”The treatments were black-and-white painted stripes, black painted stripes, and no stripes (all-black body surface)”
Weird that they didn’t have a fourth group with white painted stripes. Now, the group with black-and-white painted stripes is the only one that has white paint applied, so it could as well be that the white paint causes the difference.
I would love to drive by fields of zebra-painted cows, however it does make me wonder if there were other elements at play.
From the plos.org article above: "Biting flies are attracted to their host animals by odors, shape, movement, brightness, color, polarization and body temperature"
By painting on an animal, you are now changing not just the color (and perceived shape, which affects perception of movement), but also the odor (due to the paints) and perhaps interfering with how the flies will perceive the body temperature of the animal, too.
It would also be interesting to see how these specific data points compare between zebras and the cows used for these kinds of tests.
This is a short term fix at best.
Eventually, only those that can bite will survive.
I don't see how it can go the other way. Where eventually since only half of them bite, that ratio declines to zero. Can that happen with evolution?
I suppose there is a tipping point where if enough of the population can't find each other then they all die alone. Like rats in Alberta.
Another element at play could be that (I’m making this up, but it doesn’t seem impossible to me) zebras have thicker skin than cows, so that only half the fly species (or perhaps even only older, larger flies) can extract blood from them.