Unpredictable movement as an anti-predator strategy

Abstract

Prey animals have evolved a wide variety of behaviours to combat the threat of predation, and these have been generally well studied. However, one of the most common and taxonomically widespread antipredator behaviours of all has, remarkably, received almost no experimental attention: so-called 'protean' behaviour. This is behaviour that is sufficiently unpredictable to prevent a predator anticipating in detail the future position or actions of its prey. In this study, we used human 'predators' participating in 3D virtual reality simulations to test how protean (i.e. unpredictable) variation in prey movement affects participants' ability to visually target them as they move (a key determinant of successful predation). We found that targeting accuracy was significantly predicted by prey movement path complexity, although, surprisingly, there was little evidence that high levels of unpredictability in the underlying movement rules equated directly to decreased predator performance. Instead, the specific movement rules differed in how they impacted on targeting accuracy, with the efficacy of protean variation in one element depending on the values of the remaining elements. These findings provide important insights into the understudied phenomenon of protean antipredator behaviour, which are directly applicable to predator-prey dynamics within a broad range of taxa.

Expecting the unexpected: the paranoid style of belief updating across species

“…Evolutionarily, departure from predictable, rational modes of behaviour might offer an adaptive mechanism for escape from intractable threat. As a protean defence mechanism, behavioural stochasticity impedes predators’ abilities to create accurate, actionable countermeasures 41,65,66 . If driven by excessive noradrenergic gain, protean defence may represent an extreme state along a heavily conserved, continuous common mechanism underlying vigilance and false alarms 67-69 , arousal-linked attentional biases and selective processing (i.e., focusing on narrow, most salient features versus broader context 70 ; attending to and learning from predisposition-conforming features 55 ), and behavioural and cognitive flexibility in response to unexpected uncertainty and Bayesian surprise (i.e., prediction error) 53,54,71 .…”

Maternal diet affects juvenile Carpetan rock lizard performance and personality

“…Because of their lower quality (i.e., poorer climbing speed), juveniles from control mothers potentially are under higher predation risk, as they cannot flee as quickly as their conspecifics. Expressing behavior in an unpredictable way might be an effective antipredator strategy, as predators often rely on predictable patterns in prey locomotion (Briffa, ; Highcock & Carter, ; Richardson, Dickinson, Burman, Pike, & Pike, ). Hence, this pattern is somewhat in line with the predictions of state‐dependent safety principle (Dosmann, Brooks, & Mateo, ; Luttbeg & Sih, ; Sih et al, ), where individuals with low climbing speed suffer higher predation risk while being active and should thus be less predictable (but see Urszán et al, ).…”

Species‐specific strategies increase unpredictability of escape flight in eared moths

“…Higher manoeuvrability allows prey to abruptly change its movement trajectory, making its behaviour variable and unpredictable. Unpredictable, erratic or “protean” behaviour is a common escape strategy found in numerous prey taxa (Chance & Russell, ; Humphries & Driver, , ), making it more difficult for predators to catch the prey (Jones, Jackson, & Ruxton, ; Richardson, Dickinson, Burman, & Pike, ). Increased trait variability to increase the trait's unpredictability is found not only in evasive flight, but also in other contexts.…”

“…, making it more difficult for predators to catch the prey (Jones, Jackson, & Ruxton, 2011;Richardson, Dickinson, Burman, & Pike, 2018). Increased trait variability to increase the trait's unpredictability is found not only in evasive flight, but also in other contexts.…”