Premier Presentation: A bat’s perspective on the autumn movements of migratory noctuid moths

Movements of migratory noctuid moths represent a substantial threat to agriculture and are well documented in spring when crops are vulnerable.  However, surprisingly little is known about their return migrations in autumn in North America. These movements represent large spatial and temporal fluctuations in biomass, providing a valuable resource base for predators.  Those predator-prey interactions are often driven by continental-scale weather patterns and are difficult to study, but they may illuminate mechanisms driving migrations across trophic levels.  We tracked migrations of five species of agricultural pest noctuid moths over the 2010-2012 fall seasons as the moths traveled past a large colony of migratory Brazilian free-tailed bats (Tadarida brasiliensis) in central Texas.   Increases in moth abundance, mass of bats, and duration of bat activity outside of the cave were significantly correlated with passage of cold fronts over the study area and related increases in northerly wind.  Moth responses to weather patterns varied among species and seasons, but overall moth abundances were low in late summer and spiked after one or more cold front passages in September and October.  Molecular analysis of moth consumption by bats may reveal interesting insights into the system.  Weather-driven migration is at considerable risk from climate change, and bat and moth responses to that change may have significant impacts on agricultural systems and bat ecosystem services.