Zebras and their unique black and white stripes have posed a longtime mystery for scientists. Why does the species have the unique pattern, and how have the stripes helped the animals to survive?
Researchers at the University of California at Davis believe they have the answer: to keep the flies off.
Publishing their findings in the journal Nature Communications, the team found evidence that zebras and other horse-related species with stripes tend to live in areas that are heavy with bloodsucking insects, NBC News reported.
Alfred Russel Wallace and Charles Darwin considered the riddle of the zebra's stripes around 120 years ago, coming up with several possibilities. Their hypotheses for the stripes' purpose included a form of camouflage; a pattern to confuse predatory carnivatores; a method of heat management; a social function; and a way to avoid attack from parasites like flies.
"No one knew why zebras have such striking coloration," lead author Tim Caro, a 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 UC Davis team examined the areas that seven species of zebras, horses and asses call home, also looking at the animals' subspecies and thickness of stripes. Next, they analyzed a set of variables that included woodland areas, ranges of large predators, temperature, and the geographic distribution of tsetse flies and horseflies, both of which are biting flies.
"I was amazed by our results," Caro said in a statement. "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."
Zebras especially need something to ward off biting flies, which reduce weight gain, spread disease and lower milk production in the animals, because their thin coats of hair are not as protective as those in other species such as the antelope.
"It's clear that the flies can get through that hair and get to the skin," Caro told NBC News.