Social information use for spatial decision in the common lizard, Zootoca vivipara

Individuals' movements are conditioned by the acquisition of information from personal interactions with the environment or from social sources. Despite the importance of social information in movement decision making, little is known about how individuals proceed when social information comes from multiple sources. Here, we specifically tackled this issue by experimentally testing (1) how social information from multiple sources is used to make relocation decisions and (2) whether a contrast in this information enables individuals to orient themselves in space. Using the common lizard as a model species, we conducted repeated experiments in which a focal neonate received information from two other neonates coming from distinct peripheral environments before being given the opportunity to relocate to either peripheral environment. Specifically, we focused on information on resource availability and intraspecific competition by considering informants' body mass (BM) at birth and their subsequent food intake. Our analyses revealed that the amount of resources in the informants' environments affected relocation decisions, depending on the focal individual's phenotype. We found the probability of relocation increased when both the informants' food intake and the focal individual's BM increased or decreased. We also found the relocation increased when both the informants' and focal individual's BM increased or decreased. Our findings suggest that focal individuals adjust their relocation response to social information according to their needs and/or physical abilities. Conversely, we found no significant effect of differences in BM between informants or spatial variability in resource availability on spatial orientation. This study highlights that multiple sources of social information that reflect the quality of the surrounding environment (competition or resource availability) can be used for movement decision making.