The stripes on a zebra are quite striking and cry out for an explanation. The popular one is that it helps camouflage them against predators by mimicking long grass or trees. But a new study suggests that stripes came about because they help to repel flies. Yes, really.
Researchers from the University of California at Davis knew that certain flies avoid black and white surfaces, so they wondered: Could zebra stripes have evolved to keep the animals free from suffering the bites of those very same flies, which can carry fatal diseases? To tackle that question, the researchers examined the distribution of zebras and the locations of the best breeding grounds for the stripe-averse flies. Sure enough, they found that they overlap. The same was true for other animals in the horse family that had stripes on various parts of their bodies.
I am always a little wary of evolutionary explanations for characteristics that seem a little too glib, because of the danger of falling for ‘just so stories’ of superficial plausibility and ignoring the problem of confounding variables. So even if stripes repel certain kinds of flies, would this provide sufficient selection pressure to drive the process? Could there be other factors that have a greater effect?
As we like to say in science, more research is needed.