Status of Tadarida brasiliensis cynocephala, Le Conte's free-tailed bat, in Tennessee and surrounding states.
It has been 20 years since David H. Snyder of Austin Peay State University discovered the first Brazilian Free-tailed bat (BFT), Tadarida brasiliensis, in Clarksville, Montgomery County, Tennessee (Snyder, 1993). This species has the most extensive range of any bat species and is one of the most abundant mammals in the United States (Wilkins, 1989; Nabte et al., 2011). It is known to congregate in large numbers (>1 million) throughout its range at only a few roost sites, some which are typically human-made structures (particularly the southeastern subspecies cynocephala), and most notably in the southcentral United States (O'Shea et al., 2003) as, for example, the Congress Bridge site in Austin, Texas.
The subspecies that occurs in the southeastern United States (T. b. cynocephala) is referred to as Le Conte's Free-tailed bat (1) and is often distinguished from other subspecies by its geographic location and behavior (Russell and McCracken, 2006). The subspecies does not migrate and is considered locally common (Harvey et al., 2011).
Snyder (1993) mentioned that the biological significance of his discovery of the species in Montgomery County, Tennessee, was unknown and that he did not know if the bat was a vagrant or a pioneer. Authors of two articles mentioned in his manuscript (Lee and Marsh, 1978; Saugey et al., 1988) suggested that the BFT populations they observed were expanding their range into Arkansas and North Carolina. The range expansion into locations near Tennessee might explain the two occurrences in Montgomery County and should be considered as dispersal of young or from large roost colonies. With regard for Snyder's original discovery and publication, we reexamine the status of the Brazilian Free-tailed bat in Tennessee and surrounding states.
In December of 2007 the authors found a BFT in the Dunn Center on the Austin Peay State University Campus. The bat was first observed 3 December on the ceiling of the 2nd floor hallway and was captured the next morning using a handmade "soft" net. The individual was a healthy juvenile male with a dark brown coat (Hershey-colored). It had the following measurements: right forearm, 41 mm, left forearm, 40 mm; right wing, 130 mm, left wing, 134 mm; and ear length, 15 mm. Based on published information, we believe this specimen to be the subspecies T. b. cynocephala (Russell and McCracken, 2006). Digital photographs were taken of the individual (Fig. 1) before it was released on a tree at Dunbar Cave State Natural Area. The first BFT known to be captured alive in Tennessee was the [19 March] 1991 record (Snyder, 1993). The next closest occurrence of an individual was in Murray, Calloway County, Kentucky during 1971 (Kentucky Bat Working Group).
The collection of this healthy young male raises two alternative questions: Is this recent finding a random occurrence? or Are more investigative surveys needed on the status of the BFT's range in Tennessee and the southeast region?
Materials and Methods
A variety of techniques was used to collect data on the past and present occurrence of the BFT in the Southeast. A review of current literature on its range and distribution suggests that little is known concerning this species in the southeast. We used published data to identify areas the species has previously colonized and areas known to contain established populations. A review of historical data for the species obtained from surrounding area museums, universities, bat working groups, as well as state and federal agencies, assisted in defining the suggested range of distribution for the southeast. We also contacted individuals from universities, state and federal agencies, and bat working groups in the surrounding states for access to any records of the species. Other professionals who regularly come into contact with bats were also asked about observations of the species. We requested voucher specimens, site records, or photographs to ensure proper identification of each individual specimen.
All data collected--including historical records, literature sources, personal communications, and voucher specimens or photographs--were placed on a geographic information systems (GIS) map. The map contained point data, county data, and range data. The geo-database was constructed to contain all the information that was provided for each locality, such as latitude and longitude, sex, health status, and band number (if banded). The GIS map and metadata enabled us to review the species' distribution, known dispersal, and population status to compare the present published ranges with the range constructed by our data.
