Riddle this zebra question: Is a zebra black with white stripes, or white with black stripes? That problem, tossed around for some time, is surprisingly not the one ardently debated by a group of researchers from the University of Calgary and University of California. Their hypothesis? Those unique, dizzying zebra stripes have nothing to do with keeping the African equids safe from salivating lions and hyenas.
Reports Sci-News on Jan. 25: “In a study published online in the journal PLOS One, scientists found that zebra stripes cannot be involved in allowing the animals to blend in with the background of their environment, because at the point at which predators can see a zebra’s stripes, they probably already have heard or smelled their zebra prey.”
Not only that, but the researchers showed that predators to the zebras can easily make out the stripes when close to the zebras during the daytime, and at night, the stripes blend in and provide no benefit of camouflage.
The study, read here in its entirety, states in its 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.”
Researchers found that once a zebra stands over 165 feet away from a predator in daylight, or about 100 feet away on moonlit nights – the time when most predators hunt – the zebra’s stripes, which can be resolved by humans at that distance, cannot be seen by lions and hyenas. They simply see the outline of the zebra. On cloudy nights, the stripes cannot be seen by predators beyond 30 feet.
In woodland areas, it was thought that the zebra’s black stripes mimicked small trees and the white stripes made it appear as if shafts of light were filtering down between the trees.
“The most longstanding hypothesis for zebra striping is crypsis, or camouflaging, but until now the question has always been framed through human eyes,” commented Amanda Melin, the study’s lead author from the University of Calgary.
“We, instead, carried out a series of calculations through which we were able to estimate the distances at which lions and spotted hyenas, as well as zebras, can see zebra stripes under daylight, twilight, or during a moonless night,” she said.
Added Prof. Tim Caro, from the University of California Davis’ Department of Wildlife, Fish and Conservation Biology, who participated in the study: “The results from this new study provide no support at all for the century-old idea that the zebra’s stripes provide some type of anti-predator camouflaging effect. Instead, we reject this hypothesis that was debated by Charles Darwin and Alfred Russell Wallace.
So what’s the deal with the stripes? Explains NewsMax: “Researchers have shown in previous studies that a zebra’s stripes give the animal some evolutionary advantage by discouraging biting flies, a natural pest of the species.” The striped coat also deflects about 70 percent of the heat that hits its body.
And the answer to the black or white stripes: Well, it depends.
The striped pattern is the result of a process called pigment activation, which creates the black areas, and pigment inhibition, which creates the white areas. So black is the actual fur color, and the white are the areas where the pigment is lacking. Therefore, the most accepted answer is that zebras are black with white stripes.