  Family bonding does not exist and group members frequently intermix when groups share communal drinking holes.  On reaching social maturity at 2.5-3 years, heifers leave their group and either join an existing family herd or establish a new herd.  Most male calves are driven away from the family by the bull soon after weaning and the majority of heifers are driven away by their mothers 2-3 months after weaning. Males then join a bachelor herd and females the heifer group.  The bachelor groups have a distinct social hierarchy based on size and strength, and conflict is frequent.  They are allowed to cross territories as long as the bachelors do not attempt to associate with the family groups.  The bulls become territorial at an age of 6-7 years.

Waterbuck family

Photo: Deon Furstenburg

Management

Waterbuck population densities in Uganda vary from 0.15-17.8/km².  Other recorded densities from aerial surveys are >10.0/km² in Lake Nakuru National Park, 0.05-0.15/km² in areas where the species is reasonably common and 0.2-0.9/km² in remote areas.  Additional ground surveys show density estimates of 0.4-1.5/km².  An advisable maximum stocking density in an optimal habitat is 12.5 ha/waterbuck or 80 waterbuck /1 000 ha or 8/km².

Calf mortality is exceptionally high due to predation by lion, leopard, hyena and Cape hunting dog.  The incidence of bull death due to territorial fighting is also high and the ratio of adult bulls must be well controlled at one bull per 6-8 cows, or a total population structure of one male to 3-4 females across all ages.

The meat of young waterbuck can be used for human consumption if the carcass is skinned immediately after shooting.  It should not be handled or transported without skinning as the oil glands may taint the meat.

Information table

Waterbuck information table

Characteristic

Bull

Cow

Adult body weight 

kg

220 - 270 

150 - 200 

Adult shoulder height 

cm

130 - 150 

100 - 125 

Expected longevity

years

18

16

Age of sexual maturity 

months

14 

13 

Age of social adulthood (1st mating) 

years

5 - 6 

2,5 

Age of post maturity

years

10

13

Gestation           

months

 

8,5 

1st lamb/calf born at

years

 

3,3

Lambing/calving interval             

months

 

14  - 16 

Rutting season 

Throughout the year

Lambing/calving           

 

Year round

Weaning age

months

7

Gender ratio:  Natural (all ages)

1

1,5 – 1,8

Gender ratio:  Production (all ages)

1

3 – 4

Mating ratio:  Natural (adults)

1

3 – 4

Mating ratio:  Production (adults)

1

6 – 8

Calf birth ratio

1

1

Re-establishment: Absolute minimum number needed

3

2

Re-establishment: Smallest viable population size

3

5

Spatial behaviour: Home range

ha

150 - 750

250 - 750

Spatial behaviour: Territory range

ha

40 - 150

None

Large stock grazing unit (adult): 

Dietary ratio (grass):

LSU

0,55 per animal

(84% of diet)

0,45 per animal

(84% of diet)

Browsing unit  (adult):

Dietary ratio (browse):

BU

1,33 per animal

(16% of diet)

1,29 per animal

(16% of diet)

Maximum stocking load

80 waterbuck per 1 000 ha  (at 350 – 500 mm rain)

Minimum habitat size required

ha

300

Annual population growth

15  - 35% (mean 28%)

Optimal annual rainfall

350–500 mm

Optimal vegetation structure:

Grass height

Woody canopy cover

 

12–45 cm

25–45%

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. Furstenburg, D, 1970-2008. Personal field notes (unpublished).
  2. Furstenburg, D, 2005. Waterbok. Wild & Jag 11(3).
  3.  Herbert, HJ, 1972. The population dynamics of the waterbuck in the Sabi Sand Wildtuin. Mammalia Depicta. Hamburg: Paul Parey.
  4. Hirst, SM, 1975, Ungulate-habitat relationships in a South African woodland savannah ecosystem. Wild Monogr. 44:60.
  5. IEA (Institute of Applied Ecology), 1998. Kobus ellipsiprymnus. In: African Mammals Databank - A Databank for the Conservation and Management of the African Mammals Vol 1 & 2. European Commission Directorate, Bruxelles`
  6. IUCN, 2009. IUCN Red list of Threatened Species, Version 2009.1, Gland, Switzerland
  7. Kat, P, 1993. Genetic analyses of East African bovids: a preliminary report. Gnusletter 12(3):7-10.
  8. Kingdon, J, 1997. The Kingdon Field Guide to African Mammals. Princeton University Press, Princeton.
  9. Kingdon, J, 1982. East African Mammals, Vol. IIID, Bovids:  An atlas of evolution in Africa. Academic Press, London.
  10. Kingswood, SC, Kumamoto, AT, Charter, SJ, Aman, RA & Ryder, OA, 1998. Centric fusion polymorphisms in waterbuck. J. Hered. 89:96-100.
  11. Melton, DA, 1978. Ecology of waterbuck in the Umfolozi Game Reserve. D.Sc. thesis, University of Pretoria.Melton, DA, 1983. Population dynamics of waterbuck in the Umfolozi Game Reserve. Afr. J. Ecol. 21:77-91.
  12. Nowak, R, 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.
  14. Skinner, JD & Chimba CT, 2005. The Mammals of the Southern African Subregion, 3rd edn. Cambridge University Press.
  15. Smithers, RHN, 1983. The Mammals of the Southern African Subregion, 1st edn. University of Pretoria, CTP Book Printers, Cape Town.
  16. Spinage, CA, 1968. The life of the waterbuck. Animals 11:257-261.
  17.  Spinage, CA, 1969. Territoriality and social organization of the Uganda defassa waterbuck. J. Zool., Lond. 159:329-361.
  18. Tomlinson, DNS, 1978. The daily activity and behaviour patterns of waterbuck in relation to its seasonal utilization of feeding habitats in the 1. Lake McIlwaine Game Enclosure. M.Sc. thesis, University of Rhodesia.
  19. Ungulates of the World, 2008. http://www.ultimateungulate.com 
  20. Ward, R, 2006. Rowland Ward’s Records of Big Game, 27th edn. Rowland Ward Publications.
  21. Wikipedia Encyclopedia, 2008. Kobus ellipsiprymnus. http://en.wikipedia.org
  22. Wilson, DE & Reeder, DM, 1993. Mammal Species of the World: A Taxonomic and Geographic Reference. 2nd edn. Smithsonian Institution Press, Washington.
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