CSULB Biologist Involved in Renewed Debate on Zebra Stripes

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Researchers have recently found that the evolution of a zebra’s stripes is much more complicated than originally thought. In an article in the Sept. 30 online journal Royal Society Open Science, California State University, Long Beach (CSULB) Biological Sciences Assistant Professor Theodore Stankowich and University of California, Davis (UC Davis) Wildlife Biology Professor Tim Caro provide mixed comments on another zebra study conducted by professors at the University of California, Los Angeles (UCLA) and the University of Tübingen, Germany.

In the past, Stankowich and Caro have published several research articles on the ecology and evolution of animal defense mechanisms and predator-prey behaviors. In the new paper, titled “Concordance on zebra stripes: a comment on Larison et al. (2015),” they compare their previous findings to those of a team led by UCLA’s Brenda Larison that appeared in a January 2015 Royal Society Open Science article, “How the zebra got its stripes: a problem with too many solutions.”

“Based on their findings, they suggest that zebra stripes serve as a way to regulate body temperature and to cool off the animal because they found significant associations of variation in the pattern with temperature — more intense striping in environments that have higher temperatures,” Dr. Stankowich said. “They also found an association with areas with high precipitation as well, but they focused on temperatures as the most powerful of their findings. Intense striping was associated with high ambient environmental temperatures.”

However, the Stankowich and Caro team, which published their results in the April 1, 2014 issue of Nature Communications, found that biting fly activity was more important as a mechanism for striping evolution than temperature alone.

“We combined a factor of high temperature and high humidity for at least six to seven months of the year, which is a good proxy for biting fly activity. We found that this proxy was strongly associated with intense striping. That was clearly the best predictor; it was almost a perfect match for species that had leg stripes and body stripes, as well.”

An additional difference appeared in that Larison’s group studied the plains zebra, one of three zebra species, while Stankowich and Caro’s team examined all seven equid species and 21 subspecies.

“Their study focused on one single species of zebra. So, it can only speak to explaining variation within the species that they examined, which is really interesting on its own!” said Stankowich. “Whereas, our study, because it looked at striping in zebras and non-striped equids, sheds light on how these factors influenced the original evolution of striping in this entire group.”

The two research groups found agreement in that more investigation should be directed toward trying to unlock what the mechanism is behind either biting fly avoidance or cooling.

“Those appear to be potentially important explanations,” said Stankowich. “We both agree that more research is needed.”

The Royal Society is the independent scientific academy of the UK and the Commonwealth, and the world’s oldest scientific organization.

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