The Indiana bat, Myotis sodalis, is listed as an endangered species by the U.S. Fish and Wildlife Services. Like many of the bats that make Tennessee their home, Indiana bats spend the winter in caves across middle Tennessee. Larger winter populations can be found in east Tennessee. During the spring, Indiana bat, primarily the females, make migrations from these caves to their summer maternity grounds.
We initiated a migration telemetry study several years ago in an effort to identify maternity trees for this species within Tennessee. In 2013, we were able to identify several maternity trees in middle Tennessee for the first time. Identifying these trees is very important because they only use dead or dying trees that have sloughing bark. Indiana bats crawl under this bark, forming colonies from just a few individuals to several hundred and the pups are born and reared under this same bark. This type of narrow habitat preference is one of many reasons why this species is endangered in the United States. Identifying maternity trees is important to aiding with conservation efforts of this species.
Once an Indiana bat is captured, transmitters are attached prior to migration and last approximately 21 days. Shortly after the transmitter fails, it falls off the bat. Migrations to the maternity grounds rarely last longer than 21 days and normally only take approximately 7-10 days. Migration distances of 50 to almost 290 miles have been observed during this study.
We have been able to identify maternity roosts in 5 states, including states south of Tennessee. Maternity colonies located south are unique because it has been believed this species only migrates north from winter sites to summer sites.
Following the location of a maternity colony, Wildlife Diversity personnel continue to monitor these colonies with nightly emergence counts, mist netting for attachment of new transmitters and continued telemetry, and analysis of vegetation surrounding the maternity trees and across the landscape. During the project in 2013, we identified 11 primary or secondary roost trees in middle Tennessee.
The largest colony had 56 bats emerge during a single nightly emergence count. Late summer telemetry at one colony allowed for the identification of a foraging area a short distance away from the roost tree. Roost trees were found in a variety of habitats on the landscape and include ridge tops, edges of fields and forested areas.