Scientists Painted Cows Like Zebras — and It Cut Fly Landings by Half

In recent years, scientists have been looking at why zebras have stripes, and one idea keeps coming up: the stripes might help keep biting flies away. That sounds odd at first, but it’s not just a wild guess. Researchers have been testing it—on horses and even on cows—and the results are worth paying attention to, especially for farmers who deal with fly problems every day.

Let’s start with a study that got quite a bit of attention in 2019. A team of scientists in the UK, including biologist Tim Caro, studied how flies behaved around horses dressed in different patterned coats. Some of the horses wore zebra-striped coverings, others wore plain black or white ones.

The researchers found that horseflies still flew near the animals no matter what they were wearing—but when it came time to land, they had a much harder time sticking the landing on the striped coats. This suggested that the stripes were interfering with how the flies approached or visually processed their target.

That was an important finding, but it raised a practical question: could this same idea actually help livestock that are common on farms? After all, farmers aren’t putting coats on horses just for the fun of it, and certainly not on cows. So a team of Japanese researchers decided to try something more direct: they painted stripes onto cows.

In a 2019 field experiment, six Japanese Black cows were used in a rotating setup. Each cow went through three stages—no paint, solid black paint, and zebra-style black-and-white stripes painted directly on their bodies. The cows were observed in open fields during fly season, and researchers counted how many biting flies landed on them and how often the cows reacted by flicking their tails or shaking their heads.

The results showed a clear drop in fly landings when the cows had zebra-style stripes. Specifically, there was a reduction of more than 50% in the number of biting flies compared to unpainted cows. Even compared to cows painted with solid black stripes, the difference was significant. The striped cows also showed fewer fly-avoidance behaviors, meaning they were probably more comfortable.

The scientists believe that, similar to the horse study, the stripes confuse the flies’ vision. Flies rely on visual cues to land, and the contrasting patterns seem to interfere with how they judge distance or movement. In simple terms, the flies try to land, but they miss or abort the attempt.

Now, painting cows is not exactly a long-term solution, especially on large farms. It’s time-consuming, and the paint wears off. But the study opens the door for exploring new, low-tech, and chemical-free ways of managing fly problems in livestock. This could be especially helpful in regions where fly-borne diseases are a serious threat or where using pesticides isn’t ideal.

It’s worth noting that there was a correction published to the cow study in 2020, updating some behavior counts like head throws. However, the main findings didn’t change. The fly-reduction effect was still there, and the authors stood by their conclusions.

Taken together, the horse and cow studies offer more than just a quirky fact about animal patterns. They give researchers and farmers a clearer picture of how visual cues can affect insect behavior, and how nature’s solutions—in this case, the zebra’s pattern—might have applications beyond the wild.

These studies don’t claim that stripes are the full story behind zebra evolution. There are other ideas out there too, like temperature control or camouflage. But in terms of helping reduce insect bites, the evidence is starting to stack up.

For farmers battling biting flies, this research is interesting not just for what it says about zebras, but for what it might lead to: creative, simple tools based on how insects see the world.