Big Brown Bat - Eptesicus fuscus
FWP Conservation Tier
A larger bat with overall brown to copper-colored fur. The muzzle is distinctively round and dark. Forearm length is 43-52mm. The uropatagium is unfurred on the posterior half and a keel is present on the calcar.
Central Canada to northwestern South America and many Caribbean islands in many habitats.
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
(Records associated with a range of dates are excluded from time charts)
Summer day roosts include attics, barns, bridges, rock outcrops and bat houses. Hibernacula include caves and mines.
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
Shrubland, Steppe and Savanna Systems
Sparse and Barren Systems
Wetland and Riparian Systems
Mostly beetles, but a variety of other insects including ants, flies, mosquitoes, mayflies, stoneflies, moths, aphids, and true bugs. Stomach contents analysis of 29 specimens from Carter County yielded a variety of insects including: Cleoptera, Diptera, Hemiptera, Lepidoptera, Homoptera, Hymenoptera, Neuroptera, Odoncata, and Trichoptera. Evidence suggests that beetles were trimmed of hard body parts prior to consumption.
Emerge at dusk to forage, flying at 20-33 feet above ground, and traveling in fairly direct paths to foraging areas. Large size and steady flight make this species relatively recognizable. After feeding, they fly to favored night roosts to rest and digest meals.
Mating can occur anytime between September and March. In Montana, females have one young, usually born in late June. Young become capable of independent flight in 3-4 weeks.
- Additional ReferencesLegend: View WorldCat Record View Online Publication
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- Adams, R. A. 2003. Bats of the Rocky Mountain West: natural history, ecology and conservation. University Press of Colorado: Boulder, CO. 289 p.
- Betts, B. J. 1998. Effects of interindividual variation in echolocation calls on identification of big brown and silver-haired bats. Journal of Wildlife Management 62:1003-1010.
- 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.
- ECON, Inc. (Ecological Consulting Service), Helena, MT., 1979, Annual wildllife report of the Colstrip Area for 1979, including a special raptor research study. Proj. 216-85-A. March 1, 1980.
- Fenton, M. B. 1972. Distribution and over-wintering of Myotis leibii and Eptesicus fuscus (Chiroptera: Vespertilionidae) in Ontario. Royal Ontario Museum,, Life Sciences Occas. Pap. (21):1-8.
- Foresman, K. R. 2001. The wild mammals of Montana. American Society of Mammologists, Special Publication Number 12. Lawrence, KS. 278 p.
- Hamilton, I. M. and R. M. R. Barclay. 1994. Patterns of daily torpor and day-roost selection by male and female big brown bats (EPTESICUS FUSCUS). Can. J. Zool. 72:744-749.
- Hendricks, P. 2000. Preliminary bat inventory of caves and abandoned mines on BLM lands, Judith Mountains, Montana. Montana Natural Heritage Program, Helena, Montana. 21 p.
- Hendricks, Paul., 1998, Bats surveys of Azure Cave and the Little Rocky Mountains: 1997-1998. November 1998.
- Jones, J.K., Jr., R.R. Lampe, C.A. Spenrath, and T.H. Kunz. 1973. Notes on the distribution and natural history of bats in southeastern Montana. Occasional papers (Texas Tech University Museum) 15:1-11.
- Kalcounis, M. C., and R. M. Brigham. 1998. Secondary use of aspen cavities by tree-roosting Big Brown Bats. Journal of Wildlife Management 62:603-611.
- Kurta, A. and R. H. Baker. 1990. Eptesicus fuscus. American Society of Mammalogists, Lawrence, KS. Mammalian Species No. 356:1-10.
- Lausen, C. L., and R. M. R. Barclay. 2002. Roosting behaviour and roost selection of female big brown bats (Eptesicus fuscus) roosting in rock crevices in southeastern Alberta. Canadian Journal of Zoology 80:1069-1076.
- 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.
- Maxim Technologies, Inc., 2002, Western Energy Company Rosebud Mine, Colstrip, Montana: 2002 Annual Wildlife Monitoring Report; December 1, 2001 - November 30, 2002. Febr. 24, 2002.
- Reid, F. 2006. Peterson Field Guide to Mammals of North America, 4th Edition. Houghton Mifflin Company: Boston and New York, 608 pp.
- Schowalter, D. B. and J. R. Gunson. 1979. Reproductive biology of the big brown bat (EPTESICUS FUSCUS) in Alberta. Canadian Field-Naturalist 93(1):48-54.
- Thompson, L.S. 1982. Distribution of Montana amphibians, reptiles, and mammals. Bozeman: Montana Audubon Council. 24 pp.
- U.S. Fish & Wildlife Service., 1985, Charles M. Russell National Wildlife Refuge, Montana: Final Environmental Impact Statement.
- Waage, Bruce C., 2000, Western Energy Company Rosebud Mine, Colstrip, Montana: 1999 Annual Wildlife Monitoring Report; December 1, 1998 - November 30, 1999. February 2000.
- Western Energy Co., Colstrip, MT. Unpub., 1983, Western Energy Company's Application for Amendment to Surface Mining Permit NO. 8003, Area B: sections 7, 8, 17,18 T1N R41E, sections 12, 13 T1N R40E, Mining Expansion. March 1983.
- Western Technology and Engineering, Inc. (WESTECH)., 1996, Wildlife Monitoring Absaloka Mine Area Annual Report, 1995. Montana SMP 85005. OSMP Montana 0007D. Febr. 23, 1996.
- Whitaker, J.O., Jr. and S.L. Gummer. 1992. Hibernation of the big brown bat, Eptesicus fuscus, in buildings. J. Mammal. 73(2): 312-316.
- Williams, L. M., and M. C. Brittingham. 1997. Selection of maternity roosts by Big Brown Bats. Joumal of Wildlife Management 61 :359-368.
- Wunder, L. and A.B. Carey. 1996. Use of the forest canopy by bats. Northwest Science 70:79-85.