Townsend's Big-eared Bat - Corynorhinus townsendii
Very large ears (30 to 39 millimeters) joined across forehead are a prominent feature in Townsend's Big-eared Bat; the tragus is long and pointed. The dorsal hairs are brownish at the tips, contrasting a little or considerably with the lighter underfur; ventral hairs are dark brownish-gray in color with brown to cinnamon tips. The hairs on the toes do not project beyond the toenails. There are two large, fleshy lumps on the snout, the basis for one of its common names, "lump-nosed bat." Total length is 90 to 113 millimeters; forearm length is 39.0 to 47.6 millimeters; adult mass is 5.0 to 13.5 grams. The greatest length of the skull is 15.2 to 17.4 millimeters; the skull has 36 teeth (Handley 1959, Kunz and Martin 1982, Nagorsen and Brigham 1993).
Townsend's Big-eared Bat differs from other Montana bats by its combination of extremely long, brownish ears that are joined at the base, the prominent lumps on the nose, the absence of large, white spots in the pelage (as with the Spotted Bat) and a dorsal pelage that is darker at the tips than the base (opposite that of the Pallid Bat, which is also larger-bodied).
Western Hemisphere Range
Summary of Observations Submitted for Montana
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
Little information on movement is available for this species. Townsend's Big-eared Bat is present year-round in Montana, with summer or winter records from several localities (Hoffmann et al. 1969, Swenson and Shanks 1979, Hendricks 2000, Hendricks et al. 2000, Hendricks and Kampwerth 2001), but movements of individuals have not been reported or studied.
Habitat use in Montana has not been evaluated in detail, but seems to be similar to other localities in the western United States. Caves and abandoned mines are used for maternity roosts and hibernacula (Worthington 1991, Hendricks et al. 1996, Hendricks 2000, Hendricks et al. 2000, Foresman 2012, Hendricks and Kampwerth 2001); use of buildings in late summer has also been reported (Swenson and Shanks 1979). Habitats in the vicinity of roosts include Douglas-fir and lodgepole pine forests, ponderosa pine woodlands, Utah juniper-sagebrush scrub, and cottonwood bottomland. In hibernacula, ambient temperatures ranged from -1.0 to 8.0 degrees (30 to 46 when torpid Townsend's Big-eared Bats were present) (Hendricks and Kampwerth 2001). Temperatures at maternity roosts are poorly documented; the temperature was 12 degrees (54 in mid-July near a colony in an abandoned mine in Lake County), and 18 degrees (66 in August near a colony in a large and relatively open cave chamber in Lewis and Clark County). Most caves and mines in Montana appear to be too cool in summer for use as maternity roosts.
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at email@example.com
or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
- Dobkin, D. S. 1992. Neotropical migrant land birds in the Northern Rockies and Great Plains. USDA Forest Service, Northern Region. Publication No. R1-93-34. Missoula, MT.
- Foresman, K.R. 2001. The wild mammals of Montana. Special Publication No. 12. Lawrence, KS: The American Society of Mammalogists. 278 p.
- Hart, M.M., W.A. Williams, P.C. Thornton, K.P. McLaughlin, C.M. Tobalske, B.A. Maxell, D.P. Hendricks, C.R. Peterson, and R.L. Redmond. 1998. Montana atlas of terrestrial vertebrates. Montana Cooperative Wildlife Research Unit, University of Montana, Missoula, MT. 1302 p.
- Hutto, R.L. and J.S. Young. 1999. Habitat relationships of landbirds in the Northern Region, USDA Forest Service, Rocky Mountain Research Station RMRS-GTR-32. 72 p.
- Maxell, B.A. 2000. Management of Montana’s amphibians: a review of factors that may present a risk to population viability and accounts on the identification, distribution, taxonomy, habitat use, natural history, and the status and conservation of individual species. Report to U.S. Forest Service Region 1. Missoula, MT: Wildlife Biology Program, University of Montana. 161 p.
- Werner, J.K., B.A. Maxell, P. Hendricks, and D. Flath. 2004. Amphibians and reptiles of Montana. Missoula, MT: Mountain Press Publishing Company. 262 p.
- Commonly Associated with these Ecological Systems
Forest and Woodland Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
- Occasionally Associated with these Ecological Systems
Forest and Woodland Systems
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
Townsend's Big-eared Bat feeds on various nocturnal flying insects near the foliage of trees and shrubs, but appears to specialize primarily on small moths (Kunz and Martin 1982); other insects in the diet include lacewings, beetles, true flies, and wasps. There are reports of gleaning insects from foliage, but most are captured in the air, often near foliage. In a California study, individuals hunted primarily around the perimeter of trees, usually 10 to 30 meters off the ground, between mid-canopy and near the top of the canopy (Fellers and Pierson 2002). The diet and foraging behavior of Townsend's Big-eared Bat in Montana have not been reported or studied.
