Antelopes: running and jumping.
The term antelope is applied to any agile member of the Bovidae, thus distinguishing them from the heavyweight bovids such as oxen, bison, and buffalo (the Bovinae) on the one hand, and from the sheep, goats, and chamois (the Caprinae) on the other. Yet the term is rather ambiguous because there are antelopes that are bovines and others that are caprines. In fact, zoologists distinguish five subfamilies of the Bovidae family (Bovinae, Cephalophinae, Hippotraginae, Antilopinae, and Caprinae), almost all of them containing at least one antelope, especially the Hippotraginae and the Antilopinae, the most typical antelopes.
The bovines (Bovinae) include: all domesticated cattle, sheep, and goats, and their closest wild relatives such as the buffalo and bison; the enormous elands (Taurotragus); the "forest" antelopes, two Asian species; the nilgai (Boselaphus tragocamelus); the four-horned antelope (Tetracerus cuadricornis); and the African genus Tragelaphus, species linked to forests and wetlands such as the sitatunga (T. spekei), though some also occur in the savannah (the kudus [T. strepsiceros and T. imberbis], for example).
Few of the small cephalophine (Cephalophinae) antelopes occur in the savannah. They are known by the Boer name duikers (which means divers) because they jump headfirst into the scrub to hide.
The caprines (Caprinae) are also rare in the savannah. Only two of the fourteen genera can be considered antelopes (Saiga and Pantholops), although they are not members of the savannah fauna, as they live in the cold mountains of central Asia.
Most true antelopes are members of the subfamilies Hippotraginae and Antilopinae. Only two genera live in desert or subdesert environments (Addax and Oryx, respectively), while others such as the antelope (Pelea capreolus) or the klipspringer (Oreotragus oreotragus) are specialized to live in steep rocky places.
Most of the typical gazelles (Gazella) live in more arid areas of savannah, together with the remarkable gerenuk (Litocranius walleri), the springbok (Antidorcas marsupialis), and the dibatag (Ammodorcas clarkei). Other species are more characteristic of the typical grassy savannahs: among them are the impala (Aepyceros melampus), the two species of gnu (Connochaetes taurinus and C. gnou), red hartebeest (Alcelaphus buselaphus), roan antelope (Hippotragus equinus), the bonteboks (Damaliscus), the handsome common waterbuck (Kobus ellipsiprymnus), reedbucks (Redunca), oribi (Ourebia ourebi), the tiny dik-diks (Madoqua), and the even smaller royal antelope (Neotragus pygmaeus), the smallest living antelope, weighing only 7-9 lb (3-4 kg).
The antelopes that live in open environments are normally territorial and social. In the driest months, when they undertake long migrations in search of water and fresh grazing, some species gather into enormous groups, up to 200,000 in the case of the gnu. For the rest of the year, they split into three types of groups: solitary adult males, small groups of adolescent males, and larger groups of females with their young. The young are highly precocious and can stand upright and walk after their mother within a few hours of birth. This precocity helps them deal with the lack of suitable shelters from predators and the herd's need to move continuously in search of new pasture.
Antelopes feed on the savannah grasses or the leaves of the acacias and the other scattered trees. This explains the appearance and habits of the gerenuk (Litocranius walleri), which has an unusually long neck and stands upright on its hind legs to reach the branches it browses (see photo 61, p. 111). Grass is usually abundant, but it is not very nutritious and is hard to digest. Antelopes are ruminants, a physiological adaptation that may well have evolved in the savannah-dwelling herbivores. Ruminants bolt their food down, hardly chewing it, and store the cud in a compartment of the stomach where it remains for a few hours and starts to ferment. Later, when the animal is resting somewhere quieter, it regurgitates the food into the mouth and chews the cud, then swallows it again into other stomach compartments. This ensures better digestion and makes grazing safer.
Antelopes' difficult relationship with the savannah predators has favored specialization in running away very fast, and also in some cases, jumping. Gazelles and impalas can reach speeds of 37 mph (60 km/h), and impalas can also jump a distance of 33 ft (10 m) and up to 10 ft (3 m) in the air. The springbok (Antidorcas marsupialis) can jump distances of up to 49 ft (15 m). Their gregarious habits greatly help their defense against predators. In a large herd, one will always give the alarm in time if there is any danger, and in the worst case the loss of one member allows the rest of the flock to disperse. It is significant that almost all the antelopes that live in steep rocky locations lead relatively solitary lives and are not so adept at running away.