Zebras' Stripes Won't Offer Protection From Predators Like Once Thought

First Posted: Aug 12, 2015 02:38 PM EDT

Previous studies have suggested that zebras have stripes to help camouflage them from potential predators in the wild. But is this really the case? 

New findings published in the Frontiers in Zoology reveal that stripes might not offer protection for animals living in groups, including the zebra, as previously believed.

"We found that when targets are presented individually, horizontally striped targets are more easily captured than targets with vertical or diagonal stripes," said researchers Anna Hughes, University of Cambridge, in a news release. "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. 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."

Researchers noted just how you might think zebras' stripes make them more visible. However, this is not quite the case in the wild. As many have wondered how their striking patterns evolved, in a concept termed ‘motion dazzle', predators mistake the speed and direction of the moving animals; this suggests that 'motion dazzle' might be the strongest in groups, such as a herd of zebras.

In this recent study, a total of 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 when several targets were present and when just one target was present.

Findings revealed that when single targets were present, horizontal striped targets were easier to capture than those with uniform colors or vertical or diagonal stripes. On the other hand, when multiple targets were present, all striped targets irrespective of 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," Hughes concluded. "The evolution of pattern types is complex, for which there isn't one over-ruling factor, but a multitude of possibilities. More work is needed to establish the value and ecological relevance of 'motion dazzle'. Now we need to consider whether color, stripe width and spatial patterning, and a predator's visual system could be important factors for animals to avoid capture." 

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