Zebras' beautiful black and white stripes have been a mystery to scientists for years. Scientists could not understand the evolutionary reason why the animals have such striking markings. 

Researchers at the University of California at Davis have finally discovered that zebras have stripes to keep flies away, according to NBC News. 

The research team found evidence that zebras and other horse-related species with stripes live in areas that have lots of bloodsucking insects. The team published their findings in the science journal Nature Communications.

Charles Darwin and Alfred Russel Wallace tried to understand why zebras have stripes 120 years ago, and came up with a number of hypotheses. They considered that the stripes act as a form of camouflage, or as a pattern to confuse predatory carnivores. They also believed they could be a method of heat management, a social function or a way to avoid flies and other parasites. 

"No one knew why zebras have such striking coloration," lead author Tim Caro, UC Davis professor of wildlife biology, said in a statement. "But solving evolutionary conundrums increases our knowledge of the natural world and may spark greater commitment to conserving it."

The research team examined regions that have seven species of zebras, horses and donkeys, and also researched the animals' subspecies and the thickness of their stripes. 

They then analyzed a set of variables that included temperature, ranges of large predators, woodland areas and the geographic distribution of tsetse flies and horseflies, which are both bloodsucking parasites. 

"I was amazed by our results," Caro said. "Again and again, there was greater striping on areas of the body in those parts of the world where there was more annoyance from biting flies."

More than some other animals, zebras need to ward off flies because they cause weight gain, spread disease and lower milk production.

Zebras' coats of hair are also thinner than some other animals and are as not protective as those of other species, such as the antelope. 

"It's clear that the flies can get through that hair and get to the skin," Caro said.