Nanger granti

Geographic Range

Nanger granti is found only in eastern Africa, where they range up to 2,000 meters in altitude.

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.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

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.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• desert or dune desert or dune
• savanna or grassland savanna or grassland

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 ( Gazella 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. Gazella granti is paler and has bigger horns than Thompson's gazelles.

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.

The young are more darkly colored than adults.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• ornamentation ornamentation

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 G. granti as well as G. thomsonii .

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.

• Mating System
• polygynous polygynous

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.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• induced ovulation induced ovulation
• viviparous viviparous

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 G. granti .

• Parental Investment
• altricial altricial
• female parental care 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.

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.

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 G. granti either show interest or withdraw.

One way in which G. 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.

As a form of anti-predatory behavior, G. 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.

Gazella 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, G. granti avoid foraging in locations where selective defecation has taken place.

• Key Behaviors
• cursorial
• terricolous
• diurnal diurnal
• motile motile
• nomadic nomadic
• migratory migratory
• territorial territorial
• social social
• dominance hierarchies dominance hierarchies

Home Range

Throughout the year, G. granti range in an area of about 290 square km.

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.

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

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• pheromones pheromones
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Gazella granti are primarily browsers, rather than grazers. A large part of their diet consists of leaves and stems.

Since G. 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.

• Primary Diet
• herbivore herbivore
  • folivore folivore

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

Predation

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

Gazella 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.

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.

Gazella 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.

• Ecosystem Impact
• disperses seeds
• creates habitat

Economic Importance for Humans: Positive

The inadvertent control of the pouched mice ( Saccostomus campestris ) populations by G. 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.

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

Economic Importance for Humans: Negative

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

Conservation Status

According to the IUCN, a threat to G. 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.

Additional Links

Encyclopedia of Life

Contributors

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

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 .