Japanese scientists painted cows like zebras to stop flies biting them, and it actually worked - the bizarre experiment that won an Ig Nobel in 2025

What if the simplest way to stop flies from biting a cow was to make the cow look like a zebra? It sounds like the setup for a joke. Instead, Japanese researchers took the idea seriously enough to paint cattle with black-and-white stripes and then watch what happened when biting flies came looking for a meal. The strange experiment was built around a very ordinary problem. Biting flies are more than an annoyance for cattle. Their bites can irritate animals, cause them to waste energy trying to escape the insects, and potentially affect their health and productivity.

Researchers wanted to know whether the distinctive stripes found on zebras might offer a natural defense against these insects. The answer, they found, was intriguing.

Why paint a cow like a zebra?

The bizarre experiment was not a joke or a publicity stunt. Led by Japanese scientist Tomoki Kojima, it was published as a peer-reviewed research paper in PLOS ONE on October 3, 2019, under the title “Cows painted with zebra-like striping can avoid biting fly attack.”

The study was inspired by an unusual observation about zebras. Unlike most horses and related animals, zebras have striking black-and-white stripes across their bodies. Scientists have proposed several explanations for the pattern, including camouflage, social recognition and protection against biting insects.

The researchers focused on the last possibility. Instead of simply studying zebras, they created their own unusual test subjects: ordinary cattle painted with zebra-like stripes.

The cows were divided into groups. Some were painted with black-and-white stripes, while others were painted black or left unpainted. Researchers then observed how the animals behaved and counted the number of flies landing on them.

The study also found that the striped cows displayed fewer fly-repelling behaviors, including head throwing, ear beating, leg stamping, skin twitching, and tail flicking. The researchers concluded that zebra-like striping could reduce biting-fly landings by about 50%, suggesting that the technique could potentially provide an alternative to conventional pesticides in livestock production.

In other words, the paint was not merely making the cows look unusual. It appeared to interfere with the flies' ability to land and bite.

What makes zebra stripes so effective?

The researchers proposed that the stripes may disrupt the insects' visual perception as they approach the animal. For a biting fly trying to land on a moving animal, a body covered in contrasting stripes may be harder to target accurately than a uniformly colored surface.

The idea offers a possible explanation for why zebras evolved such distinctive patterns. But the experiment also had a practical purpose.

If painting livestock with zebra-like stripes can reduce fly attacks, farmers could potentially have another way to protect cattle without relying entirely on insecticides.

That possibility is particularly interesting because excessive use of chemical insecticides can create environmental concerns and contribute to resistance among insects.

The experiment's bizarre premise eventually earned it recognition from the Ig Nobel Prizes (2025) in Biology, which celebrate scientific research that makes people laugh before making them think.