DOTS AND LINES—ZEBRAS.

DOTS AND LINES—ZEBRAS. There is an ongoing mystery about the evolutionary reasons why zebras have their stripes. This article gives four conjectures: predator avoidance, social benefits, thermoregulation, and protection from biting tsetse flies. This article in the Economist (February 11) describes a recent experiment that provides support for the theory that the answer is the avoidance of tsetse flies. There are limits to the experiment. It was done with horseflies rather than tsetse flies. And zebras move too much so that mockups of zebras were used. Nevertheless, in the experiment, horseflies were less attracted to stripes and in particular less attracted to stripes of the width of those on zebras. Perhaps because of the indirect nature of the experiment, the comments on the article in the Economist (here) suggest other possible evolutionary mechanisms for zebra stripes.