Impala

The impala is an African antelope, and it is neither a gazelle nor a deer, even though many people search for it as the impala gazelle or the impala deer. Deer belong to a different family and grow antlers that fall off and regrow every year. The impala, like all antelopes, belongs to the cattle family, the Bovidae, and its horns are permanent. It is not a gazelle either. True gazelles, such as the Thomson's gazelle that shares the plains with impalas in Kenya and Tanzania, belong to another group. The impala is so different from all other antelopes that scientists place it alone in its own genus, Aepyceros, and its own tribe, and its basic body plan has stayed much the same for at least five million years. Genetic studies link it most closely to small antelopes such as the suni. Its scientific name, Aepyceros melampus, means black footed high horn in Ancient Greek. The word impala comes directly from Zulu, and it was first used in English in 1875. Before that, English speakers called it pallah, from the Tswana word phala, meaning red antelope, and in Afrikaans it is the rooibok, the red buck. There are two subspecies: the common impala, sometimes called the African or Kenyan impala, and the much rarer black faced impala.

The impala is a medium sized antelope with a light, athletic build. Its head and body measure about 130 centimeters (51 inches), plus a bushy tail of about 30 centimeters (12 inches). Males stand 75 to 92 centimeters (30 to 36 inches) at the shoulder and weigh 53 to 76 kilograms (117 to 168 pounds). Females are smaller, at 70 to 85 centimeters (28 to 33 inches) and 40 to 53 kilograms (88 to 117 pounds). Only males have horns. They are ridged, curve back and then up and out in a lyre shape, and measure 45 to 92 centimeters (18 to 36 inches). The coat is glossy and comes in three tones: reddish brown on the back, tan on the flanks and white on the belly, with white rings around the eyes and black tips on the ears. Seen from behind, the impala carries its most famous marking. A black stripe runs down the middle of the white tail and another runs down each rear thigh, and together they look like the letter M. Just above each hind hoof there is a tuft of black hair that covers a scent gland, which gave the species its name melampus, black foot. The black faced impala is larger and darker, with a dark stripe from the nose to the eyes and a longer, bushier tail.

Impalas live in eastern and southern Africa, from central and southern Kenya and northeastern Uganda south to northern KwaZulu-Natal in South Africa, and west to Namibia and southern Angola. The IUCN lists them as native in 13 countries: Angola, Botswana, Eswatini, Kenya, Malawi, Mozambique, Namibia, Rwanda, South Africa, Tanzania, Uganda, Zambia and Zimbabwe. They once also lived in Burundi, where they have disappeared. The favorite habitat of the impala is the edge between open grassland and woodland, where it can graze in the open and browse among the trees. It avoids dense forest and very dry, open plains, and it is rarely far from water. Impalas live from sea level up to about 1,700 meters (5,600 feet). In good habitat they can be extremely common: densities go from less than one impala per square kilometer in dry parks such as Mkomazi in Tanzania to 135 per square kilometer near Lake Kariba in Zimbabwe. About a quarter of all impalas live in protected areas, such as the Okavango Delta, the Maasai Mara, Kruger National Park, the Serengeti, Ruaha, the Luangwa Valley and Hwange. Many more live on private game ranches in southern Africa. The black faced impala lives only in southwestern Angola and northwestern Namibia, with a large share in Etosha National Park.

Impalas are mixed feeders, which means they both graze on grass and browse on leaves, and this is one of the secrets of their success. Over a whole year, their diet is roughly 45 percent grasses, 45 percent leaves, shoots and herbs, and 10 percent fruits. The mix changes with the seasons. After the first rains, when fresh green grass sprouts, grass can make up as much as 90 percent of what they eat. Later in the wet season and through the dry months, when the grass dries out, they turn to the leaves and shoots of bushes and trees, flowers, fruits and acacia pods. Because they can switch like this, impalas can stay in the same area all year while grazers such as zebras and wildebeest have to move. Females and bachelor males eat more leaves than territorial males, which tend to stay on the best grassy patches. Impalas spend a large part of the day feeding: from about 58 percent of daylight hours in the early dry season up to 75 percent in the late dry season, when food is poorest. They like to be near water and usually drink regularly. When water is scarce, they get moisture from juicy plants. Like other antelopes, they chew the cud, bringing food back up to chew it a second time.

