Tragelaphus spekii, Speke, 1863

Don E. Wilson & Russell A. Mittermeier, 2011, Bovidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 444-779 : 605

26.

Lake Victoria Sitatunga

Tragelaphus spekii

French: Sitatunga de Speke / German: Ostafrika-Sitatunga / Spanish: Sitatunga del Lago Victoria

Other common names: East African Sitatunga, Marsh Buck

Taxonomy. Tragelaphus spekii Speke, 1863 ,

Karagwe, E of Lake Victoria, Tanzania.

The diploid number of the sitatunga group (30 for males and females) is lower than any of the other species in the tribe Tragelaphini . Given the sitatunga group’s dependence on discrete and often widely intermittent wetland habitats throughout a large geographical area in South and Central Africa from Gambia to Kenya, it is not surprising that these animals have differentiated into five distinct taxa. Many subspecies of T. spekii have been described, but most commonly five are recognized. Because of disparate skull, horn, and pelage coloring and patterning, spekii , sylvestris , larkenii, gratus , and selousi have been elevated to individual species here and below. This new separation of T. spekii into five species, each with its own nomenclatural history, makes demarcation of current ranges difficult. Now considered monotypic.

Distribution. Discontinuous and limited to wetland environments in SE Sudan, perhaps the Rift Valley of Ethiopia, W Kenya surrounding Lake Victoria (two locations, very rare), Uganda, Burundi, Rwanda, NW Tanzania, and NE DR Congo. Maps and distributional information here are provisional pending future research.

Descriptive notes. Head-body 151-170 cm (males) and 135-144 cm (females), tail 20-26 cm, shoulder height 88-125 cm (males) and 75-90 cm (females); weight 75— 125 kg (males) and 50-57 kg (females). Only head-body lengths are specific to the Lake Victoria Sitatunga; the other measurements are general for the sitatunga group and should be considered provisional until further information is available. Sitatungas are among the most sexually dimorphic tragelaphines, with males weighing as much as 170% of the weight of females. Unique to the sitatunga group, the hooves of all but the Nkosi Island Sitatunga (7. sylvestris ) are very elongated, with flexible toe joints and large false hooves that help prevent them from sinking into the mud and vegetation mats in their preferred swampy habitats but make them clumsy on dryland. Their pelage tends to be shaggy, oily, and water-repellent, and males develop a scraggly mane as they age. The coat of the Lake Victoria Sitatunga is said to be silky. White stripes and other spotting on the body, typical of many tragelaphines, are slight or lacking in both sexes of the Lake Victoria Sitatunga. Male and females are dissimilar in color. Males are medium gray-brown, and females are dull reddish-brown. Males have a prominent preorbital chevron and occasionally cheek spots, but females have no or faint preorbital markings. The dark dorsal crest of males only rarely has white on it. Females may have rump spots or flank spots, but they are generally faint. Young are a uniform yellow-brown or dull reddish-brown, with faint or no white marks; however, preorbital spots may be distinct in young females. The young are red on the head, but the neck is paler. Relative to other sitatungas, the skull of Lake Victoria Sitatunga is relatively small and the horns are long. Male-only keeled horns are spiraled 1-5 times and average about 55 cm in length, with maximum lengths of 81-90 cm on fully mature males. Dental formulais10/3,C0/1,P 3/3, M 3/3 (x2) = 32.

Habitat. Sitatungas as a group, except the Nkosi Island Sitatunga, are described as semi-aquatic, limiting most of their activities to swamps, bogs, and marshes associated with rivers, streams, lakes, and lowland forests of poor drainage that are scattered intermittently throughout their range. They are excellent swimmers, will avoid danger by escaping into deep water, and are capable of submerging their entire body with little more than their nostrils above the surface. In the Rushebeya-Kanyabaha wetland complex in south-western Uganda, 49% of the observations of Lake Victoria Sitatunga were made in wetland habitats, but it was clear that they made use of adjacent nonwetland areas (23% of observations were in lightly open sedge/papyrus clearings). Open grasslands and, interestingly, very marshy and boggy areas were least preferred.

