Scientists have finally discovered why zebras have stripes

Scientists have finally discovered the real reason why zebras have stripes after years of debate.

The research, published in the Journal of Experimental Biology, was led by Professor Tim Caro and Dr Martin How – both from the University of Bristol’s School of Biological Sciences.

Researchers believe the animal developed their black and white markings to ward off bugs – such as horseflies – from biting them.

Prof Caro said: "We knew that horseflies are averse to landing on striped objects - a number of studies have now shown this, but it is not clear which aspects of stripes they find aversive.

"Is it the thinness of the stripes? The contrast of black and white? The polarized signal that can be given off objects? So we set out to explore these issues using different patterned cloths draped over horses and filmed incoming horseflies."

The team discovered that tabanid horseflies are attracted to large dark objects. However, less so towards dark broken patterns.

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All-grey coats were associated with the most landings by far. This was followed by coats with large black triangles placed in different positions, then small checkerboard patterns in no particular order.

In a separate experiment, researchers found contrasting stripes attracted few flies, whereas they were more drawn to homogeneous stripes.

Professor Caro added: "This suggests that any hoofed animal that reduces its overall dark outline against the sky will benefit in terms of reduced ectoparasite attack."

Now, the team are eager to learn why natural selection has driven striping in equids (the horse family) but not other hoofed animals.

Professor Caro added: "We know that zebra pelage – fur - is short, enabling horsefly mouthparts to reach the skin and blood capillaries below, which may make them particularly susceptible to fly annoyance, but more important, perhaps, is that the diseases that they carry are fatal to the horse family but less so to ungulates. This needs investigation."

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