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BC Conservation Data Centre: Species Summary


Corynorhinus townsendii
Townsend's Big-eared Bat


 
Scientific Name: Corynorhinus townsendii (Cooper, 1837)
English Name: Townsend's Big-eared Bat
 
Classification / Taxonomy
Scientific Name - Concept Reference: Baker, R. J., L. C. Bradley, R. D. Bradley, J. W. Dragoo, M. D. Engstrom, R. S. Hoffman, C. A. Jones, F. Reid, D. W. Rice, and C. Jones. 2003a. Revised checklist of North American mammals north of Mexico, 2003. Museum of Texas Tech University Occasional Papers 229:1-23.
Classification Level: Species
Taxonomy Comments: Handley (1950) recognized two subspecies in BC: C. t. townsendii (coastal BC) and C. t. pallescens (BC interior). However, based on a study of mitochondrial DNA, Piaggio and Perkins (2005) classified the BC populations as a single subspecies- C. t. townsendii.
Species Group: Vertebrate Animal
Species Code: M-COTO
Kingdom Phylum Class Order Family
Animalia Craniata Mammalia Chiroptera Vespertilionidae
   
Conservation Status / Legal Designation
Global Status: G4 (Apr 2016)
Provincial Status: S3 (Feb 2022)
BC List: Blue
Provincial FRPA list:   
Provincial Wildlife Act:
COSEWIC Status:
SARA Schedule:
General Status Canada: 2 - May be at risk (2005)
   
Ecology & Life History
General Description: Very large ears, 30-39 mm, joined across forehead; dorsal hairs slate or gray with pale cinnamon brown to blackish brown tips that contrast little with the base; ventral hairs slate, gray, or brownish, with brownish or buff tips; two large fleshy lumps on snout; hairs on toes do not project beyond toenails; total length 90-112 mm; forearm 39.2-47.6 mm; greatest length of skull 15.2-17.4 mm; 36 teeth; adult mass 5-13 g (Handley 1959, Hall 1981, Kunz and Martin 1982, Ingles 1965).
Global Reproduction Comments: Mating begins in autumn, continues into winter. Ovulation and fertilization are delayed until late winter/early spring. Gestation lasts 2-3.5 months. A litter of one is born in late spring/early summer (beginning mainly in late May in California, the second week of July in Washington, and June in southwestern Texas). Throughout the U.S. range, the earliest births occur in mid-April, the latest in late July (see Handley 1959). Young can fly at 2.5-4 weeks and are weaned by 6-8 weeks. Females are sexually mature their first summer. Males are not sexually active until their second year (California). Nearly all adult females breed every year. Maximum longevity exceeds 21 years (Perkins 1994).

Females commonly form nursery colonies generally of up to about 200 (west) or 1,000 (east) individuals, but solitary pregnant females are frequently encountered (Handley 1959); males roost separately (apparently solitarily) during this time.
Global Ecology Comments: Crude population density in Oklahoma was estimated at one bat per 46.6 sq. km (see Kunz and Martin 1982), about 3-4 times greater than that reported for populations in California (Pearson et al. 1952).

These bats hibernate singly, or in clusters in some areas (Caire et al. 1989, Schmidly 1991). They tend not to associate with other species of bats in daytime or in hibernation roosts, though scattered individuals of other normally colonial species occasionally may be present (Handley 1959).

Pre-weaning post-natal mortality generally is low. Adult survivorship is relatively high (about 70-80% in females in California). Estimates of annual survival of wintering Townsend's big-eared bats in 3 locations in Washington ranged from 54 to 76.0 percent and varied by location, time or trends, and sex (Ellison 2010)..

Predation has been suggested as the primary limiting factor in Kansas and Oklahoma (see Handley 1959).

Pearson et al. (1952) believed that a population increase might be dependent on the establishment of new nursery colonies (colonies remained static in size year after year); how new nursery colonies become established is not known (Handley 1959).
Migration Characteristics:
(Global / Provincial)
 
    Nonmigrant:
    Local Migrant:
    Distant Migrant:
    Within Borders Migrant:
Y /
Y /
N /
na /
Global Migration Comments: These bats are nonmigratory or move moderate distances between breeding and nonbreeding sites. Nightly foraging bouts may be localized near the day roost or may cover more than 150 km.

