Thomson's gazelle (Eudorcas thomsonii) is one of the best known species of gazelles. It is named after explorer Joseph Thomson and is sometimes referred to as a "tommie". It is considered by some to be a subspecies of the red-fronted gazelle and was formerly considered a member of the genus Gazella within the subgenus Eudorcas, before Eudorcas was elevated to genus status.
Thomson's gazelles can be found in numbers exceeding 200,000 in Africa and are recognized as the most common type of gazelle in East Africa. A small fast antelope, the Thomson's gazelle is said to have top speeds up to 80–90 km/h (50–55 mph). It is the fourth-fastest land animal, after the cheetah (its main predator), pronghorn, and springbok.
Thomson's gazelle is a relatively small gazelle; it stands 60–70 cm (24–28 in) at the shoulder. Males weigh 20–35 kg (44–77 lb), while the slightly lighter females weigh 15–25 kg (33–55 lb). Facial characteristics of the gazelle include white rings around the eyes, black stripes running from a corner of the eye to the nose, rufous stripes running from the horns to the nose, a dark patch on the nose, and a light forehead.
A Thomson's gazelle, showing the facial markings and the dark lateral stripe
The coat is sandy brown to rufous; a black band runs across the flanks, from the upper foreleg to just above the upper hind leg. A buff band occurs above the black stripe. Short, black streaks mark the white rump. The black tail measures 15–27 cm (5.9–10.6 in). Males have well-developed preorbital glands near the eyes, which are used for scent-marking territories. Both sexes possess horns that curve slightly backward with the tips facing forward. The horns, highly ringed, measure 25–43 cm (9.8–16.9 in) in males and 7–15 cm (2.8–5.9 in) in females. However, females have more fragile horns; some are even hornless. Grant's gazelle is very similar to Thomson's gazelle, but can be differentiated by its larger size and the white patch on the rump extending top over the tail.
The two subspecies differ in their appearance. The eastern Thomson's gazelle is the larger of the two, with fainter facial markings. The Serengeti Thomson's gazelle has a whiter face with more conspicuous markings. The horns of females are shorter than those of males to a greater degree in the eastern Thomson's gazelle and the horns are more divergent in the eastern Thomson gazelle.
Thomson's gazelle lives in East Africa's savannas and grassland habitats, particularly the Serengeti region of Kenya and Tanzania. It has narrow habitat preferences, preferring short grassland with dry, sturdy foundation. It does, however, migrate into tall grassland and dense woodland. Gazelles are mixed feeders. In the wet seasons, they eat mainly fresh grasses, but during the dry seasons, they eat more browse, particularly foliage from woody plants bushes and herbaceous forbs.
Cheetahs are the main predators of Thomson's gazelle.
Thomson's gazelles are dependent on short grass. Their numbers can be highly concentrated at the beginning of the rains when the grass grows quickly. In the Serengeti, they follow the larger herbivores, such as plains zebras and blue wildebeests as they mow down the taller grasses. In the wild, Thomson's gazelles can live 10–15 years. Their major predators are cheetahs, which are able to attain higher speeds, but gazelles can outlast them in long chases and are able to make turns more quickly. This small antelope can run extremely fast, up to 80 km/h (50 mph), and zigzag, an adaptation which often saves it from predators. Sometimes, they are also taken by leopards, lions, African wild dogs, hyenas, Nile crocodiles and African rock pythons, and their fawns are sometimes the prey of eagles, jackals, and baboons. A noticeable behaviour of Thomson's gazelles is their bounding leap, known as stotting or pronking, used to startle predators and display strength.
During the wet season, a time when grass is abundant, adult male gazelles graze extensively. They spread out more and establish breeding territories. Younger males usually spend their time in bachelor groups, and are prevented from entering the territories. Females form migratory groups that enter the males' territories, mostly the ones with the highest-quality resources. As the female groups pass through and forage, the territorial males may try to herd them, and are usually successful in preventing single females from leaving, but not whole groups. Subadult males usually establish dominance through actual combat, while adults are more likely to do rituals. If a bachelor male should be passing through a territorial male's region, the male will chase the offender out of his territory.
When patrolling his territory, a male may use his horns to gore the grass, soil, or a bush. Males also mark grass stems with their preorbital glands, which emit a dark secretion. Territories of different males may share a boundary. When territorial males meet at the border of their territories, they engage in mock fights in which they rush towards each other as if they are about to clash, but without touching. After this, they graze in a frontal position, then in parallel and then in reverse, and move away from each other while constantly grazing. These rituals have no victor, but merely maintain the boundaries of the territories. Territorial males usually do not enter another male's territory. If a male is chasing an escaping female, he will stop the chase if she runs into another territory, but the neighboring male will continue the chase.
