What do you think of this fact?
Why does a zebra have stripes? Camouflage, cooling, a signal for the herd: over the years there have been plenty of ideas. A team from the UK and the US tested one of them very directly, with horses in zebra outfits.
A horse farm as a lab
The study was published in 2019 in the journal PLOS ONE. According to the University of Bristol, Tim Caro of the University of California, Davis, and Martin How of the University of Bristol watched zebras and domestic horses at a livery in North Somerset, England. They filmed horse flies as they approached the animals.
According to ScienceDaily, the flies circled and touched zebras and horses about equally often. But they landed on zebras less than a quarter as often. The reason: before landing on a horse, the flies slowed down. With zebras they didn’t, and often simply bumped into the animal and flew off again.
The costume test
You could argue that zebras smell or behave differently from horses. That’s where the second part of the experiment came in. The same horses wore black, white and zebra-striped coats in turn. According to the University of Bristol, fewer horse flies landed on the striped coats than on the plain ones.
One detail makes the result especially convincing. According to ScienceDaily, the horses’ uncovered heads were landed on just as often as usual. So it really was the pattern, not the horse.
Bonus fact: According to the University of Bristol, the flies that did make it onto a zebra stayed for less time, and few even tried to suck blood.
Stripes as fly protection
The researchers see this as strong evidence that zebra stripes evolved mainly to fend off blood-sucking horse flies. Their guess: the stripes confuse the flies at close range so they can’t land cleanly. According to the University of Bristol, striped fly rugs could therefore help horses too.
So the most famous pattern on the savanna isn’t a fashion statement. It’s a fly screen.