Townsend’s Big-eared Bat (Corynorhinus townsendii): A Technical Conservation Assessment Prepared for the USDA Forest Service, Rocky Mountain Region, Species Conservation Project October 25, 2006 Jeffery C. Gruver1 and Douglas A. Keinath2 with life cycle model by Dave McDonald3 and Takeshi Ise3 1Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada 2Wyoming Natural Diversity Database, Old Biochemistry Bldg, University of Wyoming, Laramie, WY 82070 3Department of Zoology and Physiology, University of Wyoming, P.O. Box 3166, Laramie, WY 82071 Peer Review Administered by Society for Conservation Biology Gruver, J.C. and D.A. Keinath (2006, October 25). Townsend’s Big-eared Bat (Corynorhinus townsendii): a technical conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http:// www.fs.fed.us/r2/projects/scp/assessments/townsendsbigearedbat.pdf [date of access]. ACKNOWLEDGMENTS The authors would like to acknowledge the modeling expertise of Dr. Dave McDonald and Takeshi Ise, who constructed the life-cycle analysis. Additional thanks are extended to the staff of the Wyoming Natural Diversity Database for technical assistance with GIS and general support. Finally, we extend sincere thanks to Gary Patton for his editorial guidance and patience. AUTHORS’ BIOGRAPHIES Jeff Gruver, formerly with the Wyoming Natural Diversity Database, is currently a Ph.D. candidate in the Biological Sciences program at the University of Calgary where he is investigating the physiological ecology of bats in northern arid climates. He has been involved in bat research for over 8 years in the Pacific Northwest, the Rocky Mountains, and the Badlands of southern Alberta. He earned a B.S. in Economics (1993) from Penn State University and an M.S. in Zoology and Physiology from the University of Wyoming (2002). Doug Keinath is the Zoology Program Manager for the Wyoming Natural Diversity Database, a research unit of the University of Wyoming and a member of the Natural Heritage Network. He has been researching Wyoming’s wildlife for the past 8 years and has over 10 years experience in conducting technical and policy analyses for resource management professionals. His broader scope of research focuses on bat and small mammal ecology, survey, and monitoring at the population and landscape scales, and more recently on the spatially explicit predictive distribution modeling of sensitive elements (i.e., animals, plants, communities) of the Rocky Mountain West. Mr. Keinath earned a B.S. in Interdisciplinary Engineering (1993; magna cum laude) and a B.S. in Natural Resource Management (1993; with Distinction) from the University of Michigan and an M.S. in Wildlife Biology from the University of Wyoming (2000). COVER ILLUSTRATION CREDIT Townsend’s big-eared bat (Corynorhinus townsendii) in flight (© R. Smith). Original artwork by R. Smith. Used with permission. 2 3 SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF TOWNSEND’S BIG-EARED BAT There is general concurrence among bat biologists that there has been a downward trend in abundance of Townsend’s big-eared bat (Corynorhinus townsendii) in the western portion of its range over the past half-century. Western populations, which are the focus of this assessment, do not enjoy federal legislation protecting either them or their habitat. Various regional, state, and private organizations consider Townsend’s big-eared bat to be vulnerable to extirpation due to: 1) apparent rarity and long-term decline in numbers; 2) narrow roosting requirements; 3) loss, modification, and disturbance of roosting habitat; and 4) general lack of information regarding the species. The likelihood of long-term persistence of Townsend’s big-eared bat in Region 2 and elsewhere can be enhanced by actions that address the primary threats to the species (listed below). Though we summarize the threats below in order of priority, it should be recognized that the best results will come from concurrently addressing these threats when crafting and implementing management plans. v Loss, modification, and disturbance of roosting habitat resulting from: ² Uninformed closure of abandoned mines: This is probably the most egregious act regularly performed by management agencies with respect to cavernicolous species of bats in general and Townsend’s big-eared bat specifically. At a minimum, closure of historic or abandoned mines eliminates potential roosting habitat for Townsend’s big-eared bat. In the worst case scenario, bats using a mine when it is closed have little chance of escape, resulting in both loss of habitat and direct loss of bats. ² Recreation: Human activity at roosts, particularly recreational exploration of caves and mine interiors, may lead to abandonment of the roost or unnecessary expenditure of