It's dangerous being a zebra. These ungulates, which graze on the plains (as well as mountains and grasslands) of Africa, face many existential threats. For instance, the very act of eating grass can be lethal, as anthrax spores reside in the soil. Ingesting these spores can lead to a deadly gastrointestinal infection. Zebras must also avoid human hunters. And they need lots of water, so they must never wander very far away from waterholes. However, the waterhole is deceptively tranquil; simply taking a quick drink can result in being eaten by a lion. 
 
 Fortunately for the zebras, they have evolved white and black stripes as camouflage to confuse lions. That's the conventional wisdom, anyway. But, as is so often the case, the conventional wisdom appears to be wrong. 
 
 New research in Nature Communications concludes that zebras' stripes are actually for preventing bites from nasty insects, such as tabanids (horse flies). For some reason, these flies avoid landing on black and white striped surfaces. 
 
 For their study, the authors collected stripe pattern data on seven wild equids: plains zebra, Grévy's zebra, mountain zebra, African wild ass, Przewalski's horse, kiang, and Asiatic wild ass. They then overlaid a map of these equids' ranges with information on predators' ranges, temperature, biomes, tsetse fly ranges, and tabanid ranges (which were determined by proxy using measurements on temperature and humidity). They found that the presence of equid stripes most closely correlated with the ranges of biting flies, such as tabanids and tsetse flies. In other words, equids are more likely to have stripes if they live in an area that also has biting flies. 
 
 Simultaneously, the authors' map mostly eliminated the other possible explanations that exist for zebra stripes: camouflage, predator confusion, body temperature control, and social identification. However, the presence of rump and leg stripes correlated with the range of hyenas, so it is possible that the stripes play a role in keeping hyenas at bay. The authors argue, though, that adult zebras are generally too big and powerful for hyenas to hunt, so it is unlikely that striping patterns play an important role here. Also, Asian equids that were once hunted by wolves and tigers do not have stripes. 
 
 Thus, the evidence from this and previous studies indicates that zebras have stripes to avoid flies, not lions. Now, they need to find a way to avoid humans. 
 
 Source: Tim Caro, Amanda Izzo, Robert C. Reiner Jr, Hannah Walker & Theodore Stankowich. "The function of zebra stripes." Nature Communications 5:3535. (2014). DOI: 10.1038/ncomms4535 
 
 (Image: Zebras via Paulmaz/Wikimedia Commons) 

 Zebras' black and white stripes keep biting flies away, according to a new research. 
 
 A zebra races with wildebeest across the tall grasses of the Masai Mara National Reserve in the southwestern corner of Kenya in this picture taken in 2003 
 
 The stripes on zebras are not just there for looks; they are an effective defense mechanism against blood-sucking flies, according to a new study. 
 
 The riddle of zebras' stripes has intrigued researchers for many years. Since the time of Alfred Russel Wallace and Charles Darwin, various hypotheses have been floated. Some scientists suggested that the stripes helped cool the zebras. Other suggested that the stripes were a form of camouflage, or a way of confusing predators. Others proposed that the stripes served a social function. 
 
 And according to another theory, the stripes were effective in deterring ectoparasites such as biting flies. Early tests of this hypothesis employed striped cardboard pieces with glue stuck on them, to check if flies were attracted to them or not, says lead author Tim Caro, a UC Davis professor of wildlife biology. 
 
 To solve the puzzle, Dr. Caro and his team mapped out geographic distributions of the seven different living species of zebras, horses, and asses, including their 20 subspecies found in the Old World, and tested them against all the previous hypotheses. 
 
 The team first looked at the variation in striping patterns in different parts of the body – from their neck to face and so on, says Caro. 
 
 They then mapped their geographic distribution in the Old World. They also mapped distribution of their predators, such as lions and hyenas, along with the distribution of flies, forests, and temperatures, and other factors that might have brought about the evolution of the stripes. 
 
 Both the mapping distributions were compared to each other and fed into a statistical model to examine the "overlaps." 
 
 "We observed that stripped species have a great degree of geographical range overlap with biting flies," Cato told the Monitor. 
 
 And "conversely, there is no consistent support for camouflage, predator avoidance, heat management or social interaction hypotheses," according to the findings published in a paper titled "The function of zebra stripes" in the online journal Nature Communications on April 1. 
 
 But to map distribution of biting flies such as, tabanids (horseflies, deer flies), the scientists had to create an "environmental proxy" for their distribution. Unlike tsetse flies, which can be found only in Africa, tabanids such as horseflies and deer flies live all over the world, except at the poles and Oceana. 
 
 But the hot and humid conditions in Africa are most conducive to large tabanid populations. After analyzing the distribution and mapping, the team noted significant overlap between tabanids and striping. 
 
 "I was amazed by our results," said Caro. "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." 
 
 Further research in this area will explore why such patterns dissuade biting flies. It could have to do with the way flies see things, says Caro. Also, susceptibility to ectoparasite attack could be due to short coat hair of zebras, blood loss, or disease transmission. But exactly how the flies harm zebras needs to be explored further, say researchers.
– The centuries-old puzzle of why zebras have stripes has been solved, and they're not there to confuse lions or for decoration, researchers say. A new study backs up the theory that stripes evolved as a way to deter biting flies, Real Clear Science reports. Researchers gathered stripe pattern data on a variety of equids and discovered that the animals were a lot more likely to have stripes if they lived somewhere plagued by biting flies—like the plains of Africa. "I was amazed by our results," the lead researcher says. "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." Earlier research revealed that biting flies don't like to land on striped surfaces, though scientists aren't sure why this is, the Christian Science Monitor reports. No word on whether people wearing striped clothes will enjoy similar benefits.