Zebra Stripes Evolved to Keep Biting Flies Away, Study Reveals

Scientists claim to have finally solved the great mystery of the distinctive white and black signature stripes of the zebra and say annoying flies might have been the evolutionary drivers for the bands.

Researchers at the University of California, Davis have successfully solved the riddle of the zebra stripes. They discovered that biting flies including horseflies and tsetse were the main evolutionary driver for the stripes. 

Several hypotheses were proposed for the stripes on the zebra. Some suggest that the stripes are a form of camouflage to offer protection to the animals. Another theory is that the stripes provide protection against heat or maybe play a social role and also that they repel insects.

.The scientists tried to delve deeper into the mystery and all clues pointed in one direction that the stripes were there to drive away the flies and insects

The researchers mapped the geographic distribution of  the seven species of  the equid group that includes the zebras, horses and asses as well their 20 subspecies.  Further, the thickness, location and intensity of the stripes on various parts of their bodies were also noted.  This data was compared to the animal's geographic range along with several other variables such as woodland areas, ranges of large predators, temperature and the geographic distribution of tsetse flies (glossinid) and the biting flies (tabanid).

They checked for regions where the striped animals overlapped with the other variables. On analyzing the data, they were surprised to notice that the stripes correlated with number of biting flies present in the location.

"I was amazed by our results," lead author Tim Caro, a UC Davis professor of wildlife biology said in a news 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."

The study lacked maps of horseflies and deerflies. Rather, the researchers mapped the locations of the breeding conditions for these flies and mimicked a similar environment for their distribution. They noticed that the striping is strongly linked with the reproduction of these biting flies.

Scientists say that only zebras developed the stripes and no other African hooved mammals is  because the zebra's body hair is shorter than the sting bite length of the flies, due to which they are highly vulnerable to the biting flies.

"No one knew why zebras have such striking coloration," Caro said. "But solving evolutionary conundrums increases our knowledge of the natural world and may spark greater commitment to conserving it."

The finding was documented in the journal Nature Communications.