Nine years of Indiana bat (Myotis sodalis) spring migration behavior

Abstract

The endangered Indiana bat (Myotis sodalis) congregates in large hibernation groups in winter and travels after spring emergence to form summer maternity colonies, but information on migration behavior in this species remains limited to mostly band recovery observations. We tracked female Indiana bats in spring migration toward summer grounds using aerial radiotelemetry. Adult female Indiana bats were radiotagged in spring from 2009 through 2017, with 15 individuals successfully tracked to summer grounds and an additional 11 bats located in summer grounds via aerial telemetry after migration was complete. This resulted in the location of 17 previously unknown summer grounds for female Indiana bats, including adding Georgia, Alabama, and Mississippi to the summer maternity range. Two of the colonies identified in this study were south of the previously known southernmost colony in Tennessee, expanding the summer maternity range for the species by 178 km. Time-stamped location fixes along the migration path provided information about nightly and overall distances traveled, duration of travel, migration speed, and weather-related influences on bat behavior. Bats traveled 164.6 ± 26.2 km (± SE) on average from hibernacula to summer grounds and were migrating for an average of 7.3 ± 1.4 calendar nights. Bats alternated between foraging and traveling throughout each night of their migration route. Nightly migration rate was 9.9 ± 0.8 km/h and bats were active on the landscape for an average of 6.1 ± 0.4 h/night. Lower nighttime temperatures and lower barometric pressure correlated with use of layover areas during a migration night. Understanding bat behavior during migration can provide pertinent information for land managers to consider in efforts to conserve potential migration corridors, foraging areas, and roosting habitats of species in decline.

Climatic drivers of (changes in) bat migration phenology at Bracken Cave (USA)

“…Baker, 1978; Davis et al., 1962; Petersons, 2004). Temperature, precipitation, pressure, wind conditions, and lunar illumination have all been suggested as likely migratory drivers (Dechmann et al., 2017; Pettit & O'Keefe, 2017; Roby et al., 2019; Smith & McWilliams, 2016). While perhaps all of these weather conditions may, to a certain degree, have a direct impact on (migratory) flight activity, the exact cues, drivers, and underlying mechanisms of seasonal bat migration have not been identified due to a lack of long‐term (i.e.…”

“…Further insights into rough spatiotemporal movement patterns have also been gained from museum specimens (Cryan, 2003), stable isotope analyses (Britzke et al., 2009; Lehnert et al., 2018), acoustics (Rydell et al., 2014; Smith & McWilliams, 2016), and genetic analyses (Russell & McCracken, 2006; Russell et al., 2005). Gaining detailed insights into the migratory behaviour of individuals or populations has, however, proven difficult due to the lack of appropriate monitoring tools or technology to either: (a) mark and track individual bats (Holland & Wikelski, 2009; Krauel & McCracken, 2013; Roby et al., 2019); or (b) study the spatiotemporal dynamics of entire populations. Many bat species are rather small (and light‐weight), limiting possibilities for long‐term tracking devices (Moussy et al., 2013; but see Weller et al., 2016).…”

Habitat suitability and connectivity modeling reveal priority areas for Indiana bat (Myotis sodalis) conservation in a complex habitat mosaic

“…Accordingly, in Illinois, many patches of M. sodalis habitat are isolated. The most influential landscape variables were typically at the 95-ha scale in our models, while 10.1 km is the median distance migrating M. sodalis travel before they stop in habitat to forage or roost (Roby et al 2019). Our results suggest that allocating resources close to hibernacula may yield the greatest return on investment; thus distance to hibernacula should be considered in studies on other hibernating bat species.…”

“…Bats are capable of traversing a matrix of suitable and unsuitable patches; however, they do require protective cover, foraging habitat, and roosting stops along migration routes. We used the median distance traveled by M. sodalis between foraging bouts during spring migration (Roby et al 2019) to define dispersal distance in CS26; if a patch was 10.1 km from another patch (based on Euclidean distance of the links), it was defined as 50% likely to be connected to another patch. Distances [ 10.1 km were assigned a lower probability of dispersal.…”

“…The Indiana bat (Myotis sodalis) is an insectivorous species listed as ''Endangered'' under the USA Endangered Species Act (ESA) and ''Near Threatened'' on the International Union for Conservation of Nature's Red List of Threatened Species. The species communally hibernates in caves and mines (Whitaker and Brack 2002) and migrates regionally in spring (Krauel et al 2018), traveling away from hibernacula to summer grounds, using stopover habitat to roost and forage along the way (Roby et al 2019). At summer grounds, females form large maternity colonies, usually under the bark of dead trees, and remain in the area, rearing young until migrating back to hibernacula in the fall (Guthrie 1933).…”