Home | Ungulates | About Us | Glossary | Links | Search | Contact Us
An Ultimate Ungulate Fact Sheet
Cephalophus adersi
Aders's duiker
Click on the pictures above for larger views of the photographs
Quick Facts Detailed Information References

Classification
 

Kingdom:
Phylum:
Class:
Order:
Suborder:
Family:
Subfamily:
Genus:

Animalia
Chordata
Mammalia
Artiodactyla
Ruminantia
Bovidae
Cephalophinae
Cephalophus

Cephalophus adersi [Thomas, 1918].
Citation: Ann. Mag. Nat. Hist., [ser. 9], 2:151.
Type locality: Tanzania, Zanzibar.

The taxonomic record (above) is taken from Wilson and Reeder (1993). Aders's duiker is usually placed within the subgenus Cephalophorus [Gray, 1842] (Nowak, 1991). Its taxonomic status has been debated by authorities - it is considered by some to be a subspecies of Cephalophus natalensis (or C. harveyi), and has been lumped by others into a superspecies with C. natalensis and C. callipygus (see Wilson, 1987). C. adersi is monotypic (Wilson, 1987).

Physical Characteristics

Aders's duiker is a small duiker, typically weighing less than 12 kg. Kingdon (1982) reports a clinal variation in weight on Unguja (Zanzibar), with the smallest individuals being found in the southern end of the island. Wilson (2001) refutes this claim based on limited empirical evidence, suggesting that age may have been a factor in Kingdon's samples. Head and body length are approximately 70 cm and shoulder height is around 40 cm.

Reported measurements for Aders's duiker (Cephalophus adersi)
Source Adult Weight Head & Body Length Shoulder Height Tail Length

Kanga and Mwinyi, 1999
in Wilson, 2001

8.7-10.2 kg
6.8-10.1 kg
63-78 cm 37.5-44.0 cm 6.0-13.8 cm
Kingdon, 1982

6.5-12 kg

66-72 cm

30-32 cm

9-12 cm

Wilson, 1987

6-12 kg

66-62 cm [sic]

-

9-12 cm

Wilson, 2001
from 5 individuals

8.5-12.4 kg 67.0-73.0 cm
40.0-43.5 cm

10.0-13.1 cm

The pelage of Aders's duiker is soft and silky throughout (Kingdon, 1982). The overall color is a tawny red, which grows somewhat greyer on the neck and is brightest on the rump (Kingdon, 1982; Wilson, 2001). Specimens from the Jozani forest of southern Zanzibar are reportedly paler in coloration (Kingdon, 1982), although Wilson (2001) suggests that the specimens described might be immature. The belly is bright white (Wilson, 2001). The most distinctive feature of this duiker species is the wide white band (approximately 15 cm wide) which runs across the rump and thighs, merging cranially with the pale underparts (Kingdon, 1982; Wilson, 1987). The legs are red for most of their length, but gradually darken towards the hooves, becoming black below the dewclaws (Wilson, 2001). The forelegs in particular are marked with small, irregular white blotches, although some freckling is present on the hind legs (Kingdon, 1982; Wilson, 2001). There is often a distinct white spot just above hooves (Kingdon, 1982; Wilson, 2001).The tail is thin with a terminal tuft of whitish hair (Wilson, 2001).

The forehead bears a bushy tuft of bright red hair; this does not end in a point as in some duikers, but is an even shock of hair (Kingdon, 1982; Wilson, 2001). On either side of this crest are found the short, simple spiked horns, which grow no more than 6 cm in length (Kingdon, 1982). Nine male specimens measured by Kanga and Mwinyi (1999, in Wilson, 2001) had an average horn length of 4.6 cm (range: 3.5-5.3 cm); Four males measured by Wilson (2001) had an average horn length of only 3.8 cm (2.9-4.8 cm). The horns of females are much shorter (mean values form different samples reported as 1.5 and 2.8 cm), and almost hidden by the tuft of hair surrounding them (Wilson, 2001). The muzzle is pointed, and the nose has a flat front (Kingdon, 1997). The preorbital glands are greatly reduced compared to other duikers, with the external slit less than 1 cm long (Wilson, 2001). There is a marked cowlick or whorl of hair on the nape of the neck (Kingdon, 1982).

