Impala (Aepyceros melampus)
|Size||Male weight: 60 kg (2)|
Female weight: 40 kg (2)
Classified as Least Concern (LC) on the IUCN Red List. Subspecies: black-faced impala (A. m. petersi) classified as Vulnerable (VU), common impala (A. m. melampus) classified as Least Concern (LC) (1).
The graceful impala is a noisy antelope renowned for its agile leaps. It has reddish-brown upperparts becoming paler on the sides (2) (3). The underparts, belly, throat and chin are white, as is the tail, which has a thin, black line down its centre (3). A black line also extends down each buttock (2) (3). At the back of the hind leg, just above the hoof, is a characteristic tuft of black hair, which covers the fetlock gland (3). A high kick sends out a puff of scent from the gland, which is thought to be used to lay trails and help regroup herds (4). Males have lyre-shaped horns, up to 0.7 meters long and deeply ringed for most of their length (2) (3). Two subspecies of the impala are recognised, based on morphological and genetic differences; Aepyceros melampus petersi, the black-faced impala, is significantly larger and darker than the common impala, Aepyceros melampus melampus, and has a characteristic dark facial blaze (2) (5). At certain times of the year, guttural roars followed by a series of snorts can be heard as the males advertise their territories (2).
The common impala has a wide distribution, from South Africa to Kenya, Namibia to Mozambique (6). The black-faced impala occurs in a small isolated population in north-western Namibia and south-western Angola (3).
Impala generally inhabit savanna woodland, especially close to water (7), and can also be found in grassland with scattered bush cover during the rainy season (3) (4).
Impala have a complex social structure and an interesting mating system. Like other antlered ungulates, impala mate during a certain period of time called the rut. During this period, the adult males, which normally live in bachelor herds, become territorial (2). Physical changes also occur in the males during this time; their necks thicken, their coats become darker from the grease of sebaceous secretions and they acquire a musky scent (4). The males fight for territories to attract females with which to mate, and their roars and snorts can be heard day and night (2). After the rut, the male’s territoriality and fighting urge wanes, and they regroup into bachelor herds or join breeding herds (2). A brief resurgence of this activity in some of the males occurs again in a secondary rut later in the year (2).
Female impala and their young live in breeding herds (2). The majority of young are conceived in the first rut and are born after a gestation period of 194 to 200 days (2). Females give birth to a single young in a secluded spot, remaining nearby and returning frequently to suckle their young (4). After a few days the young will begin to follow the mother, a time when they are particularly vulnerable to predators; about half the young are lost to predation within the first few weeks (4). Young males are evicted from breeding herds by territorial males and remain in bachelor herds until they are old enough to establish a territory (2). Impala can live for around 15 years (4).
Impala have a varied diet compared to closely related species. During the wet season, they mostly graze on grass, and as this dries they browse more on shrubs and bushes (2) (7). Impala also consume fruits and Acacia pods when available (2). This varied diet means that impala can obtain relatively high quality food throughout the year in a small home range, without undertaking massive migrations as many African mammals do (7).
The common impala is not yet considered to be threatened; however, the black-faced impala has been assessed as vulnerable to extinction (1). In Angola, the black-faced impala is thought to be nearly extinct (8), and in Namibia, the population has been decimated by drought and increased hunting pressure during periods of war (8). To guard against its extinction in this region, 310 individuals were moved to Etosha National Park in 1968-1971, where the population has steadily grown to over 1,500 (5). Naturally occurring populations in Namibia outside this protected area remain fragmented and threatened by poaching and competition with livestock, and presently (2007) number less than 500 individuals (5) (8).
Black-faced impala from Etosha National Park were subsequently moved to private farms in northern Namibia. Whilst well intended, the movement of black-faced impala to many farms which also hold common impala, has resulted in the potentially serious threat of interbreeding. Although there is no direct evidence of this yet, it is widely believed to occur on farms with mixed herds (8). Interbreeding between subspecies also poses a potential threat to the black-faced impala of Etosha National Park, due to the purchase of common impala by neighbouring farms. Fortunately, there is as yet no evidence of interbreeding within the park (9).
Ironically, the listing of the black-faced impala as Endangered by the U.S. Department of the Interior in 1980 has exacerbated the problem of interbreeding. American trophy hunters do not hunt the black-faced impala because they are not permitted to import the trophies into the United States. Without the incentive of the high-spending American market, few Namibian farmers are willing to pay high prices for black-faced impala when they can buy common impala cheaply. Interviews with Namibian farmers indicate that the lack of American hunting revenues provides no incentive for farmers to prevent interbreeding between the black-faced and common impala (8).
The translocation of the black-faced impala to Etosha National Park has successfully created a population that is less threatened by poaching and competition, than those outside the park. However, care should be taken to ensure that the Etosha population does not come into contact with common impala, which could threaten their persistence due to interbreeding. This highlights the need for conservation of black-faced impala populations in areas removed from farms containing common impala. Solving the problem of interbreeding in private farm populations requires cooperation between governments and private land owners. Political action may be required, as permitting the import of black-faced impala trophies to the United States would create an economic incentive for farmers to maintain pure black-faced impala populations. Raising awareness in farmers of the uniqueness and rarity of the black-faced impala would also aid conservation efforts (8).
For further information on the impala see:
- African Wildlife Foundation:
For further information on the common impala see:
- Lorenzen, E.D., Arctander, P. and Siegismund, H.R. (2006) Regional genetic structuring and evolutionary history of the impala Aepyceros melampus. Journal of Hererdity, 97(2): 119–132.
Authenticated (28/09/07) by Eline Deirdre Lorenzen, Institute of Biology, University of Copenhagen.
- Interbreeding: cross-breeding with a different species or subspecies.
- Morphological: referring to the visible or measurable characteristics of an organism.
- Subspecies: a population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
IUCN Red List (July, 2014)