Okapi

Distribution

This species is endemic to north and east former Zaire and adjacent areas probably extending as far east as western Uganda (East, 1996; Bodmer & Rabb, 1992; Wilson & Reeder, 1993). They prefer altitudes between 500 and 1,000 m, although they may venture above 1,000 m in the eastern montane rainforests. One sighting occurred at 1,450 m on Mt. Hoyo, in the upper Ituri. The range of the okapi is limited by high montane forests to the east, swamp forests below 500 m to the west, savannas of the Sahel/Soudan to the north, and open woodlands to the south. Okapis are most common in the Wamba and Epulu areas (Bodmer 1992). Its distribution map was first obtained from Bodmer & Rabb (1992) and then revised by Dr. R. East ( 23 June '97 ). The preliminary map was updated on the basis of more recent information found in Kingdon (1997)

Categorical-discrete (CD) distribution model

Okapis occur in the dense rainforests at middle elevations within their range. They frequent river banks and stream beds and may occasionally venture into areas of secondary forest growth (Bodmer 1992).

The okapi has a form superficially resembling that of a horse. Average body length is 2.5 m, and average height at the shoulder is 1.5 m. The neck is relatively long in comparison to that of other ruminants, and the ears are large and flexible. The body is chocolate-brown, with creamy white horizontal stripes on the legs and hindquarters and white stockings on the ankles. The cheeks, throat, and chest are whitish-gray or tan (Bodmer 1992). The unique color pattern of the okapi allows it to disappear into the background of dense vegetation and rotting leaves where it lives (Grzimek 1990). Male okapis have hair-covered horns not exceeding 15 cm in length. The horns are fused to the frontal bones over the orbits and project rearward. Females may be slightly red in color, lack horns, and average 4.2 cm taller than males. Both males and females have interdigital glands on the front and hind feet (Bodmer 1992). The most giraffe-like feature of the okapi is the long black tongue which is used for plucking buds, leaves, and branches from trees and shrubs as well as for grooming (Kingdon 1979). In addition, the walking gait of the okapi closely resembles that of a giraffe. Both giraffe and okapi simultaneously step with the front and hind leg on the same side of the body rather than moving alternate legs on either side like other ungulates (Dagg, 1960).

Reproduction

In the wild, okapis are solitary, coming together primarily for mating. Okapi courtship and mating rituals are known only from observations done in zoos. Partners begin courtship by circling, sniffing, and licking eachother. Eventually, the male asserts his dominance by extending his neck, tossing his head, and thrusting one leg foreward. This display is followed by mounting and copulation. After mating, the male and female part (Grzimek 1990). The gestatation period lasts about 440 days (Bodmer 1992), and females retreat into dense forest vegetation to give birth (Grzimek 1990). Newborn okapis weigh 14-30 kg at birth. They are precocial and may nurse after 21 minutes and stand after just 30 minutes. Young spend the first day or two of life following the mother around and exploring the environment. After this, they find a suitable hiding spot and make a nest. For the next two months, they spend 80% of their time in this nest. Hiding behavior appears to promote rapid growth and provides protection from predators. A disturbed calf lies motionless in its nest, and a female okapi will rush to aggressively defend her calf from danger. During the hiding stage, young nurse relatively infrequently and do not defecate. These strategies help keep them undetected by predators. Weaning occcurrs at about 6 months, although young may continue to suckle for more than a year. Young males begin developing horns at one year of age, and both males and females reach adult size at about three years. In captivity, the youngest female to breed was 1 year 7 months old, and the youngest male was 2 years 2 months old. The okapi's lifespan is about 30 years in captivity, but data from wild populations is unavailable (Bodmer 1992).

Behavior

Okapis occur alone or in mother-offspring pairs. They have overlapping home ranges of several square kilometers and typically occur at densities of about 0.6 animals per square kilometer. The home ranges of males are generally slightly larger that those of females. Although they are not social animals, okapis tolerate eachother in the wild and may even feed in small groups for short periods of time. Knowledge of okapi social behavior comes primarily from observations of captive animals. Males appear to mark with urine, and both males and females mark by rubbing their necks on trees. Okapis seem to exhibit several aggressive behaviors including kicking and headthrowing. In captivity, dominant animals hold their necks straight and heads higher than subordinates, and the placing of the neck and head on the ground is a clear sign of submission. In addition, social grooming and play behavior seem to be common for both juveniles and adults. Vocal communication is important in many captive social interactions including mother-offspring bonding and distress calls, as well as courtship behavior (Bodmer 1992).

