But how exactly do the stripes achieve that? Now scientists can eliminate one theory, according to a new study published Tuesday in the journal Proceedings of the Royal Society.
Researchers looked at the nature of the disorientation effect in flies, and ruled out the hypothesis that a common optical illusion, known as the “aperture effect”, plays a role in their brilliance.
“Not only will these exciting studies bring us closer to understanding one of the most iconic and photogenic species in the world, they will be of great importance to farmers trying to reduce the damage caused by flybites and even general business for horsework, “said Tim Caro, a senior co-author of the study and a professor at the University of Bristol’s School of Biological Sciences, in a release.
Caro and his colleague Martin How, a research fellow from Bristol, have placed zebra print jackets on domestic horses for their research, a good alternative to studying zebras in the wild.
Tabanide horseflies could not slowly land on horses wearing the striped coats, public previous studies, and would occasionally fly past the masquerading animals as in them instead of landing.
This time, the researchers observed the flying behavior of round horses with gray coats, striped coats and checkered coats, and learned that flights “prevented landing on, flew faster close, and approached not so close to striped and checked carpets” compared to gray, according to the study.
Scientists thought whether the aperture effect – the optical illusion that drives us to see the stripes on a barber shop pole as if going upwards instead of just turning – was a factor in the disorientation experienced by the flies.
“Our findings show that this effect does not work – based on the behavior of the flies around cartridge cases – because if it were, flies would have to land on controls, but not on stripes. Checks cannot repeat the hairdressing effect in an eye of the fly or brain, “Caro told CNN.
“It must be something else,” he said.
The performance of checkered jackets was unexpected.
“This suggested that there is nothing per se specifically about stripes to prevent horseflies from landing, but it should be the sharp contrast between different elements on the coat,” Caro told CNN.
Future research will focus on which coat patterns are most effective, and on a better understanding of the role of pattern size and contrast in limiting flies.
Evolution and protection against flight
Protection against horse flies is currently the most accredited hypothesis about why zebras have stripes.
“Horses in Africa carry diseases that are fatal to members of the horse family – the equidae. The pressure not to bite through these flights is therefore very strong, “Caro explained.
“Evolution will find the coat pattern matches what is most effective at stopping the landing of flies – given developmental constraints of how patterns develop in utero. Our research and that of colleagues show that stripes do this job very well, added Caro.
The fact that zebras have their stones almost continuously and have an odor that is also absent from flies supports the opinion that these animals are mainly affected by flies, Caro claimed.
“Very few mammals have developed sharp repetitive streaks that suggest that zebras suffer particularly acutely from horseflies and the diseases they carry,” he told CNN.
Horses in the US
Domestic horses have also suffered from horse bite bites, and Sonja Swiger, associate professor in the department of entomology at Texas A&M University, said “the consequences are very severe.”
Tabanid horseflies have a different anatomy compared to other blood-sucking insects, such as mosquitoes, which have needle-like mouths that can penetrate the skin.
“They have very large serrating mouthparts. They have to cut a hole in the skin to start flowing the blood, then they drink it,” Swiger explained.
The “sloppy eating habit” of tabanids causes pain and discomfort to animals such as horses and cattle, and exposes them to the transmission of diseases, including infectious anemia in horses.
Horseflies are common in the United States but are widespread in warmer climates, Swiger said. Southern states may have two generations of horseflies each year, while in Northern areas there will simply be one, she explained.
Containing horseflies is “almost impossible,” according to Swiger.
Chemical pesticides are not useful because the flies typically bite once a day, leaving the pesticides insufficient time to be effective. A blanket like a coat is an effective tool, and for that reason, the study by Bristol scientists is exciting and promising, Swiger argued.
Do horse herds bite people? While we are not their first choice, they do, Swiger said. On your next day on the farm as an excursion with horse riding, you may want to consider yourself as striped or checkered patterns. You will be stylish, and potentially bite-free.
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