The zebra’s striped coat is simultaneously extraordinary and stunning. So wondrous, in fact, that many people have imagined it to be evidence of God’s infinitely artistic hand. Over the years, there have been many more rational explanations, but that all-important scientific consensus has remained elusive.
Charles Darwin certainly found the zebra’s stripes to be a conundrum. In The Descent of Man, he dismissed the idea they could act as camouflage, citing William Burchell’s observations of a herd.
Although both males and female zebras are similarly striped, Darwin hedged that “he who attributes the white and dark vertical stripes on the flanks of various antelopes to sexual selection, will probably extend the same view to the … beautiful zebra.” In other words, the stripes help males and females make sensible choices about whom they mate with.
Alfred Russel Wallace begged to differ. “It is in the evening, or on moonlight nights, when they go to drink, that they are chiefly exposed to attack,” he wrote in Darwinism. “In twilight they are not at all conspicuous, the stripes of white and black so merging together into a grey tint it is difficult to see them at a little distance.”
Tim Caro of the University of California, Davis, has puzzled over contrasting colouration in mammals before. Now, in a new study published in Nature Communications this week, he and his colleagues have focused their attention on the zebra.
They take a completely original approach, stepping back from one species of zebra and attempting to account for the differences in patterning across different species and subspecies of zebras, horses and asses. Is there anything about the habitat or ecology of these different equids that hints at the function of stripes?
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