Stripes don't save zebras from predators: New Study

Contrary to popular opinion, stripes do not help zebras evade predators and in fact, the distinctive pattern may make the animals easier, rather than harder, to catch, according to a new study.

The research suggests that stripes may not offer the 'motion dazzle' protection thought to have evolved in animals such as zebra and used as ship camouflage during both World Wars.

In the study, humans playing a computer game captured striped targets more easily than uniform grey targets when multiple targets were present. The finding runs counter to assumptions that stripes evolved to make it difficult to capture animals moving in a group, such as zebra.

"We found that when targets are presented individually, horizontally striped targets are more easily captured than targets with vertical or diagonal stripes," said Anna Hughes, a researcher in the Sensory Evolution and Ecology group at the University of Cambridge's Department of Zoology.

"Surprisingly, we 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," Hughes said.

Stripes, zigzags and high contrast markings make animals highly conspicuous, which one 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 dazzle' is a reference to a type of camouflage used on ships in  World War I and World War II, where ships were patterned in geometric shapes in contrasting colours. Rather than concealing ships, this dazzle camouflage was believed to make it difficult to estimate a target's range, speed and heading.

In the study published in the journal Frontiers in Zoology, 60 human participants played a game to test whether stripes influenced their perception of moving targets. They performed a touch screen task in which they attempted to 'catch' moving targets - both when only one target was present on screen and when there were several targets present at once.

When single targets were present, horizontal striped targets were easier to capture than any other target, including uniform colour, or vertical or diagonal stripes.

However, when multiple targets were present, all striped targets, irrespective of the orientation, were captured more easily than uniform grey targets. "Motion may just be one aspect in a larger picture. Different orientations of stripe patterning may have evolved for different purposes. The evolution of pattern types is complex, for which there isn't one over-ruling factor, but a multitude of possibilities," said Hughes.