Food and Feeding. Dietary assessments of all sitatunga species are difficult to make from direct feeding observations, which underrepresent forage obtained in forested areas that are used primarily at night and those obtained while they are concealed in swampy areas. Lake Victoria Sitatungas often feed immersed up to their backs in water and will stand on their hindlegs to reach preferred forage. In the Ituri Rainforest, DR Congo, isotopic analyses of plants and teeth of the Lake Victoria Sitatunga suggest a diet of plants primarily occurring in forest gaps and clearings. About 82% of feeding observations of Lake Victoria Sitatungas in the Kipsain-Saiwa Swamp in western Kenya found them eating only four plant species: Typha domingensis (37%), Hydrocotyle ranunculoides (20%), Pycreus lanceus (14%) and Oenanthe palustris (11%). In the Rushebeya-Kanyabaha wetland complex in south-western Uganda, 40 plant species were eaten by Lake Victoria Sitatunga, and 60% of their diet was made up of leaves, mostly from sedges (14%, Cyperus latifolius and 10%, C. papyrus), grasses (5%, Digitaria scalarum), vines (7%, Rubus pinnatus), and various herbaceousspecies, including cultivated sweet potato (7%, Ipomoea batatas). Depredation of the sweet potato plants, particularly when they were young and tender, by the Lake Victoria Sitatunga was significant enough in fields adjacent to the wetland complex they used that farmers changed to planting of unpalatable crops such as sugarcane and pumpkins. Other crops that Lake Victoria Sitatungas damaged included Irish potato, maize, and cabbage. Distance from the wetland complex to cultivated fields played a role in levels of depredation; 90% ofall observations of Lake Victoria Sitatungas were within 100 m of the wetland’s edge. New growth of plants after fires is attractive to Lake Victoria Sitatunga.

Breeding. In most locations, breeding behavior and births take place throughout the year. Breeding behavior of captive sitatungas in the Audubon Zoo, New Orleans, USA, presumed to be Lake Victoria Sitatungas, follows a pattern typical of the tragelaphine group. Males frequently horn the ground and vegetation and spar with other males with locked horns while pushing and twisting; this behavior did not seem to be serious fighting but rather “play-fighting,” perhaps to establish dominance. Males investigated the anogenital region of females daily, typically approaching in a low-stretch posture with neck extended and then sniffing and licking the females. If the female urinated, the male displayed the lip-curl response. Estrus lasted three days, during which a male was in constant contact with the female. Anogential investigations by the male became very vigorous, to the point oflifting her hindquarters off the ground. The male rested his chin on the female’s hindquarters, and if she did not move away, he mounted. Copulation was brief but sometimes took several attempts to be successful. In the wild, the courtship ritual has not been observed very often but appears to be comparable to captive observations. In the Kipsain-Saiwa Swamp in western Kenya, one male repeatedly approached a female’s hindquarters with his head lowered and held forward, his horns lying along his back. He smelled her genital region and rubbed the side of his head against her flank. After 20 minutes of repeated approaches, the female let the male mount. Sometimes, as a courting male slowly and deliberately approaches a female, instead of slowly walking away, she will bound off erratically, stand still for a minute, and then dash off again. The male just continues his slow, deliberate following of such a female. Gestation is 7-5-8 months in captivity, with a birth interval of 11-6 months, indicating that captive females typically conceive about four months after giving birth. In captivity, twinning is very rare, only 0-18% of births. Females give birth on dry reed platforms that they create by trampling the vegetation, and they keep their neonates well concealed until the young can move through the dense swamp vegetation. Females groom their offspring often, and the pair remain very close to each other for several months; young may remain with their mothers even after the next offspring is born.

Activity patterns. In the Rushebeya-Kanyabaha wetland complex in south-western Uganda, Lake Victoria Sitatunga were in cover resting/ ruminating from about 10:00 h to 17:00 h, and they were most visible and active between 05:30 h and 09:00 h and after 18:00 h. In Akagera National Park, Rwanda, Lake Victoria Sitatunga were most active in the morning from 07:00 h to 10:00 h, and secondarily from 17:00 h to 18:00 h, making detection of individuals during systematic surveys very difficult from 10:00 h to 17:00 h. The same basic activity pattern was noted in the Kipsain-Saiwa Swamp in western Kenya.