crucial energy reserves. Like other bats, Townsend’s big-eared bat is particularly sensitive to variations in survival and reproductive output. Therefore, human activity in and near roosts must be curbed, especially during reproductive and hibernal periods. ² Renewed mining at historical sites: An increase in renewed mining can directly impact Townsend’s big-eared bats using abandoned mines in two ways: ³ by disturbing and displacing bats that may have been using a mine ³ by eliminating potential roosting habitat. Furthermore, renewed mining can liberate heavy metals and other toxic materials, leading to contaminated water impoundments. In either case, with its close association to abandoned mines and reliance on open water for drinking, Townsend’s big-eared bat may be more susceptible to ingestion of toxins following renewed mining at historical sites. v Loss, modification, and disturbance of foraging habitat resulting from: ² Elimination of forest canopy: Although Townsend’s big-eared bat forages in a variety of habitat types, its flight and echolocation style makes it well suited to forage among the canopies and along the edges of mature forested stands. This species typically does not use large clear-cuts or regenerating stands in early seral stages. ² Elimination or alteration of wetland habitat: Forest wetlands represent abundant sources of insect prey and fresh water for drinking. Activities that reduce the productivity of wetlands likely impact local populations of Townsend’s big-eared bat by reducing the quality of important foraging and drinking sites. Activities that alter the surface and subsurface hydrology of wetlands, including draining, stream diversion, and removal of shrub and overstory vegetation (e.g., through logging or grazing), ultimately reduce the value of wetlands to this species. As well, activities that increase sediment loads into wetlands (e.g., logging, grazing, road construction, mining) likely alter wetland soil and water chemistry and thus have potential to decrease the value of the wetland to Townsend’s big-eared bats. ² Conversion of native shrub and grasslands to urban or agricultural uses: Encroachment of urban development and agriculture into areas of native vegetation likely alters the composition and abundance of insect prey in an area, and may affect the ability of Townsend’s big-eared bat to find adequate prey. Encroachment may also disturb roosts by increasing the rate of human visitation, and increasing predation pressure from cats and other generalist predators associated with human settlement. 2 3 v Exposure to environmental toxins: Pesticides and heavy metals, if ingested by bats, can cause death or reduce reproductive ability. Pesticide application can indirectly affect bats via reduction of insect prey. Accumulation of pesticides and their residues in fat and brain tissue of bats may represent under-appreciated sources of mortality and loss of reproductive output. In addition, when bats drink from water impoundments produced by industrial or mining activities, they risk ingesting toxins and heavy metals, which may result in mortality of the bats. To insure the long-term persistence of Townsend’s big-eared bat in Region 2, the following conservation elements should be employed to address the noted threats, as discussed in the body of this assessment: v Institution of long-term education program: As with other species of bats, Townsend’s big-eared bat is often the victim of accidental or deliberate destruction, both to individual colonies and to their habitat. In part, this may result from commonly held misconceptions about bats and the lack of understanding by the public of the benefits that bats provide. Therefore, conveying the positive benefits of bats and dispelling baseless myths about them form the base for a strong management-oriented conservation program for this species v Protection of known roosting sites: Townsend’s big-eared bats are extremely sensitive to disturbance at roosts sites, particularly during the reproductive season and during hibernation. Disturbances during these times likely contribute to reduced reproductive output. Populations are especially susceptible to variations in survival and reproductive output. Therefore, human activity in and near roosts must be minimized or eliminated, especially during reproductive and hibernal periods. v Assessment of patterns of roost use and movement: Townsend’s big-eared bat is often assumed to exhibit a high degree of roost-site fidelity. Although certain types of colonies may show high fidelity to roosts (e.g., maternity colonies in caves), others may not (e.g., hibernation colonies in mines). A better understanding of patterns of roost use and fidelity is necessary to adequately