Oryx gazella

Geographic Range

The range of gemsbok, Oryx gazella , mostly consists of southern east Africa, though formerly the range included South Africa.

Gemsbok have been introduced into Mexico, as well as the southwestern United States.

• Biogeographic Regions
• nearctic nearctic
  • introduced introduced
• ethiopian ethiopian
  • native native

Habitat

Gemsbok are found at elevations from 900 to 1,200 meters, in wooded grasslands as well as wetter grasslands. They can survive in areas of low productivity. Gemsbok prefer stony plains with at least limited water access, but can subsist in areas of dunes, rocky mountainous areas, and arid habitats with little seasonal water. Gemsbok also frequent open areas more than areas with increased tree density.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial

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

Physical Description

Gemsbok are large bovids with very thick, muscular necks, covered in dense, inelastic skin. Oryx gazella is the largest of the Oryx species. Gemsbok measure 115 to 125 cm high at the shoulder, and have total body lengths between 180 and 195 cm. Females weigh from 180 to 225 kg, whereas males are slightly larger, weighing between 180 and 240 kg. The slightly curved, ringed horns range from 60 to 150 cm in length. The horns of females are often shorter and more slender than those of males.

Black markings on the face extend down from the base of the horns to above the muzzle, and sweep back in stripes over the eyes and cheeks. Black continues down the neck and around the underbody, forming bands around all four legs. A stripe also runs up the spine, starting at the tip of the tail and ending at a short thick mane of black. There are black markings on the front of all four legs. The lower portion of the legs, muzzle, and underbelly are all white, whereas the body and neck are a gray or tan color. In instances of high productivity grazing, fat deposits under the skin become noticeable.

Inidividuals in northern populations have characteristic black tufts on the ears and are generally darker in color with thinner black markings than are individuals from southern populations.

Gemsbok are able to increase their body temperature to 45 degrees from 35.7 degrees C in order to delay evaporative cooling.

• Other Physical Features
• endothermic endothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Gemsbok are polygynous. The resident bull of the herd mates with receptive females. Solitary territorial males are known to attempt to herd mixed or nursery herds onto their territories, thereby securing exclusive mating access to the females.

• Mating System
• polygynous polygynous

There is not a specific breeding season for gemsbok, though young within a herd tend to be of similar ages, indicating a reproductive synchrony in females. Females become sexually mature at about 2 years of age, and can conceive almost immediately after an 8.5 month gestation. Gemsbok are classified as "hiders", meaning the young are not seen present with the mother, but are hidden in the general vicinity, with the mother returning to nurse the calf 2 to 3 times each day. The young weigh between 9 and 15 kg at birth. At birth, calves are entirely brown in color. They develop the characteristic markings at about 3.5 months. At this point, the young are weaned. The males disperse and females join the maternal herd about a month after weaning.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• post-partum estrous

Like most ungulates, pregnant gemsbok isolate themselves from the herd before calving. The single neonate is kept concealed, usually within sight of the mother. This hiding behavior continues up to six weeks of age, ending with reconciliation with the herd.

Males are not reported to participate directly in parental care, so the feeding, sheltering, protection, and grooming of the young are all accomplished by the mother. As is the case with most bovids, the young are able to stand shortly after birth, and can move around with the mother as needed.

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

Lifespan/Longevity

The average life span is approximately 18 years in the wild, and 20 in captivity.

Behavior

Gemsbok are typically gregarious and nomadic in nature, forming groups that can range from about 50 individuals to 200 in times of rain or migration, but the average is about 14. In larger groups, the sex ratio is typically female-biased, but the herd remains mixed. In smaller groups, however, composition can consist of all females and young (nursery herds), females with one male, or all males (bachelor herds).

The sociality of males and females differs. A large proportion of males remain solitary and defend a territory. This may be due to differences in activity budget optimization. Single sex groups are more optimal for grazing. However, smaller herd sizes limit protection from predators. Also, increasing distance from the opposite sex limits reproduction.

Within groups, a distinct hierarchy is in place. The dominant male is at the top, followed by the dominant female. In large groups, there may be a second-ranked male, called a beta male. Herd leaders are typically identifiable by their position in the herd. The dominant male typically brings up the rear and retrieves stragglers. The dominant lead female typically takes the foremost position. The male will lead by aggressive displays, playing the role of main director of the movement of the animals. This hierarchy remains intact until a water scarcity, at which point the males take precedence over all females.

