Sesse Islands Sitatunga

Found exclusively in the northwestern part of Lake Victoria in Uganda on Bugalla, Bubembe, Fumve and Nkosi Islands, which make up the Sesse Islands.

This animal has been somewhat controversial in that it is thought to be indistinguishable from the East African variety (Tragelaphus spekei spekei), which live all around them.

The main distinguishing factor for this subspecies appears to be that the Sesse Islands Sitatunga is smaller, with shorter horns and much shorter, stronger hoofs. This species have not been studied much and very little information on it is available.

Habitat

The sitatunga is semi aquatic, and so specialized that it occurs only in swamps or permanent marshes. Partial to papyrus and phragmites within swamps, it may also occur in wetlands dominated by bullrushes, reeds, and sedges. They frequent the deepest parts of the swamp. (Estes, 1991; Nowak, 1991)

Physical Description

The Sitatunga, a swamp-dwelling antelope, exhibits great elongation of the hooves, which have a wide splay and naked pad like pattern. They possess unique flexibility of the joints at the feet, representing structural adaptations for walking on boggy and marshy ground.

Coloration varies geographically and individually. Males are gray-brown to chocolate-brown, females are brown to bright chestnut, and calves are bright rufous-red, woolly coated, spotted, and striped. Adults are long coated and have characteristic whiteish marks on the face, ears, cheeks, body, legs, and feet.

Males are considerably larger than females (100 cm tall vs. 75-90 cm tall). Males possess horns ranging in length from 508-924 mm. Horns are characterized by two twists and are ivory tipped. (Estes, 1991; Nowak, 1991)

Behaviour

Social organization: Sitatunga are semi-social, non territorial, and sedentary. Swamps are highly productive ecosystems and sitatunga's can live at densities of 55/km^(2) or higher. Females tend to form herds and males associate together or with females until sub adult. As adults, males avoid one another.

Activity: Sitatunga's move through the swamp along established pathways. These have numerous side branches leading to feeding grounds and neighbouring riverine forest. They are active both diurnally and nocturnally and may move into marshy land at night. They typically feed at any hour in areas where they are protected. They also lie on platforms of vegetation that each animal prepares for itself by repeated circling and trampling. They also stand and ruminate in the water.

Locomotion: Sitatunga's are slow and clumsy land runners, but their plunging run works well in water. Their broad and splayed hooves keep them from sinking in soft ground as deeply as other ungulates. They are usually slow and inconspicuous, and are good swimmers.

Vocal communication: Males often bark at night, sometimes as an alarm signal, or perhaps as a way of announcing their location. Females have a single higher-pitched bark. A male following a female in a low stretch may utter a suppressed roar. (Estes, 1991)

Food Habits

Alchornea cordifolia, common around Lake Victoria, provides a favourite browse for sitatunga. Foraging takes place in both dry land and swamp. Sitatunga select plants in the flowering stage. They often emerge at night from swamplands to graze on nearby dry land, as well as in adjacent forests where they browse on foliage and creepers. Feeding activity is apt to be concentrated in a small area of swamp for many days at a time, then they suddenly shift to new grounds. Sitatunga feed while immersed up to their shoulders and move slowly through the vegetation. Sometimes forelegs may be immersed while hind legs are elevated. They may rear to reach flowers of tall reeds, sedges, grasses and foliage, and males have been known to break branches with their horns. When feeding on long leaves, a sitatunga wraps its tongue around a clump, pulls it into its mouth, and crops it with its incisors. (Estes, 1991; Kingdon, 1974)

Other Comments

The sitatunga and bushbuck are close enough genetically to produce viable hybrids in captivity, and almost indistinguishable from the nyala except for pelage and hooves. (Estes, 1991)

Sitatunga is a common host animal for the parasite Schistosoma, a blood fluke found in mesentery blood vessels. (Delany, 1979)

When being pursued, sitatunga's may avoid detection by submerging in swamps until only their nostrils and eyes remain above water. (Estes, 1991)