The Tommy, as the Thomson's is affectionately known, is considerably smaller and redder than the Grant's. An easy way to distinguish these species is to look at the white marking at the rear of the animals. In Tommies the white comes up to the tail whereas in Grant's it comes over the tail and onto the rump. Tommies of both sexes have strongly marked lateral stripes whereas in the Grant's it is only the female which is marked in this way. Grant's are larger and are pale fawn with white underparts.
Horns are present in both male and female of the two species but are much larger in the male.
Tommies are the main prey of the plains- dwelling wild dogs and cheetahs and the staple diet of resident lions during the dry season when their preferred prey, zebras and wildebeest, have migrated out of reach. Hyenas and leopards also take their toll, while jackals are the main predator on young fawns of both gazelles. Unlike nearly all other antelopes, female gazelles will team up to defend their young against jackals, which often hunt in pairs. Newborn gazelle fawns are even taken by some of the larger birds of prey including the martial eagle. Both species spend a good deal of their time on the long-grass plains after a fire but will be seen in other areas of the Park.