Sitatunga

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Sitatunga
Sitatunga at Oji Zoo.JPG
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Bovidae
Subfamily: Bovinae
Genus: Tragelaphus
Species: T. spekii
Binomial name
Tragelaphus spekii
(Sclater, 1863)
Synonyms[2]
  • T. albonotatus (Neumann, 1905)
  • T. baumii (Sokolowsky, 1903)
  • T. inornatus (Cabrera, 1918)
  • T. larkenii (St Leger, 1931)
  • T. speckei (Neumann, 1900)
  • T. typicus (R. Ward, 1910)
  • T. ugallae (Matschie, 1913)
  • T. wilhelmi (Lönnberg and Gyldenstolpe, 1924)

The sitatunga or marshbuck (Tragelaphus spekii) is a swamp-dwelling antelope found throughout central Africa, centering on the Democratic Republic of the Congo, Cameroon, parts of Southern Sudan, Ghana, Botswana, Zambia, Gabon, Tanzania, Uganda and Kenya. The species was first described by the English explorer John Hanning Speke in 1863. The sitatunga is a medium-sized antelope. Males reach approximately 81–116 cm (32–46 in) at the shoulder, while females reach 72–90 cm (28–35 in). Males typically weigh 76–119 kg (168–262 lb), while females weigh 24–57 kg (53–126 lb). The sitatunga has a shaggy, water-resistant coat. The body of this antelope is specially adapted to its swampy habitat. Only the males possess horns. The spiral horns have one or two twists, and are 45–92 cm (18–36 in) long.

Sitatunga are active mainly during the early hours after dawn, the last one or two hours before dusk, and night. They are not territorial. Sitatunga are selective and mixed feeders. They feed mainly on new foliage, fresh grasses, aquatic plants, sedges and browse. Females are sexually mature by one year of age, while males take one and a half years to mature. Breeding occurs throughout the year. Gestation lasts for nearly eight months, after which generally a single calf is born. Parturition occurs throughout the year, though a peak may occur in the dry season. Average lifespan recorded in captivity is 22 to 23 years.

The sitatunga is confined to swampy and marshy habitats. Here they occur in tall and dense vegetation of perennial as well as seasonal swamps, marshy clearings in forests, riparian thickets and mangrove swamps. Habitat loss is the most severe threat to the survival of the sitatunga. The species has been classified under the Least Concern category by the International Union for Conservation of Nature and Natural Resources (IUCN), and under Appendix III (Ghana) of the Washington Convention (CITES). Though the population is sporadic in some countries, the animal is common in many areas such as the Okavango Delta and Bangweulu Swamp.

Taxonomy and genetics[edit]









Giant eland



Common eland





Greater kudu




Mountain nyala






Bongo



Sitatunga




Kéwel











Nyala




Lesser kudu



Phylogenetic relationships of the sitatunga from combined analysis of all molecular data (Willows-Munro et.al. 2005)

The scientific name of the sitatunga is Tragelaphus spekii. The species was first described by the English explorer John Hanning Speke in 1863.[2][3] Speke first observed the sitatunga at a lake named "Little Windermere" (now Lake Lwelo, located in Kagera, Tanzania). In his book Journal of the Discovery of the Source of the Nile, Speke called the animal "nzoé" (Kiswahili name for the animal) or "water-boc" (due to its resemblance to the waterbuck), and added in a footnote that the species had been named Tragelaphus spekii by English zoologist Philip Sclater.[4] The scientific name has often been given differently as T. spekii or T. spekei, and the authority for the same has also been confused between Speke and Sclater. However, according to Article 50.1.1 of the International Code of Zoological Nomenclature and International Commission on Zoological Nomenclature, that acknowledges the person who first described the species, this is insufficient to state Sclater as the author.[2] Hence, Speke was recognised as the correct authority and T. spekii (where spekii is the genitive of the Latinised "Spekius") was considered as the correct name for the species.[5]

The sitatunga is placed under the genus Tragelaphus and in the family Bovidae. In 2005, Sandi Willows-Munro of the University of KwaZulu-Natal (Durban) carried out a mitochondrial analysis of the nine Tragelaphus species. mtDNA and nDNA data were compared. The results showed that sitatunga plus bongo form a monophyletic clade with the mountain nyala and kéwel.[6] The greater kudu clade split from the clade formed by sitatunga, bongo, mountain nyala and kéwel approximately 8.6 million years ago.[7][8]

