Of course – sorry – it was not a living thylacine, and I’m both impressed and dismayed that the real answer – Zebra duiker or Banded duiker Cephalophus zebra – had been posted within 20 minutes of publication [adjacent photo of C. zebra from the Zebra duiker page on the outstanding Ultimate Ungulate]. Well done Chris (of Catalogue of Organisms) for getting there so quick. I saw the Zebra duiker photo (taken at Sapo National Park in Liberia by a team gathering data on pygmy hippos), on the EDGE blog (here) and thought it would be fun to use for this purpose. And of course now I have a good excuse to talk (briefly) about duikers…
Duikers, or cephalophines, are an entirely African group of bovids, and so far as we know they have never gotten out of Africa. Virtually nothing is known of their early history: there’s a partial maxilla and a molar from the Miocene, and a few Pliocene and Pleistocene records, some of which are of extant species. The Miocene molar is interesting as it’s from northern Africa, where no duikers occur today. However, Manlius (2001) suggested that an animal depicted in a 4th dynasty hunting scene (dating to c. 2561-2459 BC) at Atet’s tomb in Meidum, Egypt, is a Jentink’s duiker C. jentinki, and proposed on the basis of this that an isolated population of this species might have persisted in Egypt until at least this time. Flores (2001) pointed out that duiker bones were identified from an Egyptian tomb in 1948, perhaps providing support for this idea. Given the present range of C. jentinki (Sierra Leone, Liberia, Ivory Coast), a purported presence in ancient Egypt is very difficult to believe, but maybe these discoveries do show that duikers did occur north of the Sahara until recently.
Phylogenetic work suggests that duikers belong to four distinct lineages. Maxwell’s duiker C. maxwelli and the Blue duiker C. monticola – together sometimes called the blue duikers or the ‘conservative dwarfs’ – seem to form a clade that is the sister-group to all other duikers. They differ from the others in lacking inguinal glands, in having an untufted tail and in other features. On the basis of these differences the blue duikers have sometimes been given their own genus, Philantomba, and the distinct status and monophyly of this taxon was recently supported by Jansen van Vuuren & Robinson (2001). A widespread and very successful savannah specialist (the Bush duiker, Grey duiker, Common duiker or Grimm’s duiker Sylvicapra grimmia: over 40 subspecies have been named) forms the sister-taxon to a combined giant duiker and red duiker clade (Jansen van Vuuren & Robinson 2001). The phylogenetic position of the Zebra duiker and Ader’s duiker C. adersi are uncertain and they may represent distinct lineages within the giant duiker + red duiker clade [adjacent image shows the duiker case at the Walter Rothschild Museum in Tring. From The Art of Jane Tomlinson].
Containing about 20 species and a substantially greater number of subspecies, the duiker radiation appears to have occurred rapidly and recently (post-Miocene), with the amount of divergence between the major lineages being relatively minor. The exact placement of duikers within Bovidae is uncertain but they’re almost certainly antilopines close to gazelles, dwarf antelopes and so on (Hassanin & Douzery 1999a, b, Price et al. 2005). Their small size and ‘slinker’ ecomorphotype (read on) have generally led to the assumption that duikers are primitive. However, their complex brains, reduced horns, and shortened faces led Kingdon (1997) to suggest that they’re dwarfed from larger ancestors rather than primitive, and the genetic and fossil data do suggest that they’re a young group.
Ranging in size from about 4 to about 80 kg, duikers include diurnal, cathemeral and nocturnal species (cathemeral animals are active at any hour). Mostly forest dwellers, they also include savannah species as well as taxa that frequent montane environments (Ruwenzori duiker C. rubidus) and swamps (Black-fronted duiker C. nigrifrons). Some species have been reported to climb on sloping tree trunks. Most species are coloured in reds and browns but some are blackish. Jentink’s duiker, the largest species, has a black head and neck, a white collar over the shoulders, and a grizzled grey body (despite its size and striking appearance, it wasn’t scientifically discovered until 1884 and not named until 1892) [adjacent photo of Jentink’s duiker from here on Ultimate Ungulate]. Reddish crests that virtually conceal the small, posteriorly placed horns are common. Apparently, duiker’s hearts are huge, being about twice as large, proportionally, as that of a human (Ralls 1973).
Duikers are what is known as slinkers: mostly small-bodied, they rely on concealment and rapid acts of explosive saltation to avoid and escape predators, they are highly territorial, monogamous, and with sexes that (generally) are similarly sized* and similarly armed (slinking has also been termed the ‘microcursorial adaptive syndrome’, but that ain’t so catchy). The ability of duikers to dive rapidly into deep cover explains their common name (it’s Afrikaans for diver). It’s apparently pronounced like ‘biker’, and not ‘doy-kah’ as I’ve been saying for the last few decades. Duikers possess large preorbital (or maxillary) glands as well as pedal glands and (in some) inguinal (= groin) glands, and they frequently mark objects in their territory, in some cases doing so about every 10 minutes.