In Oregon, individuals moved up to 24 km from hibernacula to foraging areas (Dobkin et al. 1995). Both sexes apparently used a series of interim roost sites between emergence from hibernation and the time females entered maternity colonies, with little individual fidelity to these sites.

In Marin County, California, foraging individuals traveled up to 10.5 kilometers from primary day roost (site of maternity colony, but the study was conducted in September after nursery period had ended), and they tended to forage in the same areas each night. The mean center of activity for females was 3.2 +/- 0.5 kilometers from the roost, whereas the mean center of activity for males was only 1.3 kilometers from the roost. Between 41 and 88 percent of tagged bats returned to the roost each night; nine alternate roosts were located, all used by single bats (Fellers and Pierson 2002).

However, Townsend's big-eared bats (in the west) evidently move longer distances than indicated by initial studies. Genetic data suggest gene flow between C. t. pallescens and C. t. townsendii roosts that are at least 310 km apart (Piaggio et al. 2009). Further, recent studies of maternity colonies indicate that they may occupy multiple roosts in an area where more than one underground feature is available, and radio-tracking from aircraft shows that pregnant individuals can travel over 150 km in a night of foraging (see Piaggio et al. 2009).

Individuals may move among different hibernacula in winter (Clark et al. 1997).

Subspecies virginianus: In West Virginia, females traveled up to 11.3 km from a maternity cave to foraging areas, but, 80 percent of the utilized foraging habitat was within 6 km of the cave (Stihler 2011b). Individuals may move 32 km between summer roosts and hibernacula (C. Stihler data, cited by USFWS 2008).
Habitats:
(Type / Subtype / Dependence)
Anthropogenic / Industrial / Facultative - frequent use
Anthropogenic / Urban/Suburban / Facultative - frequent use
Forest / Conifer Forest - Dry / Facultative - frequent use
Forest / Conifer Forest - Mesic (average) / Facultative - frequent use
Forest / Conifer Forest - Moist/wet / Facultative - frequent use
Forest / Deciduous/Broadleaf Forest / Facultative - frequent use
Forest / Mixed Forest (deciduous/coniferous mix) / Facultative - frequent use
Grassland/Shrub / Grassland / Facultative - occasional use
Grassland/Shrub / Shrub - Logged / Facultative - occasional use
Grassland/Shrub / Shrub - Natural / Facultative - occasional use
Riparian / Riparian Forest / Facultative - occasional use
Subterranean / Caves / Obligate
Global Habitat Comments: Throughout much of the known range, these bats commonly occur in mesic habitats characterized by coniferous and deciduous forests (Kunz and Martin 1982), but they occupy a broad range of habitats (e.g., see Handley 1959). Generally they are uncommon in prairies and extreme desert, although they occur in the lower elevations of the arid plateau and desert ranges of northcentral Mexico and the arid valleys south of the transverse volcanic belt. They are known in Mexico mostly from relatively arid regions (e.g., grassy hills with nearby pine-oak woodland) but also from more humid localities with oak, pine, juniper, cypress, madrone, and manzanita (Handley 1959). Ozark and Appalachian populations inhabit caves mostly in oak-hickory forest (Handley 1959).

On the West Coast, Townsend's big-eared bats are found regularly in forested regions and buildings, and in areas with a mosaic of woodland, grassland, and/or shrubland. In California and Washington, they are known from limestone caves, lava tubes, and human-made structures in coastal lowlands, cultivated valleys, and nearby hills covered with mixed vegetation (Handley 1959). Fellers and Pierson (2002) studied a population in Point Reyes National Seashore, California, that foraged along the edges of redwood and Douglas-fir forests and woodlands, primarily along the edges of riparian vegetation. Individuals avoided grassland wherever possible, even while commuting to foraging grounds. Individuals hunted primarily around the perimeter of trees, usually 10-30 meters off the ground, between mid-canopy and near the top of the canopy (Fellers and Pierson 2002).