Within Tragelaphus, the kéwel, bongo, sitatunga and nyala are particularly close relatives. The sitatunga and bushbuck are genetically similar enough to hybridise.[9] Hybrids between the bongo and sitatunga have proved to be fertile.[10][11] The sitatunga is more variable in its general characters than any other member of the tribe Strepsicerotini, probably because of their confinement to swampy and marshy habitats.[12]

On the basis of physical characteristics such as hair texture, coat colour and the presence or absence of stripes, as many as ten subspecies of the sitatunga have been described. However, these factors might not be much reliable since hair texture could vary with the climate, while pelage colour and markings vary greatly among individuals. Moreover, the coat might darken with age especially in old males, and the stripes and spots on it might fade with age, particularly in males.[5] The species might even be monotypic,[5] however, based on different drainage systems, at best only three different subspecies are identified:[13][14]

  • T. s. spekii (Speke, 1863): Nile sitatunga or East African sitatunga. Found in the Nile watershed.
  • T. s. gratus (Sclater, 1880): Congo sitatunga or forest sitatunga. Found in western and central Africa.
  • T. s. selousi (W. Rothschild, 1898): Southern sitatunga or Zambezi sitatunga. Found in southern Africa.

Description[edit]

Sitatunga - male and female
Male 
Female 

The sitatunga is a medium-sized antelope. It is sexually dimorphic, with males considerably larger than females. The head-and-body length is typically between 136–177 cm (54–70 in) in males and 104–146 cm (41–57 in) in females. Males reach approximately 81–116 cm (32–46 in) at the shoulder, while females reach 72–90 cm (28–35 in). Males typically weigh 76–119 kg (168–262 lb), while females weigh 24–57 kg (53–126 lb). The tail is 14–37 cm (5.5–14.6 in) long. The saucer-shaped ears are 11–17 cm (4.3–6.7 in) long.[5] The sitatunga is almost indistinguishable from the nyala, except in pelage and spoor.[9] Speke pointed out that, though "closely allied" to the waterbuck, the sitatunga lacks stripes and is spotted instead.[4]

The coat colour varies geographically, but, in general, is a rufous red in juveniles and chestnut in females.[15] The coats of males darken with age, becoming gray to dark brown. Males develop a rough and scraggy mane, usually brown in colour, and a white dorsal stripe.[9] There is a chevron between the eyes of the males.[16] There are white facial markings, as well as several stripes and spots all over, though they are only faintly visible. White patches can be seen on the throat, near the head and the chest.[17]

The body of this antelope is specially adapted to its swampy habitat. The hooves of the male are elongated and widely splayed, serving as another adaptation to the marshy environment.[18] The rubbery, shaggy, water-repellent coat and allows the animal to have an advantage over slimy and muddy vegetation. The wedge-like shape and lowering of the head, coupled with the backward laying of the horns (in males) provides for easy navigation through dense and tangled vegetation. Their pointed toes allow them to walk slowly and almost noiselessly through the water.[19] Moreover, the colour of the coat provides an excellent camouflage. Hearing is acute, and the ears are so structured that the sitatunga is able to pinpoint the direction from where a sound has originated. This adaptation is of profound use in habitats so dense and dark that a long sight is of very little value.[5]

As a prominent sign of sexual dimorphism, only the males possess horns. The spiral horns shown one or two twists, and are 45–92 cm (18–36 in) long.[14] Both horns are tipped with ivory.[15] The pasterns are flexible.[17] The hooves can reach a length of up to 16 cm (6.3 in) in the hindlegs and 18 cm (7.1 in) in the forelegs.[18] A pair of inguinal scent glands are present.[9]

Ecology and behaviour[edit]

Sitatunga submerged in water

Sitatunga are active mainly during the early hours after dawn, the last one or two hours before dusk, and night.[19] A lot of time is spent in feeding.[20] Basically sedentary, they rest in flat areas and reed beds, usually during the hotter part of the day.[21][22] They seldom leave their swamp habitat during the daytime. They mainly form pairs or remain solitary, and many groups contain adult females.[20] Loose groups may be formed but interaction among individuals is very low.[21] Individuals generally associate only with their own sex.[5]

