Certainly not for camouflage. (BBC):
“Zebra stripes have long confused evolutionary biologists, right back to Darwin and Wallace,” said lead author Dr Martin How.
“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.”
To test this latest theory that the patterns confuse predators and pests, Dr How analysed photographs and video footage of zebras.
Computer models that tracked the appearance of the patterns revealed that they worked as optical illusions to provide “misleading information”.
They upset motion detection, according to these researchers.
Then just why the effect became so pronounced only in zebras (and so muted in other equines) is still puzzling. In human horse breeds, these “primitive markings” are often simply bred out or in (but in a refined way). But as the linked photos show, they are not comparatively noticeable anyway.
This vid suggests various benefits to zebras:
But if the zebra is one of the few grazers to actually find the loud stripes an advantage, there must be something specific to its own environment that makes them an advantage. Otherwise, more grazers would surely display such strategies. Optical illusions involving stripes can be powerful: