Zebra Stripes are not for Camouflage: UC Davis Study
Don’t you ever think that the black-and-white stripes on Zebra’s body are for what purpose? Leave, it not a big question for you, but for scientists the latest study has come up with a breath of relief. From past many years, scientists have been trying to find out the reason behind the black-and-white stripes on Zebra’s body. They were having the belief that the stripes might act as camouflage for them, with the esteemed likes of Charles Darwin making such theories. But, the latest study proves them wrong as it has been confirmed that Zebra’s stripes do not protect the animal from its predators.
In the new research published Friday in the journal PLOS ONE, researchers from the University of Calgary and the University of California decided to view the enquine creatures through the eyes of the big cats that hunt them. Till now, the hypothesis regarding the stripes on Zebra’s body was seen through human eyes, but for the first time, the research was being conducted in a different way. During the research, the team passed digital images taken in the field in Tanzania through spatial and color filters that stimulated how the zebras would appear to their main predators as well as to the other zebras.
This allowed researchers to figure out at what distances predators, as well as zebras, can see the stripes. They tested this under twilight, daylight and moonless night conditions. The data showed Zebras stripes are only distinguishable from 29 feet during a moonless night or in woodland or low-brush environment. In addition, they only would be visible inside 98 feet at twilight. This would make the stripes useless as camouflage because predators at such short distance could easily locate prey by sound or smell. Researchers draw conclusion that stripes do not allow zebras to blend in with the background of their environment. At the point at which predators can see zebra’s stripes, they probably already have heard or smelled their zebra prey. Thus, it rules out the hypotheses of camouflage protection.
The study confirms the fact that Zebra’s stripes does appear to rule out camouflage. But, the study failed to found that zebras are unable to tell the difference between striped and solid patterns at long distances, showing the stripes probably do not serve a social purpose either.
Study’s lead author, Amanda Melin, an assistant professor of biological anthropology at the University of Calgary, Canada conducted the study with Tim Caro, a UC Davis professor of wildlife biology. In earlier studies, Caro and other colleagues have provided evidence suggesting that the zebra’s stripes provide an evolutionary advantage by discouraging biting flies, which are natural pests of zebras.
To test the hypothesis that stripes camouflage the zebras against the backdrop of their natural environment, the researchers passed digital images taken in the field in Tanzania through spatial and color filters that simulated how the zebras would appear to their main predators — lions and spotted hyenas — as well as to other zebras.
They also measured the stripes’ widths and light contrast, or luminance, in order to estimate the maximum distance from which lions, spotted hyenas and zebras could detect stripes, using information about these animals’ visual capabilities.
They found that beyond 50 meters (about 164 feet) in daylight or 30 meters (about 98 feet) 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 species to distinguish beyond 9 meters (about 29 feet.) This suggests that the stripes don’t provide camouflage in woodland areas, where it had earlier been theorized that black stripes mimicked tree trunks and white stripes blended in with shafts of light through the trees.
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.
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