Fungal diseases are a major threat to wildlife, sometimes resulting in significant population declines or even causing the extirpation of populations or species. White-nose syndrome, caused by the cold-loving fungus Pseudogymnoascus destructans, has become a major cause of death for hibernating bats in North America. European bats survive when infected by the same fungus during hibernation. What are the reasons for such a contrast in outcomes? A scientist team led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) has now analysed the humoral innate immune defence of European greater mouse-eared bats to the fungus.