Research published in the latest issue of the Journal of Experimental Biology suggests the stripes are an adaptation which helps deter blood-sucking flies.
The zebra model used in the study by scientists from Hungary and Sweden. © Gábor Horváth
They tested the attractiveness of white with spots, brown, dark, and striped cutout horse models, trapping the insects with oil and glue.
The researchers had expected that the striped model would attract an intermediate number of flies, somewhere between the numbers attracted to the darker and lighter cutouts.
They found that the black-and-white striped model was the least attractive of all.
The researchers first tested black-and-white stripes by varying the width, density and angle of the stripes, as well as the direction of polarization of the light they reflected.
They found the striped patterns attracted fewer flies as the stripes became narrower, with the narrowest stripes attracting the fewest.
They then put the striped version up against white, brown and dark horse models, finding that the striped model was the least attractive of all.
The key, they found, was how the striped patterns reflected light.
Egri, Á., Blahó, M., Kriska, G., Farkas, R., Gyurkovszky, M., Åkesson, S. and Horváth, G. (2012). Polarotactic tabanids find striped patterns with brightness and/or polarization modulation least attractive: an advantage of zebra stripes. J. Exp. Biol. 215, 736-745.