Grant's Gazelle
Grant's gazelles resemble Thomson's gazelles, and
the two species are often seen together. They are similarly colored
and marked, but Grant's are noticeably larger than Thomson's and easily
distinguished by the broad white patch on the rump that extends upward,
beyond the tail and onto the back. The white patch on the Thomson's
gazelle stops at the tail. Some varieties of Grant's have a black
stripe on each side of the body like the Thomson's gazelle; in others
the stripe is very light or absent. A black stripe runs down the thigh.
Physical Characteristic
The various types of Grant's gazelle differ mainly in color and in
the size and shape of the horns. Grant's are large, pale, fawn-colored
gazelles with long legs. The males are larger and heavier and their
horns longer than the females.
The lyre-shaped horns are stout at the base, clearly ringed and
measuring from 18 to 32 inches long. The width of the spaces between
the horns and the angles of growth differ among the various types
of Grant's gazelles. One type, in northwest Tanzania, has widely
diverging horns, with the tips directed downwards.
On the females black skin surrounds the teats, with white hair
on the udder. This probably helps the young recognize the source
of milk. When a fawn is older and moving about with its mother,
the dark stripe on the white background may serve as a beacon for
it to follow.
Habitat
Grant's gazelles are especially fond of open grass
plains, and although they frequent bushy savannas, they avoid areas
of high grass.
Behavior
Grant's gazelles may remain in areas where food
is plentiful. Mature males establish territories they may hold as
long as eight months. A male tries to detain the female herds of 10
to 25 individuals as they pass through these territories while they
move about to feed. At the same time males chase off rival males and
try to mate with females in estrus.
Grant's gazelles have developed several ritualized postures. For
example, the territorial male stretches and squats in an exaggerated
manner while urinating and dropping dung. This apparently warns
other males to stay away and reduces the number of confrontations.
Younger males will fight, but as they grow older the ritualized
displays often take the place of fights. When fighting does occur,
it also is ritualized. It starts with "pretend" grooming,
repeated scratching of the neck and forehead with a hind foot and
presenting side views of the body. If neither combatant is intimidated,
they may confront one another and clash horns, trying to throw the
other off-balance.
Diet
The gazelles vary their diet according to the season.
They eat herbs, foliage from shrubs, short grasses and shoots. Grant's
gazelles are not restricted to certain habitats by a dependency on
water, but obtain the moisture they need from their food. Grant's
have unusually large salivary glands, possibly an adaptation for secreting
fluid to cope with a relatively dry diet. They typically remain in
the open during the heat of the day, suggesting an efficient system
to retain the necessary fluid in their bodies.
Caring for the Young
Breeding is seasonal, but not firmly fixed. Gestation
is approximately 7 months, and the young are born in areas that provide
some cover. The newborn fawn is carefully cleaned by the mother who
eats the afterbirth. Once the fawn can stand up and has been suckled,
it seeks a suitable hiding place. The mother watches carefully and
evidently memorizes the position before moving away to graze. She
returns to the fawn three to four times during the day to suckle it
and clean the area. The lying-out period is quite long-two weeks or
more.
The fawn eats its first solid food at about 1 month, but is nursed
for 6 months. Grant's become sexually mature at about 18 months.
By that time the young males will have joined an all-male bachelor
herd, but it will be some time before they become territory holders,
if at all. Males from the bachelor herds challenge the territorial
males, but only the strongest win territories, which they mark with
combined deposits of dung and urine.
Predators
All the major predators kill Grant's gazelle, but
cheetahs and African hunting dogs are the most prevalent. In some
areas jackals prey on the young. Because of its adaptation to semi-arid
and subdesert ranges as well as its good meat and valuable skin, Grant's
gazelle has been one of the species that scientists consider as a
potential source of protein for humans.
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