Females form maternity colonies during the spring and summer. Colonies are typically composed of 20 to 180 females, each giving birth to one pup after a gestation period of 55 to 100 days (Pearson et al. 1952, Genter personal observation). Pups are able to fly in 3 weeks and are weaned at 6 weeks. Both sexes congregate at cooler caverns (called swarming sites) in late summer/early fall.
Townsend's Big-eared Bat emerges from day roosts in coastal California and central Oregon within an hour after sunset (Dobkin et al. 1995, Fellers and Pierson 2002); limited information from Montana indicates a similar emergence time (P. Hendricks and J. Carlson personal observation). In Oregon, individuals moved up to 24 kilometers from hibernacula to foraging areas (Dobkin et al. 1995). In California, foraging individuals traveled less than 10.5 kilometers from primary day roosts and tended to forage in the same areas each night. The mean center of activity for females was 3.2 kilometers from the roost, and 1.3 kilometers for males; 41 to 88% of tagged bats returned to their roost each night. Individual bats used nine alternate roosts (Fellers and Pierson 2002).
Townsend's Big-eared Bat tends to hibernate singly, but does occur in clusters during winter in some areas (Schmidly 1991). It tends not to associate closely in day roosts and hibernacula with other species of bats, although individuals of other species may be present elsewhere in the roost (Handley 1959, Kunz and Martin 1982, Genter 1986, Choate and Anderson 1997, Kuenzi et al. 1999). In Montana, Townsend's Big-eared Bat has been found at summer and winter roosts in the presence of other bat species (Swenson and Shanks 1979, Worthington 1991, Hendricks et al. 2000, Hendricks and Kampwerth 2001), although it usually hibernates in the open and alone, rather than in clusters or wedged in cracks.
Crude population density in Oklahoma was estimated at one bat per hectare (Humphrey and Kunz 1976, Kunz and Martin 1982), about 3 to 4 times greater than that reported in California (Pearson et al. 1952). Natality rates for colonies of adult females typically exceed 90%, but may be as low as 35% (Kunz and Martin 1982, Fellers 2000); pre-weaning post-natal mortality of adults generally is 4 to 5%. Adult survivorship is relatively high (about 70 to 80% in females in California). Regional population increases in California may be dependent on the establishment of new nursery colonies (Pearson et al. 1952), since colony size has been reported to remain static year after year. Predation has been suggested as the primary limiting factor in Kansas and Oklahoma (Handley 1959), although lack of suitable roosting habitat seems more likely to limit population size in this region (Humphrey and Kunz 1976). Predators of Townsend's Big-eared Bat are poorly documented, but include the Black Rat and Eastern Woodrat (Clark et al. 1990, Fellers 2000), as well as the Black Ratsnake, Spotted Skunk, Domestic Cat, and Ringtail (Pierson et al. 1999); predators can significantly depress reproductive success in some maternity colonies. No demographic data or estimates of population size are available for any population in Montana, nor have any predators been documented.
No published studies are available on the reproductive biology of this species in Montana, and other documentation is very limited. Only five maternity colonies are known in Montana, with an estimated size in recent years of 25 to 100 adult females each. Lone adult females captured in early August in the Pryor Mountains were non-lactating (P. Hendricks and J. Carlson personal observation); flying juveniles appear in the same region sometime between late June and early September (Worthington 1991).
Based upon studies in other areas of the species' range mating begins in autumn and continues into winter. Ovulation and fertilization are delayed until late winter/early spring. Gestation lasts 2.0 to 3.5 months. A single young is born during a five week period, beginning mainly in late May in California, June in west Texas, and the second week of July in Washington (Pearson et al. 1952, Easterla 1973, Kunz and Martin 1982). Young can fly at 2.5 to 3.0 weeks, and are weaned by 6 weeks. In central California, summer colonies start to break up in August when the older young are just over 3 months old. Females become sexually mature their first summer; males are not sexually active until their second year. Young fly at 1 month of age and are weaned at 2 months. Most adult females breed every year. Maternity colonies are often smaller than 100 adult females, but up to 550 adult females are present in some (Easterla 1973, Humphrey and Kunz 1976, Pierson et al. 1991, Szewczak et al. 1998, Fellers 2000, Sherwin et al. 2000, Fellers and Pierson 2002). Males roost separately (apparently solitary) during this time. Maximum longevity is estimated to be about 16 to 17 years (Kunz and Martin 1982).
