"Hmm. Thirty black and only 29 white. Looks like you're black with white stripes after all. Dilemma solved."
That's what Alex the Lion tells Marty the Zebra in the 2005 animated film "Madagascar," anyway. But the dilemma about how many stripes a zebra has — and why they have them — is surprisingly much more debated.
Scientists at the University of Calgary and University of California, Davis, however, say they've determined why zebras like Marty bear their striped markings. The findings were published in a new study in the journal PLOS ONE, and question the long-standing theory that the stripes are simply for camouflaging.
The researchers used digital photography to simulate how zebra predators such as lions and hyenas see their zebra prey at different distances and under different light conditions. What they found was the stripes simply couldn't help the animals blend into their environment, because, and most importantly, by the time a predator could see the zebra's stripes, it would certainly already detect it by smell.
In addition, the study did not find any evidence to suggest that zebras use their stripes for any kind of social advantage — another idea commonly associated with zebras. From these findings, the scientists draw one conclusion: Zebra stripes are for meant for discouraging biting flies.
John Register, the Houston Zoo hoofed stock supervisor and program leader for Plains Zebras Association of Zoos and Aquariums, agrees with some aspects of the study. "There's been an ongoing conversation since 2014 about what zebra stripes are for," he says. "There's always been an assumption that they were for camouflage." That notion doesn't work, he says, because lions and other predators can smell their prey from at least a mile away.
But Register says he does think the stripes do help cause confusion. "As prey get closer to a group of striped animals like zebra, they can make it more difficult to pick out one individual from the group," he says. "So I think there is still some truth to the idea that they can confuse predators."
He supports the idea that stripes help control biting flies, as well. Other studies have shown that insects land on striped surfaces like zebras less than they do on other surfaces. Register says there's likely much more to a zebra's stripes than simply deterring biting flies, however.
"Temperature control is where I tend to believe the stripes are most useful," he says. "Studies have shown that zebras with wider, more defined stripes are found in tropical climates, and those with minimal stripes are found in colder climates." Meaning the warmer the temperature, the more stripes on the zebra.
This is called the "cooling eddy" theory, which says when air hits a zebra, currents flow stronger and faster over the black stripes and slower over the white. When the two currents meet, they might create a "swirling eddy" of air that helps cool the zebra's skin.
Temperature control, bug control, prey control. Why a zebra got its stripes is a chicken-and-egg sort of question.
"I don't think we're ever going to know why they developed stripes," Register says. "It's probably for a multitude of reasons. They are outside and eating in the sun all day. That leaves them susceptible to heat and biting flies. And who knows if stripes help confuse predators, but I do think it's interesting that they work out for them."