Why do zebras have stripes? Confuse the flies

Zebra stripes deter biting flies, a new study reveals.

The zebra's emblematic striped pattern has been a source of scientific interest for hundreds of years. Hypotheses such as camouflage, predator avoidance and, more recently, thermoregulation attempt to explain their function.

The latest study, led by Tim Caro of the University of California Davis in the United States, looked closely at the behavior of flies (belonging to the family Tabanidae) in a small population of zebras and captive horses – and the results could be the definitive answer to this question. long-standing mystery.

Previous studies have shown that zebras (Equus Burchelli) suffer less attack from horse flies and tsetse flies than unmarked mammals such as antelopes or cattle, but until now, the reason why little was known is clear.

Scientists used high-speed video footage showing the flight and stinging behavior of horseback flies in striped fur and regular fur. The flies circled and flew zebras and horses at similar rates, but landed less than a quarter of the same.

Video analysis showed that landing flies were affected by zebra stripes. Insects did not slow down in a controlled manner, then veered at high speed. Many simply "hit zebras but did not land".

The behavior of flies was also assessed near horses wearing black, white and striped coats – with the same result. The flies have not managed to land on the bodies of the horses dressed in a zebra, but it is obvious that the animals were bitten as usual.

Caro and her colleagues have also carefully described the behavioral reactions of flies in zebras and horses. If a horse fly, also known as tabanid, managed to land on a zebra, the animal would respond quickly by wagging its tail or simply by escaping. These behavioral measures were used at a much higher rate than in horses.

"Because of these two morphological and behavioral defenses, very few tabanids are able to search for a meal of zebra blood," note the researchers.

The results, published in the journal PLOS One, conclude that "we now think that zebra bands have evolved to thwart attacks by biting flies."

The mechanism by which bands confuse the visual systems of flies has been studied in the field and in the lab, but Caro and his team still think that "interlocking black and white stripes are likely to prevent an evaluation precise angular velocity of menacing objects (like a zebra). in order to require further investigation ".

Source link