The response by Townsend's Big-eared Bats to human activities is largely undocumented in Montana. The maternity colony at Lewis and Clark Caverns has persisted for over a century, even though it is exposed daily to tour groups. In eastern Montana, numerous abandoned coal mines have been completely closed in recent decades, several of which were used as hibernacula; these mines are no longer accessible to bats. Abandoned mine reclamation has also been underway in western Montana during the same time. During the last decade, mine surveys prior to closure have been undertaken by land management agencies to determine the potential of abandoned mines as bat habitat. In some cases bat-friendly gates were installed at known Townsend's Big-eared Bat roosts, and the roosts have continued to be used after gate installation (Hendricks 1999, Hendricks and Kampwerth 2001). Some caves in the Pryor Mountains and Little Rocky Mountains with documented use by Townsend's Big-eared Bat are protected with bat-friendly gates (Worthington 1991, Hendricks et al. 2000). Abandoned mines should be surveyed for Townsend's Big-eared Bats or other bat species prior to any reclamation activity. Surveys should follow protocols in the conservation assessment and conservation strategy (Pierson et al. 1999). Installation of bat-friendly gates should be considered as a protective measure for all Townsend's Big-eared Bat roosts. Other land management activity (cave management, pesticide spraying, timber harvest, other vegetation conversion) at or near known roosts should also be conducted according to the best management practices outlined in the conservation assessment and strategy. Maternity roosts and hibernacula should be routinely monitored to establish population trends across the state. Undiscovered maternity colonies and hibernacula undoubtedly exist in Montana. All observations of Townsend's Big-eared Bat roosts should be reported to the appropriate land management agency, the Montana Natural Heritage Program, or the Montana Department of Fish, Wildlife and Parks.
- Literature Cited AboveLegend: View Online Publication
- Choate, J. R. and J. M. Anderson. 1997. Bats of Jewel Cave National Monument, South Dakota. Prairie Naturalist 29:39-47.
- Clark, B. K., B. S. Clark, and D. M. Leslie, Jr. 1990. Endangered Ozark big-eared bat eaten by eastern woodrat. Prairie Naturalist 22:273-274.
- Dobkin, D. S., R. D. Gettinger, and M. G. Gerdes. 1995. Springtime movements, roost use, and foraging activity of Townsend's big-eared bat (Plecotus townsendii) in central Oregon. Great Basin Naturalist 55:315-321.
- Easterla, D. A. 1973. Ecology of the 18 species of Chiroptera at Big Bend National Park, Texas. Part I and II. Northwest Missouri State University Studies 34:1-165.
- Fellers, G. M. 2000. Predation on Corynorhinus townsendii by Rattus rattus. Southwestern Naturalist 45:524-527
- Fellers, G. M. and E. D. Pierson. 2002. Habitat use and foraging behavior of Townsend's big-eared bat (Corynorhinus townsendii) in coastal California. Journal of Mammalogy 83:167-177.
- Foresman, K.R. 2012. Mammals of Montana. Second edition. Mountain Press Publishing, Missoula, Montana. 429 pp.
- Genter, D. L. 1986. Wintering bats of the upper Snake River plain: occurrence in lava-tube caves. Great Basin Naturalist 46(2):241-244.
- Handley, C. O., Jr. 1959. A revision of American bats of the genera Euderma and Plecotus. Proceedings of the U.S. National Museum 110:95-246.
- Hendricks, P. 2000. Preliminary bat inventory of caves and abandoned mines on BLM lands, Judith Mountains, Montana. Montana Natural Heritage Program, Helena, Montana. 21 pp.
- Hendricks, P. and D. Kampwerth. 2001. Roost environments for bats using abandoned mines in southwestern Montana : a preliminary assessment. Report to the U.S. Bureau of Land Management. Montana Natural Heritage Program, Helena, Montana. 19 pp.
- Hendricks, P., D. L. Genter, and S. Martinez. 2000. Bats of Azure Cave and the Little Rocky Mountains, Montana. Canadian Field-Naturalist 114 :89-97.
- Hendricks, P., K. A. Jurist, D. L. Genter and J. D. Reichel. 1996. Bats of the Kootenai National Forest, Montana. Unpublished report. Montana Natural Heritage Program, Helena, Montana. 99 pp.
