How did zebras get their stripes? It's hard to get a black-and-white answer.
Some scientists say the stripes are a form of camouflage that protects zebras from hungry lions. Others say they're key to zebra mating rituals. Just last year, researchers published research suggesting that the stripes repel biting flies, thus protecting the animals from diseases flies sometimes carry.
But a peculiar new study offers yet another possible explanation: the stripes help the zebras stay cool in their sometimes sweltering habitats.
"We discovered that temperature is an important predictor of how stripy plains zebra are," Dr. Brenda Larison, an assistant researcher at the University of California, Los Angeles and the study's lead author, told The Huffington Post in an email. "Zebra in areas with seasonal cold temperatures are less stripy than those in areas with sustained warm temperatures."
For the study, the researchers analyzed variations in the stripes seen in plains zebras at 16 sites in Africa. The researchers then examined the relationship between the stripe patterns and 29 environmental variables, including climate to predation to biting flies.
What did the analysis show? The extent of striping was correlated more closely with hot weather than with other environmental variables. In other words, the hotter their habitat the more stripes zebras tended to have.
One hypothesis for the correlation is that bold black and white stripes cool zebras by creating convection currents in the air around the animals' bodies. That is, air moves faster over sunlight-absorbing black stripes and slower over white stripes to create cooling airflow, National Geographic reported.
Indeed, preliminary observations using a digital thermometer gun showed that grazing zebras maintain a significantly lower surface body temperature (84.6 degrees Fahrenheit) than nearby antelopes that are similar in size but have brown coats (90.5 degrees).
But this doesn't mean the zebra stripes mystery has finally been solved, according to Larison.
"We need to give all the hypotheses for zebra striping serious consideration," she said in the email. "We don't see any of the hypotheses as being out of the running yet and there is no reason to think there has to be just one answer. Multiple functions of a trait are not unheard of."
The study was published in the journal Royal Society Open Science on Jan. 14, 2015.