My PhD is part of a project on the host-parasite interactions in collaboration with Prof. Peter Vogel, Raphaël Arlettaz and Philippe Christe. We are interested on two sympatric species of bats the greater and lesser mouse-eared bat (Myotis myoti and Myotis blythii) and their ectoparasite, a mite (Spinturnix myoti, Acarina, Mesostigmata). Despite their coexistence in nursery roots, the two sibling species have an interspecific difference in the prevalence of this mite. So, we would like to understand which factors influence this pattern. We are studying simultaneously different aspects by combining observations and experiments on both free-ranging and captive bats. We are mainly looking at the life-history traits of both host and parasites, the host immune system, the host specificity, the energetic and fitness costs induced by the parasite and the evolutionary history of this host-parasite interactions.