Scientists Just Solved The Mystery Of Why Zebras Have Stripes By Making Horses Wear Zebra Costumes

Why do zebras have stripes? To hide from predators? To stay cool? To attract a mate? These are questions that have long baffled zoologists, but researchers at the University of Bristol and UC Davis, California, USA think they have the answer.

The zebra's stripes confuse parasites.

All  11 species of zebra are subtly different, but what unites these African equids is that they have a two-tone coat that, according to the latest research, helps avoid blood-sucking parasites such as horse flies.

To set-up the experiment, researchers at the University of Bristol's School of Biological Sciences used video analysis on tabanid horse flies and captive zebras and domestic horses at a livery in North Somerset, UK. 

At a distance, the zebra's stripes made no difference, and the horse flies began circling the zebras and horses alike. However, when the horse flies got closer to the zebras, they failed to slow down, so couldn't land. "Horse flies just seem to fly over zebra stripes or bump into them, but this didn't happen with horses," said Professor Tim Caro, Honorary Research Fellow from the University of Bristol's School of Biological Sciences. "Consequently, far fewer successful landings were experienced by zebras compared to horses."

This research paper, published on PLOS ONE, builds on Caro's previous research into zebras, which revealed that zebras in parts of Africa with more biting flies have greater striping. 

Dr Martin How, Royal Society University Research Fellow in the School of Biological Sciences, 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."

"Stripes may dazzle flies in some way once they are close enough to see them with their low-resolution eyes."

Why zebras evolved anti-fly stripes is to avoid horse flies, which in Africa often carry dangerous diseases such as trypanosomiasis and African horse sickness.

However, zebras are also skilled at dealing with horse flies by their behavior. During the experiment, researchers observed zebras running away and tail swishing at a far higher rate than horses, so any horse flies that didn't get slowed down by the stripes were dispatched quickly. 

If zebra stripes are so good at getting rid of parasites, why not dress-up horses as zebras? In a second experiment, horses were dressed in different colored cloth coats: black, white and zebra-striped livery. The horses wearing coats with striped patterns experienced fewer horse fly landings compared to when they wore single-color coats.

The research could make 'zebra coats' common for horses, which is more ethical than when a zoo in Egypt was accused of painting a donkey to look like a zebra. Either way, there's now more evidence to back-up the theory that zebras have stripes to battle parasites, and not to disguise themselves from predators.

--

Follow me on Twitter @jamieacarter, @TheNextEclipse or read my other Forbes articles via my profile page.