ArsTechnica [arstechnica.com]:
Granted, it was a small sample size, but those results were encouraging enough to convince Jordan to conduct a more ambitious study over the last four years. His team worked with local farmers in the Okavango delta region, painting the cattle in 14 herds (a total of 2,061 animals). They used acrylic paint (black and white or yellow), applied with foam stencils in the shapes of the inner and outer "eye." The colors were chosen "because of their highly contrasting and aposematic features, common in natural anti-predator signaling settings," the authors wrote.
Roughly one-third of the cattle in each herd got the eye patterns, one-third got simple cross-marks, and one-third weren't painted at all. The results confirmed Jordan's preliminary findings. Cattle with the painted eyes on their rumps were significantly more likely to survive than those cattle that had crosses painted on their butts and those that weren't painted at all. But the authors were surprised to find that even the painted crosses offered some survival advantage over the unpainted cattle. Over the course of the four-year study, 15 (out of 835) unpainted and four (out of 543) cross-painted cattle were killed by lions; none of the 683 cattle with painted eyes were killed.
The tactic will likely fail to deter the cattle's main predator...