The species occurs at low altitudes in Mediterranean regions  and in limestone areas. It roosts almost exclusively in karst caves, though it can be spotted in other underground sites, such as mines. Its maternity roosts can reach 300 individuals and the species is known to share caves with other species (e.g. R. euryale and M. schreibersii).

 

R. blasius feeds almost exclusively on moths which they hunt while in flight. This is a largely sedentary species with summer and winter roosts usually located in neighbouring caves.