The published distribution for the BFT is displayed in two GIS-generated maps. The first map (Fig. 2) identifies the species' range that NatureServe (NS) uses for its website database (NatureServe, 2011) without regard to subspecies. The second map (Fig. 3) shows the BFT range that the United States Geological Survey (USGS) uses for its GAP habitat analysis program (USGS, 2011), again without regard to subspecies. The third map (Fig. 4) displays both ranges from NS and USGS, without regard to subspecies. On each figure the data collected for this project are represented by the purple and blue county shadings. The dataset (Table 1) contains date of observation, county and state of occurrence, status, and source of information.
Table 1. Metadata and record data for county distribution of Tadarida brasiliensis cynocephala in the Southeast region. Year County State Status Dataset Provider 1963 Jackson Alabama Vagrant AL website 1966 Tuscaloosa Alabama Vagrant AL website 2008 or Talladega Alabama Colony Ches Smith 2009 2003 Coweta Georgia Colony Laura Finn 2012 Clayton Georgia Colony Jim Ozier n/a Clarke Georgia Single Menzel, Chapman, Ford, Menzel and Laerm n/a Hall Georgia Colony Laura Finn n/a Merriweather Georgia Colony Laura Finn 1971 Calloway Kentucky Vagrant KYBWG 2010 Choctaw Mississippi Colony David Richardson 2011-2012 Oktibbeha Mississippi Colony David Richardson, Darren Miller 1958 Scioto Ohio Vagrant Smith and Goodpaster 2003 McCormick South Vagrant Menzel, Carolina Menzel, Ford, Edwards, Sheffield, Kilgo, and Bunch 2003 Newberry South Colony Menzel, Carolina Menzel, Ford, Edwards, Sheffield, Kilgo, and Bunch n/a Pickens South Colony Mary Bunch Carolina n/a Greenville South Colony Mary Bunch Carolina 1993 Montgomery Tennessee Vagrant David Snyder 2007 Montgomery Tennessee Vagrant Andrew N. Barrass and R. Seth McCormick Year Located 1963 Alabama Department of Conservation and Natural Resources 1966 Alabama Department of Conservation and Natural Resources 2008 or Auburn 2009 University 2003 Fly by Night 2012 Georgia Dept. of Nature Resources n/a Collaborative paper n/a Fly by Night n/a Fly by Night 1971 Kentucky Bat Working Group 2010 USFWS 2011-2012 USFWS, Southern Environment Research 1958 Pennsylvania State University 2003 Collaborative paper 2003 Collaborative paper n/a SC Natural Resources n/a SC Natural Resources 1993 Austin Peay State University 2007 Austin Peay State University
The data collected during this study included historical data (>20 years), single individual occurrences, and recently discovered colonies within newly identified counties throughout the southeastern United States. Most of the single locality data were reported by biologists while surveying for other bat species, e.g., data from Ohio, Alabama, South Carolina, Tennessee (2), and Kentucky (Smith and Goodpaster, 1960; Barbour and Davis, 1969; Ches Smith, pers.com., Mary Bunch, pers.com.). The two different range maps (Figs. 2 and 3) provided by NS and USGS confirm that there are some discrepancies when defining an appropriate range for BFT. NatureServe indicates that the BFT has a more northerly extent, expanding into some of the Mid-south states (southern Tennessee, northern Alabama, northern Georgia, and northern Mississippi). The United States Geological Survey suggested the BFT range extends along the coastal plain, including North Carolina and South Carolina, and midway through other coastal southern states, but not extending into Tennessee. Our records indicate colonies for the upland region of South Carolina. Both ranges suggested by USGS and NS agree that the BFT is found along the coastal plain and midway through the southern states. When evaluating the dataset from the two published ranges for counties that did not overlap, we included those counties in the combined Austin Peay GIS map (Fig. 4). All counties with new records were located north of the USGS range (Fig. 3). The vagrant individuals data collected outside the USGS range map (Fig. 3) are mostly from historic collections (1938, 1953, and 1958, 1966-1968, 1990-1998). The NatureServe data may have included these collections in its range map data, indicating that the county records collected (Fig. 2) were included in NS range maps. The county records indicated in blue are newly established colonies found within the last six years and are not associated with any older records. Some of these newly reviewed records obtained from our sources indicate colonies are included in the NS range information but some are also found outside of both ranges.
