Why Do Zebras Have Stripes?

Scientists have finally solved one of the great mysteries of the animal kingdom ... probably.

The debate has been raging at least since the 1870s, when our evolutionary theory forefathers Charles Darwin and Alfred Russel Wallace disagreed as to how and why the zebra got his stripes.

A group of researchers led by Tim Caro, a biologist at the University of California Davis, set out to test the five prevailing theories: that the stripes repel insects, provide camouflage, confuse predators, reduce body temperature, or help the animals interact socially. They mapped the prevalence and variation of stripes on the seven species of the equid group and their 20 subspecies and compared those maps to the environmental factors of different regions that would influence the different hypotheses. Their findings, published earlier this month in the Nature Communications journal, strongly favored a single theory.

“We found again and again and again [that] the only factor which is highly associated with striping is to ban biting flies,” Caro said. That is to say, the more flies in a certain area, the more likely to find striped species, like zebras.

Two years ago, a study showed that horse flies are attracted to the polarization of reflected light, and a striped pattern disrupts this appealing polarization. This explanation is compelling, but it earned criticism for featuring sticky boards of striped colors instead of actual zebras.

Caro's study has been deemed inconclusive for looking at broad-brush factors like environmental distribution. As Brenda Larison, a biologist at the University of California, Los Angeles, said, “the story is likely to be much more complex, and this is unlikely to be the last word on the subject."

But for now, consider zebra-print to keep the flies at bay.