Giraffes and Okapi
Giraffes and Okapi
Giraffes are a species of large, long-legged, long-necked ungulates in the family Giraffidae, order Artiodactyla. Giraffes are the tallest living animals on Earth. Okapis are a close relative, but these animals do not have such long legs or neck.
The giraffe is a widespread animal of grasslands and savannas of sub-Saharan Africa. The okapi is a much rarer animal and occurs in tropical forest.
Both species are exclusively herbivorous, mostly browsing the foliage of woody plants. These animals are ruminants, meaning they have a complex stomach divided into four pouches. Each of these sections is responsible for a particular stage of the digestion process. Rumination actually specifically refers to the chewing of the cud, which is a regurgitated mass of pre-digested plantmatter from one of the fore-stomachs. The cud is re-chewed in a leisurely fashion, and then swallowed one last time, to undergo further digestion. The material then passes through the alimentary system, and nutrients are absorbed during this final passage, which is followed by defecation.
Giraffes
The most distinctive characteristics of giraffes are their very long legs, and their enormously long neck. It is interesting that, compared with related families such as the deer (Cervidae), giraffes have the same number of neck vertebrae—the remarkable elongation of their neck is due solely to lengthening of the individual vertebrae. A short, dark mane runs along the top of the length of the neck.
The fore legs are slightly longer than the hind legs, but the profile of giraffes is also influenced by the extreme development of musculature on their shoulders and base of the neck. These large muscles are used to keep the heavy neck erect, and they give the animal a rather hunched appearance, with a steeply sloping back. Giraffes have a rather long tail, which ends in a dark tassel.
Giraffes can run quite quickly, using a rather stiff, ambling gait because of their long legs. To drink, giraffes must stoop awkwardly to reach the water.
The largest male giraffes can attain a height of 19 ft (6 m). Females are somewhat shorter, by about 3 ft (1 m). Large male giraffes can weigh as much as 1,650 lb (750 kg).
The pelage of giraffes is highly variable, and several geographic races have been named on the basis
of their colors and especially their patterns. The basic color is brownish, with a network of white lines breaking up the solid profile. Formerly, two different species of giraffes were recognized on the basis of distinctive differences in the patterns of their pelage and their non-overlapping ranges. These were the relatively widespread giraffe (Giraffa camelopardalis ) and the reticulated giraffe (G. reticulata ) of east Africa. However, further study has demonstrated that these animals are fully interfertile, and their differences are not sufficiently great to warrant their designation as full species. Today, taxonomists recognize only one species of giraffe, G. camelopardalis.
The head of giraffes is relatively small, at least in comparison with the large body size of these animals. The head has a rather elongated profile, with a long, thin upper lip, which is prehensile and used along with the long, black, mobile tongue to dexterously grasp and tear foliage while the animal is feeding. Giraffes have large eyes, with very long eyelashes. Their ears are short, but quite mobile, and both hearing and vision are acute.
The horns of giraffes are two to five, permanent, knobby outgrowths on the forehead or top of the head, covered by skin. Both sexes have these horns. The horns are smaller than, but anatomically comparable to, the antlers of deer, except those of the giraffe are never shed and are always covered by skin.
Giraffes are social animals, but not highly so, as they do not occur in large herds. The largest herds can include as many as 20-50 animals, with several dominant male animals (or bulls) and many females (or cows) and offspring. Bull giraffes fight among themselves, using powerful swings of their knobby-topped heads, aiming at the neck or chest of their rival. Old bulls that are unable to maintain a harem live a life solitary from other giraffes. A single baby (or calf) giraffe is born after a gestation period of 14-15 months.
Often, giraffes will associate with other large herbivores such as zebras, gnus, and ostriches in mixed foraging groups. Giraffes commonly have ox-peckers (Buphaga spp.) riding on their backs. These useful birds feed on large insect and tick parasites that can be common on the hides of giraffes and other large mammals.
Adult giraffes are not an easy mark for their natural predators, unless they can be ambushed while in an awkward stance, such as when they are drinking. Giraffes can run quickly for a long distance, and they can inflict sharp wounds with the hooves of their front legs. The most important predators of giraffes are lions, but a pack of these large cats is required to kill an isolated adult giraffe. Young giraffes are more vulnerable, but they are generally well protected by their social group, which is very alert for the presence of nearby predators.
Giraffes are still relatively abundant in some parts of their range. However, they have become widely extirpated from large areas, equivalent to more than one-half of their original range. This substantial decline in the overall population and range of giraffes is mostly associated with conversions of their natural habitats into agriculture, as well as overhunting of these animals.
The Okapi
The okapi, or forest giraffe (Okapia johnstoni ), did not become known to European scientists until 1900, when a native pygmy hunter showed a striped-legged skin of this species to a British zoologist in what was then the Congo in central Africa. The discovery of this unusual large animal caused a quite a sensation among European naturalists and the public. As a result, many museums and zoological gardens mounted expeditions to secure
living or dead specimens of this novel, but rare animal. Wealthy big-game hunters also organized expeditions to acquire trophy heads of the “newly discovered” okapi.
By today’s standards, it seems rather barbaric for scientists and hunters to have mounted those sorts of campaigns, which could only have further endangered an already rare species. However, attitudes and morality were different in late-Victorian times, when the notions of conservation and ecology were only beginning to make faint impressions on scientists, and on the broader public.
The okapi has a much shorter neck and legs than the giraffe, and the two horns of the males are pointed and uncovered by skin at their tips (female okapis do not have horns). The okapi has a fairly uniform-chestnut pelage, but distinctive, horizontal stripes on its legs. The largest okapis stand about 79 in (2 m) tall, and weigh 550 lb (250 kg).
From the first discovery of the okapi, great efforts were made to capture live specimens and transport them to European or American zoos for display and study. For many years, these efforts were quite unsuccessful. Although methods were developed for the safe capture of wild okapis (using pits dug across the paths these animals habitually use), it proved extremely difficult to transport them to the far away zoos.
Today, because of more efficient hunting by local people (some of whom have modern weapons), coupled with extensive loss of their rainforest habitat, the okapi is an even more rare animal than it was when Europeans first discovered it. Okapis will breed in zoos, although successes in this regard are sporadic. The survival of this unusual animal will certainly require the preservation of a large area of its natural habitat of old-growth, tropical rainforest in central Africa.
KEY TERMS
Browse —A food consisting of the foliage, twigs, and flowers of woody plants.
Harem —A group of females associated with one or several males.
Ruminant —A cud-chewing animal with a four-chambered stomach and even-toed hooves.
Resources
BOOKS
Dagg, A., and J. B. Foster. The Giraffe: Its Biology, Behavior, and Ecology. Melbourne, FL: Krieger Publishing, 1982.
Lindsey, S.L., M.N. Green, and C.L. Bennett. The Okapi: Mysterious Animal of Congo-Zaire. Austin: University of Texas Press, 1999.
Nowak, R.M., ed. Walker’s Mammals of the World. 6th ed. Baltimore: John Hopkins University Press, 1999.
Wilson, D. E., and D. Reeder. Mammal Species of the World. 2nd ed. Washington, DC: Smithsonian Institution Press, 1993.
PERIODICALS
Bodmer, R.E., and G. Rabb. “Okapia johnstoni.” Mammalian Species 422 (1992): 1–8.
Henk, P., H. van der Jeugd, and H.T. Prins. “Movements and Group Structure of Giraffe (Giraffa camelopardalis ) in Lake Manyara National Park, Tanzania.” Journal of Zoology 251 (2000): 15–21.
Bill Freedman