Assessing the use of rivers as migratory corridors for temperate bats

Abstract

Investigating landscape-level movement patterns of migratory animals can be challenging, but this is a major component of some animal's life history and behavior. In particular, bat migration has been difficult to characterize, yet recent research on bat migratory ecology has made major advances. It has been largely accepted that rivers and other linear landscape features may be important migratory corridors for bats during both long-and short-distance migrations. We assessed the migratory behavior of multiple temperate bat species along the Missouri River, a major river corridor in North Dakota, during March through October of 2016-2017. Bat detectors with paired microphones were deployed and oriented parallel to the riverbank. This configuration permitted detection of directional passes of bats, approximately 10-20 m above the microphones and 40 m into the river, which were used as an estimate of migratory behavior. We found the effects of season and species explained less than 2% of the variation of directional passes, indicating an absence of season-specific movement patterns along the studied river corridor. Although our study only assessed a portion of a major river corridor, the results suggest that migratory movements of bats along rivers may not be as straightforward as once thought, highlighting the need for future studies investigating the fine-scaled movement patterns of bats during migration.