Dave Taylor's African Safari: Trophic Level II - The Herbivores - Impala

Dave Taylor's African Safari: Trophic Level II - The Herbivores - Impala - Page 28

Trophic Level II - The Herbivores
Impala
Page 28

Aepyceros melampus

Length: 120-160 cm (47-63")

Height: 75-95 cm (30-37")

Tail: 30-45 cm (12-18")

Weight: 40-55 kg (88-121 lb.)

Status: Common

Habitat: Impala inhabit the ecotones of their environment. They are an "edge species". They prefer the borders of woodlands and grasslands where the soil is well drained and the slope of the land is gentle. They will drink, but can go for lengthy periods without water.

Food: Impala are grazer and browsers. They will eat grass when the blades are growing but do not like dried, dead grass. During the dry season, they turn to browsing on tree foliage, herbs, shoots and seedpods (see Trees: Symbiotic Relationships). This species is very adaptable and may be a grazer in one park and a browser in another. In the best habitats, they reach a density of over 200 animals per square kilometer (600 per square mile).

They are found throughout the Serengeti-Mara ecosystem.

Social System: Impala have a very complex social system that has been well studied.

Male impala maintain territories and only these males sire offspring. However, during the dry season, territories are not maintained and the social system appears to break down. In fact, with the rains and a return to estrus by the females, male impala often return to the same territory they occupied last season.

Territory size varies with the quality of habitat and the density of the population. The average size is 58 hectares (143 acres) in the Serengeti.

Females and young often live in herds numbering between 6 and 20 animals. Larger herds of up to 100 are common, however.

Behavior: Female herds of impala are stable and made up of the same individuals for long periods of time. There is herd loyalty.

Territorial males spend up to 25% of their time herding females. They must also chase off intruding males but do so only if the visiting male shows interest in the females within the patrolled area. Males that enter only to feed are tolerated.

Young males that are chased out will join other non-territorial males to form bachelor herds. Friendly sparring in these herds is common as males sort out their place in the dominance hierarchy of the group. Rival territorial males will fight to the death, but this is rare. Usually the loser breaks off the fight and flees, chased by the victor. They are very vocal animals and will roar their annoyance as they run. They also roar, with their white tail raised, in order to advertise their presence in the territory. This can be heard up to 1.5 kilometers (1 mile) away.

All of this herding and breeding activity tires males out and they become vulnerable to attack by a healthier male. When this happens, the deposed male will join a bachelor herd to rest. Territorial males have a fondness for their territories and will usually return to the area in an attempt to regain it. Often, they succeed.

Impala are famous for their leaps. They can jump 3 meters (10 feet) high and a single bound may cover 11 meters (36 feet). When a predator appears, the entire herd explodes into leaps and bounds. They are not, however, very good runners and rely on cover to escape wild dogs and spotted hyenas.

Females give birth towards the end of the dry season. Fawns join the herd when they are a few days old. They are weaned by the time they are five months old, by which time the males’ horns are beginning to show. The bigger their horns become, the more unwanted attention they receive from the dominant males. All males leave by the time they are eight months old. These males generally stay in the their mother's home range. They may eventually range up to 4 kilometers (2.5 miles) away once they join a bachelor herd. They mature by age four.

Predators: Leopards are one of the main predators of impala simply because impala are so often found in and around the leopard's forest habitat. Lions and cheetah will also prey on them. Fawns may be taken by martial eagles.

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