The interindividual variation in behavioural traits (i.e. personality) is the subject of increasing attention in ecological studies. While personality is likely to be involved in several evolutionary and ecosystem processes, few studies have investigated its importance in habitat selection and alimentary niche use. For several years, the conceptual framework of the ecological niche has been studied at the individual level and is referred to as individual specialisation. My research proposes to explore the role of interindividual behavioural variation in niche differentiation, in several dimensions such as temporal, spatial, alimentary or social axes. The behavioural decisions are likely to reduce intraspecific competition, partitioning the individual niche at fine scale. This PhD project aims to (1) measure space use at individual level (i.e. spatial and temporal activity, micro-habitat selection, social environment and population density) in an natural rodent population of Eastern Chipmunk, whose behavioural phenotypes have been studied for many years, in the Mont Sutton (Québec). (2) Investigate the link between this habitat selection and the dietary specialisation of individuals. (3) Evaluate the consequences on life history traits using the long-term monitoring of this population. This project would provide important insights into ecological and evolutionary implications of the interindividual variation in behaviours linked with both habitat selection and niche specialisation.