Zebra Stripes Aren't Camouflage and Don't Deter Predators

Zebra stripes don't help the animals camouflage themselves from predators like lions and hyenas, a new study suggests. Goran Tomasevic/REUTERS

Scientists have long debated why zebras have stripes, and one of the most popular theories has held that the markings help the animals camouflage themselves. But a new study suggests that probably isn't the case.

In a paper published January 22 in the journal PLOS ONE , researchers show that zebra stripes are not as readily visible to lions and spotted hyenas, the animal's main predators, as they are to humans. At the distance that lions and hyenas can make out zebra's stripes—about 100 feet at twilight, which is when these predators do much of their hunting—it's almost certain the animals would've already heard or smelled their prey, says biological anthropologist and study first author Amanda Melin, of the University of Calgary, in a statement.

Researchers have also hypothesized that stripes disrupt a predator's ability to recognize a zebra's body outline. But the new study shows that lions and hyenas could make out zebras just as well as other similar-sized prey that don't have stripy coloration, such as waterbuck and topi.

In the paper, the scientists passed images of zebras through color filters known to simulate the vision of these predators, based on studies of their eyes and visual abilities. They found that stripes weren't easily detectable beyond 165 feet in bright light, 100 feet in dim light and 30 feet in the darkness of a moonless night. All of these distances are quite small, and predators would likely have already seen, heard and/or smelled the animal by the time they could even make out the stripes' presence, according to the study.

So why do zebras have stripes? Previous research by study senior author Tim Caro, of the University of California, Davis, suggests that stripes may serve primarily to deter flies. Research has shown, for example, that various flies are less likely to land on black-and-white surfaces than on solid-colored ones.