Incredibly, the gerenuk is believed to be independent of free water (5). This is a great advantage in its semi-arid habitat, as the gerenuk therefore does not have to undertake long journeys in search of water. Instead, the sedentary gerenuk is thought to obtain all the moisture it requires through its diet. It browses almost exclusively on tree-foliage (5), and is unique among antelopes in being able to stand on its hindlegs to reach over two meters high, attaining leaves that only giraffes can also reach (2). The gerenuk also feeds on shrubs, creepers and vines (5), where its tiny pointed muzzle can reach leaves amongst dense thorny tangles (2). Young gerenuks can be born at any time of the year, after a gestation period of 6.5 to 7 months (5). Mothers do not need long before they can fall pregnant again, and are capable of producing at least four young within three years (5). The newborn calf is well hidden in vegetation, and joins its mother only after several weeks (2). Male gerenuks are strictly territorial, and defend their land by driving away any intruding males (4). Fights can erupt between males, in which they may clash their heavy horns together by nodding or jerking their heads. Solid bone at the base of the horns, an extension braincase, provides the immediate force for these violent blows (2).