For four years, researchers painted fake eyes on hundreds of cattle butts for the sake of science. What seems like a silly prank, the “eye-cow technique” proved lifesaving for the animals as it made predators rethink their attack, choosing another meal instead.

The scientists say their method is a more humane and “ecologically sound” alternative to lethal control and fencing used to separate cattle from carnivores. The team even theorizes the technique could be used to prevent human-wildlife conflicts and reduce criminal activity, according to a news release. A study was published Aug. 7 in the journal Communications Biology.

“The eye-cow technique is one of a number of tools that can prevent carnivore-livestock conflict—no single tool is likely to be a silver bullet. Indeed we need to do much better than a silver bullet if we are to ensure the successful coexistence of livestock and large carnivores,” study co-author Dr. Neil Jordan, a researcher with the University of New South Wales in Sydney, Australia and the Taronga Western Plains Zoo, said in the news release.

“But we’re hoping this simple, low-cost, non-lethal approach could reduce the costs of coexistence for those farmers bearing the brunt,” he added.

Eye patterns can be found — naturally — on butterflies, fish, molluscs, amphibians and birds to scare predators away. Images of eyes have even been shown to reduce bike theft in people, a 2012 study showed.

So, in the Okavango Delta of Botswana in Southern Africa, where livestock and lions, leopards, hyenas, cheetahs and wild dogs coexist, such a deceptive tactic could save animals from their death sentence, the researchers thought.

Between 2015 and 2018, the team stamped eyes with acrylic paint to the behinds of 683 cattle, drew black crosses on 543 cattle and left the butts of 835 others alone, according to the study. The herds included in the research had recently suffered lion attacks, the researchers said.

During the four-year study period, none of the cattle sporting eyes on their rumps were killed, while four with crosses were eaten and 15 unpainted ones became meals. But much to the researchers’ surprise, cross-marks were better than no marks at all in terms of scaring, or confusing, predators.

Usually, cattle stay in “predator-proof” enclosures overnight, but it’s the unattended daytime grazing when most attacks occur. The team said that because carnivores rely on sneaking around without the attention of its prey, the eye-cow technique could trick the predators into thinking they lost their chance of a successful attack.

The researchers note it’s unclear if painting eyes on cattle butts will aid in keeping the livestock alive if there are no “sacrificial lambs... on the menu.” They also said predators might get used to the deception over time, eventually ignoring it and going in for the attack.

“This is a fundamental issue for nearly all non-lethal approaches, and whether the technique remains effective in the longer-term is not yet known in this case,” the news release states. “Habituation may be a key issue where resident carnivores frequently encounter ‘eye-cows’, but in many areas, carnivores may be simply passing through, and habituation is less of a concern there.”