Zebra stripes may act to repel nasty flies

LONDON • Zebra stripes are dazzling — particularly to flies. That’s the conclusion of scientists from the University of Bristol and the University of California at Davis who dressed horses in black-andwhite striped coats to help determine why zebras have stripes.

The researchers found that fewer horseflies landed on the bedecked horses than on those without the striped coats, suggesting zebra stripes may offer protection from blood-sucking insects that can spread disease.

“This reduced ability to land on the zebra’s coat may be due to stripes disrupting the visual system of the horse flies during their final moments of approach,” said Martin How, a research fellow at the University of Bristol.

“Stripes may dazzle flies in some way once they are close

ONCE THEY GET CLOSE TO THE ZEBRAS, THEY TEND TO FLY PAST.

enough to see them with their low-resolution eyes.”

From a distance, the flies were equally attracted to both horses and zebras, with the same number of insects hovering around both types of animals. But when the flies got closer, things got dicey. The flies landed less frequently on the zebras and the horses covered in striped coats.

“Once they get close to the zebras, however, they tend to fly past or bump into them,” said Tim Caro, a professor at U.C. Davis. “This indicates that stripes may disrupt the flies’ abilities to have a controlled landing.”

The work, reported in the journal Public Library of Science ONE, seeks to answer one of the oldest questions in zoology — why do zebras have stripes?

Charles Darwin had his theories. So did British naturalist Alfred Russel Wallace.

But the scientists from Britain and California sought to examine that question by studying both horses and zebras at the Hill Livery in Britain, which works with zoos in Europe on conservation for zebras. That provided a controlled environment where the horses could be dressed up and closely observed to test the theory.

“It’s one of those pieces of research that you say, ‘Why hasn’t someone done this before?’ ” said Tim Woodfine, the director of conservation at Marwell Wildlife in southern England.

“It’s simple and neat. I think it’s a great piece of work,” he said.

An expert on animal vision said there are multiple reasons to be “quite excited” about the research.

This has broader implications in terms of such technology as driverless cars, which are inspired by insect vision. If stripes disrupt a fly, they might also possibly disrupt a driverless car’s systems, for example, he said.