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Nanger grantiGrant's gazelle

By Nikhil Khankari

Geographic Range

Nanger granti is found only in eastern Africa, where they range up to 2,000 meters in altitude. (Estes, 1991; Kingdon, 1982; Skirka, et al., 1971)

Grant’s gazelles migrate seasonally over a large part of their range preferring higher, well-drained areas during the rainy season, and moving to lower, grassy valleys during the dry season. They are not dependent on water and, consequently, they migrate in the opposite direction of water-dependent species such as Thomson’s gazelles, wildebeest, zebras, and topi. In doing so, Grant’s gazelles avoid competition and are able to survive on vegetation found in this semi-desert environment. However, N. granti remain throughout the year in areas where there is a plentiful supply of food. (Estes, 1991; Kingdon, 1982; Skirka, et al., 1971)

Habitat

Grant’s gazelle habitat consists of semi-desert, open savannas, and treeless plains. They avoid acacia forests unless they are traversed by well-traveled paths. (Estes, 1991; Kingdon, 1982; Skirka, et al., 1971)

  • Range elevation
    2500 (high) m
    8202.10 (high) ft

Physical Description

Grant's gazelles are large, pale gazelles with long horns and legs. They have a distinct rectangular, white shape on the hindquarters and a contrasting black stripe running down the thigh. Thomson’s gazelles (Eudorcas thomsonii), a closely related species, have some similar physical characteristics. They both possess white coloring on the hindquarters, but Grant’s gazelles have more white than Thompson’s gazelles. Nanger granti is paler and has bigger horns than Thompson's gazelles. (Estes, 1991; Kingdon, 1982; Skirka, et al., 1971)

Males and females are dimorphic. Males are larger than females, and they have longer, thicker horns, ranging from 50 to 80 cm. The horns are ringed. In contrast to males, females have smaller horns (30 to 40 cm) that are thin and symmetrical. (Estes, 1991; Kingdon, 1982; Skirka, et al., 1971)

The young are more darkly colored than adults. (Kingdon, 1982)

  • Range mass
    45 to 65 kg
    99.12 to 143.17 lb
  • Range length
    140 to 166 cm
    55.12 to 65.35 in

Reproduction

When a female gazelle is in estrus, her urine contains sex pheromones indicating her reproductive status to males. In order to detect these, males perform flehmen behavior. Males curl their lips and suck air into their vomeronasal organs to detect whether sex pheromones are present. This behavior is done by N. granti as well as G. thomsonii. (Hart, et al., 1989; Kingdon, 1982)

If pheromones are detected, the male actively pursues the female. Courting takes place, in which the male prances with his head held high and his tail held horizontally. This eventually leads to copulation. However, if no sex pheromones are detected, the male does not further pursue the female. (Hart, et al., 1989)

Grant's gazelles reach sexual maturity at three years of age for males and about one and half years for females. Timing of the mating season depends on location. For example, in southern Kenya and Tanzania, mating takes place throughout the year. In the Serengeti, mating takes place in all months except June, July, October, and November. The gestation period is about 27 weeks. (Estes, 1991; Kingdon, 1982; Estes, 1991; Kingdon, 1982)

  • Breeding interval
    Females typically give birth once per year.
  • Breeding season
    Gran't gazelles can breed throughout the year but local climate affects the timing of reproduction.
  • Range number of offspring
    1 (low)
  • Average number of offspring
    1
  • Range gestation period
    6 to 6.63 months
  • Average gestation period
    6.3 months
  • Average weaning age
    6 months
  • Average time to independence
    1.5 years
  • Average age at sexual or reproductive maturity (female)
    1.5 years
  • Average age at sexual or reproductive maturity (male)
    3 years

After birth, the fawn is completely cleaned of any fluids by the mother. The fawn then drinks its first meal of milk and seeks protection near its mother. If the mother is going out to graze, the fawn remains in a secure hiding place which is observable to the mother from where she is grazing. The mother-fawn relationship is the only persistent relationship in N. granti. (Estes, 1991; Kingdon, 1982)

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

Lifespan/Longevity

Grant's gazelles have an average lifespan of around 12 years. (Bergin, 2006)

  • Average lifespan
    Status: wild
    12 years
  • Average lifespan
    Status: wild
    12 years

Behavior

Grant’s gazelles are migratory and they move seasonally throughout their range, except in areas with year-round supplies of forage. They migrate in groups and some groups establish home ranges. Herds may segregate into separate groups of bachelor males and females with dominant males. Social rank in this species can be seen in the way males are organized when migrating. The less dominant, younger males are towards the front of the unit, whereas the more dominant males are in the back. This organization also results in equally matched opponents in fights, as it is more likely that nearby males will display dominance and fight one another. (Estes, 1991; Kingdon, 1982)

Territorial males mark areas with a combination of feces and urine. This type of marking requires the gazelle to advertise his white rump. As a result of this advertisement, other N. granti either show interest or withdraw. (Estes, 1991; Kingdon, 1982)

One way in which N. granti show dominance is through side-by-side strutting. In strutting alongside other territorial males a male may express his dominance by raising his neck and tilting his horns slightly. A second method by which Grant’s gazelles show dominance is through fighting. When two males approach each other to fight, they quickly move their heads downwards and towards one another as one tries to throw the other off balance. Fighting displays the contender’s neck muscles. (Estes, 1991; Kingdon, 1982)

As a form of anti-predatory behavior, N. granti use alert posture, alarm snorts and stamping as signals of a predator in the vicinity. They avoid water holes, where predators are plentiful and prey are vulnerable. Females may resist when a fawn is captured by a predator, cooperating with other females to fiercely defend the abducted fawn. This defense often chases the predator away, leaving the fawn unharmed. (Estes, 1967)

Nanger granti, along with many other ungulates, display an anti-parasitic behavior of selective defecation. Grant’s gazelles defecate in specific locations in order to keep the parasites associated with dung piles away from other members of the herd. Additionally, N. granti avoid foraging in locations where selective defecation has taken place. (Ezenwa, 2004)

  • Average territory size
    290 km^2

Home Range

Throughout the year, N. granti range in an area of about 290 square km. (Estes, 1967)

Communication and Perception

Grant's gazelles communicate through territorial markings made with urine and feces, sex pheromones, and visual displays. They communicate the presence of a predator by alert posture, alarm snorts, and stamping. (Estes, 1991; Hart, et al., 1989; Kingdon, 1982)

The dark coloration around the female’s anus serves as source of visual attraction between a fawn and its mother.

