Wikipedia

Etymology and taxonomyEdit

CharacteristicsEdit

Okapi displaying its striking white stripes and short hair-covered ossicones.

The okapi is a medium-sized giraffid, standing 1.5 m (4.9 ft) tall at the shoulder. Its average body length is about 2.5 m (8.2 ft) and its weight ranges from 200 to 350 kg (440 to 770 lb).[17] It has a long neck, and large and flexible ears. The coat is a chocolate to reddish brown, much in contrast with the white horizontal stripes and rings on the legs and white ankles. The striking stripes make it resemble a zebra.[18] 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.[19] Male okapis have short, hair-covered horns called ossicones, less than 15 cm (5.9 in) in length. The okapi exhibits sexual dimorphism, with females 4.2 cm (1.7 in) taller on average, slightly redder and lacking prominent horns, instead possessing hair whorls.[20][21]

The close-up of male's head. Only the male has ossicones.

The okapi shows several adaptations to its tropical habitat. The large number of rod cells in the retina facilitate night vision, and there is an efficient olfactory system. The large auditory bullae lead to a strong sense of hearing. The dental formula of the okapi is 0.0.3.33.1.3.3.[19] Teeth are low-crowned, fine-cusped and efficiently cut tender foliage. The large caecum and colon help in microbial digestion, and a quick rate of food passage allows for lower cell wall digestion than in other ruminants.[22]

The okapi can be easily distinguished from its nearest extant relative, the giraffe. It is much smaller and shares more external similarities with the deer and bovids than with the giraffe. While both sexes possess horns in the giraffe, only males bear horns in the okapi. The okapi has large palatine sinuses, unique among the giraffids. Morphological similarities 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[23] - and a long black tongue (longer in the okapi) useful in plucking buds and leaves as well as for grooming.[22]

Ecology and behaviourEdit

The long tongue of the okapi

An okapi stands next to her calf at White Oak Conservation.

Okapis are primarily diurnal but may be active for a few hours in darkness.[24] They are essentially solitary, coming together only to breed. They have overlapping home ranges and typically occur at densities of about 0.6 animals per square kilometre.[18] Male home ranges average 13 km2 (5.0 sq mi) while female home ranges average 3–5 km2 (1.2–1.9 sq mi). Males migrate continuously, while females are sedentary.[25] 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 neck against trees, leaving a brown exudate.[19]

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.[22] 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" (contact calls used by both sexes), "moan" (by females during courtship) and "bleat" (by infants under stress). 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 predator of the okapi.[19]

DietEdit

Okapis are herbivores, feeding on tree leaves and buds, grasses, ferns, fruits, and fungi. They prefer to feed in treefall gaps. Staple foods comprise shrubs and lianas. The main constituents of the diet are woody, dicotyledonous species; monocotyledonous plants are not eaten regularly. In the Ituri forest, the okapi feeds mainly upon the plant families Acanthaceae, Ebenaceae, Euphorbiaceae, Flacourtiaceae, Loganiaceae, Rubiaceae and Violaceae.[19][25]

ReproductionEdit

Female okapis become sexually mature at about one-and-a-half years old, while males reach maturity after two years. Rut in males and estrus in females does not depend on the season. In captivity, estrus cycles recur every 15 days.[22][26] The male and the female begin courtship by circling, smelling and licking each other. The male shows his dominance by extending his neck, tossing his head and protruding one leg forward. This is followed by mounting and copulation.[20]

The gestational period is around 440 to 450 days long, following which usually a single calf is born, weighing 14–30 kg (31–66 lb). The udder of the pregnant female starts swelling two months before parturition, and vulval discharges may occur. Parturition takes 3–4 hours, and the female stands throughout this period, though she may rest during brief intervals. The mother consumes the afterbirth and extensively grooms the infant. Her milk is very rich in proteins and low in fat.[22]

As in other ruminants, the infant can stand within 30 minutes of birth. Although generally similar to adults, newborn calves have false eyelashes, a long dorsal mane and long white hairs in the stripes. These features gradually disappear and give way to the general appearance within a year. The juveniles are kept in hiding, and nursing takes place infrequently. The growth rate of calves is appreciably high in the first few months of birth, after which it gradually declines. Juveniles start taking solid food from three months, and weaning takes place at six months. Horn development in males takes one year after birth. The okapi's average lifespan is 20 to 30 years.[19]

Habitat and distributionEdit

Threats and conservationEdit

HistoryEdit

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.[31]

For years, Europeans in Africa had heard of an animal that they came to call the 'African unicorn'. In his travelogue of exploring the Congo, Henry Morton Stanley mentioned a kind of donkey that the natives called the atti, which scholars later identified as the okapi. Explorers may have seen the fleeting view of the striped backside as the animal fled through the bushes, leading to speculation that the okapi was some sort of rainforest zebra.

When the British governor of 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 grateful 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.[32]

The okapi is sometimes referred to as an example of a living fossil.[33]

See alsoEdit

ReferencesEdit

Further readingEdit

• Wolfram Bell (Nov. 2009): "Okapis – geheimnisvolle Urwaldgiraffen. Entdeckungsgeschichte, Biologie, Haltung und Medizin einer seltenen Tierart." Schüling Verlag Münster, Germany. ISBN 978-3-86523-144-4.

Edit

‏Source en.m.wikipedia.org