×In the literature, there are a lack of knowledge on how the movements of motile individuals are influenced by socially acquired information from multiple conspecifics. This thesis aims to better understand the relative importance of such information on the determinism of these movements, and its use, depending on the context, individual condition, or its nature. I began by investigating how social information provided locally by many conspecifics influences dispersal, its relative importance, and its dependence on individual phenotype. Using a 30-year markrecapture monitoring of the viviparous lizard (Zootoca vivipara), I was able to explore how natal dispersal depends on multiple components of the social context in the natal area, as well as other factors internal to the individual or abiotic. Results highlighted that dispersal is multi-determined, with several components of social context (sex ratio, age structure, body condition of conspecifics) having a concurrent impact. This study has highlighted, for this species, the particular relative importance of traits related to the sex of the individuals and the substrate’s characteristics. Finally, the results obtained appear to reveal a match between the competitiveness of the individual and the use of social information related to intra-specific competition. I also conducted experiments on the same species to test the ability to orientate when confronted with multiple sources of social information. For this, I considered the concurrent arrival of two conspecifics, from contrasting rearing conditions, in the habitat of a focal individual. Although no effect on orientation was observed, this experiment provided a better understanding of how information from competing sources was used on movement decisions, with the use of the mean information (resource accessibility and maternal phenotype), but not its contrast. Then, by using the same tracking as in the first part, I explored how immigrants-based information influences natal dispersal. I investigated whether its use depended on the local context and/or phenotype of the individual, as well as distance, variability, and the number of information sources. I observed that this information was used depending on the needs of the individuals (defined by their phenotype and context), and that information was preferentially used when it was not too uncertain (too variable or transmitted by too few immigrants) or in a way that minimized costs (preference for habitats similar to the one of birth when the information is distant or uncertain). Interestingly, individuals seem to prefer the same habitats locally and at a distance. Finally, experimental work was performed in microcosms to understand how conflicting social information influences dispersal in a ciliate (Tetrahymena thermophila). Although the initial treatment resulted in minimal effects on dispersal rates or dispersal syndromes, significant variance and mean effects of informant cell traits were identified. This suggests the existence of important physiological signals provided by informants, of which determinism remains to be explored. All these results underline the joint use of multiple social information, both local and distant, in individual movements such as dispersal. They highlight the importance of considering such information with the context in which it is studied, the individual who uses it, and its nature (What does it inform about? Is it reliable? Is it costly to exploit?).
