Abstract
The confusion effect - the decreased attack-to-kill ratio of a predator with increase in prey group size - is thought to be one of the main reasons for the evolution of group living in animals. Despite much interest, the influence of prey coloration on the confusion effect is not well understood. We hypothesized that dynamic colour change in motion (due to interference coloration or flash marks), seen widely in many group living animals, enhances the confusion effect. Utilizing a virtual tracking task with humans, we found targets that dynamically changed colour during motion were more difficult to track than targets with background matching patterns, and this effect was stronger at larger group sizes. The current study thus provides the first empirical evidence for the idea that dynamic colour change can benefit animals in a group and may explain the widespread occurrence of dynamic colorations in group-living animals.
Highlights
Group living is a widespread behavior which has evolved independently in many animals (e.g.1,2) and predator avoidance is considered as one of the primary selective agents driving the evolution of group living in animals[3]
The relationship between group size and tracking error was steeper for all the colour dynamic stimuli compared to background matching stimulus
The results may explain why group living birds and fishes often have flash marks, and support the speculations based on observations made by Denton and Brooke[30,43]
Summary
Group living is a widespread behavior which has evolved independently in many animals (e.g.1,2) and predator avoidance is considered as one of the primary selective agents driving the evolution of group living in animals[3]. The influence of prey coloration per se on the confusion effect, and group-living, remains largely unexplored (but see[27,28,29]) Many animals such as birds and fishes, which are often found in groups, have colorations that typically change during motion (Fig. 1a,b). A comparative study by Brooke[30] has found the evolution of ‘flash’ marks in shorebirds (e.g., Fig. 1a) to be associated with grouping behavior, indicating that flash coloration might be beneficial in prey aggregations He suggested that one of the benefits of flash colorations is to enhance the confusion effect - “This potential benefit of flocking, the confusion effect, could be enhanced by flash marks if they further distract the predator. Until now, whether dynamic colour change can reduce predation by increasing the confusion effect has not been experimentally tested
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