Townsend's big-eared bats are recorded from pine-fir-hemlock-broadleaf deciduous forest in western Oregon, and from the edge of spruce-fir forest in Colorado (see Handley 1959). In Utah, day roosts were associated with sagebrush steppe, juniper woodlands and mountain brush vegetation at lower available elevations (1,350-2,440 meters; Sherwin et al. 2000). In Texas, habitat ranges from desert scrub to pinyon-juniper woodland, consistently in areas with canyons or cliffs (Schmidly 1991). In New Mexico, most have been captured in evergreen forests during warm months, least commonly captured in xeric shrublands (see Kunz and Martin 1982). In Arizona, habitats include desertscrub, in shelters in desert mountains (where infrequent), oak woodland, pinyon-juniper, and conifer forests (Hoffmeister 1986). In Kansas and Oklahoma, these bats are apparently restricted to riparian communities and nearby gypsum caves in the mid-grass prairie region. In Oklahoma, foraging adult females used edge habitats of intermittent streams and mountain slopes more than expected based on relative availability of habitats (Clark et al. 1993). During the prehibernation period in Oklahoma, Wethington et al. (1996) found that females used habitats in proportion to their availability, but males used forested habitat more than expected in September, likely reflecting prey availability. Females in West Virginia used a wide range of foraging habitats, including deciduous forest, mixed deciduous/ coniferous forest, old fields, hayfields, and corn fields (Stihler 2011).

Maternity and hibernation colonies typically are in caves and mine tunnels. These bats prefer relatively cold places for hibernation, often near entrances and in well-ventilated areas. In California, most limestone caves are too warm for successful hibernation; solitary males and small groups of females are known to hibernate in buildings in the central part of the state. These bats do not use crevices or cracks; they hang from the ceiling, generally near the zone of total darkness (Schmidly 1991). In some areas, basal hollows in large trees may as roost sites, especially in areas with few caverns (Fellers and Pierson 2002, Mazurek 2004). In western Colorado, C. townsendii hibernated usually in abandoned mines with more than one opening and with portal temperatures near 0 C, though they sometimes used mines with a single opening and much warmer portal temperatures (Hayes et al. 2011).

Females gather in small nursery colonies in the warm parts of caves or mines, and not uncommonly in buildings (western North America). Individuals generally return to the same maternity roost and hibernaculum in successive years, though individuals may move among roosts during both the maternity season and in winter (Clark et al. 2002). Night roosts include caves, buildings, and tree cavities.

Maternity roosts in British Columbia exist in buildings and caves (Reid et al. 2010). In coastal California, all six known maternity colonies were in old buildings (5) or in a cave-like feature of a bridge (1) (Fellers and Pierson 2002). In northwestern California, a maternity colony was in a basal hollow of a live coast redwood; this population may have moved among multiple tree hollows in the area (Mazurek 2004). In Oregon, both sexes apparently use a series of interim roost sites between emergence from hibernation and the time females enter maternity colonies, with little individual fidelity to these sites (Dobkin et al. 1995). In Utah, caves were preferred as day roosts in summer (85% of surveyed caves used), as well as abandoned mines (21% surveyed were used); no bridges were used (Sherwin et al. 2000). In Oklahoma-Arkansas-Missouri, big-eared bats are obligate cave users year round; they are known to utilize and roost in limestone and sandstone talus caves (USFWS 2008).
Food Habits: Invertivore: Adult, Immature
Global Food Habits Comments: Diet includes various flying insects often obtained near the foliage of trees and shrubs; the species may feed primarily on moths (Barbour and Davis 1969, Leslie and Clark 2002, Dodd 2006).
Global Phenology: Hibernates/aestivates: Adult, Immature
Nocturnal: Adult, Immature
Global Phenology Comments: Activity usually begins well into the night, late relative to other bats, though activity prior to darkness has been observed in some areas. In late afternoon or evening, prior to emergence, individuals may move closer to the cave entrance. After an initial feeding period, the bats roost and rest during the night, then presumably depart for another feeding bout.

Hibernation extends from early fall through early spring. Individuals commonly arouse in winter, changing position within a hibernaculum or moving to a nearby cave or mine.
Provincial Phenology:
(1st half of month/
2nd half of month)
Colonial Breeder: Y
Length(cm)/width(cm)/Weight(g): 11/ / 12
Elevation (m) (min / max): Global: 
Provincial: 
   
 
Distribution
Endemic: N
Global Range Comment: Range includes western North America from southern British Columbia south to the Isthmus of Tehuantepec (Mexico), west to the Pacific coast, eastward to the Black Hills of South Dakota and Edwards Plateau of Texas, with isolated populations in the gypsum caves of northeastern Texas, Oklahoma, and Kansas, and in limestone regions of Arkansas, Missouri, Illinois, Indiana, Ohio, Kentucky, Virginia, and West Virginia. Elevational range extends from near sea level to at least 3,300 meters in some areas.

