Zebra's stripes help it to stave off horseflies

Washington, Feb 10 (ANI): The stripes on a Zebra are useful to the animal as they help to keep blood-sucking insects at bay, says a new study.

Horseflies (tabanids) deliver nasty bites, carry disease and distract grazing animals from feeding.

According to researchers Gabor Horvath, Susanne Akesson and colleagues from Sweden and Hungary, these insects are attracted to horizontally polarized light because reflections from water are horizontally polarized and aquatic insects use this phenomenon to identify stretches of water where they can mate and lay eggs.

However, blood-sucking female tabanids are also guided to victims by linearly polarized light reflected from their hides.

Explaining that horseflies are more attracted to dark horses than to white horses, the team also points out that developing zebra embryos start out with a dark skin, but go on to develop white stripes before birth. The team wondered whether the zebra's stripy hide might have evolved to disrupt their attractive dark skins and make them less appealing to voracious bloodsuckers, such as tabanids.

Travelling to a horsefly-infested horse farm near Budapest, the team tested how attractive these blood-sucking insects found black and white stripes by varying the width, density and angle of the stripes and the direction of polarization of the light that they reflected.

Trapping attracted insects with oil and glue, the team found that the striped patterns attracted fewer flies as the stripes became narrower, with the narrowest stripes attracting the fewest tabanids.

The study is published in the Journal of Experimental Biology at http://jeb.biologists.org/. (ANI)