It was just last month that we heard about a study which indicated that fewer horseflies landed on mannequins with stripes painted onto them. The research was inspired by observations that zebras also tend not to be bothered much by flies. A separate study now offers an explanation as to why that's the case.
Conducted by scientists from the University of Bristol and the University of California - Davis, the second study involved zebras and domestic horses living at a stable in North Somerset, UK. Utilizing video analysis techniques, it was found that while equal numbers of horseflies circled both types of horses, far fewer actually landed on the zebras.
In order to determine if the stripes were responsible for this difference, the researchers proceeded to cover all of the animals in cloth coats that were either solid white, solid black, or zebra-striped. Sure enough, regardless of whether it was a zebra or a domestic horse wearing the coat, flies landed on the solid colors while largely avoiding the stripes.
It would therefore seem to follow that other variables, such as zebras' odor or behaviour, weren't factors in keeping the flies from landing. When flies did land on the zebras, however, the wild horses were more diligent about swishing their tails or running away to get rid of them.
So, what is it that flies don't like about stripes?
"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," says U Bristol's Dr. Martin How. "Stripes may dazzle flies in some way once they are close enough to see them with their low-resolution eyes."
A paper on the research, which was led by UC Davis' Prof. Tim Caro, was recently published in the journal PLOS ONE.
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