Intensity contrast drives background choice in cephalopods

For camouflage to be effective, animals must integrate their phenotype into the environment, with background selection providing a behavioural means of doing this. At present, there is limited knowledge of what cues animals capable of dynamic colour change attend to when selecting backgrounds. Recent empirical data show that a predator’s search task is more challenging in visually complex environments, suggesting that animals capable of matching many backgrounds through adaptive colour change may use visual complexity to govern background choices. We designed a binary choice paradigm to assess whether three species of cephalopod (Sepia plangon, Sepioteuthis lessoniana, Euprymna tasmanica) prefer more visually complex environments, with complexity quantified in terms of intensity contrast. Tracking data revealed a consistent preference for the high complexity background in S. lessoniana and E. tasmanica, with a similar but weaker trend in S. plangon. Granularity analysis showed that this preference was not explained by the ability to better match one background over the other, supporting the interpretation that cephalopods were selecting for visual complexity itself. This suggests that background complexity, by means of the range of intensity contrast, may be an important cue guiding background selection in animals capable of adaptive camouflage.