Movements, Home range and Social organization. Systematic surveys of the Lake Victoria Sitatunga have been conducted in Akagera National Park, Rwanda; investigators concluded there were 9000 individuals in 600 km?, or a density of 15 ind/km?®. In Saiwa Swamp National Park in western Kenya, densities were about 55 ind/km* in the early 1970s. As a group, sitatunga are not very gregarious, and adults tend to occur alone except during breeding. Group sizes in Kenya were 45-9% single individual, 34-8% two individuals, 10-6% three individuals, 5% four individuals, and 1-7-0-3% five to nine individuals. The population structure there, based on 648 observations, was dominated by females: 50-5% adult females, 15-3% immature females, 13-1% adult males, 17-9% immature males, and only 3-2% young-of-the-year (but they were likely underrepresented because of difficulties observing them). When disturbed, male Lake Victoria Sitatungas often bark to each other, mostly at night; femalesare typically quiet but will emit low-pitched squeaks to each other while feeding. The Lake Victoria Sitatunga can live up to 20 years in captivity, and perhaps only about twelve years in the wild.

Status and Conservation. Classified as Least Concern on The IUCN Red List (under T. spekii ), which does not differentiate the five species identified here. Numbers of Sitatunga are generally stable in areas of low human population density and decreasing elsewhere. As many as 170,000 sitatungas may occur discontinuously throughout the group’s range in Africa, with about 40% living in protected areas. That number, however,is considered an overestimate, and local populations are threatened by loss of habitat, altered hydrology oftheir critical wetland habitats,livestock grazing and likely associated disease transmission, uncontrolled burning of swampland, and overharvest for subsistence and the bushmeat trade. Subsistence hunting associated with roadside agriculture in the Ituri Rainforest region of the DR Congo negatively impacts the Lake Victoria Sitatunga. In contrast, appropriately managed trophy hunting can have a positive effect by generating revenue for conservation initiatives. Major populations of the Lake Victoria Sitatunga still exist in south-eastern Akagera National Park, Rwanda, and Moyowosi-Kigosi Game Reserves, Tanzania, but the species is very rare in western Kenya and confined to swamps along Lake Victoria and the 2 km ® Saiwa Swamp National Park (which had fewer than 50 individuals in 1998). Reintroductions have been attempted in central Kenya, but their success has not been reported. Minimizing loss of wetland habitats and,critically, their interconnectedness, which minimizes isolation and permits dispersal and gene flow,is fundamental to the long-term conservation of all sitatungas, including the Lake Victoria Sitatunga.

Bibliography. Ansell (1972), Beudels-Jamar et al. (1997), Bro-Jorgensen (2008), Caro et al. (1998), Cerling et al. (2004), Cotton (1935), Densmore (1980), East (1999), Estes (1991a, 1991b), Groves & Grubb (2011), Huffman (2004q), IUCN/SSC Antelope Specialist Group (2008bi), Kingdon (1982, 1997), Lydekker & Blaine (1914), Meinertzhagen (1916), Nowak (1999), Owen (1970), Popp (1982), Rubes etal. (2008), Speke (1863), Tweheyo et al. (2010), Wallace (1978), Walther (1977, 1990a), Weigl (2005), Wilkie (1989).

Figures

On following pages: 27. Nkosi Island Sitatunga (Tragelaphus sylvestris); 28. Nile Sitatunga (Tragelaphus larkenii); 29. Western Sitatunga (Tragelaphus gratus); 30. Zambezi Sitatunga (Tragelaphus selous); 31. Bongo (Tragelaphus eurycerus);, 32. Gedemsa (Tragelaphus buxtoni).

Distribution. Discontinuous and limited to wetland environments in SE Sudan , perhaps the Rift Valley of Ethiopia , W Kenya surrounding Lake Victoria (two locations, very rare), Uganda , Burundi , Rwanda , NW Tanzania , and NE DR Congo . Maps and distributional information here are provisional pending future research.