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In the June 30 issue of Southeastern Naturalist, USDA Forest Service (FS) and Tennessee Technological University (TTU) researchers provide the first descriptions of Indiana bat maternity habitat in the southeastern United States. Susan Loeb, project leader of the FS Southern Research Station (SRS) unit in Clemson, SC, co-authored the article with TTU's Dr. Michael Harvey and Eric Britzke.
One of the first bat species recognized as endangered by the US Fish and Wildlife Service, Indiana bats hibernate in caves in the winter, some 80 percent of them in nine caves in Kentucky, Indiana, and Missouri. Even though they mate in the fall, female Indiana bats do not become pregnant until spring, when they migrate to summer tree roost sites. Forming maternity colonies of 20 to 100 members under the loose bark of roost trees, the females each bear a single young.
Declines in Indiana bat populations, first noted in the 1960s, were initially attributed to human disturbance of the hibernation caves. When populations continued to decline even after caves were gated to block access, researchers began to study maternity roost locations as a possible factor in the decline of the species.
In 1999, researchers from Tennessee Technological University (TTU) found an Indiana bat roost in a dead eastern hemlock tree in the Nantahala National Forest in western North Carolina. This was the farthest south a maternity roost had ever been found, and the first report of Indiana bats using conifers for this purpose. Female bats usually move north from their winter caves, roosting in small forest tracts within the great farmlands of Missouri, Iowa, Indiana, and Illinois. The discovery of a roost so far outside the normal range started a new round of studies on the roosting behavior and range of the endangered forest bat.
Since 2000, Loeb and her assistants, in cooperation with TTU's Harvey and Britzke, have spent long summer nights netting and tracking Indiana bats in the Great Smoky Mountains National Park in eastern Tennessee. During the summers of 2000 and 2001, they captured and radio-tagged several male and female Indiana bats and found two large maternity roosts and several smaller ones. The Southeastern Naturalist article provides a detailed description of the newly found maternity sites and the surrounding habitat.
"Although male Indiana bats have been found roosting in pine snags during the summer," said Loeb, "this study describes the first use of conifers for maternity colonies. This is very exciting because it expands the kind of habitat this endangered species can potentially use to reproduce in."
Like other tree-roosting bats, female Indiana bats choose several alternatives to their primary roost. The study found that the primary roosts were generally located in trees that were taller than the surrounding forest, while alternative roost trees were usually shorter than the trees around them. "Research has shown that maternity roosts are often exposed to sunlight, and that increased temperature inside roosts can speed the development of the young," said Loeb. "Sun exposure may be particularly important for the roost we found in the Nantahala National Forest, since it was located at a much higher elevation than any previously reported for the species."
The researchers emphasized that, although the surrounding habitat and species of the maternity roost trees differed from that usually found for Indiana bats, the structure of the roost trees was essentially the same--dead or dying trees with shedding bark. "Finding maternity roosts far outside the known range and typical habitat of this species is important," said Loeb. "We need to continue to look for summer roosts in other areas of the Southeast previously considered outside the range of the Indiana bat."