Reproduction and Development

Virtually nothing is known about the reproduction of Aders's duiker. Kingdon (1997) and Rogers & Swai (1988, in Wilson, 2001) report that this species breeds throughout the year without providing data. Pregnant females with late-term fetuses have been captured between June and November, and a lactating female was observed in December (see Wilson, 2001). I personally observed a very pregnant female showing signs of udder development on Mnemba Island in October 2013.

Ecology

A generalized species, Aders's duiker inhabits coastal forests, woodlands, and thickets (Kingdon, 1982; Wilson, 1987). This species can live in quite dry scrub near the sea or among coral outcrops - on Unguja (Zanzibar) they are restricted to tall thicket forest growing on waterless coral rag (Kingdon, 1982; Kingdon, 1997). In Arabuko-Sokoke (Kenya) Aders's duikers are most often caught by hunters within Cynometra manilkera forest, especially on "red soil" (Kanga, 1995; Wilson, 2001).

Aders's duiker is sympatric in at least parts of its range with Harvey's duiker (Cephalophus harveyi), blue duiker (Philantomba monticola sundevalli) and suni (Neotragus moschatus), although nothing is known regarding their ecological separation (Kingdon, 1982; WIlson, 2001). Population densities on Unguja, Zanzibar were estimated by Swai (1983 in Wilson, 2001) as 4.3 Aders's duikers per km2; this is similar to the 1996 estimate by Williams et al. of 4.5 ndividuals per km2. In the Arabuko-Sukoke Forest (Kenya), Aders's duiker occurs at a population density of only 2.8 per km2 (by way of comparison, blue duikers in the same region have a population density of ~12 per km2). The large predators in Zanzibar (i.e., leopards and pythons) have all been greatly reduced, although these likely preyed on this species in earlier times (Wilson, 2001).

Aders's duiker feeds primarily on fallen flowers, fruits, and leaves, often following birds or Zanzibar red colobus and Syke's monkeys in order to feed on food items dropped from the trees (Kingdon, 1997; Wilson, 2001). There appears to be a particular dependence on the flowers and berries from trees like ebony (Diospyros consolataei), kudu berry (Cassine aethiopica), and bush guarri (Euclea schimperi), and bushes such as turkey barry (Canthium spp.) and Polyspheria (Kingdon, 1997). Wilson (2001) noted fresh droppings beneath Mystroxylon aethipicum and Ficus sur trees, and by the creeper Tetracella littoralis, suggesting that these may be food plants; the latter two have been confirmed by rumen content analysis, which also found fruits from Diospryros consolatae. Aders's duikers will also eat sprouts, buds, and other fresh growth found at ground level (Kingdon, 1997). This duiker species can apparently manage without drinking (Kingdon, 1982).

Behavior

Aders's duiker is reported by Kingdon (1997) to live in pairs, although the majority of observations are of solitary animals. On Mnemba Island, where these duikers are protected and live at high density, I observed on numerous occasions pairs of duikers foraging together, including pairs of adult males, an adult female and a subadult (potentially her grown offspring), and an adult male and adult female (personal observation, October 2013). On one occasion, a group of three - adult male, adult female, and subadult - were observed. They are believed to be territorial (Kingdon, 1982). Wilson's (2001) observations of the reduced preorbital glands suggest that scent marking does not play a large role in the defense of territories, although secretions are still deposited on twigs (Daniels, 2004). Fecal piles may also serve to delineate territories (Swai, 1983 in Finnie, 2008).

This species is almost completely diurnal, and it is very rare to observe them at night (Kingdon, 1982; Wilson, 2001; Mwinyi et al., 2012). Camera-trap observations in Kenya also show a crepuscular/diurnal activity pattern (Andanje et al., 2011). Feeding occurs from dawn to around 1100 hours, which is followed by a period of rest and rumination (Kingdon, 1997). At about 1500 hours Aders's duikers generally become active, and will continue foraging until nightfall (Kingdon, 1997). This species is very shy, alert, and has a keen sense of hearing (Kingdon, 1997; Wilson, 2001). As a result, people commonly hunt the species by using the brute-force method of driving the duikers into nets with dogs, or silently ambushing them at feeding sites (Kingdon, 1997).

