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Contact information
For information on Wisconsin's rare vertebrate animals, contact:
Rich Staffen
Conservation Biologist
For information on Wisconsin's rare invertebrates, contact:
Jay Watson
Conservation Biologist

Big Brown Bat (Eptesicus fuscus)



Big Brown Bat (Eptesicus fuscus) is a Threatened species in Wisconsin. It has a dark brown dorsal fur coat and may have light-brown ventral fur. During the summer months, big brown bats are found in various habitats including mixed landscapes of deciduous woodlands, farmlands, edges near water and urban areas. Females may form large colonies in bat houses and buildings over the summer. During the winter months, they are found in natural and manmade structures such as caves, mines and human dwellings. The big brown bat is insectivorous and feeds primarily on small beetles found among tree foliage. Mating occurs in the fall at cave and mine entrances and females store sperm until the spring. One to two pups are born in early June and mature after six weeks. See the species guidance document for avoidance measures and management guidance from the Natural Heritage Conservation Program.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - both state and federal - and the rank (S and G Ranks) for Big Brown Bat (Eptesicus fuscus). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where occurrences of this species meet NHI data standards and is not meant as a comprehensive map of all observations.

Note: Species recently added to the NHI Working List may temporarily have blank occurrence maps.

Documented locations of Eptesicus fuscus in the Natural Heritage Inventory Database as of July 2015.
Summary Information
State StatusTHR
Federal Status in Wisconsinnone
State RankS2S4
Global RankG5
Tracked by NHIY

Species guidance

This document contains identification and life history information for Big Brown Bat. It also describes how to screen projects for potential impact to this species, lists avoidance measures, and provides general management guidance.

Big Brown Bat Species Guidance [PDF]



Big Brown Bat

Photo © Dave Redell.

Wildlife Action Plan

Wisconsin Wildlife Action Plan graphic

Natural community (habitat) associations

The table below lists the natural communities that are associated with Big Brown Bat. Only natural communities for which Big Brown Bat is "high" (score=3) or "moderate" (score=2) associated are shown. See the key to association scores for complete definitions. Please see the Wildlife Action Plan to learn how this information was developed.

Ecological landscape associations

The table below lists the ecological landscape association scores for Big Brown Bat. The scores correspond to the map (3=High, 2=Moderate, 1=Low, 0=None). For more information, please see the Wildlife Action Plan.

This map shows the probability of Big Brown Bat occurring in each of Wisconsin's Ecological Landscapes.  Actual scores can be found in the table to the left.

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Landscape-Community combinations of highest ecological priority*

Ecological priorities are the combinations of natural communities and ecological landscapes that provide Wisconsin's best opportunities to conserve important habitats for a given Species of Greatest Conservation Need. The 10 highest scoring combinations are considered ecological priorities and are listed below. More than 10 combinations are listed if multiple combinations tied for 10th place. For more information, please see the Wildlife Action Plan.

Ecological LandscapeCommunity
Central Lake Michigan Coastal Lacustrine Mud Flat
Central Lake Michigan Coastal Warmwater rivers
Central Lake Michigan Coastal Warmwater streams
Central Sand Hills Lacustrine Mud Flat
Central Sand Hills Southern Sedge Meadow
Central Sand Hills Warmwater rivers
Central Sand Hills Wet-mesic Prairie
Central Sand Plains Caves and Subterranean Cultural
Central Sand Plains Floodplain Forest
Central Sand Plains Riverine Impoundment - Reservoirs
Central Sand Plains Riverine Lake - Pond
Forest Transition Warmwater rivers
Forest Transition Warmwater streams
Northern Lake Michigan Coastal Lacustrine Mud Flat
Northern Lake Michigan Coastal Warmwater rivers
Northern Lake Michigan Coastal Warmwater streams
Southeast Glacial Plains Caves and Subterranean Cultural
Southeast Glacial Plains Floodplain Forest
Southeast Glacial Plains Oak Opening
Southeast Glacial Plains Riverine Mud Flat
Southeast Glacial Plains Small Lake--other
Southeast Glacial Plains Southern Sedge Meadow
Southeast Glacial Plains Warmwater rivers
Southeast Glacial Plains Warmwater streams
Southeast Glacial Plains Wet Prairie
Southeast Glacial Plains Wet-mesic Prairie
Southern Lake Michigan Coastal Lacustrine Mud Flat
Southern Lake Michigan Coastal Warmwater streams
Southern Lake Michigan Coastal Wet-mesic Prairie
Southwest Savanna Lacustrine Mud Flat
Southwest Savanna Oak Opening
Southwest Savanna Spring Pond, Lake--Spring
Southwest Savanna Springs and Spring Runs (Hard)
Southwest Savanna Springs and Spring Runs (Soft)
Southwest Savanna Warmwater streams
Western Coulee and Ridges Algific Talus Slope
Western Coulee and Ridges Caves and Subterranean Cultural
Western Coulee and Ridges Floodplain Forest
Western Coulee and Ridges Lacustrine Mud Flat
Western Coulee and Ridges Oak Opening
Western Coulee and Ridges Riverine Lake - Pond
Western Coulee and Ridges Riverine Mud Flat
Western Coulee and Ridges Spring Pond, Lake--Spring
Western Coulee and Ridges Springs and Spring Runs (Hard)
Western Coulee and Ridges Springs and Spring Runs (Soft)
Western Coulee and Ridges Warmwater rivers

* Ecological priority score is a relative measure that is not meant for comparison between species. This score does not consider socio-economical factors that may dictate protection and/or management priorities differently than those determined solely by ecological analysis. Further, a low ecological priority score does not imply that management or preservation should not occur on a site if there are important reasons for doing so locally.

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Issues/threats and conservation actions

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for rare animals

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Last revised: Thursday, October 08, 2020