February 10, 2012
Zebra Stripes Repel Bloodsucking Flies
In an amazing discovery, researchers report they have discovered that Zebra´s stripes repel bloodsucking horseflies, otherwise known as tabanids.
The tabanids, which are a major nuisance for zebras, cows, horses and other related creatures, irritate the animals while grazing and carry deadly blood-borne diseases.
Susanne Akesson, an evolutionary ecologist at Lund University in Sweden previously discovered that the flies were more attracted to dark animals than to light ones, probably due to how the light reflects off of the darker skins. The light reflected off of the darker skin becomes horizontally polarized, which attracts the tabanids.
Tabanids use the horizontally polarized light beams to lead them to water and mud where they mate and lay eggs. But zebras have both light and dark skin and the researchers wondered if this had an intermediate effect on attracting the flies.
In order to test their theory, the researchers setup several models on a horsefly infested farm in Budapest. To see what would attract the flies the most they varied the patterns on the models. Jane J. Lee of Science Now reports that some models were solid black or white, or black and white striped squares, as well as black, brown, white, or striped life-sized plastic horses. They also used gray squares with varying amounts and widths of stripes to see how patterns affected tabanid preference.
The tabanids were caught in vegetable oil as they landed on the experimental squares. They also coated the plastic models with clear, odorless glue to catch the flies as they landed.
The researchers found that the stripes were the least attractive pattern to the horseflies more so than the solid white surface. The striped pattern, it turns out, reflects light in multiple directions, whereas solid colors reflect light in uniform patterns that flies prefer.
What the scientists don´t know is whether what is found in the laboratory still holds true for real life. Because odors may attract more flies despite them being turned off by the scattered light patterns and Zebras emit very strong odors. And the flies may be more attracted yet as the Zebra hangs out around the water-hole, where the flies originate.
The report is published in the Journal of Experimental Biology.
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