Okapi
The okapi, also known as the forest giraffe, zebra giraffe and Congolese giraffe, is an artiodactyl mammal that is endemic to the northeast Democratic Republic of the Congo in central Africa. However, non-invasive genetic identification has suggested that a population has occurred south-west of the Congo River as well. It is the only species in the genus Okapia. Although the okapi has striped markings reminiscent of zebras, it is most closely related to the giraffe. The okapi and the giraffe are the only living members of the family Giraffidae.
The okapi stands about tall at the shoulder and has a typical body length around. Its weight ranges from. It has a long neck, and large, flexible ears. Its coat is a chocolate to reddish brown, much in contrast with the white horizontal stripes and rings on the legs, and white ankles. Male okapis have short, distinct horn-like protuberances on their heads called ossicones, less than in length. Females possess hair whorls, and ossicones are absent.
Okapis are primarily diurnal, but may be active for a few hours in darkness. They are essentially solitary, coming together only to breed. Okapis are herbivores, feeding on tree leaves and buds, grasses, ferns, fruits, and fungi. Rut in males and estrus in females does not depend on the season. In captivity, estrus cycles recur every 15 days. The gestational period is around 440 to 450 days long, following which usually a single calf is born. The juveniles are kept in hiding, and nursing takes place infrequently. Juveniles start taking solid food from three months, and weaning takes place at six months.
Okapis inhabit canopy forests at altitudes of. The International Union for the Conservation of Nature and Natural Resources classifies the okapi as endangered. Major threats include habitat loss due to logging and human settlement. Illegal mining and extensive hunting for bushmeat and skin have also led to a decline in populations. The Okapi Conservation Project was established in 1987 to protect okapi populations.
Etymology and taxonomy
Although the okapi was unknown to the Western world until the 20th century, it may have been depicted since the early fifth century BCE on the façade of the Apadana at Persepolis, a gift from the Ethiopian procession to the Achaemenid kingdom.For years, Europeans in Africa had heard of an animal that they came to call the African unicorn. It was brought to prominent European attention by speculation on its existence found in press reports covering Henry Morton Stanley's journeys in 1887. In his travelogue of exploring the Congo, Stanley mentioned a kind of donkey that the natives called the atti, which scholars later identified as the okapi.
When the British special commissioner in Uganda, Sir Harry Johnston, discovered some Pygmy inhabitants of the Congo being abducted by a showman for exhibition, he rescued them and promised to return them to their homes. The Pygmies fed Johnston's curiosity about the animal mentioned in Stanley's book. Johnston was puzzled by the okapi tracks the natives showed him; while he had expected to be on the trail of some sort of forest-dwelling horse, the tracks were of a cloven-hoofed beast.
Though Johnston did not see an okapi himself, he did manage to obtain pieces of striped skin and eventually a skull. From this skull, the okapi was correctly classified as a relative of the giraffe; in 1901, the species was formally recognized as Okapia johnstoni.
Okapia johnstoni was first described as Equus johnstoni by English zoologist Philip Lutley Sclater in 1901. The generic name Okapia derives either from the Mbuba name okapi or the related Lese Karo name o'api, while the specific name is in recognition of Johnston, who first acquired an okapi specimen for science from the Ituri Forest.
In 1901, Sclater presented a painting of the okapi before the Zoological Society of London that depicted its physical features with some clarity. Much confusion arose regarding the taxonomical status of this newly discovered animal. Sir Harry Johnston himself called it a Helladotherium, or a relative of other extinct giraffids. Based on the description of the okapi by Pygmies, who referred to it as a "horse", Sclater named the species Equus johnstoni. Subsequently, zoologist Ray Lankester declared that the okapi represented an unknown genus of the Giraffidae, which he placed in its own genus, Okapia, and assigned the name Okapia johnstoni to the species.