The sitatunga is not territorial. Males may engage in locking horns other males and attacking vegetation using horns.[22] They may perform feinting by raising their forelegs with the hindlegs rooted in the ground as a threat display. Sitatunga interact with each other by first touching their noses, which may be followed by licking each other and nibbling. Alarmed animals might turn motionless, with the head held high up and one leg raised. Sitatunga may occasionally give out a series of coughs or barks, usually at night, which may be joined in by others, and heard across the swamp. This barking may be used by females to ward off other females. Males often utter a low bellow on coming across a female or a herd of females in the mating season. A low-pitched squeak may be uttered while feeding. Mothers communicate with their calves in bleats.[5]

Sitatunga can feed or rest close to southern lechwe herds, but do not interact with them. They often attract yellow-billed oxpeckers, African jacanas and great egrets. Sitatunga are good swimmers but limit themselves to water with profuse vegetation, in order to escape crocodiles. In some cases, for instance when troubled by flies or pursued by predators, the sitatunga might submerge themselves in the water fully except for the nose and the eyes, which they keep slightly above the water surface. They often dry themselves under the sun after feeding in the water.[5] Predators of the sitatunga include lions, wild dogs, crocodiles and leopards.[15]

Diet[edit]

Sitatunga are selective and mixed feeders. They feed mainly on new foliage, fresh grasses, sedges and browse. Preferred plants include: bullrushes (Typha), sedges (Cyperus), aquatic grasses (Vossia, Echinochloa, Pennisetum ,Leersia, Acroceras, Panicum, species in Umbelliferae and Acanthaceae in Saiwa They feed mostly in the wetland fringes. Diet preferences may vary seasonally in swamps where water levels change notably. Like the gerenuk, the sitatunga might stand on its hindlegs to reach higher branches of trees, or even use its horns to lower the branches.

A study recorded forty major species eaten by the animal, majority of which were herbs. Sweet potato was the most preferred crop. The study predicted an increase in preference for crops due to seasonal food variations.[23] Another study showed that annual floods affect the seasonal movement and feeding patterns of the species. These floods force the animals out of the reed beds onto the flooded grasslands when the water levels are high. At low water levels the cattle take over the flooded plains and send the sitatunga back to their original place.[21]

Reproduction[edit]

Juvenile sitatunga in Salzburg Zoo, Austria

Females are sexually mature by one year of age, while males take one-and-a-half-year for the same. Breeding occurs throughout the year. When females gather, the males compete among each other for the right to mate, showing polygyny in males.[24] The rutting male approaches the male in a lower bending posture, sniffing her vulva. The female may move slowly or behave nervously. Even if the female flees, the male continues pursuing her steadily, without showing aany hurry. A receptive female will raise her head with her mouth wide open, following which the male will make mounting attempts. At the time of mounting the female lowers her head, while the male first bends and then straightens his forelegs and rests his head and neck on her back. The two form a "bond" for one or two days, during which the male ensures that no other male can approach the female.[5]

Gestation lasts for nearly eight months, after which generally a single calf is born. Parturition occurs throughout the year, though a peak may occur in the dry season.[5] Calves are hidden very well, and brought out only in the presence of many other sitatunga. The mother gazes intently and nods at the calf to summon it for nursing. A calf follows its mother about, even after she has given birth to another calf. The mother suckles and licks her calf for about six months. The calf takes time to master the specialised gait of the sitatunga, and as a result keeps falling inside the water.[9] Males, and even some females, have been observed to leave their herds even before reaching sexual maturity due to intrasexual competition.[24] Average lifespan recorded in captivity is 22 to 23 years.[15]

Habitat and distribution[edit]

Range of sitatunga

The sitatunga is confined to swampy and marshy habitats. Here they occur in tall and dense vegetation of perennial as well as seasonal swamps, marshy clearings in forests, riparian thickets and mangrove swamps.[24] Sitatunga move along clearly marked tracks in their swampy habitat, often leading to reed beds.[20] These tracks, up to 7 m (23 ft) wide, can lead to feeding grounds and nearby riverine forests.[9] In savannas, they are typically found in stands of papyrus and reeds (Phragmites species and Echinochloa pyramidalis). They share their habitat with the Nile lechwe in the Sudd swamps and with the Southern lechwe in Angola, Botswana and Zambia.[1]