- Hoffmann, R. S., D. L. Pattie and J. F. Bell. 1969. The distribution of some mammals in Montana. II. Bats. Journal of Mammalogy 50(4): 737-741.
- Humphrey, S. R. and T. H. Kunz. 1976. Ecology of a Pleistocene relict, the western big-eared Bat (Plecotus townsendii) in the southern Great Plains. Journal of Mammalogy 57(3):470-494.
- Kuenzi, A. J., G. T. Downard, and M. L. Morrison. 1999. Bat distribution and hibernacula use in west central Nevada. Great Basin Naturalist 59:213-220.
- Kunz, T. H. and R. A. Martin. 1982. Plecotus townsendii. Mammalian Species Number 175 :1-6.
- Nagorsen, D. W. and R. M. Brigham. 1993. Bats of British Columbia. Volume I. The Mammals of British Columbia. UBC Press, Vancouver. 164 pp.
- Pearson, O.P., M.R. Koford, and A.K. Pearson. 1952. Reproduction of the lump-nosed bat (Corynorhinus townsendii) in California. Journal of Mammalogy 33:273-320.
- Pierson, E. D., and 14 others. 1999. Species conservation assessment and strategy for Townsend's big-eared bat (Corynorhinus townsendii townsendii and Corynorhinus townsendii pallescens). Idaho Conservation Effort, Idaho Department of Fish and Game, Boise, Idaho. 68 pp.
- Pierson, E. D., W. E. Rainey, and D. M. Koontz. 1991. Bats and mines: experimental mitigation for Townsend's big-eared bat at the McLaughlin Mine in California. In: R.D. Comer et al. eds. Proceedings V: issues and technology in the management of impacted wildlife. pp. 31-44. Thorne Ecological Institute, April 8-10, Snowmass, Colorado.
- Schmidly, D. J. 1991. The bats of Texas. Texas A and M University Press, College Station. 188 pp.
- Sherwin, R. E., D. Stricklan, and D. S. Rogers. 2000. Roosting affinities of Townsend's big-eared bat (Corynorhinus townsendii) in northern Utah. Journal of Mammalogy 81:939-947.
- Swenson, J.E. and G.F. Shanks, Jr. 1979. Noteworthy records of bats from northeastern Montana. Montana. Journal of Mammalogy 60:650-652
- Szewczak, J. M., S. M. Szewczak, M. L. Morrison, and L. S. Hall. 1998. Bats of the White and Inyo mountains of California-Nevada. Great Basin Naturalist 58:66-75.
- Worthington, D. J. 1991. Abundance, distribution, and sexual segregation of bats in the Pryor Mountains of south central Montana. M.A. Thesis. University of Montana, Missoula, Montana. 41 pp.
- Additional ReferencesLegend: View Online Publication
Do you know of a citation we're missing?
- Adams, R.A. 2003. Bats of the Rocky Mountain West: natural history, ecology and conservation. University Press of Colorado: Boulder, CO. 289 pp.
- Albers, Mark., 1995, Draft Biological Assessment: Tongue River Basin Project. May 1995. In Tongue River Basin Project Draft Environmental Impact Statement. Appendix B. June 1995.
- Bogdanowicz, W., S. Kasper, and R. D. Owen. 1998. Phylogeny of plecotine bats: reevaluation of morphological and chromosomal data. Journal of Mammalogy 79:78-90.
- Butts, T. W. 1993. Azure Cave bat surveys, Little Rocky Mountains, Montana, September 1992 and March 1993. Unpublished report for Zortman Mining, Inc. 13 pp.
- Butts, Thomas W., Western Technology and Eng., Helena, MT., 1993, Continental Lime Indian Creek Mine, Townsend, MT. 1993 Life of Mine Wildlife Reconnaissance. June 1993. In Life-of-Mine Amendment. Continental Lime, Inc., Indian Creek Mine & Plant. Vol. 2. October 13, 1992.
- Clark, B. K., B. S. Clark, and D. M. Leslie, Jr. 1997. Seasonal variation in use of caves by the Endangered Ozark Big-eared Bat (Corynorhinus townsendii ingens) in Oklahoma. Am. Mid. Nat. 137:388-392.
- Fitzgerald, T. 1989. New records of bats from northeastern Colorado. Journal of the Colorado-Wyoming Academy of Science 21:22.
- Foresman, K.R. 2001. The wild mammals of Montana. American Society of Mammologists, Special Publication Number 12. Lawrence, KS. 278 pp.
- Frost, D. R., and R. M. Timm. 1992. Phylogeny of plecotine bats (Chiroptera: "Vespertilionidae"): proposal of a logically consistent taxonomy. Am. Mus. Novitates 3034:1-16.