The impala is famous for its leaps. It can jump up to 3 meters (10 feet) high, clearing bushes and even other impalas, and cover up to 10 meters (33 feet) in a single bound. It uses two kinds of leap. The first is the long, high jump it makes when running away. The second is a series of jumps in which it kicks its hind legs high in the air, often while fleeing. When a herd is attacked, the impalas burst away in all directions at once, leaping over each other and changing direction suddenly. This explosion of bodies makes it hard for a lion or a leopard to keep its eyes on one animal. The impala does not need to outrun every predator over a long distance. It needs a quick start, sudden turns and the cover of nearby bushes. How fast it runs is less clear than how far it jumps. Figures in books and on safari websites go from about 60 to 90 kilometers per hour (37 to 56 miles per hour), but no one has timed wild impalas with precise equipment, so treat any single number with care. What is certain is that it is fast and agile enough to escape most attacks: many chases end with the predator giving up.

Impalas are active mainly by day and live in three kinds of groups. Females and their young form herds of 6 to 100 animals that move over home ranges of 80 to 180 hectares. Young and non territorial males gather in bachelor herds of up to about 30. Adult males that win a territory try to keep females on it. In East Africa some males hold territories for much of the year, while in southern Africa they are territorial only during the rut. The rut is a short, intense breeding season of about three weeks near the end of the rains, usually in May in southern Africa. Territorial males have almost twice the testosterone of bachelors. They stop eating, chase rivals, herd females and roar: one to three loud snorts followed by up to ten deep grunts that can be heard 2 kilometers (1.2 miles) away. Many males lose condition fast, and most hold a territory for only a few months. Impalas also do something very unusual. They are thought to be the only hoofed animals that both groom themselves and groom each other, using their lower front teeth as a comb. Two impalas take turns, each grooming the other 6 to 12 times, which helps remove ticks. Oxpeckers also ride on impalas to pick off ticks.

After the rut, pregnancy lasts six to seven months. In southern Africa, where the rut is short, most calves are born within a few weeks of each other early in the rainy season, around November and December, when fresh grass is plentiful. Closer to the equator, in East Africa, births are spread over more of the year. Being born at the same time as many others helps: predators can only eat so many calves, and the rest grow up quickly while food is abundant. The female usually leaves the herd to give birth, often around midday, and has a single calf. For the first few weeks the calf hides in thick cover while its mother feeds nearby and returns to nurse it. Then it joins a nursery group of young impalas inside its mother's herd. Calves nurse for four to six months. The bond between mother and calf is fairly weak and ends soon after weaning. Young males are pushed out of the female herd and join bachelor groups. Males are able to breed at about one year old, but most do not win a territory and mate until they are around four. Females can conceive from about a year and a half. Impalas usually live around 12 to 15 years.

Because impalas are so common and live where many big hunters live, they are one of the most important prey animals in Africa. Lions, leopards, cheetahs, African wild dogs and spotted hyenas all hunt them, and crocodiles and pythons take them when they come to drink or pass through thick cover. Calves are especially at risk during their first weeks. Safari guides in southern Africa often call the impala the McDonald's of the bush. The joke comes from the black M on its rump, and from the fact that it is fast food for almost every predator. For leopards in particular, impalas are a staple, and a leopard will often drag an impala carcass up into a tree to keep it away from lions and hyenas. Cheetahs also hunt them often, relying on a short burst of speed, while wild dogs chase them over longer distances. Impalas fight back with numbers and alertness. A herd has many eyes and ears, and when one impala spots danger it gives a sharp alarm snort that puts the whole group on guard. If the attack comes, the herd scatters in every direction, leaping and changing course.

The IUCN lists the impala as Least Concern, in an assessment from 2016, with a stable population of about two million mature animals. That makes it one of the most numerous antelopes in Africa. About a quarter of them live in national parks and reserves, and many more live on private land, especially game ranches in southern Africa, where the impala does well and is valued by landowners. Its range has stayed mostly intact, although it has disappeared from Burundi. The threats the IUCN lists are livestock farming and ranching, hunting and trapping, and droughts. Outside protected areas, impalas are often hunted for meat, and they have been lost from places where people and cattle have taken over the land. The picture is very different for the black faced impala. This subspecies, found only in southwestern Angola and northwestern Namibia, is listed as Vulnerable by the IUCN, with 3,000 to 4,000 mature animals and a continuing decline. It suffered from poaching, droughts and the loss of habitat, and between 1968 and 1971, 310 black faced impalas were moved to Etosha National Park for protection. Today a new threat is mixing with common impalas that have been moved onto farms in Namibia, which can dilute its unique genes.