According to Handley (1959), the range of subspecies townsendii includes southwestern British Columbia, western Washington, western Oregon, and northwestern and west-central California; this subspecies intergrades with subspecies pallescens over a wide area in central and northern California and northward between the Cascades and the Rockies; subspecific allocation of specimens from much of this area is uncertain; some authors have applied the subspecific name intermedius to populations in the area of intergradation (Handley 1959). Handley characterized the range of subspecies pallescens as extending from southern British Columbia southward through the western United States to northwestern Mexico; west to central Washington, central Oregon, eastern and southern California, Sonora, and islands in the Gulf of California; east to South Dakota, Kansas, western Oklahoma, and Texas. As defined by Handley, subspecies australis ranges from the mountains of central and northern Mexico to western Texas.

However, a range-wide study of molecular phylogeny by Piaggio and Perkins (2005) found that geographic patterns of genetic (DNA) variation do not conform with the ranges of subspecies townsendii and pallescens as defined by Handley based on morphological characteristics. Piaggio and Perkins (2005) concluded that subspecies townsendii is broadly distributed from the Pacific coast of the United States and British Columbia (including Vancouver Island) southward to coastal regions of the Sonoran Desert in Mexico, eastward to the Colorado Plateau and the Black Hills, whereas subspecies pallescens is much more restricted and ranges from New Mexico to central and eastern Colorado, where it reaches its northern limits in northern Colorado or southern Wyoming. The molecular phylogenetic results conformed with the geographic scope of australis as defined by Handley.

Subspecies ingens: Range includes the Ozark Highlands and Boston Mountains ecoregions in northeastern Oklahoma, northwestern Arkansas, and (at least formerly) southwestern Missouri.

Subspecies virginianus: Range encompasses the Appalachian Mountains in Virginia, West Virginia, North Carolina, and eastern Kentucky. Presently these bats occur in decreased numbers throughout much of the historical range. The largest colonies are in several caves in Pendleton County, West Virginia; some caves serve as both hibernation and maternity sites, others are primarily maternity caves. Colonies occur also in Lee County and surrounding counties, Kentucky (the best known site being Stillhouse Cave); in Bath, Highland, Rockingham, Bland, and Tazewell counties, Virginia (Dalton 1987); and in Avery and Watauga counties, North Carolina (including Black Rock Cliffs Cave) See Matthews and Moseley (1990) and Handley (1991).

The molecular phylogeny of Piaggio and Perkins (2005) agreed with the morphologically defined taxonomic/geographic scope of subspecies ingens and virginianus as defined by Handley (1959).
 
Authors / Contributors
Global Information Author: Hammerson, G.
Last Updated: Apr 23, 2014
Provincial Information Author:
Last Updated:
   
