Search

Many animals have colour patterns that appear to change dynamically when the animal moves. Experiments have suggested that such colour patterns, termed 'dynamic flash' coloration, can reduce predatory attacks by misrepresenting the prey's location. However, the conditions that make this coloration effective are not known. We here tested the influence of two factors, target size and unpredictable movement, on the efficacy of dynamic flash coloration. Both these factors have independently been shown to affect the predator's ability to attack a moving prey accurately, but whether they interact with prey coloration remains unclear. Using a virtual predation experiment with human participants, we found that the effectiveness of dynamic flash coloration, when compared to background-matching coloration, declined as the size of the target increased, but only when the target movement was linear (i.e. predictable). However, when the movement was unpredictable (i.e. when the target adopted a 'protean' motion), we found dynamic flash coloration to be effective in reducing the number and accuracy of attacks irrespective of target size. Under most conditions, the effectiveness of dynamic flash coloration did not differ from that of a uniform luminance-matched grey target. Our results suggest that the efficacy of dynamic flash coloration is limited by prey size, but animals can overcome this constraint by employing an unpredictable movement trajectory. The study also provides direct empirical evidence that protean antipredator behaviour influences the effectiveness of prey coloration that works in motion. • Dynamic change in prey colour during motion may reduce predatory attacks. • We tested the factors affecting the effectiveness of dynamic coloration. • When movement was linear, dynamic coloration was effective only in small targets. • It was effective irrespective of size when the movement path was unpredictable. • Its evolution might be affected by prey size and escape trajectory. [ABSTRACT FROM AUTHOR]

Longfin squid, Loligo pealeii, were exposed to two predators, bluefish, Pomatomus saltatrix, and summer flounder, Paralichthys dentatus, representing cruising and ambush foraging tactics, respectively. During 35 trials, 86 predator–prey interactions were evaluated between bluefish and squid, and in 29 trials, 92 interactions were assessed between flounder and squid. With bluefish, squid predominantly used stay tactics (68.6%, 59/86) as initial responses. The most common stay response was to drop to the bottom, while showing a disruptive body pattern, and remain motionless. In 37.0% (34/92) of interactions with flounder, squid did not detect predators camouflaging on the bottom and showed no reaction prior to being attacked. Squid that did react, used flee tactics more often as initial responses (43.5%, 40/92), including flight with or without inking. When all defence behaviours were considered concurrently, flight was identified as the strongest predictor of squid survival during interactions with each predator. Squid that used flight at any time during an attack sequence had high probabilities of survival with bluefish (65%, 20/31) and flounder (51%, 18/35). The most important deimatic/protean behaviour used by squid was inking. Inking caused bluefish to startle (deimatic) and abandon attacks (probability of survival=61%, 11/18) and caused flounder to misdirect (protean) attacks towards ink plumes rather than towards squid (probability of survival=56%, 14/25). These are the first published laboratory experiments to evaluate the survival value of antipredator behaviours in a cephalopod. Results demonstrate that squid vary their defence tactics in response to different predators and that the effectiveness of antipredator behaviours is contingent upon the behavioural characteristics of the predator encountered. [Copyright &y& Elsevier]