Why does the zebra have its rays: to deter flies from landing there | Science



The mystery of how the zebra got its stripes might have been solved: the researchers say the pattern seems to confuse the flies, dissuading them from landing for a quick bite.

The study, published in the journal Plos One, featured horses, zebras and horses disguised as zebras. The team stated that the research supported not only earlier work suggesting that the stripes could act as a deterrent to insects, but also helped to explain why, revealing that the patterns only produced an effect when the flies approached.

Dr. Martin How, co-author of the University of Bristol research, said: "The flies seemed to behave relatively naturally between the two [zebras and horses]until landing.

"We saw that these flies came very fast and almost turned away or sometimes even collided with the zebra, rather than making a nice controlled flight."

The researchers made their discovery by spending more than 16 hours standing in the fields and noting how horse flies interacted with nine horses and three zebras, one of which, quite puzzling, called Spot.

While horse flies encircled or touched animals at similar rates, landing was another matter, with the observed rate being lower in zebras than in horses.

To check the effect was not caused by a different smell of zebras and horses, for example, researchers applied black, white and zebra coats on seven horses in turn. Although there is no difference in the speed with which flies land on the exposed heads of horses, they touch and land much less often on the zebra coat than black or white clothing.

Additional information, collected through video recordings of zebras and a smaller group of horses, revealed that flies did not steadily slow down as they approached zebras, contrary to what was the case for horses, and was often limited to animals.

The team stated that the study showed that the stripes were not a long-term deterrent, but had an effect when the flies came closer – perhaps because of the low-resolution vision of the flies.

"At distances greater than about two meters, a zebra would look like a gray horse – they will not be able to see the scratches at all," said How. He added that the most likely mechanisms of the deterrent effect are either the "sudden unveiling" of the closely spaced stripes, or the surprise of the insects and causing them to be fired, to be an interference with their perception of the rate at which objects cross, affecting their ability to land.

The team said the results supported the idea that the tapes may have evolved in response to biting flies.

"Zebras – from the point of view of evolution – have developed in areas of the world where flies carry rather unpleasant diseases. Therefore, being bitten by flies can have very serious consequences on their shape. While domestic horses did not have the same kind of driving force, "said How.

However, he added that the explanation may not be complete: researchers have already suggested that tapes can camouflage, help with thermoregulation or play a social role. Although How said that there is evidence to support them, he pointed out that lions, for example, did not seem baffled by the stripes. "Zebras are a favorite prey for many predators, so it does not really stop. [them]," he added.

That said, how was it noted that the last experiment was conducted at Somerset rather than around the biting flies of Africa. Among other limitations, there was the fact that the flies 'trajectory could only be seen in two dimensions from video recordings and that the horses' coats were made of different materials.

How could these outdoor enthusiasts draw inspiration from zebras, suggesting patterned tops and body painting as useful tools to help them dodge their bites.


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