Food Habits

Okapis are diurnal and forage along fixed, well-trodden paths through the forest (Grzimek 1990). They feed primarily on the leaves, buds, and shoots of more than 100 different species of forest vegetation (Bodmer 1992). Many of the plant species fed upon by the okapi are known to be poisonous to humans. Additionally, okapis eat grasses, fruits, ferns, and fungi. Examination of okapi feces has revealed that the charcoal from trees burnt by lightning is consumed as well. Field observations indicate that the okapi's mineral and salt requirements are filled primarily by a sulfurous, slightly salty, reddish clay found near rivers and streams (Grzimek 1990).

Conservation Status

The okapi was not discovered until 1900, when Harry Johnston sent two pecies of "zebra-like" skin to London (Kingdon 1979). More recently, the okapi has been extirpated from Uganda and, since 1933, protected by law in Zaire. Despite its patchy distribution, the okapi is common in much of its current range and is therefore not listed as a threatened species by international agreement. However, habitat loss due to deforestation as well as poaching continue to restrict the range of the species and take their toll on the population. Another great danger to the okapi is lack of knowledge about it outside of zoos. Little field research has been done on the species due to its relatively recent discovery, inaccessible habitat, and reclusive nature (Bodmer 1992).

Other Comments

The okapi has been the subject of considerable genetic interest ever since chromosome research revealed that individuals having 2n=45 were more common than those having the expected 2n=46. This anomaly has been related to the Robertsian fusion phenomenon (Bodmer 1992).

The only known living relative of the giraffe, the okapi was first described to western science by P. L. Sclater in 1901. Henry Stanley first penetrated the dense Ituri Forest of the Congo in 1890, exposing the existence of the okapi in his book "In Darkest Africa". In his writings, he remarked of his surprise when the native Wambutti pygmies didn't marvel at his horses, saying that they sometimes caught a donkey-like animal in their pits, which they called o'api (misinterpreted by Stanley as atti). Rumours of this strange, ass-like animal reached Sir Johnston, which spurred him to make a journey into the Congo in 1899. After winning the confidence of the Wambutti, Johnston was able to learn more about the mysterious atti - including its real name. After hearing its description - a dark brown animal resembling a donkey with striped legs - Johnston was sure that the o'api was a species of forest zebra still awaiting a scientific description. Later that year, in the Belgian Fort at Mbeni, Johnston was able to obtain two headbands, made from the striped pieces of okapi skins, which he sent to the Zoological Society of London in 1900. From these pieces of skin, an announcement of a new species - Equus? johnstoni - was made. Back in the Congo, Johnston was shown a set of tracks by the natives which they insisted were made by an okapi. However, as the tracks were cloven-hoofed, Johnston dismissed them as they did not fit his notion that the okapi was a member of the horse family. Meanwhile Karl Eriksson, Commandant at Fort Mbeni, was able to secure a complete skin and two skulls, which he sent to Johnston. Armed with these findings, Johnston wrote back to the Zoological Society of London, sending the priceless cargo along. The skulls were the key to the puzzle, allowing scientists to determine that this new species was not a horse, but a forest giraffe. Okapi is a corruption of the native name o'api. Sir Harry H. Johnston (1858-1927), explorer and author, discovered the okapi while in the Colonial Administration of British Central Africa.

Contributors

Eric Palkovacs (author), University of Michigan: October, 2000.

References

Bodmer, R.E., and G.B. Rabb. 1992. Okapia johnstoni. Mamm. Species, 422:1-8

Dagg, A.I. 1960. Gaits of the Giraffe and Okapi. Journal of Mammalogy, 41(2):282

Grzimek, B. 1990. Grzimek's Encyclopedia of Mammals. Vol. 5. McGraw-Hill Publishing Company, New York.

Kingdon, J. 1979. East African Mammals an Atlas of Evolution in Africa. Vol. 3. Academic Press, London.