Why do zebras have stripes? For a long time, researchers assumed they were to confuse predators while zebras stood in herds. But increasingly, scientists are reaching a different conclusion: Stripes protect zebras from biting insects. To reach this conclusion, scientists tested their theory on a group of horses and zebras wearing different kinds of coats. The researchers dressed both horses and zebras in black coats, white coats, and striped zebra coats. The idea was to test how flies reacted to each type of coat, and the researchers used both horses and zebras to make sure it really was the coat that was making the difference.