Africa's animal kingdom Matira Magazin

Impala – The Perfect Antelope

The perfect antelope – that is what Impalas are for many visitors. Elegantly build, harmoniously colored, swiftly moving. One can watch them for hours, enjoying Africa’s wildlife wonders. But they have some fascinating evolutionary tricks in their sleeves, too. And after all, they offer great lessons in the complex social life of antelopes – there is always something to discover when you are with their herds

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.

A herd of Impala in their classic environment: The mosaic of bush and grassland in the Mara offers them their favored habitat.

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.

Females live in clans of some hundred animals. There are no individual bonds and the females do not defend any territory but roam home ranges of several hundred ha which they share in part with other clans. During the rains they are in the open, preferring higher areas.
In thick bush predators can stalk close. Impalas react with explosive high jumps in all directions, confusing the attacker. Their leaps are famous: three meters high and up to ten meters far! When jumping, the glands at their hindlegs disperse scent. This might mark an area as dangerous but also might help to bring dispersed herds together again
Impalas are not as fast runners as Thomson gazelles. Given the choice, in the open cheetahs prefer to attack Impalas, even when they are farer away. (Photo: Gabriele Mierke-Radke)

 

To give birth, females retreat from the herd. The fawns are left concealed in hiding for the first days. Females visit them only for short nursing sequences. Only after two weeks or so, the young are brought to the herd. (Photo: Gabriele Mierke-Radke)

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!

A bachelor herd of non-territorial males. The long-curved horns are seen from far.

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.

 

Horns have evolved for such contests, not for anti-predator action. The ridges help binding the horns, preventing wounds by the sharp tips.

 


Nevertheless, sometimes furious fights develop, with males savagely trying to stab each other. That is why territorial males have a dermal shield of thick skin at their neck, preventing many wounds.

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.

 

Impala male roaring, tail up to show the white underside. This is meant to impress rivals while the females seem to enjoy it. Typical for territorial males is the spot of bare skin under the eye.

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.

Black-faced Impala in Etosha National Park in Namibia.

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