The sitatunga is native to Angola, Benin, Botswana, Burundi, Cameroon, Central African Republic, Chad, The Democratic Republic of the Congo, Equatorial Guinea, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Mozambique, Namibia, Nigeria, Rwanda, Senegal, South Sudan, Tanzania, Uganda, Zambia and Zimbabwe. It is extinct in Niger, where it formerly occurred in the Lake Chad region, and is feared to be extinct in Togo, where its habitat has been taken over by dense human settlements. Though now localised and sporadic in western Africa, the sitatunga remains widespread and common in the forests of central Africa and some swampy regions in central, eastern and southern Africa.[1] [25]

Threats and conservation[edit]

Habitat loss is the most severe threat to the survival of the sitatunga. The increasing loss of wetlands has isolated many populations. The animal is vulnerable to long-term changes in the water level as it alters the vegetation in their habitat. Vast areas of Bangweulu and Busanga (in Kafue National Park) are burnt every year, placing animals like sitatunga at grave risk given the inflammability of swamps.[1] The sitatunga has been classified under the Least Concern category by the International Union for Conservation of Nature and Natural Resources (IUCN),[1] and under Appendix III (Ghana) of the Washington Convention (CITES).[2]

In Senegal intensive hunting for meat and habitat degradation have made the sitatunga very rare. Formerly it was common throughout Gambia, but now it is confined to a few inaccessible swamps; a population has been introduced in the Abuko Nature Reserve. On the other hand, though the animal is hunted by locals primarily for food, Botswana still supports a large portion of the total population. The species is of great economic significance for northern Botswana, that produces some of the world's biggest sitatunga trophies.[1][25] Its status is unclear in Chad, Ghana, Guinea, Burundi and Mozambique and Zimbabwe. Good populations still exist in countries such as Cameroon, Central African Republic, The Democratic Republic of Congo, Equatorial Guinea, Gabon, Tanzania and Zambia.[25] The inaccessibility of its habitat has rendered population estimates very difficult. In 1999, Rod East of the IUCN SSC Antelope Specialist Group estimated a total population of 170,000, but it is likely to be an overestimate. Its numbers are decreasing in areas of heavy human settlement, and are stable elsewhere.[1]

Around 40 percent of the populations (using the overestimate of 170,000) occurs in protected areas, mainly in Okavango Delta and Linyanti and Chobe swamps (Botswana); Dja Faunal Reserve and Lobéké National Park (Cameroon); Bangassou (Central African Republic); Odzala National Park, Lake Télé Community Reserve, Likouala and Salongo (The Democratic Republic of Congo); Monte Alen National Park (Equatorial Guinea) ; Saiwa Swamp National Park (Kenya); Akagera National Park (Rwanda); Moyowosi and Kigosi Game Reserves (Tanzania); Bangweulu and Busanga swamps (Zambia);. However, only a few are well-protected and managed.[1][25]

References[edit]

