This month, I would like to start a series of articles focusing on animals that are frequently overlooked because they are so often seen. Oxymoron? Indeed. True? In my opinion, definitely. Let me explain…
With their shiny rust-coloured coats and long slender legs, Impala (Aepyceros melampus) are amongst the most graceful and beautiful of antelope − yet they are rarely given a second glance. The reason? Because they are ‘common’.
Despite their obvious abundance, they are unique enough to be classified in a tribe of their own, the Aepycerotini; and are the only extant representative of the genus Aepyceros − from the Greek aipos ‘high’, ceros ‘horn’. Fossil evidence shows that modern impalas have remained practically unchanged since the Miocene Epoch 6.5 million years ago. According to author Mitch Reardon, “This is a powerful endorsement for the impala’s original design, particularly when contrasted with the closely-related hartebeest and wildebeest, which have split into new species at least 18 times since they evolved from the impala or a springbok-like common ancestor around eight million years ago.”
Among their unique morphological characteristics are the black hair tufts located just above the ankle joint on the hind legs. Beneath these tufts are the metatarsal glands which release a scent (said to smell like cheese!) when the animal is startled. It is postulated that this scent acts as a chemical cue for other herd members to follow during a chase and is dispersed by the upward kicking of the hind feet. Another distinctive trait is their modified second and third incisors and incisiform canines. These teeth are thin and needle-like, and arranged in the form of a comb on both sides of the lower jaw. The upward movement of this comb-like array against the skin provides an effective means of removing ticks and other ectoparasites. Impala are fastidious groomers, engaging in both self- and allogrooming. The latter removes parasites as well as strengthening social bonds between herd members.
Impala herd structure has characteristics all of its own. At different times of the year, there may be as many as five distinct social groupings, with herds ranging in size from 10 to 100 individuals depending on the season. Territoriality amongst males was once a matter of considerable debate within the scientific community. Unlike their wildebeest and springbok relatives, male impalas are only territorial when it counts – during the breeding season – and even then, a single male is likely to hold a territory for only a week at a time. A breeding ram is so intent on passing down his genes during this time that he hardly has time to eat, or groom himself, so rapidly loses condition and is deposed by another ram. Not content with calling it quits, he then resumes feeding and conditioning himself until he is ready to compete for his females again.
At other times of the year, most especially during the dry season, territorial behaviour is suspended and impalas occur in mixed herds. It is interesting to note that it is shorter days which lead to the release of high levels of hormones that ultimately culminate in the peak of the rutting season in May. During this time, dominant males become highly territorial, making extraordinary roaring sounds that can be heard more than 1km away. At the height of the rut, a territorial ram may roar nearly 200 times an hour! This roaring, combined with herding of the females, helps advance oestrus in ewes and synchronise their ovulation. Synchronised mating leads to synchronised births, with most fawns being born seven months later in a two- to three-week period. This strategy of ‘flooding the market’ swamps predators, so that fewer impalas are taken at their most vulnerable age. Most births also occur at midday, a time when predators are at their most inactive.
We have come to think of the African elephant (Loxodonta africana) as the archetypal savanna architect, uprooting trees and trampling grasses. Impalas, however, are no less important in the structural shaping of the landscape. Because of their significant abundance and their ability to both graze and browse, they act as savanna architects, modifying vegetation structure and composition. They are also considered to be an indicator species: a species so closely associated with an ecosystem that its presence (or absence) is indicative of the health of the ecosystem.
So, the next time you are on a drive through a game reserve, instead of dismissing the impala you see as ‘Kruger goats’ or “Bushveld McDonalds’, pause for a moment and marvel at their ancient history, unique design, and extraordinary success. As Aristotle said, “There is something of the marvellous in all things of nature”.
By Lorraine Doyle