Cephalophus silvicultor (Afzelius, 1815)

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 : 721

247.

Western Yellow-backed Duiker

Cephalophus silvicultor

French: Céphalophe a dos jaune / German: Gelbriickenducker / Spanish: Duiker de dorso amarillo occidental

Taxonomy. Antilope sylvicultrix Afzelius, 1815 ,

Liberia.

Three subspecies are recognized.

Subspecies and Distribution.

C. s. silvicultorAfzelius, 1815 — S Senegalto W Nigeria (W of Niger River).

C.s.longicepsGray,1865—ENigeria(EofNigerRiver)toSChadandSWSudan,StoCongoRiver.

C. s. ruficrista Bocage, 1869 — DR Congo S of Congo River, Angola, and Zambia.

Descriptive notes. Head-body 115-145 cm,tail 11-18 cm, shoulder height 65-85 cm; weight 45-80 kg. The Western Yellow-backed Duikeris the largest duiker species. The pelage is soft and oily. Color is an overall glossy brownish-black; the legs may be slightly darker. The underparts (including the inguinal region) are similarly dark. This species is named for the triangular patch of erectile yellowish hairs that runs along the spine; it is narrowest behind shoulders and widens on the rump. The size and extent of the yellow back are variable among individuals, but the hairs within this patch are always longer than adjacent dark hairs, and are longest (6-7 cm long) at the widest end of the triangle. Caudal to the dorsal patch, the rump has very short hairs and tends to be paler brown compared to the rest of the body;this area may be bordered with yellow hairs. The tail is short and thin, with a small black terminal tuft. The sides of the head are grayish, with no conspicuous markings besides the white lips and the prominent slits of the preorbital glands. The ears are dark on the back and rimmed with a border of white hairs inside. A coronal tuft is present on the top of the head, and typically surrounds the bases of the horns. This crest is rufous or orange in color, and usually 5-8 cm long. Horns are present in both sexes; these are smooth, slender spikes that extend backward from the skull. Horn length is typically 8-15 cm, with measurements from males being at the upper end of this range. Maximum recorded horn length is 21-3 cm. Dental formula is 10/3, C0/1,P 3/3, M 3/3 (x2) = 32.

Habitat. The Western Yellow-backed Duiker is found in a wide variety of habitats including primary and secondary rainforest; gallery, riparian, and montane forests; semideciduous forests; and more open bush and savanna woodlands. Population density is estimated to be 0-5-2-1 ind/km?® in areas of good habitat in Gabon.

Food and Feeding. Fruits and seeds constitute the largest portion of the diet (71-3% of the contents of four stomachs examined in Gabon, on a dry matter basis), followed by petioles and stems (25-5%). Leaves are consumed in small quantities (3-1%), flowers, fungi, and grasses have not been recorded in the diet. Fruits are frequently eaten whole (both flesh and seeds); the large mouth and strong teeth are also able to crack hard seeds and break apart seed pods. Items up to 4-7 cm in size may be swallowed, including the stones of Irvingia gabonensis, Mammea africana , and Detarium macrocarpum; the flesh of Klainedoxa gabonensis, another large-stoned species, is usually chewed off of the stone and eaten without swallowing the pit. Other plant species consumed in Gabon include Eremospatha wendlandiana, Pseudospondias longifolia, Polyalthia suaveolens, Ricinodendron heudeloti, Pentaclethra eetveldeana, and Strychnos camptoneura. In the Central African Republic,fruits, seed pods, and leaves from Piliostigma thonningii, Swartzia madagascariensis, Nauclea latifolia , and Gardenia sp. are consumed. The Western Yellowbacked Duiker has been recorded feeding on several types of animal matter, including insects, newly hatched tortoises (Testudo pardalis), chameleons, and doves.