  1. ^ a b c d e f g h IUCN SSC Antelope Specialist Group (2008). Tragelaphus spekii. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 29 March 2009. Database entry includes a brief justification of why this species is of least concern.
  2. ^ a b c d Wilson, D.E.; Reeder, D.M., eds. (2005). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 699. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  3. ^ Groves, C.; Grubb, P. (2011). Ungulate Taxonomy. Baltimore, Maryland: Johns Hopkins University Press. p. 135. ISBN 1421400936. 
  4. ^ a b Speke, J. H. (1863). Journal of the Discovery of the Source of the Nile. England: William Blackwood and Sons. p. 223. 
  5. ^ a b c d e f g h i j Kingdon, J.; Happold, D.; Butynski, T.; Hoffmann, M.; Happold, M.; Kalina, J. (2013). Mammals of Africa. London: Bloomsbury. pp. 172–8. ISBN 9781408122570. 
  6. ^ Willows-Munro, S.; Robinson, T. J.; Matthee, C. A. (June 2005). "Utility of nuclear DNA intron markers at lower taxonomic levels: Phylogenetic resolution among nine Tragelaphus spp.". Molecular Phylogenetics and Evolution 35 (3): 624–36. doi:10.1016/j.ympev.2005.01.018. 
  7. ^ Ropiquet, A. (2006). "Etude des radiations adaptatives au sein des Antilopinae (Mammalia, Bovidae)". Ph.D. Thesis, Université Paris 6 (1-247). 
  8. ^ Hassanin, A.; Delsuc, F.; Ropiquet, A.; Hammer, C.; Jansen van Vuuren, B.; Matthee, C.; Ruiz-Garcia, M.; Catzeflis, F.; Areskoug, V.; Nguyen, T.T.; Couloux, A. (2012). "Pattern and timing of diversification of Cetartiodactyla (Mammalia, Laurasiatheria), as revealed by a comprehensive analysis of mitochondrial genomes". Comptes Rendus Biologies 335 (1): 32–50. doi:10.1016/j.crvi.2011.11.002. 
  9. ^ a b c d e f Estes, R. D. (2004). The Behavior Guide to African Mammals : Including Hoofed Mammals, Carnivores, Primates (4th ed.). Berkeley: University of California Press. pp. 175–7. ISBN 0520080858. 
  10. ^ Koulischer, L.; Tijskens, J.; Mortelmans, J. (1973). "Chromosome studies of a fertile mammalian hybrid: the offspring of the cross bongo × sitatunga (Bovoidea)". Chromosoma 41 (3): 265–70. doi:10.1007/BF00344021. 
  11. ^ Tijskens, J. (January 1968). "Preliminary notes on the F1 Bongo antelope x sitatunga hybrids Taurotragus eurycerus x Tragelaphus spekei at Antwerp Zoo". International Zoo Yearbook 8 (1): 137–9. doi:10.1111/j.1748-1090.1968.tb00464.x. 
  12. ^ Leakey, L.S.B. (1965). Olduvai Gorge. Cambridge: Cambridge University Press. p. 42. ISBN 052105527X. 
  13. ^ "Tragelaphus spekii ". Integrated Taxonomic Information System. Retrieved 13 March 2014. 
  14. ^ a b Kingdon, J. (2015). The Kingdon Field Guide to African Mammals (2nd ed.). London: Bloomsbury Publishing. pp. 515–6. ISBN 9781472921352. 
  15. ^ a b c d Coash, M. "Sitatunga Tragelaphus spekii". University of Michigan Museum of Zoology. Animal Diversity Web. Retrieved 14 March 2014. 
  16. ^ Vlies, C. V. D. (2010). Southern Africa Wildlife and Adventure. South Africa: Trafford On Demand Publications. p. 145. ISBN 1426919328. 
  17. ^ a b Nowak, R. M. (1999). Walker's Mammals of the World (6th ed.). Baltimore, Maryland: Johns Hopkins University Press. pp. 1136–7. ISBN 0801857899. 
  18. ^ a b Liebenberg, L. (2000). A Photographic Guide to Tracks and Tracking in Southern Africa. Cape Town: Struik. p. 121. ISBN 186872008X. 
  19. ^ a b Williamson, D. T. (December 1986). "Notes on sitatunga in the Linyanti Swamp, Botswana". African Journal of Ecology 24 (4): 293–7. doi:10.1111/j.1365-2028.1986.tb00373.x. 
  20. ^ a b c Owen, R. E. A. (August 1970). "Some observations on the sitatunga in Kenya". African Journal of Ecology 8 (1): 181–95. doi:10.1111/j.1365-2028.1970.tb00839.x. 
  21. ^ a b c Games, I. (January 1983). "Observations on the sitatunga Tragelaphus spekei selousi in the Okavango delta of Botswana". Biological Conservation 27 (2): 157–70. doi:10.1016/0006-3207(83)90086-1. 
  22. ^ a b Starin, E. D. (December 2000). "Notes on sitatunga in The Gambia". African Journal of Ecology 38 (4): 339–42. doi:10.1046/j.1365-2028.2000.00262.x. 
  23. ^ Tweheyo, M.; Amanya, B. K.; Turyahabwe, N. (December 2010). "Feeding patterns of sitatunga (Tragelaphus Spekii) in the Rushebeya-Kanyabaha wetland, south western Uganda". African Journal of Ecology 48 (4): 1045–52. doi:10.1111/j.1365-2028.2010.01210.x. 
  24. ^ a b c Magliocca, F.; Quérouil, S.; Gautier-Hion, A. (February 2002). "Grouping patterns, reproduction, and dispersal in a population of sitatungas". Canadian Journal of Zoology 80 (2): 245–50. doi:10.1139/z01-224. 
  25. ^ a b c d East, R.; IUCN/SSC Antelope Specialist Group (1999). African Antelope Database 1998. Gland, Switzerland: The IUCN Species Survival Commission. pp. 123–6. ISBN 2831704774. 

External links[edit]