In 1902, Swiss zoologist Charles Immanuel Forsyth Major suggested the inclusion of O. johnstoni in the extinct giraffid subfamily Palaeotraginae. However, the species was placed in its own subfamily Okapiinae, by Swedish palaeontologist Birger Bohlin in 1926, mainly due to the lack of a cingulum, a major feature of the palaeotragids. In 1986, Okapia was finally established as a sister genus of Giraffa on the basis of cladistic analysis. The two genera together with Palaeotragus constitute the tribe Giraffini.
Evolution
The earliest members of the Giraffidae first appeared in the early Miocene in Africa, having diverged from the superficially deer-like climacoceratids. Giraffids spread into Europe and Asia by the middle Miocene in a first radiation. Another radiation began in the Pliocene, but was terminated by a decline in diversity in the Pleistocene. Several important primitive giraffids existed more or less contemporaneously in the Miocene, including Canthumeryx, Giraffokeryx, Palaeotragus, and Samotherium. According to palaeontologist and author Kathleen Hunt, Samotherium split into Okapia and Giraffa. However, J. D. Skinner argued that Canthumeryx gave rise to the okapi and giraffe through the latter three genera and that the okapi is the extant form of Palaeotragus. The okapi is sometimes referred to as a living fossil, as it has existed as a species over a long geological time period, and morphologically resembles more primitive forms.In 2016, a genetic study found that the common ancestor of giraffe and okapi lived about 11.5 million years ago.
Description
The okapi is a medium-sized giraffid, standing tall at the shoulder. Its average body length is about and its weight ranges from. It has a long neck, and large and flexible ears. In sharp contrast to the white horizontal stripes on the legs and white ankles, the okapi's coat is a chocolate to reddish brown. The distinctive stripes resemble those of a zebra. These features serve as an effective camouflage amidst dense vegetation. The face, throat, and chest are greyish white. Interdigital glands are present on all four feet, and are slightly larger on the front feet. Male okapis have short, hair-covered horn-like structures called ossicones, less than in length, which are similar in form and function to the ossicones of a giraffe. The okapi exhibits sexual dimorphism, with females taller on average, slightly redder, and lacking prominent ossicones, instead possessing hair whorls.The okapi shows several adaptations to its tropical habitat. The large number of rod cells in the retina facilitate night vision, and an efficient olfactory system is present. The large auditory bullae of the temporal bone allow a strong sense of hearing. The dental formula of the okapi is. Teeth are low-crowned and finely cusped, and efficiently cut tender foliage. The large cecum and colon help in microbial digestion, and a quick rate of food passage allows for lower cell wall digestion than in other ruminants.
The okapi is easily distinguished from its nearest extant relative, the giraffe. It is much smaller than the giraffe and shares more external similarities with bovids and cervids. Ossicones are present only in the male okapi, while both sexes of giraffe possess this feature. The okapi has large palatine sinuses, unique among the giraffids. Morphological features shared between the giraffe and the okapi include a similar gait – both use a pacing gait, stepping simultaneously with the front and the hind leg on the same side of the body, unlike other ungulates that walk by moving alternate legs on either side of the body – and a long, black tongue useful for plucking buds and leaves, as well as for grooming.
Ecology and behaviour
Okapis are primarily diurnal, but may be active for a few hours in darkness. They are essentially solitary, coming together only to breed. They have overlapping home ranges and typically occur at densities around 0.6 animals per square kilometre. Male home ranges average, while female home ranges average. Males migrate continuously, while females are sedentary. Males often mark territories and bushes with their urine, while females use common defecation sites. Grooming is a common practice, focused at the earlobes and the neck. Okapis often rub their necks against trees, leaving a brown exudate.The male is protective of his territory, but allows females to pass through the domain to forage. Males visit female home ranges at breeding time. Although generally tranquil, the okapi can kick and butt with its head to show aggression. As the vocal cords are poorly developed, vocal communication is mainly restricted to three sounds — "chuff", "moan" and "bleat". Individuals may engage in Flehmen response, a visual expression in which the animal curls back its upper lips, displays the teeth, and inhales through the mouth for a few seconds. The leopard is the main natural predator of the okapi.