Remember “Why zebras have stripes? This time we really mean it!“? Yes, same time last year:
Forget all that! Now, from ScienceDaily:
Looking through the eyes of zebra predators, researchers found no evidence supporting the notion that zebras’ black and white stripes are for protective camouflage or that they provide a social advantage.
In the new study, Melin, Caro and colleagues Donald Kline and Chihiro Hiramatsu found that stripes cannot be involved in allowing the zebras to blend in with the background of their environment or in breaking up the outline of the zebra, because at the point at which predators can see zebras stripes, they probably already have heard or smelled their zebra prey.
“The results from this new study provide no support at all for the idea that the zebra’s stripes provide some type of anti-predator camouflaging effect,” Caro said. “Instead, we reject this long-standing hypothesis that was debated by Charles Darwin and Alfred Russell Wallace.”
Okay, so that’s why all those researchers’ life and health insurance policies got cancelled in one single day. It would have been all right to dump on Wallace but not on Darwin, the author of the single greatest idea anyone ever had! 😉
It gets worse.
In addition to discrediting the camouflaging hypothesis, the study did not yield evidence suggesting that the striping provides some type of social advantage by allowing other zebras to recognize each other at a distance.
While zebras can see stripes over somewhat further distances than their predators can, the researchers also noted that other species of animals that are closely related to the zebra are highly social and able to recognize other individuals of their species, despite having no striping to distinguish them.
Maybe the stripes just came with the package? Like, you wanna be a zebra, you gotta have stripes.
See also: Natural selection: Could it be the single greatest idea ever invented?
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Here’s the abstract:
The century-old idea that stripes make zebras cryptic to large carnivores has never been examined systematically. We evaluated this hypothesis by passing digital images of zebras through species-specific spatial and colour filters to simulate their appearance for the visual systems of zebras’ primary predators and zebras themselves. We also measured stripe widths and luminance contrast to estimate the maximum distances from which lions, spotted hyaenas, and zebras can resolve stripes. We found that beyond ca. 50 m (daylight) and 30 m (twilight) zebra stripes are difficult for the estimated visual systems of large carnivores to resolve, but not humans. On moonless nights, stripes are difficult for all species to resolve beyond ca. 9 m. In open treeless habitats where zebras spend most time, zebras are as clearly identified by the lion visual system as are similar-sized ungulates, suggesting that stripes cannot confer crypsis by disrupting the zebra’s outline. Stripes confer a minor advantage over solid pelage in masking body shape in woodlands, but the effect is stronger for humans than for predators. Zebras appear to be less able than humans to resolve stripes although they are better than their chief predators. In conclusion, compared to the uniform pelage of other sympatric herbivores it appears highly unlikely that stripes are a form of anti-predator camouflage. Open access – Amanda D. Melin, Donald W. Kline, Chihiro Hiramatsu, Tim Caro. Zebra Stripes through the Eyes of Their Predators, Zebras, and Humans. PLOS ONE, 2016; 11 (1): e0145679 DOI: 10.1371/journal.pone.0145679