Food Habits

Nanger granti are primarily browsers, rather than grazers. A large part of their diet consists of leaves and stems. (Kingdon, 1982; Spinage, et al., 1980)

Since N. granti live in an arid environment, water conservation and consumption is important for survival. While Thomson’s gazelles uses evaporative cooling as a method of decreasing body temperature, Grant's gazelles allow their body temperature to rise with air temperature, dissipating body heat to the surrounding air when temperatures fall. At night they may also eat leaves, which contain more water during the cooler, nighttime hours. (Vaughan, et al., 2000)

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

Predation

While many predators are threats to N. granti, cheetahs (Acinonyx jubatus), wild dogs (Lycaon pictus), and golden jackals (Canis aureus) are particularly fond of N. granti fawns. During the rainy season, when the ground is soft, cheetahs (Acinonyx jubatus) take advantage of the greatly reduced speed of these gazelles. (Kingdon, 1982)

Nanger granti uses anti-predatory signals including alert posture and alert snorts. They avoid areas with a high density of predators and employ cooperative defense to protect vulnerable fawns. (Kingdon, 1982)

Ecosystem Roles

Grant’s gazelles are prey for cheetahs (Acinonyx jubatus), wild dogs (Lycaon pictus), and golden jackals (Canis aureus). They are also important herbivores in the habitats in which they live. (Estes, 1991; Kingdon, 1982)

Nanger granti inadvertently affects the population density of pouched mice (Saccostomus mearnsi) in eastern Africa by depleting the supply of food for these rodents. In areas where Grant’s gazelles are less common, S. mearnsi populations flourish. (Keesing, 1998; Keesing, 1998)

  • Ecosystem Impact
  • disperses seeds
  • creates habitat

Economic Importance for Humans: Positive

The inadvertent control of the pouched mice (Saccostomus campestris) populations by N. granti is advantageous to humans. In addition to being agricultural pests, pouched mice may spread disease. Grant's gazelles are sometimes hunted for meat and trophies and they are sought by ecotourists. (Keesing, 1998)

  • Positive Impacts
  • food
  • body parts are source of valuable material
  • ecotourism
  • controls pest population

Economic Importance for Humans: Negative

There seems to be no negative impacts caused by N. granti.

Conservation Status

According to the IUCN, a threat to N. granti is human habitat destruction. Habitat loss is leading to population decreases of Grant's gazelles.

Other Comments

A Ugandan tribe uses Grant’s gazelles as one of their four major totems. They are also respected as animals possessing great beauty. (Kingdon, 1982)

Contributors

Nikhil Khankari (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Ethiopian

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

World Map

acoustic

uses sound to communicate

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

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

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

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

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.

female parental care

parental care is carried out by females

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.

induced ovulation

ovulation is stimulated by the act of copulation (does not occur spontaneously)

migratory

makes seasonal movements between breeding and wintering grounds

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.

nomadic

generally wanders from place to place, usually within a well-defined range.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynous

having more than one female as a mate at one time

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

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.

visual

uses sight to communicate

viviparous

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

year-round breeding

breeding takes place throughout the year

References

Bergin, P. 2006. "African Wildlife Foundation" (On-line). Accessed March 22, 2006 at http://www.awf.org/wildlives/120.

Bergstrom, R. 1992. Browse Characteristics and Impact of Browsing on Trees and Shrubs in African Savannas. Journal of Vegetation Science, 3: 315-324.

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

Estes, R. 1967. The Comparative Behavior of Grant's and Thomson's Gazelles. Journal of Mammalogy, 48: 189-209.

Ezenwa, V. 2004. Selective Defecation and Selective Foraging: Antiparasite Behavior in Wild Ungulates?. Ethology, 110: 851-862.

Hart, B., L. Hart, J. Maina. 1989. Chemosensory investigation, flehmen behaviour and vomeronasal organ function in antelope. The Zoological Society of London, 61: 197-215.

Keesing, F. 1998. Impacts of ungulates on the demography and diversity of small mammals in central Kenya. Oecologia, 116: 381-389.

Kingdon, J. 1982. East African Mammals. United States fo America: University of Chicago Press edition 1989.

Skirka, P., W. Swank, A. Dyer. 1971. African Antelope. New York: Winchester Press.

Spinage, C., C. Ryan, M. Shedd. 1980. Food selection by the Grant's Gazelle. African Journal of Ecology, 18: 19-25.

Stelfox, J., R. Hudson. 1986. Body condition of male Thomson's and Grant's gazelles in relation to season and resource use. African Journal of Ecology, 24: 111-120.

Vaughan, T., J. Ryan, N. Czaplewski. 2000. Mammalogy. United States fo America: Brooks/Cole Thomson's Learning.

Wikipedia, 2006. "Wikipedia, the free encyclopedia" (On-line). Accessed March 12, 2006 at http://en.wikipedia.org/wiki/Grant's_Gazelle.

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