Tragelaphus ornatus (Pocock, 1900)

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 : 601

24.

Chobe Bushbuck

Tragelaphus ornatus

French: Guib du Chobé / German: Sambia-Schirrantilope / Spanish: Bushbuck del Chobe

Taxonomy. Tragelaphus scriptus ornatus Pocock, 1900 ,

Lanyanti, Chobe River between Lake Ngami and the Zambezi.

The Chobe Bushbuck was formerly considered a subspecies of T. scriptus , but it is diagnostically different from other bushbucks. The mtDNA support for a clade containing specimens from Zambia, Zimbabwe, Botswana, and Angola was 94% and support for the Angola and non-Angola clades also had support values of 97 and 98%, respectively. Monotypic.

Distribution. S DR Congo, W Burundi, W Tanzania, Angola (except extreme SW), Zambia, Malawi, extreme NW & WC Mozambique, NE Namibia (Caprivi Strip), N Botswana, and N Zimbabwe.

Descriptive notes. Head—body 117-145 cm (males) and 114-132 cm (females), tail 19-24 cm, shoulder height 64-100 cm (males) and 61-85 cm (females); weight 40-80 kg (males) and 24-60 kg (females). These measurements are general for the bushbuck group and should be considered provisional until further information is available for individual species. Tragelaphines are typified by their sexual dimorphism, and the weight of males, in general, is about 160% of that of females. Bushbucks are the smallest tragelaphines, with large ears and eyes and a rather round, crested back. Their hindquarters tend to be higher and more robust than their forequarters. Male Chobe Bushbucks are rich dark rufous, becoming black on withers. The dorsal crest is white. They have 6-8 white transverse stripes and many haunch spots, but longitudinal bands, particularly the upper bands, are faint or represented only by a row of spots. The outer sides of the legs are blackish above the knees and hocks and reddish below. The inner sides of the legs are white, with a broad black garter above the knees and hocks. There is a white stripe from the knees and hocks to the pasterns. Female Chobe Bushbucks are pale red-brown and have as few as three transverse stripes. Inguinal glands occur ahead of the mammae, but there are no false hoof glands. Tails are relatively short, long-haired, and bushy, and the same color as the back, but white underneath and usually with a black tip. Only males have keeled horns, which are nearly straight with generally only one or slightly more twists. Average length of the horns of the Chobe Bushbuck is about 30 cm. Average total length of the skull is 24-3 cm. Dental formula is10/3,C0/1,P 3/3, M3/3 (x2) = 32. Eight subadult age classes from one month of age to 30 months can be deciphered from the sequence of eruption and replacement of deciduous to permanent teeth in the Chobe Bushbuck, likely comparable to other bushbuck species. Both the upper and lower molars begin to erupt at 4-5 months of age and by seven months, they have fully emerged. By 21-26 months of age, all premolars and molars except P*, P,, and M” have fully emerged. At 30 months,all permanent teeth are present. Beyond 30 months, wear classes from light to extra heavy relative to counts of cementum annuli makeit possible to age Chobe Bushbucks from 3-10 years of age. Diploid numbers for the bushbuck group are 33 for males and 34 for females.

Habitat. Generally, bushbuck species prefer forest cover and forest edge, or at least areas that provide dense cover. In the mid-Zambezi valley of Zimbabwe, where the artificially impounded Lake Kariba has altered downstream habitats, the Chobe Bushbuck uses perennial tall-grass (Vetiveria nigritana ) habitats in the absence ofits typical preferred thick brush and forest habitat. Similarly, Chobe Bushbucks use thickets invaded by M:mosa following years of excessive livestock grazing in the Chobe National Park, Botswana. According to Y. Moodley and M. W. Bruford, the Zambezian Miombo Woodlands, Kalahari Acacia-Baikiaea Woodland, Western Zambezian and Mopane Woodland, and Zambezian Baikiaeca Woodlands are occupied exclusively by the Chobe Bushbuck haplogroup. They are usually found near free water, which may be as much a reflection of their preferred forested habitats thriving near water as a physiological need.

