'Stripes' may not shield zebra's from predators

While it was believed that "stripes" offer protection for animals living in groups, like zebra, a new research has rebuffed the assumption.

Humans playing a computer game captured striped targets more easily than uniform grey targets when multiple targets were present. This rebuked assumptions that stripes evolved to make it difficult to capture animals moving in a group.

In the study, Anna Hughes, University of Cambridge, claims that they found that when targets are presented individually, horizontally striped targets are more easily captured than targets with vertical or diagonal stripes. Surprisingly, they also found no benefit of stripes when multiple targets were presented at once, despite the prediction that stripes should be particularly effective in a group scenario. This could be due to how different stripe orientations interact with motion perception, where an incorrect reading of a target's speed helps the predator to catch its prey.

Stripes, zigzags and high contrast markings make animals highly conspicuous, which you might think would make them more visible to a predator. Researchers have wondered if movement is important in explaining why these patterns have evolved. Striking patterns may confuse predators and reduce the chance of attack or capture. In a concept termed "motion dazzle", where high contrast patterns cause predators to misperceive the speed and direction of the moving animal. It was suggested that motion dazzle might be strongest in groups, such as a herd of zebra.

Motion may just be one aspect in a larger picture. Different orientations of stripe patterning may have evolved for different purposes. More work was needed to establish the value and ecological relevance of "motion dazzle," said Hughes.

The study is published in Frontiers in Zoology.