Why Do Zebra’s Have Stripes

The striped coat of the Zebra is both stunning and extraordinary. In fact it is so beautiful that many people in the past have claimed it must be evidence of the infinitely artistic hand of God. We have come a long way since then, and over the years there have been many more rational explanations put forward, however none of them have managed to obtain a scientific consensus.

Charles Darwin found the stripes of the zebra to be perplexing and argued against the idea that they could act as camouflage. In fact Darwin attributed the stripes to sexual selection since both males and females are both similarly striped, the stripes enable the animals to make sensible mating choices.

There are other potential explanations as well. One argument is the stripes behave as some sort of zoological barcode, enabling individuals within the herd to recognize one another. Others claim the stripes help with thermoregulation. Another explanation entails the stripes acting as some kind of deterrent to parasitic flies.

Tim Caro a researcher at the University of California, Davis has spent a long time thinking about the stripes of a zebra. Dr. Caro and his colleagues take a completely original approach and step back from one species of zebra and try to account for pattern differences across multiple species and subspecies of horses, asses and zebra’s. They ask the question of whether there is anything in ecology or habitat that gives any hints as towards the function of stripes.

“I was amazed by our results. Again and again, there was greater striping on areas of the body in those parts of the world where there was more annoyance from biting flies.” Says Dr. Caro

Equids tend to come in stripes wherever there are tsetse flies and wherever the flies are absent so too are stripes.

The idea that flies do not like stripes goes back to the 1930’s and since then there have been multiple studies that have all produced anecdotal support suggesting that flies prefer to alight on solid surfaces rather than on stripes. Horseflies and the tsetse are often responsible for fatal disease in horses and also probably have the ability to drain a large amount of blood ranging in the several hundred milliliters.

The claim being advanced is the tsetse fly and other biting insects drove the evolution of the zebra’s stripes. The next step is for researchers to scientifically determine whether there parasites actually have an aversion to stripes. If the evidence is forthcoming, then a scientific consensus may yet emerge.