Distribution

The range of Aders's duiker is restricted to three isolated locales in coastal East Africa. On the mainland, it is found in the Arabuko-Sokoke Forest (a remnant of lowland forest in coastal Kenya covering 420 km2) and was recently discovered in the Boni and Dodori Nature Reserves further to the north (Andanje et al., 2011). On Unguja Island (Zanzibar, Tanzania), three disjunct populations are found: in the northerly Kiwengwa Forest, the central Jozani Forest region, and to the south in the Mtende Forest (Wilson, 2001). Populations have been introduced to the small islands of Mnemba and Chumbe off the coast of Unguja.

Countries: Kenya, United Republic of Tanzania (Finnie, 2008).

Range Map
(Compiled from Wilson, 2001; Finnie, 2008; Andanje et al., 2011)

Conservation Status

Aders's duiker is classified as critically endangered by the IUCN (Finnie, 2008), but is not listed by CITES. Habitat destruction and fragmentation, as a result of expanding agriculture and harvesting of forest products, is one of several threats experienced by this rare duiker (Finnie, 2008). In addition to encroaching on the already restricted range of this species, proximity with people also increases the threats from free-ranging and feral dogs (Kingdon, 1997). Dogs are known to have destroyed an introduced population of Aders's duiker on Funzi Island, where these antelope had previously thrived (Kingdon, 1997). However, perhaps the most serious pressure experienced by this species is over-hunting (Kanga, 1995; Finnie, 2008). At Mtende, at the southern end of Unguja, Aders's duiker was estimated to form 70% of hunters' antelope kills until the late 1980's, but trapping success has been extremely low subsequently (Kanga, 1995; Kingdon, 1997). Aders's duiker is highly sought in the marketplace due to its "sweet" meat and beautiful skin (Kanga, 1995).

In 1999, the population on Unguja was estimated to be 600 animals (Williams et al., 1999), while perhaps 300-420 remain in Arabuko-Sukoke (in Wilson, 2001). The recently (2011) discovered population in Boni-Dodori has yet to be fully assessed, but the frequency with which this species is encountered in camera traps suggests that this region may be the stronghold for Aders's duiker (Andanje et al., 2011).

Zanzibar's Department of Forest and Non Renewable Natural Resources has been attempting to establish independent, protected populations of Aders's duiker on a few small islands around Unguja (see Wilson, 2001; Daniels, 2004). Translocation efforts have met with high mortality rates (Mwinyi et al., 2012), but, as of 2013, reproducing populations have been established on Chumbe Island (approximately five duikers; Mwinyi et al., 2012) and Mnemba Island (estimated to have 17 duikers on my visit in October 2013).

Remarks

Aders's duiker was interpreted by Kingdon (1982) as representative of the primitive evolutionary stock from which all modern duiker species radiated. It's small size has earned it the moniker of "dwarf red duiker", while its restricted range has also given rise to the name "Zanzibar duiker" (Wilson, 2001).

The genus name Cephalophus is derived from kephale (Greek: the head) and lophus (Greek: a crest), referring to the tuft of hair on the forehead. Dr. W. Mansfield Aders, D.Sc., was a Government Zoologist with the Zanzibar Government Service. The name duiker ("DIKE-er") is Afrikaans for "diver", a name that is derived from their habit of "diving" into the undergrowth when alarmed.

Local names
Paa nunga, Nunga [Kiswahili] (Kingdon, 1982)
Mwalimu [Kiswahili] (Wilson, 2001)
Kungu marara [Kipokomo] (Kingdon, 1982)
Harake [Sanga] (Wilson, 2001)
Guno [Kiawer] (Andanje et al., 2011)
 
French
Céphalophe de Aders (Kingdon, 1997)
 
German
Adersducker (Kingdon, 1997)
Quick Facts Detailed Information References