References and Related Literature
Arita, H. T. 1993. Conservation biology of the cave bats in Mexico. Journal of Mammalogy 74:693-702.
Bagley, F. M. 1984. Recovery plan for the Ozark big-eared bat and the Virginia big-eared bat. U.S. Fish and Wildlife Service. 119 pp.
Bagley, R. and J. Jacobs. 1985. Census techniques for endangered big-eared bats proving successful. Endangered Species Tech. Bull. 10(3):5-7.
Barbour, R. W., and W. H. Davis. 1969. Bats of America. The University of Kentucky Press, Lexington, Kentucky. 286 pp.
Blood, D.A. 1998. Townsend's Big-eared Bat. B.C. Minist. Environ., Lands and Parks, Wildl. Branch. 6pp.
Burford, L. S., and M. J. Lacki. 1995. Habitat use by Corynorhinus townsendii virginianus in the Daniel Boone National Forest. American Midland Naturalist 134:340-345.
Caire, W., J. D. Tyler, B. P. Glass, and M. A. Mares. 1989. Mammals of Oklahoma. University of Oklahoma Press, Norman. Oklahoma. 567 pp.
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.
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.
Firman, M.C. 2000. Townsend's Big-Eared Bat (Plecotus townsendii) in the East Kootenays. P. 435 in L.M. Darling, ed. 2000. Proc. Conf. on the Biology and Manage. Species and Habitats at Risk, Kamloops, B.C., 15-19 Feb., 1999. Vol. 1; B.C. Minist. Environ., Lands and Parks, Victoria, BC, and Univ. College of the Cariboo, Kamloops, BC. 490pp.
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.
Hall, E. R. 1981a. The Mammals of North America, second edition. Vols. I & II. John Wiley & Sons, New York, New York. 1181 pp.
Hamilton, W. J., Jr., and J. O. Whitaker, Jr. 1979. Mammals of the eastern United States. Cornell Univ. Press, Ithaca, New York. 346 pp.
Handley, C. O., Jr. 1959. A revision of American bats of the genera Euderma and Plecotus. Proceedings U.S. National Museum 110:95-246.
Holroyd, S.L., R.M.R. Barclay, L.M. Merk, and R.M. Brigham. 1994. A Survey of the Bat Fauna of the Dry Interior of British Columbia. B.C. Minist. Environ., Lands and Parks, Wildl. Branch. Working Rep. WR-63. 80pp.
Ingles, L. G. 1965. Mammals of the Pacific States. Stanford University Press, Stanford, California.
Jones, C. 1977. Plecotus rafinesquii. American Soc. Mamm., Mammalian Species No. 69. 4 pp.
Kunz, T.H. and R.A. Martin. 1982. Plecotus townsendii. American Society Mamm., Mammalian Species No. 175. 6 pp.
Pearson, O.P., M.R. Koford and A.K. Pearson. 1952. Reproduction of the lump-nosed bat (Corynorhinus rafinesquii) in California. J. Mamm. 33:273-320.
Ports, M. A., and P. V. Bradley. 1996. Habitat affinities of bats from northeastern Nevada. Great Basin Naturalist 56:48-53.
Schmidly, D. J. 1991. The bats of Texas. Texas A & M University Press, College Station, Texas. 188 pp.
Schwartz, C. W., and E. R. Schwartz. 1981. The wild mammals of Missouri. University of Missouri Press, Columbia. 356 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.
Stevens, V., and S. Lofts. 1988. Species Notes for Mammals. Vol. 1 in A.P. Harcombe, tech. ed. Wildlife Habitat Handbooks for the Southern Interior Ecoprovince. B.C. Minist. Environ., Lands and Parks, Wildl. Branch. Tech. Rep. R-15. 174pp.
Stihler, C. W. 2011b. Radiotelemetry studies of female Virginia big-eared bats (Corynorhinus townsendii virginianus) in Pendleton County, West Virginia. Pages 139-146 in Loeb et al., editors. Conservation and management of eastern big-eared bats. USDA Forest Service, Southern Research Station, General Technical Report SRS-145.
Thomas, D. W. and S. D. West. 1989. Sampling methods for bats. USDA Forest Service, Pacific Northwest Research Station Gen. Technical Report PNW-GTR-243. 20 pp.
Tumlison, R., and M. E. Douglas. 1992. Parsimony analysis and the phylogeny of the plecotine bats (Chiroptera: Vespertilionidae). Journal of Mammalogy 73(2):276-285.
van Zyll de Jong, C.G. 1985. Handbook of Canadian Mammals. Vol. II, Bats. National Museum of Natural Sciences, National Museums of Canada, Ottawa, Canada. 212 pp.
Vonhof, M.J., and J.C. Gwilliam. 2000. A Summary of Bat Research in the Pend dOreille Valley in Southern British Columbia. Columbia Basin Fish and Wildlife Compensation Program, BC Hydro, B.C. Minist. Environ, Lands and Parks, B.C. Fish. in partnership with B.C. Minist. For. 116pp.
White, D. H., and J. T. Seginak. 1987. Cave gate designs for use in protecting endangered bats. Wildlife Society Bull. 15:445-449.
 

Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.

Suggested Citation:

B.C. Conservation Data Centre. 2014. Species Summary: Corynorhinus townsendii. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 15, 2024).