Okapi

The okapi (; Okapia johnstoni), 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.

thumbnail|upright|Illustration from an original painting by Sir Harry Johnston, based on preserved skins (1901)

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. The generic name Okapia derives either from the Mbuba name or the related Lese Karo name , while the specific name (johnstoni) 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

thumb|upright|Despite the vast difference in neck length, the okapi (left) and the giraffe (right) both have seven [[cervical vertebrae (as do all mammals except for manatees and sloths).]]

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 (23–10 million years ago), including Canthumeryx, Giraffokeryx, Palaeotragus, and Samotherium. According to palaeontologist and author Kathleen Hunt, Samotherium split into Okapia (18 million years ago) and Giraffa (12 million years ago). 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 (e.g. Samotherium).

In 2016, a genetic study found that the common ancestor of giraffe and okapi lived about 11.5 million years ago.

Description

upright|left|thumbnail|Male okapi displaying his striking horizontal stripes

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. 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 . – and a long, black tongue (longer in the okapi) 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. They are unique in the Ituri Forest as they are the only known mammal that feeds solely on understory vegetation, where they use their tongues to selectively browse for suitable plants. The tongue is also used to groom their ears and eyes. They prefer to feed in treefall gaps. The okapi has been known to feed on over 100 species of plants, some of which are known to be poisonous to humans and other animals. Fecal analysis shows that none of those 100 species dominates the diet of the okapi. 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. The male and the female begin courtship by circling, smelling, and licking each other. The male shows his interest by extending his neck, tossing his head, and protruding one leg forward. This is followed by mounting and copulation. 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. Calves are known not to defecate for the first month or two of life, which is hypothesized to help avoid predator detection in their most vulnerable phase of life. The growth rate of calves is appreciably high in the first few months of life, after which it gradually declines. Juveniles start taking solid food from 3 months, and weaning takes place at 6 months. Ossicone development in males takes 1 year after birth. The okapi's typical lifespan is 20–30 years. In 2008, it was recorded in Virunga National Park. There is also evidence that okapis were also observed in the Semuliki Valley in Uganda by Europeans, but later became extinct in the late 1970s. The Semuliki Valley provides a similar habitat to the Congo Basin.

Status

Threats and conservation

thumb|left|Okapi at [[Disney's Animal Kingdom]]

The IUCN classifies the okapi as endangered. It is fully protected under Congolese law. The Okapi Wildlife Reserve and Maiko National Park support significant populations of the okapi, though a steady decline in numbers has occurred due to several threats. Other areas of occurrence are the Rubi Tele Hunting Reserve, the Abumombanzi Reserve, the

Sankuru Nature Reserve, the Lomami National Park. Major threats include habitat loss due to logging and human settlement. Extensive hunting for bushmeat and skin and illegal mining have also led to population declines. A threat that has emerged quite recently is the presence of illegal armed groups around protected areas, inhibiting conservation and monitoring actions. A small population occurs north of the Virunga National Park, but lacks protection due to the presence of armed groups in the vicinity. as well as all 14 okapis at their breeding center.

The Okapi Conservation Project, established in 1987, works towards the conservation of the okapi, as well as the growth of the indigenous Mbuti people.

Okapis in zoos

thumb|thumbtime=0:09|1960 Dutch newsreel about okapis in [[Diergaarde Blijdorp]]

Around 100 okapis are in accredited Association of Zoos and Aquariums (AZA) zoos. The okapi population is managed in America by the AZA's Species Survival Plan, a breeding program that works to ensure genetic diversity in the captive population of endangered animals, while the EEP (European studbook) and ISB (Global studbook) are managed by Antwerp Zoo in Belgium, which was the first zoo to have an Okapi on display (in 1919), as well as one of the most successful in breeding them.

In 1937, the Bronx Zoo became the first in North America to acquire an okapi. With one of the most successful breeding programs, 13 calves have been born there between 1991 and 2011. The San Diego Zoo has exhibited okapis since 1956, and their first okapi calf was born in 1962. Since then, there have been more than 60 okapis born at the zoo and the nearby San Diego Zoo Safari Park, the most recent being Mosi, a male calf born on 21 July 2017 at the zoo. The Brookfield Zoo in Chicago has also greatly contributed to the captive population of okapis in accredited zoos. The zoo has had 28 okapi births since 1959.

Other North American zoos that exhibit and breed okapis include: Denver Zoo and Cheyenne Mountain Zoo (Colorado); Houston Zoo, Dallas Zoo, and San Antonio Zoo (Texas); Disney's Animal Kingdom, White Oak Conservation, Zoo Miami, and ZooTampa at Lowry Park (Florida); Los Angeles Zoo, Sacramento Zoo, and San Diego Zoo (California); Saint Louis Zoo (Missouri); Cincinnati Zoo and Botanical Garden and Columbus Zoo and Aquarium (Ohio); Memphis Zoo and Nashville Zoo (Tennessee); The Maryland Zoo in Baltimore (Maryland); Sedgwick County Zoo and Tanganyika Wildlife Park (Kansas); Roosevelt Park Zoo (North Dakota); Henry Doorly Zoo and Aquarium (Nebraska); Philadelphia Zoo (Pennsylvania); Potawatomi Zoo (Indiana); Oklahoma City Zoo and Botanical Garden (Oklahoma); Blank Park Zoo (Iowa); and Potter Park Zoo (Michigan).

In Europe, zoos that exhibit and breed okapis include: Chester Zoo, London Zoo, Marwell Zoo, The Wild Place, and Yorkshire Wildlife Park (United Kingdom); Dublin Zoo (Ireland); Berlin Zoo, Frankfurt Zoo, Wilhelma Zoo, Wuppertal Zoo, Cologne Zoo, and Leipzig Zoo (Germany); Zoo Basel (Switzerland); Copenhagen Zoo (Denmark); Rotterdam Zoo and Safaripark Beekse Bergen (Netherlands); Antwerp Zoo (Belgium); Dvůr Králové Zoo (Czech Republic); Wrocław Zoo (Poland); Bioparc Zoo de Doué and ZooParc de Beauval (France); and Lisbon Zoo (Portugal).

In Asia, three Japanese zoos exhibit okapis: Ueno Zoo in Tokyo; Kanazawa Zoo and Zoorasia in Yokohama.

References

External links

The okapi management site ()
Monograph of the Okapi (1910) by E. Ray Lankester and William George Ridewood