The sporadic pattern that our dataset displays suggests a number of different conclusions. The BFT is losing its roost sites (old buildings) throughout the southeastern United States (David Saugey, pers.com.). The species is known to colonize man-made structures, unlike the other species of bats in the southeast that utilize caves or large trees, and the other western subspecies (T.b. mexicana) which prefer caves (Barbour and Davis, 1969). These urban roost sites are likely to be disturbed or destroyed by human activity, forcing colonies to disperse, move elsewhere, and possibly extend the range (David Saugey, pers.com.). The exploration or searching within urban areas by the BFT and the disturbance of new roost sites could force the BFT to extend its established range (colony sites) into novel areas (see Table 1). This urban expansion phenomenon could explain the sporadic movement or distribution observed with new records in the southeast. Further dispersion of individuals could occur into new areas. Expansion of the subspecies could occur as vagrancy or as the occurrence of new colonies, and these may be observed as survey findings of individuals in mixed colonies, e.g., with big brown bats, Eptesicus fuscus (David Richardson and Ches Smith, pers.com.). The BFT is known for its extensive range and, if disturbed, for its propensity to relocate easily to another area, e.g., Tennessee, Ohio, and Kentucky (Kentucky Bat Working Group, 2010; O'Shea et al., 2003; Smith and Goodpaster, 1960; Snyder, 1993). The most likely limiting factor for this species is its inability to survive cold winters, restricting its dispersal patterns into more north latitudes, as evidenced by only observing one or two individuals in our records (Laura Finn, pers.com.). Our data suggest that the range for the BFT species could be extended northward, and the range of this bat species should be further reviewed as a part of continuing bat surveys. As an example, acoustic bat surveys currently incorporated as part of the White-nose Syndrome state surveys could be utilized to identify new colonies or individuals in mixed species feeding groups.
Another range expansion possibility suggested by our data is that bat field surveys are not searching in the right habitat for this species. Most bat surveys explore natural environments (caves, forests, etc.) and may overlook species that use urban areas to roost or feed. As urban settings are changed or destroyed, this species may decline or more widely disperse. Determining if the sporadic movements of the BFT are caused by human disturbance or from normal range expansion (e.g., post-natal male dispersal behavior) is paramount to understanding how this species survives. Note that both the Snyder specimen and our specimen were young males. Also, the status of the BFT must be more vigorously examined in terms of the recent data, site records, location of colonies, and the status of those colonies. If human actions are extirpating BFT bats by excluding colonies, we must also determine where the bats may be safely relocated (e.g., large bat houses, old barns) by professional, permitted biologists.
We thank the following individuals for their willingness to share information on this bat species: M. Bunch (SC Natural Resources), L. Finn (Fly by Night), D. Miller (Southern Environment Research), J. Ozier (Georgia Dept. of Natural Resources), D. Richardson (USFWS), J. D. Saugey (USFS-retired), C. Smith (Auburn University), and all other colleagues who shared their experiences with this species. We also thank A. F. Scott (Austin Peay State University) for reviewing this paper and providing suggested improvements. We also wish to thank anonymous reviewers for their comments and suggested improvements to the manuscript. This project was supported by The Center of Excellence for Field Biology (APSU).
Barbour, R. W., and W. H. Davis. 1969. Brazilian Free-tailed bat. P. 197 in Bats of America. The University Press of Kentucky, Lexington, Kentucky.
Harvey, M. J., J. S. Altenbach, and T. L. Best. 2011. Brazilian Free-tailed bat. P. 116 in Bats of the United States and Canada. The John Hopkins University Press, Baltimore, Maryland.
