Scientists Reexamine Why Zebra Stripes Mysteriously Repel Flies

A potential evolutionary advantage that would explain the difference between zebra species was the focus of the current study. The theory that the repulsion needed an illusion that could only happen at a distance was ruled out by the experiment. The box is made of plexiglass.

The experiment was set up by an undergrad from the lab. The team hung two pelts with clothespins and then counted how many flies landed on each one. The impala was compared to a zebra with wide stripes. The impala and the Grevy's zebra are both zebras. The skins from the two zebras were put against each other. There were 100 rounds for each pair.

The flies preferred the impala skin more than the zebra skin. The team found no obvious difference between the stripes.

What makes it work? It is important to know that flies do not see the world the same way as you do. The flies have pound eyes that combine input from thousands of photoreceptors, each pointing in slightly different directions from their eye's rounded surface They don't have a good sense of color. They can sense motion and light 10 times faster than we can, but those images are very low-resolution.

Like you, flies are fooled by the barber pole illusion. There is a rotating pole outside of a barber shop, but it is not going up. It creates a false perception of motion. She believes that a zebra's stripes make it harder for flies to gauge the timing and speed of a landing. She says that a fly can move at a very fast rate. It makes sense that this illusion works as the fly is on the way to land.

A stronger barber pole illusion should be created by narrowing stripes. She says that only a couple of previous studies looked at width, and only one tested painted stripes up to 5 inches wide, which is beyond what any real zebra has. She says that her team's results show that width doesn't make a difference in zebra stripes.

Ted Stankowich, an evolutionary ecologist from California State University Long Beach who was not involved in the work, said all that mattered was that zebras have them. Random genetic drift could be one of the reasons for additional variation. He says that the anti-fly effect is achieved by having stripes. Many other sources can affect that trait.