Impala (Aepyceros melampus)
Species Aepyceros melampus
Traditionally taxonomists recognize six subspecies, including:
South African impala (Aepyceros melampus melampus) - Southeast Angola south
Malawi impala (A. m. johnstoni) - North Mozambique, Malawi, East Zambia
Katanga impala (A. m. katangaei) - Southeast Congo
Black-faced impala (A. m. petersi) - Southwest Angola, Southwest Africa
Kenyan impala (A. m. rendilis) - Kenya, Uganda
Tanzanian impala (A. m. suara) - Tanzania, Rwanda
The impala is found from northeast South Africa to Angola, south Zaire, Rwanda, Uganda,and Kenya.
The impala is found in woodland which contains little undergrowth and low to medium height grassland. Also a close source of water is desired, however is not needed when there is abundance of grass.
Impala are sexually dimorphic. In this species only the males have S shaped horns that are 45-91.7 cm long. These horns are heavily ridged, thin, and the tips lie far apart. Both sexes are similarly colored with red-brown hair which pales on the sides. The underside of the belly, chin, lips, inside ears, the line over the eye, and tail are white. There are black stripes down the tail, foreheard, both thighs, and eartips. These black stripes might aid in recognition between individuals. Aepyceros melampus also have scent glands on their rear feet beneath patches of black hair as well as sebaceous glands on the forehead.
Female impalas are reproductively mature and conceive at 1.5 years. Males have the ability to breed at age 1, but often do not establish territories until age 4. Reproduction is closely linked to annual rainfall. In equatorial Africa breeding is continuous throughout the year and births occur in all months. In East Africa, birth peaks are associated with the two rainy seasons in March and November. In southern Africa there is a peak in mating from April - June and a single well-defined birth peak occurring during the single wet season. Gestation is 194-200 days. Males test the females' urine to detect estrous. (The estrous cycle is 12-29 days and lasts 24 - 48 hours.) The male then roars, snorts, or low stretches to advertise himself. After chasing the female, the male may show behaviors such as nodding and tongue flicking before copulation.
The female impalas isolate themselves before calving. Calving usually occurs in the midday. Usually there is only one calf. The mother and calf will rejoin the herd after 1-2 days. Impalas place the young in creches which are groups of young that play, groom, and move together. Growth is extremely rapid, with weaning occurring in 5-7 months. Both sexes are independent in less than a year. Males are physiologically capable of reproduction at 13 months and females may conceive at 18 months.
Impala are diurnal and spend the night ruminating and lying down. The peak activity times for social activity and herd movement are shortly after dawn and before dusk.
Impala have different social structures depending on the season. The average size of the female herd is between 15-100 individuals depending on space available. Females live in clans within a home range of 80-180 ha. During the wet season the ranges are heavily defended, but during the dry season there is much overlap between individuals in the clan and even between different clans. There are slight differences between behavior in southern and eastern impala. Southern impala are more likely to intermix during the dry season, while eastern impala will remain more territrorial during the dry season.
Impala form distinct social groups during the wet season. Three main organizations are found: territorial males with and without breeding females, bachelor herds of non-territorial adult and juvenile males, and breeding herds of females and juveniles (including young males less than 4 years). During the dry season, males can be found together or mixed with female herds.
The male impala changes its territory to match the season. During the breeding season the male keeps a much smaller territory which is heavily defended. The males will imprint on their original territory and always come back to that same territory to declare dominance.
The male impala uses a variety of techniques to defend its territory (including keeping females). Tail-raising, forehead marking, forehead rubbing, herding, chsing, erect posture, fighting, and roaring are used.
Aepyceros melampus uses various antipredatory techniques as well. The most common is to take flight and outrun or confuse the predator. Commonly impala will leap up or 3 meters in the air. They often leap up or out in any direction to confuse the predator. Another unique characteristic of leaping is when impala land on their front legs and kick the back legs into the air.
Impala are ruminants. The upper incisors and canines are absent and the cheek teeth are folded and sharply ridged. Impala are intermediate feeders. While predominately a grazer, the impala will adapt to any amount of grass and browse. The ration of grass to browse varies from season to season and place to place. Impala are primarily grazers during the rainy season but the amount of grass ingested drops to 30% in the dry season when they enter in the woodlands and browse on shrubs, herbs, pods and seeds. The diet of impala in northwestern Zimbabwe has been reported to change from 94% grass in the wet season to 69% herbs and woody browse in the dry season.
Impala are taken by a number of predators: hyenas, leopards, wild dogs, lions and cheetahs, as well as some snakes. Fawns are small enough to be carried off by martial eagles.
The Blackfaced Impala, Aepyceros melampus petersi, which lives in Southwest Angola and northern Namibia, is listed as endangered by the IUCN. Pressure resulting from habitat loss and damage have been linked to the decline in their numbers.
The "normal" impala is not endangered.
Source 1 and source 2