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.

Abstract. The federally endangered Indiana bat (Myotis sodalis) is a concern for development projects in nearly half of the United States. The species roosts and rears young under exfoliating bark of trees, which has put it at risk for incurring adverse impacts from most projects that require tree clearing throughout its summer range. Project proponents generally incorporate avoidance and minimization strategies into the planning process. These strategies, however, are not always compatible with project goals and objectives, and mitigation is often required to offset adverse impacts to the Indiana bat. BrandenBark™ is an artificial roost structure that mimics the natural roosting habitat of Indiana bats. To date, 69 BrandenBark™ structures have been installed in 7 states (IL, KY, LA, OH, PA, TN and WV). Of these, 59 (86%) structures have been used by 6 species of bats, including northern long-eared bats (proposed for federal listing) and little brown bats (under status review); however, the majority of use (85%) has been by maternity colonies of Indiana bats confirmed by radio telemetry, capture, or genetic analysis of guano. Of the structures used by Indiana bats at Fort Knox Military Installation (n=21) in north-central Kentucky, 120 emergence counts have been conducted with an average of 81.3±7.1 bats per roost. Although the roost area under BrandenBark™ is slightly warmer ( X = 24.6±7.2°C [SD]) than that of natural bark ( X = 23.1±6.5°C), the temperature difference between BrandenBark™ and ambient ( X = 2.1±2.7°C) is less variable than the temperature difference between natural bark and ambient ( X = 3.9±4.0°C), possibly indicating a more stable thermal environment. However, both roost types are warmer than corresponding ambient temperatures. BrandenBark™ provides instant long-lasting habitat commensurate with natural roosts, is easy to install and monitor, and does not require the purchase of additional land for placement when used as a mitigation option.

As bat (Chiroptera) populations continue to decline in the eastern United States due to threats such as white-nose syndrome and interactions with wind facilities, capturing already rare species such as the federally endangered Indiana bat Myotis sodalis to assess health and demographics has become increasingly difficult. Mist-nets are a standard method for capturing and studying bats, but bats have the ability to escape from or avoid mist-nets. Past research has shown that the use of acoustic lures may increase mist-net capture success. Using prerecorded Indiana bat social calls, we tested the effectiveness of acoustic lures on capture rates across 24 nights at 37 sites in summers 2013 and 2014 in north-central Kentucky. Each site consisted of two nets (treatment and control) placed >35 m apart: we placed an acoustic lure set 1 m in front of the treatment net, whereas the control net received no lure. At the species level, we recorded significantly more captures in treatment nets (n = 262) than in control nets [n = 128; t(36) = 5.08, P < 0.001]. However, although we found a trend toward higher Indiana bat captures, the only species' with significant positive responses were evening bats Nycticeius humeralis [t(15) = 6.25, P < 0.001] and eastern red bats Lasiurus borealis [t(36) = 3.60, P < 0.001]. Further study is required to determine whether modifications to lure settings or call types result in increased Indiana bat captures.

Managing landscapes for migratory species is challenging when migratory movement patterns are unknown. Researchers have collected sufficient data to understand summer and winter habitat use for federally listed bats, but movement between these habitats in spring and fall has not been studied extensively. In addition, movement within summer habitat is less well understood than the roosting requirements. To initiate a preliminary understanding of movement patterns of gray bats (Myotis grisescens), we gathered all occurrence and band recovery data available within the range of the species to model movement. By weighting the pathways using the population of winter and summer locations (i.e., cave roosts), we created a heat map demonstrating the likelihood of landscape use by gray bats including nightly foraging, migration, and roost switching. The resulting map highlighted 2 major areas of use during spring and fall migration: 3 high likelihood pathways through central Tennessee and 1 primary migration route between northern Arkansas and central Missouri, USA. Although future data could influence the accuracy of this map, the representation in its current form can be used to anticipate bat presence when considering industrial development such as wind turbine siting.

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