Tragelaphus buxtoni (Lydekker, 1910)

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 : 609-610

32.

Gedemsa

Tragelaphus buxtoni

French: Gedemsa / German: Bergnyala / Spanish: Gedemsa

Other common names: Mountain Nyala

Taxonomy. Strepsiceros buxtoni Lydekker, 1910b ,

Bak Province, Ethiopia, east of the Rift Valley.

The Gedemsa is in a clade with the sitatungas ( T. speku , T. sylvestris , T. latkenu , T. gratus , and T. selousi ) and the Bongo ( T. eurycerus ). The male-only horns of the Gedemsa are much more open-spiraled than those ofits sister species, with a very marked and raised anterior keel, making them look superficially like those of a kudu ( Strepsiceros spp.), although there are fewer turns and the spiral is even more open. Body stripes are less obvious than in most other members of the Tragelaphini , except for some bushbuck species. Although it is sometimes called the “Mountain Nyala,” the Gedemsa and the Nyala ( Nyala angasii , but often placed in Tragelaphus ) are only distantly related and quite dissimilar. Monotypic.

Distribution. The Gedemsa is now restricted to five isolated locations in the Bale and Arsi Mt ranges of SC Ethiopia, S and SE of the Rift Valley.

Descriptive notes. Head-body 190-200 cm, tail 20-25 cm, shoulder height 120-135 cm (males) and 90-110 cm (females); weight 180-320 kg (males) and 150-200 kg (females). The weights of males in forested habitats in mountainous Ethiopia are reported to be greater than those of males in alpine/heath habitats. Tragelaphines are typified by their sexual dimorphism, and the weight of male Gedemsa is about 139% that of females. Only the male has horns. Both sexes are narrow-bodied in profile, like other tragelaphines, but the Gedemsa, along with the kudu species, has a relatively level back and longer, nearly equal front and rear legs. The coat color of both sexes at birth varies by location and habitat from a tan reddish-brown to grayish. Females generally retain their basic coloration, although it can become darker and tend toward gray. Males become a more definitive dark gray-brown as they age. Both sexes have a white throat patch, a white crescent on the chest, variable white spots on the cheeks and body in a bow from the hindquarters through the ribcage, 2-9 lateral lines from the back down the torso (most obvious on females, but not as obvious on either sex compared to some other tragelaphines), and white patches on the inner legs. The patterning and intensity of spots and stripes on both sexes is unique to each individual. Both sexes have a white chevron and dorsal mane running the length of the back. They are much more obvious on males but not as developed as in some other tragelaphines. Males have a shaggy mane on their necks. The tail is bushy, dark on top and white underneath. Overall, Gedemsa are darker dorsally, becoming paler ventrally. The coat is smooth and glossy in summer and shaggy when the weather is cooler and damper. The lyrate horns of mature males spiral 1-5-2 times, with variable spread and tightness, are yellowto ivory-tipped, and have distinct keeled ridges. Horns can be seen on young males by the time they are six months old, and the first spiral is complete by four years. The horns thicken as a male ages, and lengths of 85-119 cm are attained at maturity. Male Gedemsa can be aged in general classes based on their horn characteristics. Gedemsa have two inguinal glands and pedal glands near the hind false hooves. Dental formulais10/3,C0/1,P 3/3, M 3/3 (x2) = 32.

Habitat. Gedemsa use a variety of montane mesic habitats, typically at elevations of 1800-3500 m, but have been observed as low as 1600 m and as high as 4300 m. The current range of the Gedemsa occurs in four broad elevation zones in Ethiopia: the steep Afro-alpine zone (above 3700 m) with sparse forage and cover dominated by Alchemilla, Helichrysum, and Lobelia; the subalpine zone (3200-3700 m) with tall shrubs and trees dominated by Erica, Hagenia, and Hypericum; the moist upper Afro-montane zone (2300-3250 m) with woodlands ofJuniperus and Hagenia interspersed with montane grasslands of Festuca, Poa, and Carex; and the wetter lower Afro-montane zone (1500-2300 m) with woodlands of Aningeria, Sygium, and Ocotea. The lowest zone has not been thought of as important Gedemsa habitat in the past, but recent observations suggest otherwise. Predictive modeling of climatic, vegetative, and geographical variables suggests that minimum temperature and maximum precipitation are most associated with current Gedemsa habitat. Plantations of exotic trees are also used by Gedemsa, primarily for concealment and thermoregulation, and as travel corridors. Cultivated fields of barley and other crops in the lowlands near their native habitats are used at night and may be of increasing importance as availability of native habitats decreases with human encroachment. Gedemsa make seasonal movements elevationally to take advantage of changing foraging opportunities and thermoregulatory needs.

Food and Feeding. Gedemsa are intermediate feeders and mainly browsers throughout much of the year. Diets vary considerably by the season, however, depending on what mountainous zone they inhabit. At high elevations, Gedemsa tend to prefer leaves of Lobelia, but in lower elevation forests, they will eat considerable amounts of forest grasses (Koeleria, Poa, and Agrostis), ferns, and lichens. The flush of green vegetation following the traditional burning in the Ethiopian highlands will attract Gedemsa.

