Eco-Immunology and Oxidative Stress of Neotropical Bats

Abstract

Despite its central importance to fight pathogens, the immune system imposes costs that may have to be traded against life-history traits such as longevity. Yet, it is unknown if a trade-off with longevity occurs in free-ranging mammals. Here, we asked if age and survival are connected to immune parameters in the greater sac-winged bat Saccopteryx bilineata. We measured total white blood cell (WBC) counts, bacterial killing ability (BKA) of the plasma and immunoglobulin G (IgG) concentration, and assessed the age and survival of each individual based on our long-term population study. We found individuals with high WBC counts to disappear from the population during subsequent years. In agreement with this observation, immune cell numbers decreased with increasing age of cohorts. Similarly, although not connected with age, individuals were no longer encountered in the colonies half a year after relatively high BKA were measured. IgG concentrations increased with age but were not connected with disappearance. Our study provides evidence for age-related changes in immunological parameters in a free-ranging mammal population and reveals that elevated levels of immune components may be associated with an increased mortality risk.