Zebras Have Stripes To Repel Flies, Not To Hide Themselves As Everybody Thought — Which Makes Sense, Because Stripes Are Not Subtle
A new study published in Nature Communications suggests that zebra stripes evolved to repel flies, striking down the prevailing theory — that the stripes worked as a form of camouflage. After testing all the different wild equine species, striped and otherwise, lead author Tim Caro of UC Davis and his team couldn't find evidence of a camouflage advantage. Which should come as welcome news to anyone who's never understood how a zebra's stripes could actually help hide it from sight.
What the researchers found instead was a correlation between the distribution of striped equine species, and the presence of biting flies — nasty little buggers which, in addition to being painful nuisances, also spread disease and can shed a considerable amount of zebra blood.
Absent of their stripes, zebras would be ill-suited to battle with biting flies, whose physical specifications pose a unique challenge, according to the research.
Biting fly mouth part lengths are markedly longer than average hair depths of zebras and approximately the same as zebra hair lengths, perhaps making zebras particularly susceptible to (biting fly) annoyance.
The exact reason that the stripes function so capably as a repellent to these biting flies isn't entirely clear, except that it throws off the flies' visual abilities. This compromises their ability to land on the zebra, however tantalizing it may be:
Biting flies are attracted to hosts by odor, temperature, vision and movement that may act at different stages during host seeking, but vision is thought to be important in the landing response.
They're typically attracted to dark colors — which obviously is true of about half of the zebra — but the narrow, alternating streaks of black and white give it insurance against the flies' tiny, debilitating chomps.
Which is a somewhat stirring lesson in evolution, all things considered: The zebra is perilously vulnerable to biting flies, their hair is insufficient to fighting it. Still, the zebra perseveres, thanks to evolved visual trickery.
It doesn't hurt that the resulting aesthetic is as iconic as the zebra's stripes are, either. Who says science can't be beautiful?
It'll also be interesting to see if this new understanding yields any applications for humans trying to avoid airborne bugs. Obviously, more research needs to be done, but in the meantime, no harm in throwing on a black-and-white striped shirt, right?