Computer simulation explains why zebras have stripes

(Phys.org) —Two researchers, one from the University of Queensland, the other the University of London have published a paper together in the journal Zoology in which they claim to have solved the riddle of why zebras have stripes. In their paper, Martin How and Johannes Zankerb describe how they built a computer simulation that demonstrated that the stripes on zebras serve to confuse both pests and predators.

Evolutionary biologists have long been intrigued by the black and white striped coat sported by zebras, but have been at a loss to explain why it evolved. Because the stripes are so vivid and stand out from the environment in which the zebra live, it would seem having them would cause the animals to be targeted more by predators, rather than less. One of the more plausible arguments to explain the stripes has been that they "dazzle" predators causing them to have difficulty focusing. This idea has never been proved, however—How and Zankerb set out to do just that.

Suspecting that the stripes might be causing optical illusions in those who view them, the researchers created a simulation based on motion detection algorithms and used it to analyze various parts of the zebra body. In so doing, they discovered that the motion signals generated by the striped patterns on the zebra's body tend to result in misleading optical information.

The stripes, the researchers say, cause conflicting messages in the brains of both predators (big cats) and biting insects. They suggest the conflicting sensory information is a combination of two well documented optical illusions: the wagon-wheel effect and the barber-pole illusion. In the first, to people (and presumably lions, etc.) a spinning wagon wheel appears at certain speeds to spin in the opposite direction. In the second, a rotating barber pole appears to be rising as it turns. The net effect, the researcher say, is that when a zebra moves, it's difficult to tell which part of it is which. The illusion is even more profound, they note, when looking at more than one zebra at a time.

The findings by the pair of researchers are likely to lead to similar research on other striped animals and might even instigate some studies by military groups looking to better camouflage their ships, tanks, etc.