A team of scientists led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) investigated whether and how the immune response changes between pre-migration and migration seasons in the Nathusius pipistrelle bat. They confirmed that migratory bats favour the energetically ”cheaper” non-cellular (humoral) immunity during an immune challenge and selectively suppress cellular immune responses. Thereby, bats save energy much needed for their annual migration.