Although most people have a general vague idea of what constitutes an "antelope," yet the group of animals thus designated is one that does not admit of accurate limitations or definition. Some, for instance, may consider that the chamois and the so-called white goat of the Rocky Mountains are entitled to be included in the group; but this is not the view held by the authors of the _Book of Antelopes_ referred to below; and, as a matter of fact, the term is only a vague designation for a number of more or less distinct groups of hollow-horned ruminants which do not come under the designation of cattle, sheep or goats; and in reality there ought to be a distinct English group-name for each subfamily into which "antelopes" are subdivided.
The great majority of antelopes, exclusive of the doubtful chamois group (which, however, will be included in the present article), are African, although the gazelles are to a considerable extent an Asiatic group. They include ruminants varying in size from a hare to an ox; and comprise about 150 species, although this number is subject to considerable variation according to personal views as to the limitations of species and races. No true antelopes are American, the prongbuck (_Antilocapra_), which is commonly called "antelope" in the United States, representing a distinct group; while, as already mentioned, the Rocky Mountain or white goat stands on the borderland between antelopes and goats.
The first group, or _Tragelaphinae_, is represented by the African elands (_Taurotragus_), bongo (_Boöcercus_), kudus (_Strepsiceros_) and bushbucks or harnessed antelopes (_Tragelaphus_), and the Indian nilgai (_Boselaphus_). Except in the bongo and elands, horns are present only in the males, and these are angulated and generally spirally twisted, and without rings. The muzzle is naked, small glands are present on the face below the eyes, and the tail is comparatively long. The colours are often brilliant; white spots and stripes being prevalent. The harnessed antelopes, or bushbucks, are closely allied to the kudus, from which they chiefly differ by the spiral formed by the horns generally having fewer turns. They include some of the most brilliantly coloured of all antelopes; the ornamentation taking the form of vertical white lines and rows of spots. Usually the sexes differ in colour. Whereas most of the species have hoofs of normal shape, in some, such as the nakong, or situtunga (_Tragelaphus spekei_), these are greatly elongated, in order to be suited for walking in soft mud, and these have accordingly been separated as _Limnotragus_. The last-named species spends most of its time in water, where it may be observed not infrequently among the reeds with all but its head and horns submerged. The true or smaller bushbucks, represented by the widely spread _Tragelaphus scriptus_, with several local races (fig. 1) are sometimes separated as _Sylvicapra_, leaving the genus _Tragelaphus_ to be represented by the larger _T. angasi_ and its relatives. The genus _Strepsiceros_ is represented by the true or great kudu (_S. capensis_ or _S. strepsiceros_), fig. 2, ranging from the Cape to Somaliland, and the smaller _S. imberbis_ of North-East Africa, which has no throat-fringe. The large and brightly coloured bongo (_Boöcercus euryceros_) of the equatorial forest-districts serves in some respects to connect the bushbucks with the elands, having horns in both sexes, and a tufted tail, but a brilliant orange coat with vertical white stripes. Still larger are the elands, of which the typical _Taurotragus oryx_ of the Cape is uniformly sandy-coloured, although stripes appear in the more northern _T. o. livingstonei_, while the black-necked eland (_T. derbianus_) of Senegambia and the Bahr-el-Ghazal district is a larger and more brilliantly coloured animal. The small horns and bluish-grey colour of the adult bulls serve to distinguish the Indian nilgai (q.v.), _Boselaphus tragocamdus_, from the other members of the subfamily.