Painting Eyes on a Cow's Rear Can Actually Save Their Lives

This one weird trick can save cattle from lions biting their throats and killing them.

From 2015 to 2018, scientists from the University of New South Wales in Australia, working with the Botswana Predator Conservation Trust, painted artificial eyes on nearly 700 cows and monitored how many were killed by lions and leopards. Remarkably, while animals without the acrylic paint eyes continued to be ambushed by lions, none of the animals with the eyes painted on their rumps were killed by the apex predators.

The results were shared in a research paper titled "Artificial eyespots on cattle reduce predation by large carnivores," published in the peer-reviewed, open-access journal Communications Biology in the first week of August.

Co-authored by scientists from the University of New South Wales—zoologist Neil Jordan, ecologist Tracey Rogers, PhD candidate Cameron Radford, data scientist Ben Maslen—and Botswana Predator Conservation Trust founder and director J.W. McNutt, the paper found strong evidence that painted eyespots may provide an inexpensive solution for cattle herders in areas with high predation.

A lioness hunts for game in South Africa's Kruger National Park. Photo by Tom Stoddart/Getty Images

The researchers spread their experiment across 14 different "cattle-posts"—small, non-commercial herds, averaging about 60 head of cattle—experiencing high predation of their livestock, which roam freely across northern Botswana, in woodland and shrubland habitats. The grazing lands and the adjacent Okavango Delta, a wildlife-rich UNESCO World Heritage Site, are often in conflict over the region's ecotourism and livestock economies, particularly when it comes to tourist-attracting apex predators like lions and leopards.

"Farmers and herders direct a considerable and understandable degree of antipathy toward these predators," the paper's co-authors write. "Given the high tourism and ecological value of these apex predators, there is a clear need to resolve these conflicts while also protecting large carnivores and rural traditions and livelihoods."

To test their hypothesized solution, researchers used foam stencils to paint black and white or yellow eyes—one eye for each butt cheek—on approximately one-third of the subject cattle. Another third of the animals were marked with X-shaped "cross-marks," in white or black. Finally, a third of the animals were left unmarked. Colors were selected to maximize contrast and the long-lasting paint typically needed reapplying only once every four weeks. In total, the study used 2,061 cows, mostly the indigenous Tswana breed cattle (Bos taurus africanus).

The results were stark. Lions (or, in one case, a leopard) killed four cross-marked cows, 15 unmarked cows and none of the cows with painted eyespots. While eyespots are popular evolutionary predator deterrents, appearing among insects, fish, amphibians and birds, the researchers believe this is the first time that their effectiveness in deterring large mammalian predators has been demonstrated empirically.

The study demonstrates "simple, low-cost treatments" for reducing ambush predator attacks on free-ranging cattle, but it also has scientific implications. Despite eyespots and other circular patterns—one of several forms of "aposematic" signals used to warn or frighten off predators—appearing across a wide swath of species, zoologists are still debating the exact mechanism behind their anti-predator effects.

A Polyphemous Moth with aposematic markings that may be meant to mimic the eyes of a predator. Smithsonian Institution / public domain

One hypothesis rejected in "Artificial eyespots on cattle reduce predation by large carnivores" is known as the "deflection hypothesis," which theorizes that predators avoid the eyespots, but would still attack (or be deflected to) other body parts. This didn't happen. Instead, the researchers found support for three other theoretical mechanisms.

"Of the key hypotheses suggested to explain the evolution of eyespots in other taxa, our experiment provides some support for the 'detection hypothesis', the 'predator-mimic hypothesis', and the 'conspicuousness hypothesis,'" the authors wrote. "Distinguishing between these hypotheses is problematic, however, as predicted responses are similar, and the mechanistic difference is one of perception."

According to the conspicuousness hypothesis, the novelty of the unusual marks intimidate predators simply by being unfamiliar. While the medium protection offered by cross-marks supports this, the greater protection afforded by eye-shapes suggests more is going on than simple unfamiliarity. The predator-mimic hypothesis suggests that predators interpret the eyes as representing an intimidating enemy or possible attacker. While the painted-on eyes were too big to resemble any creature familiar to leopards and lions, the researchers couldn't discount the possibility that predators perceived the eyes as a potential threat.

However, the best fit for the evidence seems to be the detection hypothesis, which predicts predators will realize they've been spotted, making an ambush seem like a costly proposition. The researchers point out how similar detection behavior, such as hares standing up straight and staring down prowling foxes, suggests that predators are less likely to bother attempting an attack when they've lost the element of surprise. In this scenario, lions and leopards see the painted eyes and decide attacking isn't likely to succeed.

But whatever the behavioral explanation, the experiment could become a useful technique for African cattle farmers.

"In combination with other techniques, successful implementation of this technique may increase the tolerance of farmers towards large predators, reduce the application of lethal control, and increase the sustainability of the system overall," the researchers conclude.

Newsweek has reached out to Jordan, one of the paper's authors, with additional questions, but did not hear back by time of publication.