Kentucky Bat Working Group. Brazilian Free-tailed bat (Tadarida brasiliensis). http://www.biology.eku.edu/bats/brazilianfreetailedbat.html. Accessed 23 August 2011.
Lee, D. S., and C. Marsh. 1978. Range expansion of the Brazilian Free-tailed bat into North Carolina. American Midland Nationalist 100: 240-241.
Menzel, M. A., B. R. Chapman, W. M. Ford, J. M. Menzel, and J. Laerm. 2000. A review of the distribution and roosting ecology of bats in Georgia. Georgia Journal of Science 58: 143-179.
Menzel, J. M., M. A. Menzel, W. M. Ford, J. W. Edwards, S. R. Sheffield, J. C. Kilgo, and M. S. Bunch. 2003. The distribution of the bats of South Carolina. Southeastern Naturalist 2: 121-152.
Nabte, M. J., A. Andrade, A. Monjeau, J. L. Hernandez, D. Vaquero, and S. L. Saba. 2011. Mammalia, Chiroptera, Molossidae, Tadarida brasiliensis I. Geoffroy, 1824: distribution extension. Check List and Authors 7: 142-143.
NatureServe. 2011. The distribution of Brazilian Free-tailed bat. Accessed 25 August 2011. http://www.natureserve.org/explorer/servlet/NatureServe?searchSpeciesUid=ELEMENT_GLOBAL.2.102529.
O'Shea, T. J., M. A. Bogan, and L. E. Ellison. 2003. Monitoring trend in bat populations of the United States and Territories: Status of the Science and Recommendations for the Future. Wildlife Society Bulletin 31: 16-29.
Owens, R. D., R. K. Chesser, and D. C. Carter. 1990. The systematic status of Tadarida brasiliensis cynocephala and Antillean members of the Tadarida brasiliensis group, with comments on the generic name Rhizomops legendre. The Museum Texas Tech University (Occasional Papers No. 133).
Russell, A. L., and G. F. Mccracken. 2006. Population genetic structuring of very large populations: the Brazilian Free-tailed bat (Tadarida brasiliensis). Pp. 227-247 in Functional and Evolutionary Ecology of Bats (Z. Akbar, G. F. McCracken, and T. H. Kunz, eds.). Oxford University Press, New York.
Saugey, D. A., G. A. Heidt, D. R. Heath, T. W. Steward, D. R. England, and V. R. McDaniel. 1988. Distribution and status of the Brazilian Free-tailed bat (Tadarida brasiliensis cynocephala) in Arkansas. Proceedings of the Arkansas Academy of Science 42: 79-80.
Smith, E., and W. Goodpaster. 1960. A Free-tailed bat found in Ohio. Journal of Mammalogy 41: 117.
Snyder, D. H. 1993. First record of the Brazilian Free-tailed bat (Tadarida brasiliensis) from Tennessee. Journal of the Tennessee Academy of Science 68: 63-64.
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Manuscript received 24 April 2012: manuscript accepted 18 October 2012.
(1.) We chose to use the discussion by Owen (1990) that reviews the taxonomic nomenclature for the BFT and gives its subspecies designation as Le Conte's free-tailed bat, 1831. Further. Wilkins (1989) describes the subspecies identity as T. b. cynocephala.
(2.) Regarding specimens in east Tennessee, we contacted Dr. Gary McCracken, University of Tennessee, Knoxville. He suggested that specimens were collected and submitted for rabies testing to the College of Veterinary Medicine University of Tennessee. Dr. John C. New, Jr., Director of Public Health and Outreach Department, reviewed these records in association with Dr. Amy Turmelle and determined these records were BFT species but were from Treutlen County, Georgia.
Riley Seth McCormick and Andrew N. Barrass
The Center of Excellence for Field Biology. Austin Peay State University, Clarksville, TN 37040
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|Author:||McCormick, Riley Seth; Barrass, Andrew N.|
|Publication:||Journal of the Tennessee Academy of Science|
|Date:||Dec 1, 2012|
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