Albinism is a deficiency or complete absence of the pigment eumelanin, but the condition known as melanism is the presence of an excessive amount of eumelanin. Animals exhibiting this condition are said to be melanistic, and appear abnormally dark in comparison with normal-coloured specimens of their species. True melanism does not affect animals' body markings, targeting their background colouration instead.
One of the most interesting cases of melanism is of profound cryptozoological pertinence and concerns the ratel Mellivora capensis, also known as the honey badger. Although alluded to by Dr Bernard Heuvelmans in his book On the Track of Unknown Animals (1958), this is the first time that the true complexity of this case has been aired cryptozoologically.
Widely distributed in Africa and also found in India, the ratel is a pugnacious species of mustelid, which can attain an impressive total length of 3.5 ft - equivalent to a small bear. Its pelage colouration is very striking - laterally and ventrally its fur is jet black, but dorsally it sports a wide band of silver-grey fur that stretches from its brow along the entire length of its back to its hindquarters.
Today, only a single species of ratel is recognised, but this was not always the case. Just over a century ago, zoologists still distinguished several different ratel species. These differed from one another with regard to the relative proportion of pelage taken up by the silver-grey band, but all conformed to the basic ratel colour scheme - pale dorsally, jet black elsewhere - until 1906, that is.
During the early years of the 20th Century, while animal collecting in Central Africa, Major Powell-Cotton obtained two specimens of a ratel form dramatically different from all others on record, which he had discovered on the eastern fringe of the Ituri Forest, in what is now the Democratic Congo. The reason for the Ituri ratel's distinctiveness, however, was due not to its provenance but rather to its colouration. For with the exception of just a few grizzled hairs on the upper region of its head, it was totally black - exhibiting no trace of the familiar dorsal silver-grey band characterising all other ratels.
Powell-Cotton's two Ituri specimens soon came to the attention of noted British zoologist Dr Richard Lydekker, who documented them in a short paper published on 6 February 1906 by the Proceedings of the Zoological Society of London. Comparing the marked differences in habitat between the open or bush-clad country inhabited by typical ratels and the dense shadowed seclusion of the Ituri Forest, Lydekker suggested that the latter's all-black ratels may conceivably constitute something more significant than simply a melanistic mutant form (morph) of the normal ratel. Indeed, he felt that they may actually represent a separate species, one in which the conspicuous silver band had been replaced during evolution by a uniformly black pelage in order to provide effective camouflage within the Ituri Forest's unlit interior. Honouring its discoverer, Lydekker named the new ratel Mellivora cottoni - but its status as a distinct species would be short-lived.
The first hint of this came 0n 6 April 1909, with the description of yet another new ratel species, this time by carnivore specialist Reginald Pocock, which was formally christened Mellivora signata in a paper published by the Zoological Society of London's Proceedings.
Significantly, the single specimen upon which this latest species was based, which had been obtained in Sierra Leone, was somewhat intermediate in colouration between M. cottoni and the typical ratel. Although it possessed a light-coloured upper band like other ratels, in this single M. signata specimen the band was not of uniform shading throughout its length. On the specimen's brow it was silver-grey, but it became ever darker as it extended backwards across its shoulders and along its spine towards its hindquarters. Thus its shoulders and anterior back portion were speckled grey, whereas its posterior back and hindquarters were virtually black.
Shortly afterwards, yet another ratel paper (written this time by Dr F.D. Welch) appeared in the Zoological Society's Proceedings, but this was one that had considerable bearing upon the Ituri black ratel and upon the whole thorny issue of ratel classification. The subject of the paper was a former inmate of London Zoo - a ratel that had been obtained in some unrecorded African locality. When it arrived at the zoo in 1890, it was already fully-grown, and displayed the usual ratel colour scheme. During the next 12 years, however, Welch observed that its silver band gradually darkened, and by the time of the ratel's death its body's dorsal surface was coloured "black merely sprinkled with grey"; even its head, whose silver colour had suffered rather less darkening, lacked a clear demarcation line between upper and lower pelage colouration.
Later records provided similar findings. Accordingly, it became clear that all of the silver-backed ratel types formerly allocated the status of separate species, as well as M. signata, were nothing more than individual colour variations of a single species - M. capensis. And as for the all-black Ituri species, M. cottoni, this appeared to be merely an age-related artefact, for scientists now recognised that the possession of a melanistic pelage by ratels was linked not to taxonomic distinction but simply to senility. The older the ratel, the blacker it became. Exit M. cottoni from the zoological catalogue!
