Impala – The Perfect Antelope
Reinhard Radkes column on African wildlife
The name “Impala” goes back on a Zulu term, meaning “red antelope”. The scientific name relates to the black hair tufts, which they carry at their hindlegs. Under these tufts are scent glands, which disperse scent when Impalas perform their spectacular high jumps.
Impalas are adapted to the edge zone between grass- and bushland. They can switch their diet from grass (in the rain season) to foliage (in the dry season), making the best from seasonally available food. That is nothing done easily: Grass is rich in silicates, while browse contains a lot of tannins. So, it usually needs a specialized feeding and digesting apparatus to cope with that, making most of ungulates either to browsers or grazers. Impalas do both, and this saves them migration efforts as they can stay all year round in bush/grass ecotones. They even make a living in areas which are heavily overgrazed: One of the reasons why they are still quite numerous in the Mara, with dire competition by Masai cattle in the reserve.
Only males carry the beautifully curved horns, females don’t invest in such armory. A clear indication, sexes have very different roles to play in Impala society. Horns are mainly for intraspecific fighting, and females very rarely engage in physical conflicts. As defense against most predators, horns are not very effective and used only as a very last means. As a weapon against predators they should be rather short and straight daggers. But that is not what males need for their social purposes!
Impala males must cope with other challenges than females, which carry the burden of raising and nursing the young without any help by a male. To be successful, a male must fight his way up the ranks amongst the bachelors, until he finally might dare to challenge a territorial male. Impala horns are just made for such duels. To catch the opponents blows, interlocking horns, giving a grip to push and pull.
After conquering a territory, males signal their status with conspicuous displays. Impalas are special in antelopes by being very noisy. With explosive snorts, followed by loud roars they advertise dominance. This is combined with exaggerated body postures, walking proudly through the herd, head low, tail up, to show the white underside. For mating, females only accept such landlords, as they have proven that their genes are good enough to reach the top of Impala society. However, the whole undertaking is extremely strenuous for the males and most can keep such a position only for some weeks when the females are in season (usually during the rains, but in East Africa that is a long spell). Exhausted males move back to the bachelors, but strong males can make it more than once to the top. Interestingly, in southern Africa it was found, that certain males were territorial several times in the same territory.
Impalas are an isolated group amongst African bovids since four million years. They form a tribe of their own, with only one – or after some other opinions – two species. The common Impala Aepyceros melampus occurs from central Kenya (Samburu and Shaba Reserves) down to Tanzania and southeastern Africa. In southern Angola and northern Namibia occurs the black-faced Impala, with no connection to the main distribution area. Some taxonomists call it a separate species Aepyceros petersi, others keep it as a sub species Aepyceros melampus petersi.