The evolution of the zebra’s black & white coat has intrigued scientists for years. Now, researchers have added evidence to a theory that the primary purpose of the stripes is for avoiding blood-sucking parasites — horse flies. Their study shows that stripes don’t deter horse flies from a distance, with both zebras and domestic horses experiencing the same rate of circling from the flies. However, video analysis revealed differences in approach speed. When approaching zebras, horse flies fail to slow down, which is essential for a successful landing.
“Horse flies just seem to fly over zebra stripes or bump into them, but this didn’t happen with horses. Consequently, far fewer successful landings were experienced by zebras compared to horses,” the University of Bristol quoted researcher Tim Caro as saying. Researcher Martin How added: “This reduced ability to land on the zebra’s coat may be due to stripes disrupting the visual system of the horse flies during their final moments of approach.”
Researchers also made the same horses wear different coloured cloth coats: black, white or zebra-striped livery. Just as before, when horses wore coats with striped patterns, they experienced fewer horse fly landings.
Source: University of Bristol
Research paper in PLOS One: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0210831