Breeding. Little is known about various reproductive characteristics of the Gedemsa, and it has never bred in captivity. Gedemsa have been described as breeding throughout the year, but individual populations have different breeding and birthing seasons; e.g. most breeding in Bale Mountains National Park occurs in December—January, with births in August-September, but in the Galama Mountains, there appears to be a subtle bimodal pattern of breeding and birthing. Gedemsa are polygynous, and males do not establish breeding territories or harems. Males begin to breed at 5-8 years old, although they are sexually mature at 2-3 years. When females are in estrus, the displays of males are similar to those of other tragelaphines. During this time, mature males become less tolerant of each other and establish dominance more by posturing than by combat. Combat does occur and can be intense and injurious, but is rare. Males display to each other laterally and in a T-position by standing stiff with their backs arched, head held low and outstretched, and the dorsal crest erect. The tail is not curled over the back as it is in the posturing displays of some other tragelaphines. Males thrash vegetation and the ground as a form of intimidation. Displays end when the subordinate male drops his head and leaves, which may elicit a brief pursuit by the dominant male. A dominant male follows an estrous female attentively, with his neck stretched out, and frequently smells the end of the female's tail. When ready to mate, the female urinates with her tail curled back, and the attending male tests her urine with his tongue, causing the lip-curling response. Copulation is brief. The male does not tend the female afterward; he begins to search for other receptive females. Female Gedemsa breed for the first time at 2-3 years. Gestation is 8-9 months, and a single offspring is produced. Newborns remain hidden for up to three weeks. Weaning occurs atjust 3-4 months. Offspring remain with their mothers for up to two years, with males inclined to leave earlier than females.

Activity patterns. Gedemsa can be active at any time of the day, but they tend to be crepuscular and nocturnal, being most active from 16:00 h to 08:00 h. Activity patterns no doubt change seasonally given changes in temperatures and forage availability in their montane habitats. Like other ruminants, their active period likely consists of alternating periods of feeding and resting/ruminating, although specific activity budgets have not been reported.

Movements, Home range and Social organization. Gedemsa are not migratory, but they do move elevationally by the season and can range widely. During the rainy season, females may restrict their movements to about 5 km? and males to 20 km?*. Reports of densities of Gedemsa range widely from 2-7 ind/km? to 40 ind/km?*normal density is probably toward the lower end. In 2000-2001, the population in Bale Mountains National Park was 62-9 % female, 27-4% male, and 9-7% young-of-the-year. Gedemsa are gregarious and occur in groups of 2-13 individuals, with large groups of 4-10 seen in more open habitat and during the wet season and smaller groups of 2-5 in forested habitat and during the dry season. Family groups are formed with a matriarch, other mature and immature females, and offspring; about 50% of the time, a mature male will be in such a group. Outside of the breeding season, mature and old males are seen alone or in bachelor groups. Occasionally, temporary groups of 60-100 individuals aggregate at feeding and resting sites. Like other tragelaphines, Gedemsa are cautious when leaving forest cover and are described as difficult to approach because of their enhanced group vigilance under most conditions. When alarmed and fleeing, Gedemsa quickly flick and lower their tails, flashing the white undersides. They can achieve speeds of 72 km /h andjump 1-75 m. Although endangered itself and mostly a specialist in rodents, the Ethiopian Wolf (Canis simensis) has been reported to very occasionally prey on young Gedemsa. Other predators could include Leopards (Panthera pardus), Spotted Hyenas (Crocuta crocuta), and Lions (P. leo), although hyenas and lions rarely occur in the montane habitats where the Gedemsa lives.

Status and Conservation. Classified as Endangered on The IUCN Red List. Surveys of Ethiopian highland animals in the 1960s led to the establishment of Bale Mountains National Park in 1971, and the Gedemsa and Ethiopian Wolfare still its flagship species. About 50% of the known Gedemsa occur in Bale Mountains National Park. Although they and other species are protected by law, enforcementis often spotty. In the 1960s, the Gedemsa were initially thought to number 4000-5500 individuals, but they are hard to survey because of the difficulty in observing them in a systematic fashion in the forested habitats they occupy and the inaccessibility of many of those habitats due to terrain and vegetation. Numbers of Gedemsa were thought to be as low as 1000 individuals in the 1970s, 2000-4000 individuals by the late 1980s, and 2500 individuals in late 1990s, and are currently thought to number about 4000 individuals. Gedemsa have suffered from political unrest in the early 1990s, excessive hunting for meat and horns (used locally as medicine and to make nipples for traditional bottles), and encroachment by human settlement, logging, and cattle grazing. Surprisingly, regulated trophy hunting of the Gedemsa occurs, but its impact is not well understood and its sustainability questionable; pressures to increase quotas and areas that can be hunted are ongoing challenges to conservation. Recent research has led to the discovery of new but small populations beyond the current known distribution of the Gedemsa, with the prospects of other unknown populations being identified based on habitat modeling and future surveys in remote areas.

Bibliography. Bro-Jorgensen (2008), Brown (1969a, 1969b), East (1999), Estes (1991a, 1991b), Evangelista, Norman et al. (2008), Evangelista, Swartzinksi & Waltermire (2007), Hillman (1985, 1986b), Hillman & Hillman (1987), Huffman (2010e), Kingdon (1997), Lydekker (1910a, 1910b, 1911), Lydekker & Blaine (1914), Nowak (1999), Refera & Bekele (2004), Sillero-Zubiri (2008), Sillero-Zubiri & Gottelli (1994, 1995), Walther (1990a), Woldegebriel (1996).

Figures

18. Western Bushbuck (Tragelaphus scriptus), 19. Central Bushbuck (Tragelaphus phaleratus), 20. Nile Bushbuck (Tragelaphus bor), 21. Lake Tana Bushbuck (Tragelaphus decula), 22. Ethiopian Highlands Bushbuck (Tragelaphus meneliki), 23. Eastern Coastal Bushbuck (Tragelaphus fasciatus), 24. Chobe Bushbuck (Tragelaphus ornatus), 25. Cape Bushbuck (Tragelaphus sylvaticus)

Distribution. The Gedemsa is now restricted to five isolated locations in the Bale and Arsi Mt ranges of SC Ethiopia , S and SE of the Rift Valley.