Dave Taylor's African Safari: Trophic Level II - The Herbivores - Thomson’s Gazelle

Dave Taylor's African Safari: Trophic Level II - The Herbivores - Thomson’s Gazelle - Page 26

Trophic Level II - The Herbivores
Thomson’s Gazelle
Page 26

Gazella thomsonii

Length: 80-120 cm (31-47")

Height: 55-82 cm (22-32")

Tail: 15-27 cm (6-11")

Weight: 20-35 kg (44-77 lb.)

Status: Locally common and not endangered; range is decreasing

Habitat: Thomson's gazelles are found from northern Tanzania to northern Kenya. The species is found in arid areas and adjacent savanna grasslands. In these richer areas, including the Serengeti-Mara ecosystem, they reach very high population densities. There are 500,000 in the Serengeti.

Most Thomson's gazelles in the ecosystem are found in the short grass plains in the south and east portions of the ecosystem. This is the area where, during the rainy season, the wildebeest calve. At that time, there are over two million antelopes on these plains.

During the dry season, only the Tommies and few Grant's gazelles remain. These species need far less water than the wildebeest do. Thomson’s gazelles will leave the grassland to seek richer pastures before the Grant’s gazelles will. At the peak of the drought, there may only be a few Grant’s gazelles on the short grass plains.

The Thomson's gazelles of the Serengeti-Mara do migrate but they do not follow the wildebeest herds. They stay, for the most part, in drier country. However, the species is widespread and small herds of Tommies may be encountered throughout the region.

Their migration is unpredictable, especially at the beginning of the dry season. They will move west and northwest but their destination varies from year to year. More certain is their return migration. Thomson’s gazelles do not like wet feet and when the rains start, they move south and east, back onto the short grass plains. (It should be pointed out that there are several variations in this species’ movements. Thomson’s gazelles on the Mara are not as migratory and there are some local populations in the Serengeti which hardly ever migrate. The comments above refer to the main population found on the short grass plains.)

Food: Tommies are grazers and browsers. They prefer to eat the short grasses but will graze in areas the larger herbivores have eaten down. They have small, narrow mouths that are adapted for selective feeding on short grasses. When grass is not available to them, they will feed on shrubs and forbs.

Social System: Thomson's gazelles have a wide variety of social groupings. Females and young live in herds numbering 2 to 20 adults. There appears to be no social order or dominance hierarchy in these groupings. In areas where there are many such herds, females and young will move from one herd to another. There appears to be little herd loyalty. Individual animals will have a range of 15 square kilometers (5.7 square miles) where they wander with many other Tommies.

Males mark territorial boundaries with their scent glands and will create middens. This behavior is not as well-developed as it is in dikdik and klipspringers. Males try to keep the female herds within the boundaries of their territories. Territories range from 6 hectares (15 acres), in highly populated ranges, to 495 hectares (1,223 acres) in areas where food levels keep the population low.

Males fight other males if they wander into their territory. They will chase young males from their territory when they reach 6 months of age. At that time, their horn development is such that they are easily distinguished from females. Expelled males join bachelor herds. In the Serengeti-Mara, mixed herds of adult males and females are commonly seen during the migration.

Behavior: Thomson’s gazelles are known for the constant wagging of their tails. This continuous wagging of the black tail across the white rump says to other Tommies that "I'm a Tommy too". It helps them recognize their own species at a distance.

Males will herd females, much like a sheep dog herds sheep. When a male finds a female in estrus, he will follow her about. When she stands for him, he will approach by walking on his two back legs. After mating, the two animals go their separate ways. A male Thomson’s gazelle, like all members of the antelope-gazelle family, will not defend a young gazelle from predators. His only interest lies in the female.

Thomson’s gazelle calves lie-out shortly after birth (see Antelopes: Newborns).

When a predator is spotted, adults will often turn to face it. If it is moving away from them or parallel to them, they will often follow it. This behavior is called "curiosity" and is common among plains ungulates. "The predator seen is a safe predator."

Tommies flee from danger and can run 2 or 3 kilometers (1 to 1.5 miles). They zigzag so that they can see the location of the danger. This can be fatal if the predator is a courser such as a cheetah, wild dog or spotted hyena. Each zigzag allows the predator to close in on the Tommy.

Tommies seem to have a flight distance that varies from predator to predator. Even so, many are taken each year by the hunters.

Predators: Cheetah are the main predator in the Serengeti-Mara. They approach a herd as closely as possible before beginning the chase.

Lions, spotted hyenas and leopards will take them too, but prefer other prey. For a lion or spotted hyena, the Tommy is not much of a meal. They are generally hunted by these species when larger prey have migrated out of the territory.

They are hard for the leopard to catch because they avoid areas of heavy tree cover where leopards tend to hide. When wild dogs come upon Tommies, they will often chase and bring down several animals. Wild dogs are rare now and the odds of a Tommy ever seeing one are quite low.

Jackals, baboons and eagles will take young Tommies. Often, baboons will stumble across a baby that is lying out. Mother Thomson's gazelles will put up a fight to save their babies but can do little to stop a pair of jackals. Oddly, they do not seem to see baboons as serious threats and do not put up much of a fight when they see a baboon near their babies.

Select a Page:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42