News / Science & Technology

    Study: Zebras' Stripes Not Camouflage

    Zebra couples  are seen hugging in Serengeti, Tanzania in this file photo.
    Zebra couples are seen hugging in Serengeti, Tanzania in this file photo.

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    VOA News

    It has long been thought a zebra’s distinctive black and white striping serves as camouflage from predators, but a new study finds that is not the case.

    Writing in the journal PLOS ONE, researchers from the University of California Davis and the University of Calgary say they calculated how a zebra’s stripes would appear to lions, spotted hyenas and other zebras when viewed in varying levels of light.

    "The most longstanding hypothesis for zebra striping is crypsis, or camouflaging, but until now the question has always been framed through human eyes," said the study's lead author Amanda Melin, an assistant professor of biological anthropology at the University of Calgary, Canada.

    They found that the 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 distance a predator would be able to see the stripes, they would likely already have heard or smelled the zebra.

    The researchers noted that at further than 50 meters in daylight or 30 meters at twilight, a zebra’s stripes are easily seen by humans, but not so for would-be predators. On a moonless night, the researchers said the stripes were hard to see by predators and humans, even from just 9 meters away.

    This, researchers said, means that the idea that a zebra’s stripes mimicked tree trunks and shafts of light, did not make sense.

    Furthermore, in the open, where zebras are most commonly found, the stripes do not “disrupt the outline” of the zebra. Lions, researchers said, could see the the outline of zebras just as they could a solid-colored animal.

    "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,"said Tim Caro, a UC Davis professor of wildlife biology. "Instead, we reject this long-standing hypothesis that was debated by Charles Darwin and Alfred Russell Wallace."

    Another theory about the stripes, that they better allow zebra’s to see one another was also discredited by the research. While zebra’s can see the stripes over a further distance than its predators, other animals related to zebras can also see each other despite not being striped.

    While not conclusive, the researchers say one reason for the stripes might be to deter biting flies, a common zebra pest.

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    by: Jim
    January 27, 2016 12:27 PM
    If an animal "needs" a horn due to surviving its environment, evolution will create one? Right? Don't all animals that "need" horns have them? And animals that don't "need" them, don't have them? What if unique characteristics, such as a creature's "camouflage" is not a result of their environment? What if the animals that looks like beach sand, are decimated by predators in other environment except sandy beaches? Thus, through millennia, their "native" environment becomes sandy beaches because this is where they can thrive due to their sandy appearance?

    by: Jim Banville
    January 26, 2016 11:04 AM
    You guys are most likely wrong. Zebras are not the only animal to flee from predators while in herds. If the stripes "developed" as a result of their need to confuse the predator, why wouldn't all the other fleeing-while-in-herds animals develop stripes as well?
    In Response

    by: Brian
    January 26, 2016 2:34 PM
    B/c that isn't how evolution occurs. Animals will evolve whatever trait they happened to develop. That's like saying "If a rhino's horn is for protection, why don't all animals in the universe have a single-pronged horn jutting out of their skull?" You could replace "stripes" in your question with any other distinctive trait possessed by any of the multitudes of unique animals in the earth's biosphere (e.g. giraffes and their long necks, turtles and their shells, etc.)

    by: pocono from: the hills of Pennsylvania
    January 26, 2016 10:19 AM
    And to think, all commentators didn't spend thousands of dollars to know exactly why zebra have stripes. Talk about a waste of time and money that the university's involved spent.
    In Response

    by: Bill from: Oklahoma
    January 26, 2016 11:25 AM
    Since when is an attempt at understanding a waste of money?

    by: Andy
    January 26, 2016 10:09 AM
    It actually is camouflage! But not for there surroundings! When they are running from a predator, they blend in with each other! makes it hard to pick one out.
    In Response

    by: Brian
    January 26, 2016 2:35 PM
    True, that's what I learned too. I'm shocked that neither the article writer nor (evidently) the authors of this paper failed to mention that, as I believe that's the leading hypothesis. The fact that they don't makes me doubt all credibility contained therein.

    by: lydia from: midwest
    January 26, 2016 1:29 AM
    I just recently watched a program on public television stating that the reason they have stripes is to confuse the predators in the way of not being able to focus on their target. They used the example of a bike rim. When it's moving forward quickly it looks like it's moving the other way. They can't lock on the prey as easily in a short time frame.
    In Response

    by: Brian
    January 26, 2016 2:42 PM
    That's the leading hypothesis. The fact that this article (and perhaps the published authors as well) failed to address this makes the entire claim dubious.

    It also fails to mention that the stripes could have evolved by all of these things, depending on how much survival advantage each conferred. In other words, the stripes could have helped with insects, weather, and predators, but if the insects were a minimal threat historically to zebras compared with the threat of, say, hot weather, then their evolution was reinforced more by the weather than insects. Or predators if you like. All played a role in preserving/reinforcing/evolving the stripes but to varying degrees depending on the degree of threat imposed on the zebra populations.

    by: Anybody
    January 26, 2016 1:21 AM
    The stripes make it difficult for a predator to focus on a single zebra while running in a pack.

    by: Bread Ramp Jr. from: Minnesota
    January 26, 2016 1:17 AM
    Checkmate Atheists.

    by: Anonymous
    January 26, 2016 12:46 AM
    Jeeezusgawd! How many years now has it been understood that zebras' stripes create an optical movement camouflage? When they are running in a herd, the stripes play out like a psychadelic fractal image and confuse they eye of the predator, creating a larger margin of error in singling out one prey animal in the bunch....I see the people doing the research travelled back in time to regain ignorance....idiots......

    by: MSJ from: toledo, OH
    January 25, 2016 11:35 PM
    Question.. Could the stripes exist to confuse the attacking predator while the zebra herd scatters? It seems to me that the stripes of several zebra moving in different directions would have that affect.

    by: SamIAm
    January 25, 2016 11:34 PM
    Stripes camouflage the individual within the heard.
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