Now researchers at Tulane University, with collaborators at Stanford University and the Centers for Disease Control and Prevention, may have found a reason. "This completely changes our understanding of how mammalian immune systems can be organized and raises exciting new questions about why bats have been so evolutionarily successful and how they respond to viruses." While researchers have traditionally focused on bats' innate immune systems, Frank said this study highlights the importance of looking more closely at their adaptive immune system — the part responsible for producing antibodies. Bats are critical pollinators, seed dispersers and natural pest controllers but also serve as natural hosts for many viruses, Frank said. Every time we study a species that has evolved differently, we have the opportunity to discover something entirely new."