Visual and chemical signals function multimodally in species recognition

When related species overlap geographically, species recognition mechanisms should evolve if there is a significant cost associated with interspecific interactions. Species identification may primarily depend on an individual sensory modality or maybe enhanced by combining information from multiple modalities. Here, we ask whether a visually oriented lizard species (sagebrush lizard, Sceloporus graciosus) primarily uses the visual modality to discriminate between conspecifics and a syntopic congener (western fence lizard, Sceloporus occidentalis), or whether both chemical and visual modalities are informative. In the field, we presented S. graciosus males with visual (robotic motion display) and chemical (femoral gland secretions) signals that were either properly matched or mismatched based on conspecific or heterospecific identity. We found that males performed roughly twice as many visual displays in response to properly matched heterospecific signals than in response to properly matched conspecific signals and gave intermediate responses to visualechemical mismatches. There were no significant differences in chemosensory responses across treatments. These results suggest that no single modality is more informative for species discrimination. Instead, both modalities may function together to enhance species identification or may form a multimodal percept that is absent when species signals are conflicting. (c) 2025 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.