Why Do Zebras Have Stripes?

Stripes help protect the zebras from biting insects

Animal researchers have theorized for years that a zebra's stripes confuse predators like lions, but new research just published shows the stripes have a surprising benefit—they actually help protect the zebras from biting insects. Since biting pests carry many diseases as well as constantly distract animals from feeding, it is possible that the reduction in pest activity could be an even more important benefit of having stripes than protection from lions.

The researchers looked at biting horse flies in their tests. These and many other insects are able to detect polarized light as it is reflected off of surfaces like animal hides. Uniform surfaces have a very uniform polarization pattern, but stripes on a surface change the polarization pattern of the reflected light. By collecting horse flies that were attracted to black, brown, white, and striped horse models, the researchers showed that the flies were least attracted to the striped models. Further tests showed the exact thickness of the zebra stripes were an optimal thickness to reduce horse fly attacks.