Aders’ duiker (Cephalophus adersi)

Also known as: Ader's duiker, dwarf red duiker, Zanzibar duiker
KingdomAnimalia
PhylumChordata
ClassMammalia
OrderCetartiodactyla
FamilyBovidae
GenusCephalophus (1)
SizeHead-body length: 66 - 72 cm (2) (3)
Shoulder height: 30 - 32 cm (3)
Tail length: 9 - 12 cm (2) (3)
Weight6.5 - 12 kg (2) (3)

Aders' duiker is classified as Critically Endangered (CR) on the IUCN Red List (1).

The rarest and most highly endangered of Africa’s duiker species (2) (4), the diminutive Aders’ duiker (Cephalophus adersi) is also one of the smallest and most distinctive, being readily distinguished by the wide white band across the rump (2) (3) (4) (5) (6). As in other duikers, the body shape is adapted for easy movement through dense undergrowth, being small and stocky, with large hindquarters, an arched back, relatively short legs, and pointed hooves, which have a wide splay (2) (7) (8). The coat of Aders’ duiker is soft, silky, and tawny-red in colour, becoming slightly greyer on the neck, and with white ‘freckling’ on the legs. The white band across the rump merges with the paler underparts, and there is a black and white spot just above each hoof (2) (3) (4) (5) (6). The tail is relatively short, with a white tuft at the end (8).

Male and female Aders’ duikers are similar in size and appearance (2) (6) (8), and both possess short, backward-pointing horns, which may be slightly longer in males than in females, growing to about six centimetres in length (3) (4) (5) (7) (8). The top of the head also bears a reddish crest of fur (3) (4) (5), while the muzzle is pointed, with a flat front to the nose, a wide mouth, and conspicuous, slit-like ‘preorbital’ glands in front of the eyes (5) (8).

Aders’ duiker is found only on the island of Zanzibar, off the coast of Tanzania, and along small parts of the Kenyan coast (1) (2) (5) (7) (9). In Kenya, it had previously been described as widespread north of Mombasa, occurring almost up to the Somali border (3), but is now known only from the Arabuko-Sokoke Forest and Dodori National Forest Reserve (1) (9) (10) (11). The species may also have occurred on Fundo and Funzi Islands, off the coast of Pemba Island, Tanzania, but is now extinct on both (1) (6). In 2000, a small number of Aders’ duikers were translocated to Chumbe Island, off the coast of Zanzibar (1) (4) (6).

On Zanzibar, Aders’ duiker is found within tall, undisturbed coastal thicket, growing on coral outcrops known as coral rag (1) (5) (6) (9) (11). In Arabuko-Sokoke Forest, the species is commonly found in coastal Cynometra thicket and woodland (1) (5) (11).

Aders’ duiker is most active during the day, foraging for a range of leaves, seeds, buds and fruits, and often following monkey troops to take advantage of items dropped or dislodged from the canopy (1) (5) (6) (9). Some duikers also take insects and small vertebrates (2) (7) (8), although it is not known whether this is true of Aders’ duiker. The scrub and coral rag habitats this species inhabits are often dry and waterless, and Aders’ duiker appears to be able to survive long periods without drinking (3).

Aders’ duiker usually lives alone or in pairs, maintaining a small territory, which is marked with secretions from the large preorbital glands and with dung heaps (1) (2) (5) (6) (7) (9). Breeding may occur year-round (5) (9), the female giving birth to a single calf, which remains hidden in vegetation for the first few weeks of life (2). However, little else is known about reproduction in this species (1) (5) (6). Aders’ duiker is reported to be very shy, alert, and sensitive to sound (5), and is likely to dive into cover when disturbed, a behaviour for which this group of antelopes is named, ‘duiker’ coming from an Afrikaans word meaning ‘diver’ (2) (5) (7) (8).

This rare duiker appears to have undergone a drastic population decline, with estimates showing a decrease on Zanzibar from around 5,000 individuals in 1982 to just 640 in 1999. The species is now restricted to a few forest patches in the south and east of the island, where fewer than 300 may now survive (1) (4) (6). This decline is likely to be continuing, with the main threats to the species being habitat loss, due to illegal wood-cutting and the spread of agriculture, and continued illegal hunting, with the species being highly sought after for its meat and skin (1) (4) (5) (6) (9) (11). Deforestation and forest degradation has led to the severe fragmentation of the duiker’s habitat, but firewood collection unfortunately remains one of the few sources of income for many people living near the forests (1). An additional threat may be posed by the presence of feral dogs, which are thought to have destroyed an introduced duiker population on Funzi Island (5).

