Explanation for Why Zebras Have Stripes Just Got More Complicated

It turns out the answer to why zebras have stripes isn’t so black and white. Some scientists thought they settled the question once and for all last year when they proposed that zebras developed stripes as part of evolutionary adaptation to help them ward off blood-sucking flies. But a new study published Tuesday in the journal Royal Society Open Science says the adaptive significance of zebra stripes may have more to do with environment, particularly temperature. Brenda Larison of UCLA and colleagues analyzed multiple environmental variables associated with striping in the plains zebra, the most common species of zebra, found in the grasslands of eastern and southern Africa. They found that striping patterns were most highly correlated with temperature: Generally, the warmer the climate, the more stripes found on the zebra.

"In contrast to recent findings, we found no evidence that striping may have evolved to escape predators or avoid biting flies. Instead, we found that temperature successfully predicts a substantial amount of the stripe pattern variation observed in plains zebra," the researchers wrote. As to the stripes’ function, it could be that they help keep the zebra cool, or serve some other purpose.

"Much additional work is needed to elucidate the true functionality of striping in zebra," the researchers wrote. "Our work shows a correlation with temperature, but the cause of this correlation remains unknown."
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— James Eng