Aggressive displays are used by the males to establish the dominance hierarchy, and contact is usually minimal. Horns are used in both sidelong jabs and "fencing". As a result, distribution of animals in the herd is uniform, since gemsbok stand stand a horn's length from each other.

Herds are semi-closed to strangers, but not to adults older than one and a half years. Resident males will accept males into the group as well after little aggression.

• Key Behaviors
• cursorial
• terricolous
• crepuscular crepuscular
• motile motile
• nomadic nomadic
• solitary solitary
• territorial territorial
• social social
• dominance hierarchies dominance hierarchies

Home Range

Territoriality and ranging behavior are greatly influenced by access to water in low rainfall areas (50 to 250mm). Home range is of loose construct due to the nomadic nature of the animals, resulting from patchy resource availability. Solitary males have been shown to defend a territory.

Communication and Perception

Communication is particularly evident through dominance displays and aggressive behaviors. However, more subtle communication is conveyed by scent glands in the hooves, as well as urine sampling (primarily used to determine fertility). The animals have excellent hearing and smell, accounting for the prominence of stripe displays and scent marking. Although not specifically reported for these animals, as mammals it is likely that they use some accoustic means of communication. Tactile communication is also likely to play a role in reproductive activities.

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

• Other Communication Modes
• scent marks scent marks

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

Food Habits

Although generally a grazer, O. gazella will revert to browsing during droughts or whenever grasses are not available. These animals will also dig up to a meter to find tubers and roots. These, supplemented with wild tsama melons and cucumbers, provide all the water needed to sustain gemsbok (approximately three liters per 100 kg daily).

The dentition is highly adapted to cutting coarse desert grasses short, with high crowned molars and a wide incisor row. Desert dwellers can eat dry grass, but prefer green grasses. Activity at dawn and dusk allow for the consumption of the condensation present on the grasses.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• roots and tubers
• wood, bark, or stems
• fruit

Predation

Top predators of African grasslands are threats to the gemsbok. These include lions , cheetahs , leopards , and spotted hyenas . Even hunting dogs will attack them. Humans occasionally hunt these animals. The primary response to predation is flight, despite impressive weaponry. The young are typically targeted, since attacking the adults involves a risk of puncture wounds. However, it is debatable whether or not fatal stab wounds have ever been inflicted upon a predator, or whether predators show any avoidance of gemsbok in general. Predation may account for the high mortality rate in young. In the northern part of their range, 80% of spotted hyena kills are gemsbok calves.

Ecosystem Roles

Gemsbok exploit areas that few other animals can inhabit; they tend not to interact with many other species. Also, because they are nomadic, they tend not to overgraze areas.

In regions of the North American Southwest where gemsbok (and other exotic species) have been introduced, overgrazing has occurred, leading to the degradation of the areas populated by these herds.

• Ecosystem Impact
• biodegradation biodegradation

Economic Importance for Humans: Positive

Gemsbok are hunted for their thick skin, which is used for shield covers by local African peoples. The horns are also used in making spears.

This species is a common game ranch species since both females and males have horns, making trophies cheaper to produce.

• Positive Impacts
• food food
• body parts are source of valuable material

Economic Importance for Humans: Negative

There are no negative economic impacts of this species on humans.

Conservation Status

The current total population of gemsbok is around 275,000 individuals. Though the numbers do not indicate a threatened population, large declines in several areas have resulted from livestock overgrazing, human encroachment on land, climate change, and habitat destruction. Other gemsbok populations have been declining due to over hunting.

Other Comments

Gemsbok are thought to have evolved reduced sexual dimorphism to facilitate longer acceptance of juvenile male presence by the territorial males.

Gemsbok are able to increase their body temperature to 45 degrees from 35.7 degrees C in order to delay evaporative cooling.

The species has been recognized since 1758.

There are seven identified subspecies, but none of them have been formally recognized yet.

Additional Links

Encyclopedia of Life

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Barbara Lundrigan (editor, instructor), Michigan State University, Sheri Sanders (author), Michigan State University.

References

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