The new research has shown it appears zebras have stripes because it makes terrible landing strips for fliers.
The black and white stripes apparently stop the blood-sucking insects from landing on the creatures.
Behavioural ecologist Tim Caro of the University of California-Davis, the lead author of the research published in the journal Plos One said: “We showed that horse flies approach zebras and uniformly coloured horses at similar rates but that they fail to land on zebras – or striped horse coats – because they fail to decelerate properly, and so fly past them or literally bump into them and bounce off.”
Researchers described experiments demonstrating horse flies have a difficult time landing on zebras while easily landing on uniformly coloured horses.
One of the experiments saw the scientists put cloth coats bearing striped patterns on horses and observed that fewer flies landed on them than when the same horses wore single-colour coats.
Previously, there have been four main hypotheses about why the zebras have stripes.
One hypothesis is that the stripes help zebras camouflage to avoid large predators.
Another shows the stripes having a social function like individual recognition, while a third relates to thermoregulation, with stripes setting up convection currents along the animal’s back.
And now, researchers think the stripes protect the zebras from thwarting biting fly attacks.
Mr Caro said of the theories: “Only the last stands up to scrutiny.
“Most biologists involved with research on mammal colouration accept that this is the reason that zebras have stripes.”
Zebras roam Africa’s savannahs and occur in a variety of habitats, such as grasslands, woodlands, thorny scrublands, mountains and coastal hills.
In the horse species’ natural habitat, African horse flies can also be found.
The flies carry diseases such as trypanosomiasis and African horse sickness that cause wasting and can be deadly.
University of Bristol biologist and study co-author Martin How said stripes may dazzle flies somehow once the insects venture close enough to see them with their low-resolution eyes.
Mr Caro said: “In addition to stripes that prevent controlled landings by horse flies, zebras are constantly swishing their tail and may run off if horse flies do land successfully, so they are also using behavioural means to prevent flies probing for blood.”