* Female duikers are often up to 4% bigger than males.
Like all slinkers, duikers specialise on high quality food like leaves and fruits, and fungi and bark are also eaten. They also eat insects and carrion, and regularly kill and eat frogs, small mammals, lizards, and birds. That’s right: omnivorous bovids. Ants were found to make up over 10% of the stomach contents (dry weight) of Blue duiker (Ronald & Kranz 2001) and captive animals are fed dog food in addition to plants (Nowak 1999). Some duiker species have been reported to sometimes toy with prey in the same way that domestic cats do. In Angola, people believe that the Yellow-backed duiker C. sylvicultor eats the meat of Bell’s hinge-backed tortoise Kinixys belliana by forcibly blasting the tortoise’s body out of the shell (Lumpkin & Kranz 1984). I don’t think this is true but wish it was [the picture shown above – from here on Ultimate Ungulate – shows an Abbott’s duiker C. spadix photographed in the Udzungwa Mountains, Tanzania. One of the first photos ever taken of this species in the wild, it shows the duiker eating a frog].
While duikers might seem like the sort of mammals that would usually be regarded as ‘less advanced’ than the big, noble antelopes that live out on the sunny plains (and, indeed, some workers have interpreted things this way), there are indications from duiker anatomy and behaviour that they are actually among the smartest and most complex of bovids: if you like, the ‘most advanced’. Their brains are large and complex and are said to be the biggest (proportionally) of all the bovids. A relatively long gestation and slow growth rate may be consequences of a prolonged learning period (Kingdon 1997), and it seems that duikers have to learn to predict and exploit the behaviour of herbivorous canopy animals, like monkeys, fruit bats and birds. The fruits that these animals drop are eaten by the duikers.
Spinage (1986) wrote about a Common duiker that he raised as a pet and later released into the wild. It then disappeared completely, until (two months later) a grass fire destroyed all the vegetation that the duiker would have been familiar with. The duiker now reappeared, standing in the open behind the house where it had been reared, looking dejected. In a charred and blackened environment, Spinage suggested that the duiker had returned to the only familiar place. He petted it, and it went away, but when seen again on later occasions it would run up to him and stand to be stroked (Spinage 1986, p. 134) [adjacent image shows skull of Maxwell’s duiker. Image © University of Edinburgh, from here].
Evidence suggests that duikers are being harvested at unsustainable rates for the bushmeat trade, and most species are now regarded as being at risk.
Refs – –
Flores, D. V. 2001. More about duikers in ancient Egypt. Science 292, 440.
Hassanin, A. & Douzery, J. P. 1999a. Evolutionary affinities of the enigmatic saola (Pseudoryx nghetinhensis) in the context of the molecular phylogeny of Bovidae. Proceedings of the Royal Society of London B 266, 893-900.
– . & Douzery, J. P. 1999b. The tribal radiation of the family Bovidae (Artiodactyla) and the evolution of the mitochondrial cytochrome b gene. Molecular Phylogenetics and Evolution 13, 227-243.
Jansen van Vuuren, B. & Robinson, T. J. 2001. Retrieval of four adaptive lineages in duiker antelope: evidence from mitochondrial DNA sequences and fluorescence in situ hybridization. Molecular Phylogenetics and Evolution 20, 409-425.
Kingdon, J. 1997. The Kingdon Field Guide to African Mammals. Academic Press, San Diego.
Lumpkin, S. & Kranz, K. R. 1984. Cephalophus sylvicultor. Mammalian Species 225, 1-7.
Manlius, N. 2001. Were there duikers in ancient Egypt? Science 291, 1701.
Nowak, R. M. 1999. Walker’s Mammals of the World, Sixth Edition. Volume II. The Johns Hopkins University Press, Baltimore and London.
Price, S. A., Bininda-Emonds, O. R. P. & Gittleman, J. L. 2005. A complete phylogeny of the whales, dolphins and even-toed hoofed mammals (Cetartiodactyla). Biological Reviews 80, 445-473.
Ralls, K. 1973. Cephalophus maxwelli. Mammalian Species 31, 1-4.
Ronald. K. & Kranz, K. 2001. Duikers. In MacDonald, D. (ed) The New Encyclopedia of Mammals. Oxford University Press (Oxford), pp. 542-545.
Spinage, C. A. 1986. The Natural History of Antelopes. Christopher Helm, London.