Why do zebras have stripes? They make bad landing strips for flies

Zebra stripes are dazzling - particularly to flies.

Scientists conducted an unusual experiment involving zebras and horses dressed in black and white striped costumes.

In one experiment, the researchers put cloth coats bearing striped patterns on horses and observed that fewer flies landed on them than when the same horses wore single-color coats.

"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", Mr Caro said.

"From distances of greater than two metres or so, a zebra would just look like a grey horse - they won't be able to see the stripes at all", said How.

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"We conclude that zebras have evolved a coat pattern in which the stripes are narrow enough to ensure minimum attractiveness to tabanid flies", says the team.

Video footage showed that striped affected the way flies landed, with the confusing "landing strip" forcing them to crash or abort landing altogether. But the flies managed to land on zebras less than a quarter as often.

The study noted that zebras and horses respond very differently to the presence of flies.

As a result, the exact cause of stripes in zebra remain unknown. The zebra swished tails nearly continuously to ward off flies, while horses primarily twitch and occasionally swish tails to ward off flies. Scientists have proposed all sorts of hypotheses that might explain their evolutionary origin, including camouflage, signaling to other zebras, or temperature regulation. Researchers used high-resolution cameras to record insects' flight trajectories as they cruised close to zebras. Stripes may therefore offer zebras vital protection, though the researchers aren't entirely sure why the pattern seems to confuse flies.

Zebras are quite good at not getting bitten by flies. Scientists finally (probably) figured out why zebras have stripes. The striped animals nearly continuously swish their tails during the day and will stop feeding if they feel bothered.

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