Predator-prey interaction reveals local effects of high-altitude insect migration

Authors: KRAUEL, JENNIFER - University Of Tennessee; BROWN, VERONICA - University Of Tennessee; Westbrook, John; MCCRACKEN, GARY - University Of Tennessee

Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2017
Publication Date: 2/21/2018
Citation: Krauel, J.J., Brown, V., Westbrook, J.K., McCracken, G.F. 2018. Predator-prey interaction reveals local effects of high-altitude insect migration. Oecologia. 186:49-58.

Interpretive Summary: High-altitude nocturnal migrations of pest insects are responsible for considerable crop losses throughout the U.S., yet are difficult to study and poorly understood. Predator-prey interactions, specifically migratory moth consumption by high-flying bats, potentially reveal flows of migratory insects across the landscape. We examined patterns of insect species consumed by Brazilian free-tailed bats in southern Texas during autumn 2010-2012, using genetic analysis of bat fecal pellets. Bats consumed at least 22 different migratory insect species, including corn earworm moths and several other major crop pests. Cold front passages were associated with increased diversity of insect species in the bat diet. Moth species predominated in the bat diet, and the pattern of bat consumption of moth species matched that of moth species captured in pheromone traps. Our results suggest that the diet of bats represents a more effective method of tracking flux of migratory insects than traditional ground-based methods.

Technical Abstract: High-altitude nocturnal insect migrations represent significant pulses of resources, yet are difficult to study and poorly understood. Predator-prey interactions, specifically migratory moth consumption by high-flying bats, potentially reveal flows of migratory insects across a landscape. In North America, migratory moth pest species cover great distances over the Southern Great Plains and are responsible for considerable economic damage. Brazilian free-tailed bats, Tadarida brasiliensis, provide valuable crop protection by consuming these moths, but the extent of this important predator-prey relationship during migration has only been suggested. We examined patterns in the insect prey community of T. brasiliensis bats foraging during the 2010-2012 autumn seasons in southern Texas, using fecal diet analysis based on molecular sequencing of insect DNA. Bats consumed at least 8 orders of insect prey and at least 22 different migratory insect species, and the percent of identified species that were migrants increased over autumn in all 3 years. Prey included 44 species documented as agricultural or other pests. Diet richness and percent of migrants in the diet contributed weakly to mass gain in female bats. Prey community species richness increased the sampling day closest to cold front passage through the study area. Moths were dominant, and patterns in moth consumption matched those in pheromone traps. This study adds considerable detail to the previously documented consumption of insect pests and migratory moths by bats, and provides evidence that these insects are an important part of pre-migratory mass gain for T. brasiliensis in autumn. Our results suggest that the diet of bats represents a more effective method of tracking flux of migratory insects than traditional ground-based methods.