Graceful Gazelles - Superbly Adapted
Gazelles are the most widespread of all antelope, occurring not only throughout the dryer parts of Africa, but also in the Middle East, and across Asia to Siberia and China. All gazelles are extremely elegant and characterised by pale, sandy-coloured coats and ribbed, S-shaped horns. Twelve representatives occur in Africa, including the elongated gerenuk and dibatag, and the springbok.
Independent of water
The most remarkable aspect of gazelle biology is the ability of most species to survive in flourish in arid areas without surface water. Gazelles are able to extract the moisture that they need from their food and reduce moisture loss by absorption of faeces and urine fluid. Most are browsers of herbs and shrub foliage but also feed on fresh grass, so can switch diet according to environmental conditions. The smooth, sleek coat is adapted - through colour and hair structure - to reflect heat.
Most amazing, however, is the gazelle's ability to allow its own body temperature to rise - by as much a ten degrees - with the outside temperature. This strategy is also employed by camels which, like the gazelles, use the technique of forcing air through nasal passages in order to cool it. A capillary network surrounds the carotid arteries, and blood passing through is rapidly cooled before it reaches the animal's brain. Interestingly, all gazelles will drink whenever the opportunity presents itself.
Gazelles are exceptionally alert and rely on speed - as well as their choice of open country - to avoid predation. Nevertheless, the lightning-fast cheetah is equally well-adapted and is certainly the biggest threat to all gazelles. In common with many other antelopes, mature and dominant males are territorial, while females and subordinate males forage over larger, more random areas. Nomadism is a way of life, however, and male territories will last only as long as conditions are not better elsewhere.
This is a large, very pale gazelle which occurs in and adjacent to the eastern arm of the Rift Valley. It is rarely as numerous as the Thomson's gazelle, but is often seen frequenting the same areas and regularly in mixed herds. The two species avoid competition by selecting slightly different food plants. Interestingly, the Serengeti population is said to undergo a "reverse migration" to that of the wildebeest and zebra, moving on to the dry short grass plains when there is no longer enough grass to support the wildebeest, and thus avoid competition.
Less numerous and more agile than most Serengeti herbivores, Grant's gazelle have been estimated to make up just 6% of the prey of cheetah, leopard and lion. The fawns - typically left to rely on the camouflage in longer grass - are targeted by jackals which, when they hunt in pairs, are able to work together to keep the mother at bay.
Thomson's gazelle is much smaller and stockier than the Grant's gazelle, with a more boldly-patterned coat and shorter horns. The "tommy", as it is familiarly known, is a super-abundant gazelle within its favoured habitat of short grassland with dry, firm substrate. Its diet is almost a reverse of that of the Grant's gazelle, for it favours grass, only turning to foliage and pods of shrubs and forbs, when grass availability drops. This is the most water-dependent of the gazelle tribe, and Serengeti herds have been known to travel up to 16km every day or so from their feeding grounds to drink. Nevertheless, territorial males have been shown to be water independent for extended periods - putting sex before thirst!
As a member of the Serengeti-Mara grazing succession which includes wildebeest, zebra and hartebeest, the "tommy" comes last, as it is able to find enough to eat - with its much smaller mouth - when the larger-mouthed herbivores have abandoned the area. For similar reasons, it can also utilise a fire- or rain-induced green flush before the larger grazers, so it can also be the first onto the short-grass plains.
Although very similar in appearance to the East and North African gazelles, the springbok is geographically isolated (to the south-western arid zone) and is known to have a surprising number of anatomical differences. The hollow horn bases of the springbok (a trait shared by goats), in contrast to the solid horn bases of "true" gazelles, is said to be the most significant of these differences. This seemingly trivial difference has been shown by the fossil record to go back some 15 million years, and suggests that the springbok's likeness to the gazelles may be a result of convergent evolution - the result of adapting to similar environmental conditions.
The springbok is a mixed feeder, taking mostly grass in summer and herb and shrub foliage in the dry winter months. The large, velvety pods of the Camelthorn Acacia are a much favoured food source in the Kalahari.
Perhaps the springbok's most remarkable behaviour - and the obvious origin of its name - is its habit of pronking. This begins as a rocking gait, progresses to a stotting gait and then to full scale bouncing, on stiff legs with back arched. Once one animal in a herd begins to pronk, the rest soon join in to create quite a spectacle! The actual reasons for pronking are not clear - it may be a means of display or a technique for confusion predators.
Less than two hundred years ago, there were estimated to be millions of springbok in the Karoo region of South Africa, but these herds were slaughtered by the settlers and today the species survives in just a few national parks and as a "game" animal on commercial ranches.
Where to see gazelles at CCAfrica properties
Thomson's and grant's gazelle are synonymous with the Serengeti-Mara ecosystem in Tanzania/Kenya where they move nomadically, as the rains come and go. Like the millions of wildebeest, the 500 000 or so gazelles in this huge ecosystem favour the short-grass plains of the south-eastern Serengeti for dropping their lambs.
Excellent views of both gazelle species - and great photographic opportunities - can be enjoyed from Kichwa Tembo in Kenya, Grumeti Serengeti Tented Camp in Tanzania and Klein's Camp also in Tanzania. The floor of the Ngorongoro Crater in Tanzania and the dry scrublands of the Olduvai area are also home to Grant's and Thomson's gazelle, so a stay at the Ngorongoro Crater Lodge will allow plenty of opportunities to see these graceful creatures.
The springbok is found only in the dryer western parts of Southern Africa, but a small population exists in the Madikwe Safari Lodge Game Reserve in South Africa.
Kingdon, J. 1997. The Kingdon Field Guide to African Mammals.
Academic Press, London.
Estes, R.D. 1991. The Behaviour Guide to African Mammals.
Russel Friedman Books, Halfway House.
Posted: Mammals by CC Africa, Date: 21 November 2006