Effect of visual background complexity and light level on the detection of visual signals of male Schizocosa ocreata wolf spiders by female conspecifics

Abstract

For visual signaling to be effective, animal signals must be detected and discriminated by receivers, often against complex visual backgrounds with varying light levels. Accordingly, in many species, conspicuous visual displays and ornaments have evolved as a means to enhance background contrast and thereby increase the detection and discrimination of male courtship signals by females. Using video playbacks, we tested the hypothesis that visual courtship displays and leg decorations of male Schizocosa ocreata wolf spiders are more conspicuous against complex leaf-litter backgrounds. Video exemplars of courting males with manipulated leg tufts were superimposed on different backgrounds (complex leaf litter in sun or shade, featureless gray background) and presented to female spiders. Females were more likely to orient to males presented against lighter backgrounds (litter in sun, gray) than the darker ones (litter—shade). Males with larger tufts were also more likely to be detected, as latency to orient was shortest for enlarged and longest for removed tufts. Latency of females to approach was shorter against lighter backgrounds, and approach latency was longest for males without tufts. Female receptivity scores were significantly greater for males against lighter backgrounds, and males with larger tufts had higher scores. These results suggest that both complexity and light level of display backgrounds affect the detection of male visual courtship signals by females and that aspects of the male phenotype may increase chances of detection (and receptivity) against visually complex backgrounds.