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Aepyceros melampusimpala

By Barbara Lundrigan and Karen Sproull

Geographic Range

The impala is found from northeast South Africa to Angola, south Zaire, Rwanda, Uganda,and Kenya. (Wilson and Reeder, eds, 1993)

Habitat

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. (Estes, 1991)

Physical Description

Impala are sexually dimorphic. In this species only the males have S shaped horns that are 45 to 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. (Estes, 1991; Jarman, 1979)

  • Range mass
    45 to 60 kg
    99.12 to 132.16 lb

Reproduction

Males test the females' urine to detect estrous. 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. (Eltringham, 1979; Estes, 1991; Jarman, 1979)

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. Most breeding occurs in March through May. Gestation is 194-200 days. (Eltringham, 1979; Estes, 1991; Jarman, 1979)

  • Breeding interval
    Impalas breed once a year.
  • Breeding season
    Most breeding occurs in March through May.
  • Range number of offspring
    1 to 1
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    6.47 to 6.67 months
  • Range weaning age
    4 to 7 months
  • Average weaning age
    4.5 months
  • Average age at sexual or reproductive maturity (female)
    1.5 years
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    456 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    1 years
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    395 days
    AnAge

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. Young impala are weaned at 4.5 months. (Eltringham, 1979; Estes, 1991; Jarman, 1979)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • post-independence association with parents

Lifespan/Longevity

Behavior

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. (Estes, 1991; Jarman, 1979)

Communication and Perception

Food Habits

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. Impala feed mostly on grass during times of lush growth following the rains and will switch to browse during the dry season. (Estes, 1991; Jarman, 1979)

  • Plant Foods
  • leaves
  • wood, bark, or stems

Predation

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. (Estes, 1991; Jarman, 1979)

Economic Importance for Humans: Positive

  • Positive Impacts
  • food

Conservation Status

Aepyceros melampus petersi is listed as endangered by the U.S. ESA and IUCN. Pressure resulting from habitat loss and damage have been linked to the decline in impala numbers. (Delany and Happold, 1979; Wilson and Reeder, eds, 1993)

Contributors

Barbara Lundrigan (author), Michigan State University, Karen Sproull (author), Michigan State University.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

polygynous

having more than one female as a mate at one time

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Delany, M., D. Happold. 1979. Ecology of African Mammals. New York: Longman Group Limited.

Eltringham, S. 1979. The Ecology and Conservation of Large African Mammals. New York: The Macmillan Press Limited.

Estes, R. 1991. The Behavior Guide to African Mammals. Los Angeles: The University of California Press.

Jarman, M. 1979. Impala Social Behaviour: Territory, Hierarchy, Mating,and the Use of Space. Berlin: Verlag Paul Parey.

Wilson, D., D. Reeder, eds. 1993. Mammal Species of the World. Washington, DC: Smithsonian Institution Press.

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