The population of Aders’ duikers in Arabuko-Sokoke, Kenya, is believed to be even closer to extinction, with recent surveys counting only very small numbers, and hunting and trapping still common in the forest. This area is one of the last major remnants of lowland forest on the coast of East Africa, but remains vulnerable to illegal wood-cutting, and is under increasing pressure from a rapidly growing human population (1) (9) (11).

Aders’ duiker is a protected species in both Kenya and Zanzibar (1), although the law is often poorly enforced (9). A Species Recovery Plan is in place on Zanzibar, with recommendations including improved protected status for the species, the development of a new, larger conservation area with a strict anti-hunting policy, conservation education programmes, continued population monitoring, and further research into the species’ behaviour and ecology (6). A conservation and recovery plan has also been proposed for Kenya (1). In 2000, five Aders’ duikers were translocated to the well protected, privately run conservation area of Chumbe Island, where a female was already present, but the success of this programme needs to be monitored (1) (4) (6). The possibility of a captive breeding programme is also being investigated (1) (3) (6) (11), while the use of trophy hunting as a conservation tool has been suggested, but is controversial (1) (4) (6).

The range of Aders’ duiker is now partially protected, such as within the newly designated Jozani-Chakwa Bay National Park and the nature reserve of Kiwengwa Forest in Zanzibar, as well as Arabuko-Sokoke National Park in Kenya, part of which is a strict nature reserve (1). Intensive fieldwork has been performed in Arabuko-Sokoke by the Kenyan Wildlife Service, including population surveys and monitoring of illegal human activity, while on Zanzibar a community wildlife management programme commenced in 1995, in an effort to reduce antelope hunting to more sustainable levels and to provide alternative income-generating projects (1) (6). The discovery of Aders’ duikers in Dodori Forest National Reserve in 2004 raised hopes that additional populations may yet be discovered in other areas (4) (10), but further survey work is needed to determine the current status of the species there, as this isolated population may be on the brink of extinction (1). Unfortunately, unless urgent conservation efforts can reverse its decline, this small, attractive antelope remains at high risk of becoming extinct in the not too distant future (1) (4) (6) (11).

Find out more about the conservation of Aders’ duiker:

Authenticated (04/04/10) by Amrita Neelakantan, Advocacy Officer - Important Bird Areas, Bombay Natural History Society (BNHS).
http://www.bnhs.org/,
http://redbubble.com/people/amster04

  1. IUCN Red List (February, 2010)
    http://www.iucnredlist.org
  2. Macdonald, D.W. (2006) The Encyclopedia of Mammals. Oxford University Press, Oxford.
  3. Kingdon, J. (1988) East African Mammals: An Atlas of Evolution in Africa. Volume 3, Part C: Bovids. University of Chicago Press, Chicago.
  4. African Conservation Foundation: East, R., 19th April 2006. Status of Aders’ Duiker: Going, Going… (February, 2010)
    http://www.africanconservation.org/dcforum/DCForumID5/351.html
  5. Ultimate Ungulate (February, 2010)
    http://www.ultimateungulate.com/Artiodactyla/Cephalophus_adersi.html
  6. Finnie, D. (2002) Ader’s Duiker (Cephalophus adersi) Species Recovery Plan (Revised). Forestry Technical Paper No. 124. DCCFF, Zanzibar. Available at:
    http://coastalforests.tfcg.org/pubs/AderDuiker-znz.pdf
  7. Nowak, R.M. (1991) Walker's Mammals of the World. The Johns Hopkins University Press, Baltimore and London.
  8. Estes, R.D. (1992) The Behavior Guide To African Mammals: Including Hoofed Mammals, Carnivores, Primates. University of California Press, Berkeley, California.
  9. East, R. (1988) Antelopes: Global Survey and Regional Action Plans: Part 1. East and Northeast Africa. IUCN/SSC Antelope Specialist Group, IUCN, Gland, Switzerland. Available at:
    http://data.iucn.org/dbtw-wpd/edocs/1988-015-1.pdf
  10. Zoological Society of London: New hope for endangered antelope - ZSL discovers rare antelope at new site in Kenya. Press release, Monday 17th May 2004 (February, 2010)
    http://www.zsl.org/info/media/press-releases/
  11. East, R. (1999) African Antelope Database 1998. IUCN/SSC Antelope Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
    http://data.iucn.org/dbtw-wpd/edocs/SSC-OP-021.pdf