Share it! Science : What is Black and White and Read All Over? New Research on Zebra Stripes

Why do zebras have stripes? This question has been researched and hypothesized for many years. Up until now there have been four main theories for why one of our favorite African animals has its black and white coat. The prevailing theories were that the stripes a) confused predators, b) protected against biting insects that carried disease c) helped to control and maintain body temperature, and d) were used as a way of identifying with their herd. Previous research has focused on testing one of these hypotheses at a time. The latest study from a team out of UCLA's department of ecology and evolutionary biology tested a bigger set of hypotheses against one another to come to their conclusion.

Zebra (photo credit: Angela Sevin)

The research team, led by Brenda Larison, determined that the temperature of the area the zebras lived in was the biggest factor determining their striping pattern. Larison and others have committed themselves to learning more about the striping pattern of zebras, with their cutting-edge research including DNA sequencing to determine what genes code for striping. In this particular study, Larison's team observed the plains zebra, which is the most common of the three species of zebra. This zebra has a wide range of stripe patterns. By comparing sixteen different areas where the zebras lived, the scientists found that the zebras in colder areas had lighter, narrower and fewer stripes. Often these zebras did not have striping on their legs. In the warmer regions the zebras had bolder striping patterns and the stripes covered their entire bodies. This is the first evidence that we have to show that the black and white patterns on the zebras have to do with thermoregulation, or maintaining body temperature.

Other research, that has yet to be published, also investigates the zebra's body temperature. Daniel Rubenstein, one of the world's leading zebra researchers, has found evidence suggesting that the external body temperature of the zebras is about five degrees Fahrenheit colder than animals of similar size, such as antelopes. These comparable animals do not have stripes but are found living in the same areas as the zebra. This study definitely corroborates the idea of the stripes as an important factor in thermoregulation in different climates.

It takes a lot of research to make a determination that is not theoretical in evolutionary biology. There is no doubt that the prevailing theories of zebra striping do have some relevance, but having some conclusive evidence based on a combination of factors is welcome information in piecing together this evolutionary puzzle.

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