Response of leopard geckos (

Predator detection is a fundamental survival mechanism that has shaped the evolution of diverse antipredator strategies across animal taxa. The capacity to detect predators depends on the sensory modalities animals rely upon, and the integration of multiple sensory channels-multimodal perception-may enhance detection efficiency and improve survival. However, the functional significance and relative importance of multimodal perception in reptiles remain insufficiently understood. In this study, we experimentally disentangled the effects of individual sensory modalities-chemical, visual, and mechanosensory-by testing them independently and in combination, thereby assessing their relative and synergistic contributions to antipredator behavior in leopard geckos. Our results show that chemosensory information acts as the primary driver for both sensory assessment and active defense. While visual and mechanosensory stimuli did not independently increase tongue-flicking frequency compared with the control, they functioned as modulatory cues that significantly amplified chemical sampling in a multimodal context. However, overt antipredator behaviors, such as defensive posturing and mouth-open displays, were triggered exclusively by chemosensory stimuli, highlighting the dominant role of chemical cues in predator detection. Our statistical modeling suggests that sensory integration predominantly follows an additive pattern, where secondary modalities heighten alertness and facilitate threat assessment, but the initiation of costly defensive action remains strictly gated by chemoreception. These findings underscore the dominance of chemical cues for predator recognition in nocturnal environments, where multimodal inputs amplify attention but are not essential for eliciting a full defensive response.