The Thomson’s gazelle (otherwise known as "Tommie"), is named after Joseph Thomson, a Scottish explorer, travelling around Africa in 1980. Thomson’s gazelles are endemic to eastern Africa, where the overall population of this species has considerably decreased in some areas. Nevertheless, they are among the most common gazelles of the region, commonly found on farmlands, grasslands and savannas. They are the smallest and, probably, the most elegant and charming gazelles around the globe. Additionally, these ungulates are the fastest gazelles, easily escaping any predators by running. They can survive harsh droughts and long periods without drinking water. They spend the dry season on African plains, whereas most animals leave the area to find more suitable land.
The current range of these gazelles covers northern Tanzania as well as central and southern Kenya. Within this territory, Thomson's gazelles occur in acacia savannas and short grasslands, most often living in almost entirely grazed, trampled or burnt grasslands. They can survive periods of harsh drought, living on dry pastures, while most animals of the area disperse to find more suitable habitats. The migration pattern of these mammals resembles that of other ungulates of the area. However, during the dry season, Thomson's gazelles do not migrate as far north as other ungulate species of their range. Additionally, during the wet season, they remain within their range longer, as compared to other ungulates.
Thomson's gazelles are sociable creatures, forming loosely organized units, typically bachelor herds, harems or groups, composed of females and their offspring. Meanwhile, old males of this species occasionally prefer leading solitary life, while breeding males usually display highly territorial behavior. Group members always come together to socialize in the early morning and evening. During these meetings, juveniles engage in plays such as stotting, pronking (this is when an animal moves by jumping on stiff legs) as well as chasing each other by running along the territorial boundaries of their herd. These ungulates are migratory animals, travelling in large groups of thousands of individuals. These groups may also contain individuals of other species such as Grant gazelles, impalas, wildebeests or zebras. As compared to other gazelle species, Thomson's gazelles are more silent. They communicate simply through visual awareness, contracting the skin of their body and making the black stripe on their side more conspicuous. Stamping is another important form of communication among these animals: when feeling danger, an individual stamps its front legs, which acts as an alarm signal, warning community members of a potential threat.
Thomson’s gazelles are polygynous. With the onset of the reproductive season, males begin fiercely defending their home ranges, waiting for females to come into their home ranges. These animals undergo two mating seasons per year. Females may give birth year-round, but generally do so immediately the rainy seasons. Gestation period lasts for 180 days, yielding one baby, which is born and raised in a special secluded place. The newborn fawn spends nearly all of its time here, except for short periods, when the mother cleans and suckles the baby. After a while, the young gazelle starts coming out of its shelter and grazing with its mother. It gradually engages into the community life, becoming a full member of the herd within 3 - 6 months old. At 5 - 8 months old, the fawn is weaned and switches its diet to solid food. Thomson’s gazelles reach adolescence at 2 years old, by which point young males exhibit their adult, arched horns.
There are currently no major threats to the population of Thomson's gazelles as a whole. However, localized threats negatively affect populations in certain areas. Population in Ngorongoro Crater is facing a considerable decline due to water shortage, tourism, roads, fire management as well as invasion of non-native plants, leading to modification of their habitat.
According to the IUCN Red List, the total population of Thomson’s gazelles is around 550,000 animals. The largest population of this species is found in a transitional area between Tanzania and Kenya, in the Serengeti-Maasai Mara ecosystem. This is a legally protected, migratory population, estimated to as many as 174,015 animals. Currently, this species is classified as Near Threatened (NT) and its numbers continue to decrease.
Due to grazing, these animals have a considerable impact on plant communities of their range. Additionally, Thomson's gazelles serve as key prey species for lions, hyenas, jackals and other large predators of their range.