Artificial eyespots on cattle reduce predation by large carnivores

Abstract

Eyespots evolved independently in many taxa as anti-predator signals. There remains debate regarding whether eyespots function as diversion targets, predator mimics, conspicuous startling signals, deceptive detection, or a combination. Although eye patterns and gaze modify human behaviour, anti-predator eyespots do not occur naturally in contemporary mammals. Here we show that eyespots painted on cattle rumps were associated with reduced attacks by ambush carnivores (lions and leopards). Cattle painted with eyespots were significantly more likely to survive than were cross-marked and unmarked cattle, despite all treatment groups being similarly exposed to predation risk. While higher survival of eyespot-painted cattle supports the detection hypothesis, increased survival of cross-marked cattle suggests an effect of novel and conspicuous marks more generally. To our knowledge, this is the first time eyespots have been shown to deter large mammalian predators. Applying artificial marks to high-value livestock may therefore represent a cost-effective tool to reduce livestock predation.

Fig. 1. Experimental treatments applied to cattle.

a artificial eyespots (bicolour as pictured, or white/yellow inner only, or black outer only, for maximum contrast depending on cattle coat colour). b cross-marked procedural control (black or white depending on coat colour for contrast). c unmarked control. Images provided by C.R.

Fig. 2. Ambush predators were less likely to kill cattle painted with artificial eyespots than unmarked (Df = 1, p = <0.001) and cross-marked (Df = 1, p = 0.011) cattle, and less likely to kill cross-marked than unmarked cattle (Df = 1, p = <0.001).

Plot shows estimated percentage survival curve of cattle in each treatment (n = 683 cattle with artificial eyespots—green; n = 543 cross-marked cattle—red; and n = 835 unmarked cattle—blue), with 95% confidence bands from a survival analysis model. ‘+’ indicates time (days) when the treatment was reapplied. Treatment periods were for a maximum of 24 days, repeated cyclically.

Fig. 3. Cattle from each treatment group spent a similar proportion of nights outside their overnight enclosure overall.

Bar graphs showing the proportion of nights that GPS-collared cattle spend outside each cattle-post (CP) during the study period (estimated from fixes collected between 00:00–01:00). Aqua bars represent artificial eyespot treatment group, orange bars represent cross-marked treatment group, and yellow bars represent unmarked treatment group. High proportions of nights outside for the unmarked treatment in two cattle-posts (CP91 and Shorobe) and the cross-marked treatment in another cattle-post (CP93) were due to these cattle not being herded or kraaled and, hence free-ranging across the landscape. A generalised linear mixed model with a binomial error structure was used with the proportion of cattle outside (00:00–01:00) as the response variable, and treatment (artificial eyespots, cross-marked or unmarked) as the predictor variable. Overall, there was no evidence to suggest there was a difference between treatment groups (DF = 2, p = 0.111).

Fig. 4. Cattle from each treatment group did not travel different maximum daily distances from their cattle-post (Df = 2, p= 0.572).

A linear mixed model provided no evidence for a difference between treatments in the maximum daily distance of the GPS-collared cattle from the overnight enclosure. Higher maximum daily distances (metres) were considered more exposed to predation risk. The box range represents the IQR (Q1 to Q3), the whiskers represent the Q1–1.5*IQR to Q3+1.5*IQR. The dots represent outliers outside this range.