Oryx
Kenya's Tana River divides the range of East Africa's
two types of oryx the beisa oryx (Oryx g. beisa) and the fringe-eared
oryx (Oryx g. callotis). The fringe-eared oryx ranges from Kenya to
central Tanzania. The beisa oryx ranges from Ethiopia through Somalia
into northeastern Uganda and Kenya.
Physical Characteristic
The oryx is a large antelope of striking appearance with long, spearlike
horns. It has a thick, horselike neck with a short mane and a compact,
muscular body. A defined pattern of black markings that contrast with
the white face and fawn-colored body are prominently displayed in
dominance rituals to emphasize the length of horns and strength of
the shoulder.
The head is marked with black triangular patches and broad black
stripes that extend from the base of the horns over the eyes to
the cheeks. A ring of black encircles the throat and runs down the
neck to the chest. The ears end in a black tip (a black tassel hangs
from the ear tip of the fringe-eared oryx). A narrow black stripe
runs along the spine, and another one separates the lower flank
from the white underparts of the body. The white forelegs have a
black ring above the knee and a black patch below. The black tail
tassel reaches to the hocks.
The oryx's ringed horns are up to 30 inches long, making them formidable
weapons. The female's horns are often longer and thinner than the
male's.
Habitat
Originally, various oryx species were found in all
of Africa's arid regions. One species that occurred on the Arabian
Peninsula was exterminated recently but has now been reintroduced
into the wild from captive stock. Well adapted to the conditions of
their hot, arid habitats, oryx can live as long as 20 years.
Behavior
The social system of the oryx is unusual in that nonterritorial
males live in mixed groups with females, or with females and their
young. Males that dominate are territorial to a degree, marking their
areas with dung deposits. Groups are composed of 10 to 40 males and
females of all ages and both sexes; herds of up to 200 are common
in some East African habitats.
The dominance hierarchy among oryx is based on age and size. As
they grow, calves test one another in what look like games, though
in reality are tests of strength. As the hierarchy becomes established,
the need to fight is reduced. Ritual displays replace actual contact,
except when evenly matched individuals may have to fight to establish
their rank. Along with lateral displays, oryx perform a slow, prancing
walk and sometimes break into a gallop. When several males are making
these displays, they may clash horns.
Herd composition in the wild constantly changes according to need.
Oryx wanting to drink, for example, form a group to go to water,
or females with young form a group that moves more slowly. The result
is a social system that allows for individual needs but retains
the advantage of group living. Oryx range widely over a large area,
but their keen sense of smell alerts them to rain in the area, so
that groups quickly assemble, often in herds of 200 or more, to
feed on new growth.
Diet
Oryx typically feed in early morning and late afternoon
and sometimes on moonlit nights. Their diets consists mainly of coarse
grasses and browse from thorny shrubs. In desert areas they consume
thick leaved plants, wild melons, as well as roots and tubers they
dig out of the ground. They may drink if water is available but can
survive days or even weeks without it.
Plants growing in arid areas inhabited by oryx have also adapted
to the hot, dry conditions and either store water or have mechanisms
to prevent excess loss. Plants collect dew, gradually releasing
it during the hotter parts of the day. Some plants increase their
water content by 25 to 40 percent, so when oryx feed late at night
or early in the morning, it provides them with both food and water.
Caring for the Young
A female leaves the herd to give birth and hides
the calf for 2 or 3 weeks, visiting a few times a day to nurse it.
The newborn is an inconspicuous brown color. The black markings begin
to appear when the calf is ready to return to herd with its mother.
Calves are suckled for 6 to 9 months and reach maturity at 18 to 24
months. Most young males migrate out of their natal group to join
other groups.
Predators
Like other antelope species, oryx primarily depend
on flight to escape from predators such as lions, wild dogs and hyenas.
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