Colonization and extinction events play a major role in influencing long-term population dynamics, particularly in fragmented landscapes. Nevertheless, empirical knowledge on which factors drive these processes is still lacking for many mammals, likely due to difficulties in conducting long-term large-scale field studies. To determine which landscape features affect local colonization and extinction in Muscardinus avellanarius - a species highly sensitive to human landscape modifications - we collected detection/non-detection data in highly fragmented landscapes scattered through central Italy during a 7-year large-scale (≈11000 km²) study. We fitted multi-season occupancy models to our data; the results showed that both local colonization and extinction processes were driven by the level of connectivity in the landscape surrounding a patch. Specifically, the colonization probability of a patch increased with the number of patches within 1 km: the higher the number of surrounding patches, the higher the probability of colonization. Similarly, the extinction probability was positively affected by the mean edge distance to other patches within 1 km: the higher the mean edge distance - that is, surrounding patches at greater distance - the higher the probability of extinction of the local population. Our findings provide empirical evidence to support management actions aimed at conserving the hazel dormouse in areas where the populations are declining or threatened by habitat loss and fragmentation.