How a zebra's stripes can leave bloodsucking flies seeing stars

Cristina Cross
February 22, 2019

If you ever learned anything about zebras growing up, the key fact about their stripes you might believe is accurate might not be accurate at all.

But the markings also hold another advantage, scientists have discovered, after finding they disorientate bothersome bloodsucking horse flies. But, what is it about stripes that so disrupts a biting fly's ability to land on a zebra and suck its blood? They found that although flies circled and touched horses and zebras at similar rates, they landed on zebras 25pc less often.

And the footage revealed why. The flies tended to fly over or glance off the zebras; when it came to horses, many more flies were able to stick the landing. Scientists have proposed all sorts of hypotheses that might explain their evolutionary origin, including camouflage, signaling to other zebras, or temperature regulation.

Researchers do not yet understand why zebras evolved these sophisticated defense mechanisms, according to a UC Davis statement.

The research is reported in the journal PLOS ONE.

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Well, it appears stripes make bad landing strips, bamboozling the fierce blood-sucking flies that try to feast on zebras and carry deadly diseases.

The study also showed stripes did not act as a long-range deterrent but appeared to "dazzle" the flies that got up clos.

When uniformly coloured horses were dressed in "zebra coats" the flies made far fewer landings on the striped areas but were not kept away from the uncovered head.

The assumption is that the stripes somehow "dazzle flies" when they are close enough to see the stripes with low-resolution eyes. Zebras swish their tails nearly continuously during the day to keep flies off; they stop feeding if bothered by them; and if the flies are particularly persistent, the zebras will run from them. The striped animals nearly continuously swish their tails during the day and will stop feeding if they feel bothered. "The flies just can't probe for a blood meal with the zebras".

African horse flies carry diseases such as trypanosomiasis (which cause fever, headaches, joint pains and itching and can later on include behavioural changes, confusion and poor coordination) and African horse sickness that causes wasting.

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