Japanese researchers have won the 2025 Ig Nobel Prize in biology for proving that painting cows with zebra-like stripes helps them avoid being bitten by flies.
The unusual study was recognized during the 35th First Annual Ig Nobel ceremony, which celebrates research that “makes people laugh, then think.” The 2025 Ig Nobel Prize ceremony, organized by the magazine Annals of Improbable Research, was held on September 18 at Boston University.
Led by Tomoki Kojima at the Aichi Agricultural Research Center, the Biology award winning team tested whether fly attacks could be reduced by painting black Wagyu cows with white stripes. Farmers in Japan often struggle with biting flies, which cause stress, reduce fertility, and can transmit disease. Kojima’s idea was inspired by previous studies into why zebras evolved their stripes, with research suggesting that the pattern visually confuses pests.
Painted cows save flies
To test the theory, the team painted one cow with white stripes, one with black stripes, and left another unpainted. After rotating conditions across several animals, they found that the striped cows attracted significantly fewer flies and showed fewer defensive behaviors such as tail flicks and head shakes.
The findings not only confirmed a long-standing theory about zebra evolution but also provided a practical, environmentally friendly solution for farmers. Kojima noted that painting cows is inexpensive, easy, and harmless, with some farmers already adopting the method in Japan using long-lasting paint.
“I couldn’t believe it,” Kojima said after learning of the prize. “I thought I was dreaming.”
The Ig Nobel ceremony honored ten quirky but thought-provoking studies across different fields, including research into pasta sauce physics and digestive processes.