||22 to 26 inches at the
||35 to 55 pounds
||Open plains and
leopards, hunting dogs, hyenas
While perhaps not as widely distributed as Grant's, Thomson's
are still the most common gazelles in East Africa. Though
their numbers have diminished in some areas, in others they
have persisted on ranches and farmlands long after other
species have disappeared.
The graceful "tommie" is noticeably smaller than the
Grant's gazelle, which it resembles in shape and color. It is
also distinguished from a Grant's by the dark side stripe that
runs from the shoulder to the flank and the white patch on the
rump. The tommy is a dark fawn or cinnamon color on the topside
and white on the underside. The black tail seems to be
constantly in motion.
The males are larger than the females and have strongly
ridged, almost parallel horns that curve backwards, with the
tips curving forward. Female tommies have short, smooth,
pencil-slim horns, or none at all. The face is accented by a
black stripe running down from the eye, a dark marking on the
nose and a light patch on the forehead.
Although more reliant on water than Grant's gazelle, the tommy
has adapted to the open plains and grasslands of southern
Kenya and northern Tanzania.
During migration, as tommies spread out over the
plains in the wake of zebra and wildebeest herds, the strongest
males set up territories. They use an exaggerated display
posture when urinating or defecating on dung piles. To mark the
boundaries the males deposit a small amount of secretion from
their scent glands (located beneath the eyes) onto a blade of
grass, leaving these markers daily about every 20 feet. As the
herd migrates, new territories are established.
The females along with their immature offspring form groups
of five to 50 that wander through male territories. The groups
change members and numbers from hour to hour, so no obvious
patterns of hierarchy or leadership emerge. Nonterritorial males
gather together in small groups along the outskirts of the
larger herd, generally avoiding other male territories unless
one of the group attempts to take one over.
In the early morning and again in the evening, the herd,
which may have spread out during the day, comes together. This
is playtime for the younger gazelles, when they engage in
stotting and pronking (bouncing along on stiff legs) and sprint
around the perimeter of the herd.
The relatively silent tommies rely on visual awareness of one
another to stay in contact. Their distinctive coloring may
help-they can contract the skin so the black side stripe becomes
more obvious. They also stamp their front feet to signal when
they are disturbed.
Tommies congregate not only with Grant's gazelle but with
larger ungulates such as wildebeest and zebra-and even cattle,
which trample and graze on tall grass, making it easier for
the tommy to feed on short grass. Although grasses make up
about 90 percent of the tommy's diet in dry season, it also
eats seeds and browses on shrubs. When the tiny new green
shoots of grass begin to grow in areas that have been burned,
tommies often gather in large numbers to feed.
Caring for the Young
Tommies breed twice a year. Although births occur
throughout the year, they peak right after rainy seasons. After
giving birth the mother hides the newborn in the grass,
returning several times a day to nurse it. With their tawny
coloring and ability to remain motionless for long periods, the
young are surprisingly invisible when hidden in open country.
Nevertheless, predation on the young is heavy, and many
predators feed on nothing else during the calving peaks.
Cheetahs, lions, leopards, hunting dogs and hyenas prey on
young and adults alike, with adult tommy males three times
more susceptible than females. The young are also taken by
serval cats, jackals, baboons, eagles and pythons.
Did you know?
- The Thomson gazelle is exceptionally alert to sounds and
movements, and its fine senses of hearing, sight and smell
balance its vulnerability on the open plains.
- Males vigorously defend their territories. If challenged,
the defending male and his rival clash horns, with the winner
claiming the territory.