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[QUOTE]Originally posted by DD'eDeN: [QB] Zebra stripes - camouflage? 22.1.16 Zebra stripes not for camouflage? Amanda Melin (2016 PLoS, with Tim Caro, Donald Kline, Chihiro Hiramatsu): "The most longstanding hypothesis for zebra striping is crypsis (camouflaging), but until now the question has always been framed through human eyes. We carried out a series of calculations, through which we were able to estimate the distances at which lions & spotted hyenas, as well as zebras, can see zebra stripes under daylight, twilight, or during a moonless night. In earlier studies, Caro cs have provided evidence suggesting that the zebra's stripes provide an evolutionary advantage by discouraging biting flies. In the new study, Melin cs 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: at the point at which predators can see zebras stripes, they probably already have heard or smelled their zebra prey. Caro: "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: we reject this long-standing hypothesis, debated by Charles Darwin & Alfred Russell Wallace." ... the researchers passed digital images taken in the field in Tanzania through spatial & color filters that simulated how the zebras would appear to their main predators (lions & spotted hyenas) & to other zebras. They measured the stripes' widths & light contrast (luminance), to estimate the maximum distance from which lions, spotted hyenas & zebras could detect stripes, using information about these animals' visual capabilities: beyond 50 m in daylight (and 30 m at twilight, when most predators hunt), stripes can be seen by humans, but are hard for zebra predators to distinguish. And on moonless nights, the stripes are particularly difficult for all spp to distinguish beyond 9 m. This suggests that the stripes don't provide camouflage in woodland areas (earlier it been theorized that black stripes mimicked tree trunks, and white stripes blended in with shafts of light through the trees). And in open treeless habitats, lions could see the outline of striped zebras just as easily as they could see similar-sized prey with fairly solid-colored hides, e.g. waterbuck, topi, impala). It had been earlier suggested that the striping might disrupt the outline of zebras on the plains, where they might otherwise be clearly visible to their predators. Stripes also not for social purposes: The study did not yield evidence 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 spp 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. [/QB][/QUOTE]
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