Motion enhances camouflage: Retinal evidence for flicker fusion camouflage in jumping spiders.

Camouflage is often assumed to fail once prey move, yet theory predicts that rapid motion can reduce detectability through flicker fusion camouflage (FFC), where high-contrast patterns blur into perceptual uniformity. We tested this prediction using retinal tracking in the jumping spider Menemerus bivittatus, a predator with a highly modular visual system. Using computer-generated stimuli varying in pattern, speed, size, and contrast, combined with anterior lateral eye (ALE) masking, we show that small, fast-moving thin stripes strongly suppressed retinal responsiveness. Low-contrast stripes further impaired retinal tracking compared to high-contrast stripes, indicating that signal salience modulates motion processing. ALE-masking validated the motion-sensitivity of ALEs and their critical role in FFC. Together, these findings establish FFC as an ecologically plausible strategy and reveal how prey pattern, movement, and predator sensory architecture jointly shape visual detectability. Our results challenge traditional viewpoints of camouflage and highlight the dynamic nature of visual concealment in predator-prey coevolution.