- Garber, C. S. 1991. A survey for Townsend's Big-eared Bat (Plecotus townsendii) and the Spotted bat (Euderma maculatum) on Bridger-Teton and Targhee National Forests in Wyoming. Unpub. report, Wyoming Natural Diversity Database, Laramie, Wyoming. 75 pp.
- Genter, D. L. 1988. Status and distribution of the spotted bat (EUDERMA MACULATUM) and western big-eared bat (PLECOTUS TOWNSENDII) in the Custer National Forest, MT. Unpublished report to the U.S.D.A. Forest Service. Montana Natural Heritage Program, Helena, MT.
- Genter, D. L. 1989. Townsend's big-eared bat, PLECOTUS TOWNSENDII. In: T. W. Clark, A. H. Harvey, R. D. Dorn, D. L. Genter, and C. Groves, (eds.), Rare, sensitive, and threatened species of the Greater Yellowstone ecosystem. N. Rockies Conserv. Coop., Mont. Natural Heritage Program, The Nature Conservancy, and Mountain W. Envir. Serv. 153 pp.
- Genter, D. L. and L. H. Metzgar. 1985. Survey of the bat species and their habitat use in Grand Teton National Park. Pp. 65-69 in: Univ. Wyo.-Natl. Park Serv. Res. Center. Annual report 9.
- Hendricks, P. 1999. Effect of gate installation on continued use by bats of four abandoned mine workings in western Montana. Unpublished report to Montana Department of Environmental Quality. Montana Natural Heritage Program, Helena, Montana. 13 pp.
- Hendricks, Paul., 1998, Bats surveys of Azure Cave and the Little Rocky Mountains: 1997-1998. November 1998.
- Idaho State Conservation Effort. 1995. Habitat conservation assessment and conservation strategy for the Townsend's big-eared bat. Draft unpubl. rep. no. 1. Boise, Id.
- Kunz, T. H. and R. A. Martin. 1982. Corynorhinus townsendii. American Society of Mammalogists, Lawrence, KS. Mammalian Species No. 175:1-6.
- Madson, M., G. Hanson, S. Martinez, and D. Genter. 1993. Wintering bats in Montana: results of surveys in the Pryor Mountains with annotation on area caves and mines. Montana Natural Heritage Program. Helena, MT. 36 pp.
- Marcot, B. G. 1984. Winter use of some northwestern California caves by western big-eared bats and long-eared Myotis. Murrelet 65(2):46.
- Perkins, J. M., and T. Schommer. 1993. Survey protocol and an interim species conservation strategy for PLECOTUS TOWNSENDII in the Blue Mountains of Oregon and Washington. [unpublished report]. 23 pp.
- Perkins, M.J., and C. Levesque. 1987. Distribution, status and habitat affinities of Townsend's big-eared bat (Plecotus townsendii) in Oregon. Oregon Department of Fish and Wildlife, nongame wildlife program; technical report 86-5-01. Portland, OR. 49pp.
- Reid, F. 2006. Peterson Field Guide to Mammals of North America, 4th Edition. Houghton Mifflin Company: Boston and New York, 608 pp.
- Sherwin, R. E., W. L. Gannon, and J. S. Altenbach. 2003. Managing complex systems simply: understanding inherent variation in the use of roosts by Townsend’s Big-eared Bat. Wildlife Society Bulletin 31:62-72.
- Thomas, D. W. and S. D. West. 1991. Forest age associations of bats in the southern Washington Cascade and Oregon Coast Ranges. Pp. 295-303 in: Ruggiero, L. F., K. B. Aubry, A. B. Carey, and M. H. Huff (tech. coord.). Wildlife and vegetation of unmanaged Douglas-fir forests. U.S.D.A. Forest Serv., Pac. Northw. Res. Station. Gen. tech. report PNW-GTR-285. 533 pp.
- Tumlison, R., and M. E. Douglas. 1992. Parsimony analysis and the phylogeny of the plecotine bats (Chiroptera: Vespertilionidae). J. Mamm. 73:276-285.
- Verts, B. J. and L. N. Carraway. 1998. Land mammals of Oregon. University of California Press, Berkeley. xvi + 668 pp.
- Wackenhut, M.C. 1990. Bat species overwintering in lava-tube caves in Lincoln, Gooding, Blaine, Bingham, and Butte counties, Idaho with special reference to annual return of banded Plecotus townsendii . MS thesis, Idaho State Univ., Pocatello. 64 pp.