The Monitor Daily (U.S.) – Charles Darwin was wrong in assuming that zebra stripes are the equine animals’ stealth protection. A new study proves that zebra stripes serve neither camouflage nor social purposes.
Zebra stripes have been a hot topic for debate. Several hypothesis maintain that the black and white stripes are zebras’ way of camouflaging. However, the hypothesis haven’t been tested rigorously. Amanda Melin and Tim Caro with the University of Calgary and the University of California, respectively, set to test just how efficient zebra stripes may be in hiding the animals from their ferocious predators. The results of their study are published in the PLOS One journal.
Zebras’ most feared predators are the big cats of the wild. In their natural environment, zebras are on the lookout for tigers, lions or spotted cheetahs. To gain deeper insight on how these predators would perceive zebras, the research team set out to Tanzania. The ferocious hunters were used as ‘lenses’ to study the hypothesis of zebra stripes serving the purpose of camouflage.
Lead author Amanda Melin, who is also an assistant professor of biological anthropology with the University of Calgary stated:
“We 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 (…)”.
The calculations were conducted for several luminosity settings. Melin and Caro were interested in daylight, night and twilight settings. The study found that zebra stripes serve neither camouflage nor social purposes.
The digital images captured in Tanzania in the open field or among the shrubberies and trees were modified using color filters and spatial filters. The purpose of using filters to alter the images was to understand how spotted cheetahs and lions as well as zebras perceive zebra stripes.
Daylight conditions, twilight conditions and night conditions were used to measure the zebra stripes luminance and width under several scenarios. Using data on the visual capacity of zebras’ ferocious predators, the research team looked at how they could detect the zebra stripes.
Melin and Caro’s calculations revealed that zebra predators have a hard time distinguishing zebra stripes beyond 164 feet in daylight. At twilight the distance shrinked to approximately 98 feet. During the night, neither zebra predators nor zebras are able to distinguish the black and white stripes beyond 29 feet.
However, the distances are sufficiently close for the zebra predators to detect their prey following other cues. Movement or smell are certain giveaways. As for the zebras, predators can detect them as easily as any other solid-colored prey. Their sharp eyes don’t perceive any difference between the zebras and the topi, waterbucks or smaller impala. The same conditions apply to all prey.
Furthermore, the researchers found that not even zebras are able to distinguish the zebra stripes at farther distances. This finding suggests that the black and white stripes don’t serve any social purposes. As such, the study concludes that zebra stripes serve neither camouflage nor social purposes.
Photo Credits: Pixabay