The answer to a question that even puzzled Charles Darwin has finally been answered.
Zebras have a striking pattern to confuse predators, according to research published in the journal Zoology.
Scientists from the University of Queensland in Australia, used computer models to prove that the striped pattern creates an optical illusion when zebras move.
By analysing photographs and video footage of the animals, the team found that the black and white patterns translate as “misleading information” in the eyes of other creatures.
This confusing sight protects wild zebras from a range of predators: from tiny insects to big cats.
Many animals, including humans, have what scientists call “motion detection mechanisms”. These neural circuits process the direction something appears to be moving based on how its contours appear.
Optical illusions of this kind that often trick humans include the barber-pole effect, where the spiral of stripes appears to move upwards when the pole is spun.
Dr Martin How, the lead author of the project, said: “Zebra stripes have long confused evolutionary biologists, right back to Darwin and Wallace,”
“Previous theories for the function of these stripes include social communication signals, camouflage at dusk or dawn in grassy habitats, and the so-called 'dazzle' effect when being pursued by predators or blood sucking insects.”
According to Dr How, the narrow vertical stripes on a zebra’s back and neck combined with the wide diagonal stripes on its flank give off unexpected motion signals, which become stronger when a herd moves.
“We suggest that these illusions cause pests and predators to mistake the zebra's movement direction, causing biting insects to abort their landing manoeuvres and chasing predators to mistime their attacks,” said Dr How.
“The results have implications for the study of patterning in animals - there are many other species such as humbug damselfish or banded snakes that use apparently conspicuous black and white stripe body patterns.
"The results also might help us understand how similar camouflage might function in man-made situations, such as the large-scale 'dazzle' camouflage patterns used on battleships," Dr How said.