Study says zebra’s stripes helped to deter blood-sucking flies | South China Morning Post
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Study says zebra’s stripes helped to deter blood-sucking flies

PUBLISHED : Wednesday, 02 April, 2014, 9:31pm
UPDATED : Wednesday, 02 April, 2014, 9:31pm

Zebras have stripes to deter the tsetse fly and other blood-sucking insects, according to a fresh attempt to settle a debate that has raged among biologists for over 140 years.

Since the 1870s, in a dispute sparked by the founders of evolutionary theory Charles Darwin and Alfred Russel Wallace, scientists have squabbled over how the zebra got its trademark look.

Are its stripes for camouflage, protecting the zebra with a "motion dazzle confusion effect" against hyenas, lions and other predators in the savannah?

Do the stripes radiate heat to keep the zebra cool?

Or do they have a social role - for group identity, perhaps, or mating?

A new study, published in the journal Nature Communications on Tuesday, says the strongest likelihood is that the stripes discourage parasitic flies.

Lab experiments in 2012 showed how blood-feeding flies shunned striped surfaces, preferring instead to land on uniform colours.

Researchers led by Tim Caro of the University of California at Davis, say there is no black-and-white answer to the great stripe riddle, but the insect theory is by far the best bet.

The team found a strong geographical overlap between zebras and the two groups of biting flies, Tabanus and Glossina, which feed on equid species, explaining why zebras would need a shield against this pest.

There is also plenty of indirect evidence, they say.

Other equid species, such as wild horses, are far more likely to be plagued by biting insects.

Researchers find comparatively little blood from zebras in tsetse flies, even though the zebra has a thin coat with hair strands that are shorter and finer than those of giraffes and antelopes.

At the same time, zebras are far less susceptible to sleeping sickness, a tsetse-borne disease that is widespread among other African equids.

The correlation between reduced biting-fly nuisance and the presence of stripes is "significant", the study says.

"Conversely, there is no consistent support for camouflage, predator avoidance, heat management or social interaction hypothesis," researchers note.

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