The impala or rooibok (Aepyceros melampus, lit. 'black-footed high-horn' in Ancient Greek) is a medium-sized antelope found in eastern and southern Africa. The only extant member of the genus Aepyceros, and tribe Aepycerotini, it was first described to Europeans by German zoologist Hinrich Lichtenstein in 1812. Two subspecies are recognised—the grassland-dwelling common impala (sometimes referred to as the Kenyan impala), and the larger and darker black-faced impala, which lives in slightly more arid, scrubland environments. The impala reaches 70–92 cm (28–36 in) at the shoulder and weighs 40–76 kg (88–168 lb). It features a glossy, reddish brown coat. The male's slender, lyre-shaped horns are 45–92 cm (18–36 in) long.
Active mainly during the day, the impala may be gregarious or territorial depending upon the climate and geography. Three distinct social groups can be observed: the territorial males, bachelor herds and female herds. The impala is known for two characteristic leaps that constitute an anti-predator strategy. Browsers as well as grazers, impala feed on monocots, dicots, forbs, fruits and acacia pods (whenever available). An annual, three-week-long rut takes place toward the end of the wet season, typically in May. Rutting males fight over dominance, and the victorious male courts females in oestrus. Gestation lasts six to seven months, following which a single calf is born and immediately concealed in cover. Calves are suckled for four to six months; young males—forced out of the all-female groups—join bachelor herds, while females may stay back.
The impala is found in woodlands and sometimes on the interface (ecotone) between woodlands and savannahs; it inhabits places near water. While the black-faced impala is confined to southwestern Angola and Kaokoland in northwestern Namibia, the common impala is widespread across its range and has been reintroduced in Gabon and southern Africa. The International Union for Conservation of Nature (IUCN) classifies the impala as a species of least concern; the black-faced subspecies has been classified as a vulnerable species, with fewer than 1,000 individuals remaining in the wild as of 2008.
The impala is diurnal (active mainly during the day), though activity tends to cease during the hot midday hours; they feed and rest at night. Three distinct social groups can be observed – the territorial males, bachelor herds and female herds. The territorial males hold territories where they may form harems of females; territories are demarcated with urine and faeces and defended against juvenile or male intruders. Bachelor herds tend to be small, with less than 30 members. Individuals maintain distances of 2.5–3 m (8.2–9.8 ft) from one another; while young and old males may interact, middle-aged males generally avoid one another except to spar. Female herds vary in size from 6 to 100; herds occupy home ranges of 80–180 ha (200–440 acres; 0.31–0.69 sq mi). The mother–calf bond is weak, and breaks soon after weaning; juveniles leave the herds of their mothers to join other herds. Female herds tend to be loose and have no obvious leadership. Allogrooming is an important means of social interaction in bachelor and female herds; in fact, the impala appears to be the only ungulate to display self-grooming as well as allogrooming. In allogrooming, females typically groom related impalas, while males associate with unrelated ones. Each partner grooms the other six to twelve times.
Social behaviour is influenced by the climate and geography; as such, the impala are territorial at certain times of the year and gregarious at other times, and the length of these periods can vary broadly among populations. For instance, populations in southern Africa display territorial behaviour only during the few months of the rut, whereas in eastern African populations, territoriality is relatively minimal despite a protracted mating season. Moreover, territorial males often tolerate bachelors, and may even alternate between bachelorhood and territoriality at different times of the year. A study of impala in the Serengeti National Park showed that in 94% of the males, territoriality was observed for less than four months.
The impala is an important prey species for Africa's large carnivores, such as cheetahs, leopards, wild dogs (its main predator), lions, hyenas, crocodiles and pythons. The antelope displays two characteristic leaps – it can jump up to 3 m (9.8 ft), over vegetation and even other impala, covering distances of up to 10 m (33 ft); the other type of leap involves a series of jumps in which the animal lands on its forelegs, moves its hindlegs mid-air in a kicking fashion, lands on all fours (stotting) and then rebounds. It leaps in either manner in different directions, probably to confuse predators. At times, the impala may also conceal itself in vegetation to escape the eye of the predator. The most prominent vocalisation is the loud roar, delivered through one to three loud snorts with the mouth closed, followed by two to ten deep grunts with the mouth open and the chin and tail raised; a typical roar can be heard up to 2 km (1.2 mi) away. Scent gland secretions identify a territorial male. Impalas are sedentary; adult and middle-aged males, in particular, can hold their territories for years.
