Horses clothed like zebras keep flies away
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-and-white 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 that 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 horseflies 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 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 get 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 in the U.C. Davis Department of Wildlife, Fish and Conservation Biology. “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. He did not take part in the study. “It’s simple and neat. I think it’s a great piece of work,” he said.
“What we needed to do is get our mind into the eye of the fly,” How said. “They have very different eyes from us.”