What makes all of this so intriguing from a cryptozoological standpoint is that in many parts of tropical Africa, native tribes live in great fear of a mysterious and exceedingly savage carnivore known by a variety of native names, but referred to by westerners, especially in Kenya, as the Nandi bear. Reports concerning this creature (still adamantly unrecognised and undescribed by science) seem to refer to several different types of creature - but three in particular. Two of these appear to be an abnormally-coloured strain of hyaena (see below) and an exceptionally large form of baboon. The third could well be the ratel - except (at least on first sight) for two discrepancies. Firstly, those Nandi bear reports that describe ratel-like beasts affirm that the animals in question are uniformly dark; and secondly, these animals are somewhat larger than normal ratels. In reality, however, neither of these supposed discrepancies raises problems in reconciling such reports with the ratel.
As already noted here, very old ratels can be wholly black in colour. In addition, examination of preserved ratel pelts reveals that such ratels are frequently notably larger than the average size for their species. Nor should we overlook the fact that the ratel is ferocious out of all proportion to its size - authentic reports exist of a single ratel chasing a pride of lions away from their kill, with the lions not daring to approach again until the ratel had finished its meal and departed! Consequently, although Nandi bear reports describing distinctly hyaena-like or baboon-like beasts cannot be explained in this way, a number of other Nandi bear accounts may well be attributable to certain belligerent ratels that had attained a large size and had acquired a melanistic pelage due to advanced age.
Do some Nandi bear sightings involve erythristic spotted hyaenas? (Computer-generated image by Dr Karl Shuker)
Eumelanin is the most familiar form of the pigment melanin, but it is not the only one. Two other forms are phaeomelanin, which is responsible for light brown and yellow pigmentation, and erythromelanin, responsible for the rich reddish-orange hue characterising the pelage of such creatures as the red squirrel Sciurus vulgaris and the red fox Vulpes vulpes. In mammals, phaeomelanin is responsible for a wide range of different fur colours, ranging from light brown and dull red through to golden-orange, yellow, and even cream. The greater the number of phaeomelanin pigment granules present per given area of body surface, the darker the colour of the fur borne upon that surface. Sometimes, however, genetic mutations in mammals result in an abnormal increase in phaeomelanin, but often at the expense of the darker pigment, eumelanin, so that their pelage appears paler than normal. This condition is known as erythrism, and mammals exhibiting it are said to be erythristic.
Erythristic animals are certainly very striking in appearance - so much so, in fact, that several were once considered to be separate species in their own right, rather than mere colour morphs of no taxonomic significance. In 1927, for instance, zoologist Dr Ernst Schwarz revealed that a number of enigmatic African guenon monkeys formerly classed as full species were in reality nothing more than rare erythristic specimens of certain other species. These false species included Cercopithecus inobservatus (merely an erythristic morph of the moustached monkey C. cephus), C. insignis (merely a red morph of Kandt's subspecies of Sykes's monkey, i.e. C. albogularis kandti), and C. insolitus (simply an erythristic specimen of the greater white-nosed monkey C. nictitans).
Those monkeys are now ex-cryptozoological creatures. However, it is possible that erythrism is also an intrinsic component of an ongoing mystery beast saga - the afore-mentioned Nandi bear. For whereas some reports of this beast may well have been based upon large, all-black ratels, others appear to have derived from highly abnormal hyaenas. In June 1926, for instance, Arthur J. Stent trapped at Vizara in Nyasaland (now Malawi) a very strange-looking animal that seemed to be a specimen of the elusive Nandi bear. Stent considered it to be some form of hyaena, but was unable to identify it fully, and so he sent its distinctive red-furred skin to the British Museum (Natural History) for formal categorisation. It was closely examined there by the notable carnivore expert Reginald Pocock, who subsequently announced that it had come from an erythristic specimen of the spotted hyaena Crocuta crocuta - hence its extremely unusual appearance.
Although known from arid regions of Sudan and Somaliland, erythristic spotted hyaenas are very much rarer in Central Africa. Consequently, in view of the striking colouration of Stent’s beast - so different from its species' typical morphology - plus the great rarity of erythristic hyaenas in this region, it can readily be understood why native eyewitnesses spying such a creature (especially if only for a very brief period of time) might consider it to comprise a totally different type of animal from the normal spotted hyaena. A veritable Nandi bear, in fact.
A normal spotted hyaena (left) alongside a genuine erythristic specimen (right) ((c) Markus Bühler)