Zebras' stripes useless as camouflage - study

Just why zebras have stripes has long intrigued scientists (file)
Just why zebras have stripes has long intrigued scientists (file)

Behind cats, dogs, birds and horses, zebras are often one of the first animals young children learn to recognise.

Partly it's because they're an obvious choice for the letter Z when teaching preschoolers the alphabet, but also because of their distinctive stripes – hence why pedestrian crossings are often called zebra crossings.

Just why zebras have stripes has long intrigued scientists, but now one of the leading theories – that stripes confuse and dazzle predators – can probably be ruled out.

In order that no zebras were harmed, humans stood in for lions and other African predators in a new study from the UK's University of Cambridge.

Sixty people played a computer game designed to test whether stripes influenced their perception of moving targets. It was designed to test whether the stripes caused a condition known as 'motion dazzle', making it hard to judge a target's position, speed and direction.

The concept was popular in World War I and II, when ships where often painted in high-contrast geometric shapes in an attempt to throw off the enemy.

But when it comes to chasing prey, it seems 'motion dazzle' is a non-starter.

"We found that when targets are presented individually, horizontally striped targets are more easily captured than targets with vertical or diagonal stripes," says author Anna Hughes.

"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.”

When there were a number of moving targets, having stripes of any orientation made prey stand out and easier to catch than being non-striped.

"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."

Other theories on zebra stripes are that they help deter insects or enable the animal to better control its heat intake and expenditure. Studies have shown zebras in hotter climes generally have more stripes, as do those in areas with large numbers of parasites.

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