Meeting Abstract
Multimodal signalling can reinforce messages in communication. In gopher tortoises, the enlarged chin gland (CG) may serve as a visual signal during mating, but chemical signals may also occur in secretions providing information about species, sex, or individual recognition. The sensory drive hypothesis suggests transmission of signal may influence selection, and the signal that travels the furthest distance (e.g., CG olfactory cues) can be prioritized over other signals (e.g., CG visual signals) that occur at closer range. Here, we used both sexes of gopher tortoises in 2 experiments to examine chemical-only presentations of CG secretions vs. distilled water (DI) on cotton swabs and also, chemical and visual signals, with CG secretions vs. DI water on resin tortoise models in paired-choice experiments. We assessed behavior to ask if chin secretions are a social cue recognized by tortoises and we assessed the interplay of chemical and visual presentation of cues. Tortoises of both sexes spent more total time (p=0.001) and performed a higher number of behaviors (p=0.001) with the CG-treated model, relative to the negative control (DI-model). But, although tortoises individually performed the same numbers of behaviors in both swab and model experiments (e.g. approximately 3 behavior types per trial of either experiment; p=0.29), only the visual + chemical experiment showed a significant difference in numbers of behaviors towards the CG-model vs. DI-model. The preferences of the CG-treated model was also supported by multivariate analyses. Our results suggest that although visual cues may be necessary for some types of behaviors to occur, the presence of the CG chemical treatment ultimately drove behavioral patterns in tortoises, hence, tortoises may prioritize chemical cues but use both modality types in intraspecific communication.
