Scientists painted black cows with white stripes to test whether zebra markings deter biting flies — and the painted cows drew 50 per cent fewer flies, adding weight to the theory that zebras evolved their colouring not for camouflage or heat, but as a living insect repellent

The cows spent time in each treatment on natural pasture where biting flies were abundant. Zebra stripes do not reduce visibility to lions or hyenas at their normal hunting distances. Tim Caro at the University of California Davis showed in 2014 that stripe patterns across equid species correlate strongly with the geographic distribution of biting flies. Biting flies cause substantial losses in the global cattle industry, reducing weight gain in beef cattle and milk yields in dairy cows. If painted stripes can reduce fly landings by 50 percent without any chemical involvement, the implications for animal welfare and pesticide reduction are genuine.