About Okapia johnstoni (P.L.Sclater, 1901)
The okapi, scientifically named Okapia johnstoni (P.L.Sclater, 1901), is a medium-sized giraffid. It reaches 1.5 m (4 ft 11 in) tall at the shoulder, has an average body length of about 2.5 m (8 ft 2 in), and weighs 200 to 350 kg (440 to 770 lb). It has a long neck and large, flexible ears. Its coat ranges from chocolate to reddish brown, in sharp contrast to the white horizontal stripes on its legs and white ankles. These distinctive zebra-like stripes work as effective camouflage in dense vegetation. The okapi's 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, which are less than 15 cm (5.9 in) long and similar in form and function to giraffe ossicones. The okapi shows sexual dimorphism: females are an average of 4.2 cm (1.7 in) taller, slightly redder, and lack prominent ossicones, instead having hair whorls. The okapi has multiple adaptations for its tropical habitat. A large number of rod cells in its retina support night vision, and it has an efficient olfactory system. Its large auditory bullae on the temporal bone give it a strong sense of hearing. The okapi's dental formula is 0.0.3.3 / 3.1.3.3. Its teeth are low-crowned and finely cusped, and efficiently cut tender foliage. A large cecum and colon aid microbial digestion, and a quick food passage rate means it digests less plant cell wall material than other ruminants. The okapi can be easily told apart from its closest living relative, the giraffe. It is much smaller than the giraffe, and shares more external similarities with bovids and cervids. Only male okapis have ossicones, while both sexes of giraffes have this feature. The okapi has large palatine sinuses (hollow cavities in the palate), a trait unique among giraffids. Shared morphological features between okapis and giraffes include a similar pacing gait — both step simultaneously with the front and hind leg on the same side of the body, unlike other ungulates that move alternate legs on opposite sides when walking — and a long black tongue (longer in the okapi) that is used to pluck buds and leaves, as well as for grooming. Okapis are endemic to the Democratic Republic of the Congo, where they live north and east of the Congo River. Their range extends north from Maiko National Park to the Ituri rainforest, then through the river basins of the Rubi, Lake Tele, and Ebola to the west, and continues to the Ubangi River further north. Smaller populations exist west and south of the Congo River, and the species is also common in the Wamba and Epulu areas. It is extinct in Uganda; there is evidence okapis were observed in Uganda's Semuliki Valley by Europeans before going extinct there in the late 1970s, and the Semuliki Valley has a similar habitat to the Congo Basin. Okapis inhabit canopy forests at elevations of 500–1,500 m (1,600–4,900 ft). They occasionally use seasonally inundated areas, but do not live in gallery forests, swamp forests, or habitats disturbed by human settlements. In the wet season, they visit rocky inselbergs that provide forage not found elsewhere. Research conducted in the late 1980s in a mixed Cynometra forest found an average okapi population density of 0.53 animals per square kilometre. Okapis were recorded in Virunga National Park in 2008. Okapis are primarily diurnal, but may be active for a few hours during darkness. They are mostly solitary, only gathering to breed. They have overlapping home ranges, and typically occur at densities around 0.6 animals per square kilometre. 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. Males often mark territories and bushes with their urine, and females use shared defecation sites. Grooming is common, and focuses on the earlobes and neck. Okapis frequently rub their necks against trees, leaving a brown exudate. Males protect their territories but allow females to pass through to forage, and males visit female home ranges during breeding season. Though generally calm, okapis can kick and butt with their heads to show aggression. Because their vocal cords are poorly developed, vocal communication is limited to three main sounds: the "chuff", a contact call used by both sexes; the "moan", produced by females during courtship; and the "bleat", made by infants under stress. Individuals may perform the Flehmen response, a visual behavior where the animal curls back its upper lip, displays its teeth, and inhales through its mouth for several seconds. The leopard is the okapi's main natural predator. Female okapis reach sexual maturity around one and a half years old, while males reach maturity after two years. Male rut and female estrus do not follow a seasonal cycle. In captivity, estrous cycles recur every 15 days. During courtship, the male and female circle, smell, and lick each other. The male shows interest by extending his neck, tossing his head, and protruding one leg forward, before mounting and copulation. Gestation lasts around 440 to 450 days, and usually results in the birth of a single calf that weighs 14–30 kg (31–66 lb). A pregnant female's udder starts swelling 2 months before birth, and she may have vulval discharges. Birth takes 3–4 hours, and the female stays standing throughout this time, though she may rest for brief intervals. After birth, the mother eats the afterbirth and thoroughly grooms her newborn. Her milk is very high in protein and low in fat. Like other ruminants, okapi calves can stand within 30 minutes of birth. Newborn calves are generally similar to adults, but have long hairs around the eye that resemble false eyelashes, a long dorsal mane, and long white hairs within their stripes. These features gradually disappear over a year, leaving the calf with an adult-like appearance. Juvenile calves stay hidden, and nurse infrequently. Calves do not defecate for the first one to two months of life, which is hypothesized to reduce predator detection during their most vulnerable life stage. Calves have a notably high growth rate in their first few months of life, after which growth gradually slows. Juveniles begin eating solid food at 3 months old, and are weaned at 6 months old. Male okapis develop ossicones one year after birth. The okapi's typical lifespan is 20–30 years.
