BIENNIAL WINTER SURVEY FOR INDIANA BATS (MYOTIS SODALIS)
IN HIBERNACULA OF INDIANA

In 1980, as part of his Ph.D. research, ESI’s Principal Scientist, Dr. Virgil Brack, Jr. began a biennial census of caves in Indiana used as hibernacula by the endangered Indiana bat. By 2003, over 2 million hibernating bats of 7 species had been observed and counted. Three hundred twenty-one visits were made and 77 Indiana caves were investigated. This comprehensive project is one of the most significant and longest ongoing Indiana bat research projects in the U.S.

In addition to long-term monitoring of known bat populations, the project involves searches for new hibernacula, temperature monitoring, and provides a setting for research and development of new survey techniques and equipment. Peer-reviewed publications, management prescriptions, and cave protection agreements are just a few benefits to the species resulting from the research and the data collected during surveys play a crucial role in species recovery.

The biennial survey effort is a continuing partnership among ESI, the Indiana Department of Natural Resources, and the U.S. Fish & Wildlife Service. Many additional agencies, organizations, and individuals have provided time, resources, and assistance including Indiana Karst Conservancy, The Nature Conservancy, U.S. Forest Service, local landowners, university researchers, and caving organizations. 

As of 2011, 30 plus years of survey data show that populations of Indiana bats hibernating in Indiana have increased from a low of about 99,000 bats to a high of  about 240,000 bats – half of all individuals known for the species. The surveys have also shown that bats hibernate over a continuum of temperatures, with use skewed to between 5 and 10°C (rather than 3°C sometimes claimed as optimum) and as populations within hibernacula increased so too has the spread of temperatures and portion of the cave used. The best hibernacula cool without getting too cold and provide areas or relative thermal stability with temperatures between 5 and 10°C. These data clarify management needs for hibernacula of this and other species.  

An unfortunate part of the past 2 surveys has been to look for signs of spread of a disease known as white-nose syndrome, which is killing millions of hibernating bats in eastern and midwestern states. Unfortunately, the disease was found in several hibernacula during 2011. 

 

Return to: KARST, CAVES AND UNDERGROUND VOIDS PROJECTS