Visual signal dynamicity shapes detectability in the wild: an experiment with a mate-searching butterfly

For any sensory system, the detection of relevant information is a challenging task. Natural habitats are full of sensory stimulation, of which only a fraction can be detected and processed. For visual animals, some features, like the movement of the target, are known to enhance signal saliency. However, less is known about the effect of other dynamic signal properties, such as flashing or flickering, that are known to improve saliency in human contexts. Here, we used mate-seeking butterflies in their natural habitat to test how flashing, lateral back-and-forth movement, and their interaction affect the detectability of a visual stimulus. We found that both lateral movement and flashing (resulting from an oscillation that simulated 'fluttering') of the stimulus contributed independently and additively to the likelihood of detection, with some evidence that movement made the stimulus more conspicuous from greater distances. These effects did not interact, meaning that flashing did not modify the influence of movement (and vice versa). Coupled with evidence in humans, this result supports the importance of flashing as a universal, potentially independent means of increasing visual signal saliency.