by Laurent Glatz – for Athletic Carnivore
At first glance, the scene is amusing: three black Wagyu cows, one painted with broad white stripes like a zebra, another marked with black stripes, and the third left untouched. Around them, Japanese researchers count... flies.
This work, led by Tomoki Kojima alongside Kazato Oishi and Say Sato, won the 2025 Ig Nobel Prize in Biology, awarded during a ceremony at Boston University. This prize honors research that “first makes you laugh, then makes you think.”
Indeed, laughter arises at these disguised bovines. But reflection is especially warranted when considering the results.
A simple hypothesis: what if zebras were right?
The idea originated from a documentary about zebras and the work of evolutionary biologist Tim Caro. Among the many hypotheses explaining the stripes of these equids—camouflage, social recognition, thermoregulation—one gains credibility: the stripes disrupt the visual perception of biting insects.
Stable flies and horseflies use polarized light and contrasts to locate their hosts. Dark, uniform surfaces attract them particularly. Black-and-white stripes create a kind of “visual noise,” making the surface less identifiable as a target.
The Japanese team then decided to test this idea on domestic cattle.
A Nearly Handmade Methodology, Measurable Results
Three black Wagyu cows served as models. One was painted with white stripes, another with black stripes to control for the effect of paint, and the third remained untouched. Observations lasted 30 minutes, morning and evening, over three days. The animals were repainted daily.
The verdict surprised: about 50% fewer flies on the white-striped cows compared to the others. Agitation behaviors—tail flicks, head shakes, stomping—significantly decreased.
This is no folkloric anecdote. The study was published in PLOS ONE in 2019.
Fewer Flies, More Than Just Comfort
Biting flies are not merely irritating. They cause stress, energy loss, micro skin lesions, and pathogen transmission. In cattle, this chronic stress affects milk production and meat quality.
Stress activates the hypothalamic-pituitary-adrenal axis. Cortisol rises. Appetite may decrease. Energy is redirected toward vigilance rather than growth or lactation.
If stripes significantly reduce parasitic aggression, the impact could go beyond mere comfort. Less stress potentially means:
– better feed conversion
– improved weight gain
– more stable milk production
– reduced insecticide use
Some Japanese farmers have already adopted durable paints, reporting enthusiastic feedback.
An Ecological Solution… and an Evolutionary Lesson
The strength of this experiment lies in its simplicity. No chemicals, no pesticides. Just a visual pattern.
If results are reproducible on a large scale, the implications go beyond anecdote. It indirectly validates an evolutionary hypothesis about zebras: stripes are an anti-parasitic strategy selected by environmental pressure.
What seems absurd becomes biological demonstration.
Japan, Champion of Bold Science
This marks the 19th consecutive year Japanese researchers have won an Ig Nobel. The country holds a historic record in this distinction, with awards in chemistry, biology, medicine, and inventions that became famous like the Tamagotchi or karaoke.
At the 2025 ceremony, themed on digestion, traditions were respected: paper planes thrown by the audience, a mini scientific opera, handmade trophies. While Kojima received his prize, colleagues surrounded him with fake flies until he revealed a zebra-striped shirt under his jacket.
The folklore entertains. The implications remain.
A Broader Question
This study challenges a modern trend: faced with a biological problem, the response is often chemical. Insecticide, antibiotic, additive. Here, the answer is optical.
Changing appearance to alter biological interaction.
If a simple visual pattern can halve parasitic exposure, how many other ecological solutions remain ignored because they seem too simple?
And what if evolution, sometimes, had already found answers that modern agriculture simply stopped observing?
Painting a cow like a zebra makes you smile.
But perhaps behind those stripes lies a broader lesson on how we approach the living world.
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