Breeding. Breeding of the Western Yellow-backed Duiker does not appear to be seasonal. Males may be highly aggressive during courtship, chasing or driving estrous females while licking, biting, or butting the female’s hindquarters. A soft bleat or grunt is produced by the male during courtship. Flehming is used by males to test the urine of females. Copulation is very brief, lasting only one or two seconds. Gestation is reported to be 151-282 days; observationalerroris likely, especially for the shortest time periods. Based on the gestations of related species, pregnancies likely last for at least seven months. Captive birth weights are also highly variable (2:3.6-1 kg); litter size is one. Infants are a uniform brownish-black at birth; they do not follow their mothers, but hide alone in protected areas, often at the base of a tall vertical object. Solid foods may be tried as early as eight days of age. Horn growth begins at one month of age;at the same time the yellow dorsal patch begins to develop with a thin stripe of hair along the lower spine becoming paler in color. The dorsal patch is fully developed by seven months of age. Coronal crest hairs also become paler and more rufous as young animals grow. Weaning occurs around 95 days of age for hand-reared captive individuals; rearing of mother-raised Western Yellow-backed Duikers occurs by five months. The average interbirth interval in captivity is 479 days (23 birth records from four females). Maximum longevity, as recorded in captivity, is approximately 22 years.

Activity patterns. Active throughout the day and night. Captive individuals are typically active during 39% of daytime hours and 26% of the hours of darkness. Wild individuals also appear to be active throughout the 24hour day, although numerous observations have been made of Western Yellow-backed Duikers sleeping during midday. Such resting occurs in sheltered areas, such as tree buttresses, dense thickets, or near fallen trees.

Movements, Home range and Social organization. Generally solitary, occasionally observed in pairs. One isolated report exists of a group of six animals. It is unknown whether pair-bonds form or whether territories are held. Both sexes use secretions from the preorbital glands to mark vertical structures (such as trees); males perform this behavior up to three times more frequently than females. This duikeris typically a slow-moving species that often walks with the head down and back hunched. When disturbed, the Western Yellow-backed Duiker will immediately freeze in position (usually with one foreleg off the ground) and erect the yellow dorsal patch so that the hairs are perpendicular to the skin. If the source ofthe threatis visually identified during this period of motionlessness, the Western Yellow-backed Duiker will move slowly into cover. If startled or alarmed, individuals will explode into a fast trot interspersed with large Jumps. In areas with high levels of hunting by humans, they will often flee immediately.

Status and Conservation. CITES Appendix II. Classified as Least Concern on The [UCN Red List (coupled with C. curticeps). The Western Yellow-backed Duikeris less impacted by cable snare hunting than other duikers because ofits ability to break the snares (due to its size and strength). However, the species will readily approach hunters reproducing duikercalls, rendering them vulnerable to shooting. The total population is estimated to be 160,000 animals, spread across an increasingly fragmented range.

Bibliography. Barnes et al. (2002), Croes et al. (2007), Dubost (1984), Feer (1995), Happold (1987), IUCN/SSC Antelope Specialist Group (20080), Kingdon (1997), Kranz & Lumpkin (1982), Lumpkin & Kranz (1984), Newing (2001), Noss (1998), Weigl (2005), Wilson (1987, 2001).

Figures

On following pages: 245. Eastern Bay Duiker (Cephalophus castaneus); 246. Jentink’s Duiker (Cephalophus jentinki); 247. Western Yellow-backed Duiker (Cephalophus silviculton; 248. Eastern Yellow-backed Duiker (Cephalophus curticeps); 249. Abbott's Duiker (Cephalophus spadix); 250. Black Duiker (Cephalophus niger); 251. Ogilby’s Duiker (Cephalophus ogilbyi); 252. White-legged Duiker (Cephalophus crusalbum): 253. Brooke's Duiker (Cephalophus brookel); 254. Peters's Duiker (Cephalophus callipygus).

Subspecies and Distribution. C. s. silvicultorAfzelius, 1815 — S Senegalto W Nigeria (W of Niger River). C.s.longicepsGray,1865—ENigeria(EofNigerRiver)toSChadandSWSudan,StoCongoRiver. C. s. ruficrista Bocage, 1869 — DR Congo S of Congo River, Angola , and Zambia .