Sitatunga

The sitatunga or marshbuck (''Tragelaphus spekii'') is a swamp-dwelling antelope found throughout central Africa, centering on the Democratic Republic of the Congo, the Republic of the Congo, Cameroon, parts of Southern Sudan, Equatorial Guinea, Burundi, Ghana, Botswana, Rwanda, Zambia, Gabon, the Central African Republic, Tanzania, Uganda and Kenya.
The sitatunga is confined to swampy and marshy habitats. Here they occur in tall and dense vegetation as well as seasonal swamps, marshy clearings in forests, riparian thickets and mangrove swamps.

Taxonomy and genetics

The scientific name of the sitatunga is ''Tragelaphus spekii''. The species was first described by the English explorer John Hanning Speke in 1863. 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). The scientific name has often been misstated as ''T. spekei'', and either Speke or Sclater is referred to as the binomial authority.

Speke had stated in a footnote in his book that the species had been named ''Tragelaphus spekii'' by English zoologist Philip Sclater. However, according to the International Code of Zoological Nomenclature (Article 50.1.1) and the International Commission on Zoological Nomenclature, that acknowledge the person who first described the species, simply declaring Sclater as the authority in a footnote is insufficient to recognise him as the author. Hence, Speke was recognised as the correct authority and ''T. spekii'' (where ''spekii'' is the genitive of the Latinised "Spekius") was considered the correct name for the species.

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 (''T. eurycerus'') form a monophyletic clade with the mountain nyala (''T. buxtoni'') and bushbuck (''T. scriptus''). The greater kudu (''T. strepsiceros'') split from this clade approximately 8.6 million years ago.

Within ''Tragelaphus'', the bushbuck, bongo, sitatunga and nyala (''T. angasii'') are particularly close relatives. The bushbuck and sitatunga are genetically similar enough to hybridise. Hybrids between bongo and sitatunga have proved to be fertile. The sitatunga is more variable in its general characters than any other member of the tribe Strepsicerotini, that consists of the genera '' Taurotragus'' (elands) and ''Tragelaphus'', probably because of their confinement to swampy and marshy habitats.

On the basis of physical characteristics such as hair texture, coat colour and the coat stripes, up to ten subspecies of the sitatunga have been described. However, these factors may not be reliable since hair texture could vary with the climate, while pelage colour and markings vary greatly among individuals. Moreover, the coat might darken and the stripes and spots on it might fade with age, especially in males. The species might even be monotypic, however, based on different drainage systems, three distinct subspecies are currently recognised:
* ''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

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 in males and in females. Males reach approximately at the shoulder, while females reach . Males typically weigh , while females weigh . The tail is long. The saucer-shaped ears are long. Only the males possess horns; these are spiral in shape, have one or two twists and are long. The sitatunga is almost indistinguishable from the nyala, except in pelage and spoor. Speke pointed out that, though "closely allied" to the waterbuck, the sitatunga lacks stripes and is spotted instead.

The coat colour varies geographically, but, in general, is a rufous red in juveniles and chestnut in females. 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. A pair of inguinal scent glands are present. 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. There is a chevron between the eyes of the males.

The body and legs of this antelope are specially adapted to its swampy habitat. The hooves of the male are elongated and widely splayed. The rubbery, shaggy, water-repellent coat is minimally affected by slimy and muddy vegetation. The wedge-like shape and lowering of the head, coupled with the backward bend of the horns (in males) provides for easy navigation through dense vegetation. The pasterns are flexible, and the hooves, banana-like in shape, can reach a length of up to in the hindlegs and in the forelegs. The pointed toes allow it to walk slowly and almost noiselessly through the water. Moreover, the colour of the coat provides an excellent camouflage. Hearing is acute, and the ears are so structured that the animal can accurately determine the direction from where a sound has originated. This adaptation is of profound use in habitats where long sight is of very little value due to the density and darkness of the environment.

Ecology and behaviour

Sitatunga are active mainly during the early hours after dawn, the last one or two hours before dusk, and at night, and spend a large part of this time feeding. Basically sedentary, they rest in flat areas and reed beds, especially during the hotter part of the day. They seldom leave their swamp habitat during the daytime. Though sitatunga commonly form pairs or remain solitary, larger groups have also been observed. A study in Kenya recorded a herd of as many as nine individuals, comprising an adult male, four females and four juveniles. Loose groups may be formed but interaction among individuals is very low. Individuals generally associate only with their own sex.

The sitatunga is not territorial. Males may engage in locking horns with other males and attacking vegetation using their horns. 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 may stand motionless, with the head held high and one leg raised. Sitatunga may occasionally emit a series of coughs or barks, usually at night, which may cause other animals to join in, and these sounds can be heard across the swamp. This barking may be used by females to warn 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 by bleats.

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 fully submerge themselves in the water except for the nose and the eyes, which they keep slightly above the water surface. Due to its close association with water, the sitatunga are often described as " aquatic antelopes", like the waterbuck. They often dry themselves under the sun after feeding in water. Predators of the sitatunga include lions, wild dogs, crocodiles and leopards.

Diet

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

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