Food and Feeding. There is no specific information available for this species, butits diet is probably comparable to other bushbuck species, which eat a variety of shrubs, legumes, and other plants. In Chobe National Park, Botswana, Chobe Bushbucks that were feeding and drinking were associated with Chacma Baboons (Papio ursinus) in 35% of 167 observations, suggesting a commensalism. They were rarely associated with other ungulates in the area, such as Ellipsen Waterbucks (Kobus ellipsiprymnus) and Common Impalas ( Aepyceros melampus). In Botswana, Chobe Bushbucks have been observed under sausage trees (Kigelia pinnata) where Vervet Monkeys (Chlorocebus pygerythrus) were feeding on flowers. Such relationships can be symbiotic in that each mammal alerts the other to potential dangers.

Breeding. Bushbucks have been described as the most socially primitive of the tragelaphines and typically are thought of as non-terrritorial polygynous breeders. In northern Zimbabwe, spermatogenesis in male Chobe Bushbucks started and the first ovulations in females occurred at about eleven months of age. Physiologically, reproductive activity did not wane as Chobe Bushbucks aged, even up to 11:6 years in males and 9-5 years in females. Births peaked in October-November, suggesting peak breeding in April-May at the end of the rainy season and a gestation of about six months.

Activity patterns. There islittle specific information available for this species, but presumably these animals are crepuscular and nocturnal and spend much of the day resting/ruminating in forest cover, alone or in mother—offspring pairs, as is the case with other bushbuck species.

Movements, Home range and Social organization. There is little specific information available on the movements and home range of the Chobe Bushbuck, but they probably are comparable to other bushbuck species. Generally, bushbucks do not range over a wide area, and home ranges are not exclusive, but individuals may have their own, apparently exclusive, place to rest during the day. In Chobe National Park, Botswana, 72% of 167 observations of Chobe Bushbuck were ofsolitary individuals; males had a tendency to occur alone more than females, and the sex ratio was equal.

Status and Conservation. Classified as Least Concern on The IUCN Red List (under 1. scriptus ), which does not differentiate the eight species identified here. In the late 1990s, number of bushbucks range-wide was estimated conservatively at over 1-34 million and they were not particularly dependent on conservation initiatives such as protected areas if adequate cover and water were available. Bushbuck populations are considered stable range-wide, although in localized areas, some populations have decreased because of excessive illegal harvest, destruction of native habitats as human populations and livestock numbers have increased, and increased aridity. Generally, however, bushbucks can do well in areas of human habitation because of their secretive nature, non-herding tendencies, cryptic coat patterning and tendency to freeze and blend in with their surroundings when faced with danger, and flexible daily schedules, adopting a nocturnal pattern in areas of human activity. According to population estimates accumulated in the late 1990s, numbers of the Chobe Bushbuck may be the lowest of the bushbuck species, and poaching pressure may be a primary cause. Despite this, the Chobe Bushbuck may be expanding in the equatorial forest zone as clearing for settlement and wood products opens the closed canopy.

Bibliography. Ansell (1972), Attwell (1970), Bro-Jorgensen (2008), East (1999), Elder & Elder (1970), Estes (19913, 1991b), Groves & Grubb (2011), IUCN/SSC Antelope Specialist Group (2009), Kingdon (1982, 1997), Lydekker & Blaine (1914), Moodley & Bruford (2007), Moodley et al. (2009), Morris & Hanks (1974), Nowak (1999), Olson et al. (2001), Simpson (1973), Walther (1990a), Wronski & Moodley (2009).

Figures

14. Saola (Pseudoryx nghetinhensis), 16. Chowsingha (Tetracerus quadricornis), 17. Nyala (Nyala angasii)

Distribution. S DR Congo , W Burundi , W Tanzania , Angola (except extreme SW), Zambia , Malawi , extreme NW & WC Mozambique , NE Namibia (Caprivi Strip), N Botswana , and N Zimbabwe .