On the Serengeti plain, Thompson gazelle live in herds of 100 or more. Thomson's gazelles are sometimes called Tommies. Thompson gazelle carefully observes its surroundings. There might be a cheetah hiding somewhere. The gazelle isn't interested in ending up as that cat's breakfast!
Its long, twisted horns are of little use against the cheetah. The best mode of action is to run away, dodging left and right like a pro.