By Dr. Becker
The purpose of the zebra’s black and white stripes has mystified scientists and laymen alike for centuries.
But now a research team from the University of California-Davis has taken a different approach to solving the riddle of the stripes, and their explanation was recently revealed in the journal Nature Communications.1
Researchers Tested 5 Theories for Why Zebras Have Stripes
Theories for the stripes that have surfaced over the years include:
- They are a method of camouflage.
- They are defensive weapons to visually confuse predators.
- They help regulate the zebra’s body temperature.
- They deter ectoparasites (biting flies), as earlier research has shown that the flies tend to avoid black-and-white striped surfaces.
- They serve some sort of social function for the zebras
The UC-Davis team gathered information on different species and subspecies of zebras and other striped African hooved mammals, measured their data against the five theories, and ruled out all but one. They determined it is likely that biting flies such as tsetse flies and horseflies are the reason for zebra stripes, because their data showed greater striping on the animals living in parts of the world where biting flies are abundant.
Africa is well known for having a wide distribution of tsetse flies, but no such information exists for horseflies or deer flies. So the UC-Davis team mapped locations that would theoretically provide the best breeding conditions for those flies, and discovered that striping on zebras is closely linked with several consecutive months of excellent conditions for horsefly reproduction.2
Zebra Stripes May Have Evolved to Compensate for Unusually Short Body Hair
According to lead study author Tim Caro, professor of wildlife biology at UC-Davis:
“No one knew why zebras have such striking coloration. But solving evolutionary conundrums increases our knowledge of the natural world and may spark greater commitment to conserving it.”
Interestingly, the UC-Davis researchers might have uncovered another intriguing detail about zebras. It seems that unlike other hooved animals native to Africa, zebras have body hair that is shorter than the mouthpart length of biting flies, which would make them particularly vulnerable to the flies. So the stripes may have evolved as a deterrent.Parasitic flies can carry a long list of diseases they transmit when they attach to a new host. Studies on horseflies in the U.S. suggest that cows can lose over a pint of blood a day to the flies, and up to 40 pounds of weight over eight weeks.