Philantomba bicolor (Gray, 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 : 715-716

239.

Zimbabwe Blue Duiker

Philantomba bicolor

French: Céphalophe bicolore / German: Simbabwe-Blauducker / Spanish: Duiker azul de Zimbabue

Other common names: Natal Blue Duiker

Taxonomy. Cephalophus bicolor Gray, 1863 ,

Umgozy Forest, Ntunsini district, Kwa-Zulu.

Formerly classified as a subspecies of P. monticola . Monotypic.

Distribution. Mozambique and E Zimbabwe S of Zambesi River to E South Africa (Limpopo & KwaZulu-Natal).

Descriptive notes. Head-body 57-64 cm, tail 7-9 cm, shoulder height 32-37 cm; weight 4-7 kg (3.9-5. 4 kg) in males and 5-4 kg (3.8-6. 5 kg) in females. A very small duiker; females are slightly larger than males. Overall color is a dark bluish-gray or gray-brown, with the amount of gray in the pelage being highly variable. The Zimbabwe Blue Duiker is darker than the neighboring Malawi Blue Duiker (PF. hecki), but paler than the Mountain Blue Duiker ( P. lugens ). The sides are paler and brighter than the dorsal surface, usually with a distinct rufous tone. The rump and base ofthe tail are very dark. The legs are rusty brown (the front legs are paler than the hindlegs), and the fetlocks are dark, interrupted by pale reddish patches immediately above the hooves. The undersides are white. The upper surface of the tail is the same dark brown as the dorsum; the underside is white, and these hairs grow outward, creating a white fringe along the tail edge. The forehead and the bridge of the nose are dark brown, and the cheeks are pale gray with a rufous tinge. This pale coloration extends around the eyes, forming dull rufous superciliary streaks 1.1-5 cm wide The underside of the jaw is white and the throat is warm gray in color, often with an orange tinge. The ears are dark brown outside and white inside; distinct white spots are present at the bases of the ears. There is a short coronal tuft on the forehead. Horns are present in both sexes. Those of males are strongly ridged, with 4-6 annulations at their bases; typical length is 3-4—4-2 cm. Horns of females are shorter: 2:3.2-9 cm. Dental formulais10/3,C0/1,P 3/3, M 3/3 (x2) = 32.

Habitat. In South Africa, Zimbabwe Blue Duikers inhabit lowland evergreen forests with Podocarpus vegetation, coastal forest, dune forest, and montane forest up to 1370 m. Areas with dense underbrush are used for cover and are an important habitat feature; stands of Dracaena fragrans are frequently used for this purpose in Zimbabwe. Population densities in appropriate habitats tend to be high. Estimates from the Chirinda Forest in eastern Zimbabwe are 120-220 ind/km?; typical densities in South Africa are about 150 ind/km?, but may exceed 300 ind/km? in some regions.

Food and Feeding. Principally folivorous, opportunistically frugivorous. In South Africa, leaves of dicotyledonous plants comprise, on average, 69-8% of diet; 23-3% of food consumed is fruit and seeds. In the forests of Zimbabwe, where fruits are more abundant, the diet is approximately 75% fruit and 15% leaves; flowers and fungi each constitute 5% of the diet. Instead of browsing, Zimbabwe Blue Duikers feed principally on fallen leaves: freshly fallen leaves are preferred, although dry ones are also eaten. While foraging, a Zimbabwe Blue Duiker may pick up a leaf and rotate it using its tongue; if the quality is not sufficient, the leaf will be spat out. Because most foods are out of reach, the duikers may follow groups of Blue Monkeys (Cercopithecus mitis ) to capitalize on items dropped from the canopy; flocks of African olive-pigeons (Columba arquatrix) also augment the food supply by knocking fruits and leaves to the ground. Highly preferred food plants are Protorhus longifolia, Combretum molle, and Syzygium cordatum. Other preferred species (determined experimentally in palatability trials in South Africa) are Ziziphus mucronata, Ekebergia capensis, Croton sylvaticus, Albizia adianthifolia, and Carissa macrocarpa. These duikers have been observed feeding on the fallen blossoms of Strelitzia nicolai. In Zimbabwe, the fruits of Ficus spp. are an important food source. The Zimbabwe Blue Duiker will opportunistically feed on insects, especially ants. This species is able to obtain all needed moisture from food sources and is thus not dependent on drinking water.

Breeding. Breeds year-round. The estrous cycle is approximately 20 days in length. Males court estrous females by closely follow or chasing them, and may become very aggressive towards other conspecifics. During courtship, the male licks the female’s anogenital region and performs ritualized leg-kicks (“laufschlag”) between her hindlegs whenever she stops. Copulation is very brief, but occurs frequently (up to five times within a 15-20 minute interval). Gestation has been measured at 205 days in captive animals (range 197-215, from 19 births). Females choose a secluded, sheltered area in which to give birth to the single offspring. Birth weight is approximately 450-600 g. Females reach sexual maturity at 8-12 months, males at 11-14 months. Longevity in captivity may exceed 15 years.

Activity patterns. Diurnal, with the highest activity levels immediately after dawn and just prior to dusk. Between bouts of activity, it frequently retires to resting spots; 33-50% of daylight hours (05:00-19:00 h) may be spent resting. The Zimbabwe Blue Duiker tends to be more active in higher quality habitats: although foraging time is reduced, the time spent patrolling territorial boundaries and defending resourcesis significantly higher.

Movements, Home range and Social organization. Small home ranges are occupied year-round; the boundaries may be dynamic between seasons, but the core area remains constant. The central area usually contains frequently used bed sites (3—4 on average), which are used for refuge, rest, and rumination. Average home ranges are 6500-7400 m?, and are shared by a family group of an adult male and female, plus their subadult offspring. Home ranges are exclusive territories; there is no overlap between neighboring occupied areas. Each territory is transected by a number of regularly used pathways.

Status and Conservation. CITES Appendix II (under P. monticola ). Classified as Least Concern on The IUCN Red List (combined with the other nine blue duiker species within the P. monticola complex). The stronghold of the Zimbabwe Blue Duiker is in KwaZulu-Natal. It is uncommon or rare in Zimbabwe and Mozambique, with populations continuing to decline due to poaching.

Bibliography. Bowland & Perrin (1994, 1995), East (1999), Faurie & Perrin (1993), Grubb & Groves (2001), IUCN/SSC Antelope Specialist Group (2008as), Perrin et al. (1992), Weigl (2005), Wilson (2001).

Figures

233. Western Blue Duiker (Philantomba congica), 234. Bioko Blue Duiker (Philantomba melanorhea), 235. Eastern Blue Duiker (Philantomba aequatorialis), 236. Mountain Blue Duiker (Philantomba lugens), 237. Simpson’s Blue Duiker (Philantomba simpsoni), 238. Malawi Blue Duiker (Philantomba hecki), 239. Zimbabwe Blue Duiker (Philantomba bicolor), 240. Cape Blue Duiker (Philantomba monticola), 241. Angolan Blue Duiker (Philantomba anchietae), 242. Zambian Blue Duiker (Philantomba defries)

Distribution. Mozambique and E Zimbabwe S of Zambesi River to E South Africa (Limpopo & KwaZulu-Natal).