FWS Focus
Interim Tools Extended

On November 29, 2022 the U.S. Fish and Wildlife Service (Service) published a final rule to reclassify the northern long-eared bat (NLEB) as endangered under the Endangered Species Act. The bat faces extinction due to the range-wide impacts of white-nose syndrome, a deadly disease affecting cave-dwelling bats across the continent. The Service released interim guidance and tools, scheduled to be in place until April 1, 2024, to help interested parties transition to the reclassification of the species. We have extended the interim NLEB tools and guidance listed below (see “Interim Tools and Guidance Documents”) for use until final tools are issued this summer.  

The Service also is sharing drafts of the new tools and guidance documents for interested parties to preview (see “New Draft Tools” below). The Service is providing this preview so that interested parties can familiarize themselves with changes from the interim NLEB guidance and have the opportunity to ask questions before the final tools and guidance go into effect in summer 2024. Any substantive feedback on the draft materials that is shared before May 1, 2024, will be considered in the development of the final documents. These tools also support the conservation of the tricolored bat (TCB), should the species be listed. The goal is to avoid confusion and disruption for federal, state and Tribal partners, project proponents, landowners and other interested parties with projects that occur in suitable habitat within the NLEB and TCB ranges. 

Draft New Tools and Guidance Documents 

Interim Tools and Guidance Documents 

The U.S. Fish and Wildlife Service has developed several tools and guidance documents to assist stakeholders in assessing impacts of projects. 

Other Guidance Documents



The northern long-eared bat is a wide-ranging, federally endangered bat species, found in 37 states and eight provinces in North America. The species typically overwinters in caves or mines and spends the remainder of the year in forested habitats. As its name suggests, the northern long-eared bat is distinguished by its long ears, particularly as compared to other bats in the genus Myotis.

Although there are many threats to the species, the predominant threat by far is white-nose syndrome. If this disease had not emerged, it is unlikely the northern long-eared bat would be experiencing such a dramatic population decline. White-nose syndrome was the main reason for listing the species as threatened under the Endangered Species Act in 2015. Since symptoms were first observed in New York in 2006, white-nose syndrome has spread rapidly throughout the species' range in the United States. Numbers of northern long-eared bats, gathered from hibernacula counts, have declined by 97 to 100% across the species’ range. Due to continued and increased population declines and impacts from threats, on November 29, 2022, the U.S. Fish and Wildlife Service found that the species now meets the definition of an endangered species and published a final rule to reclassify the northern long-eared bat as endangered under the Endangered Species Act. 

Other sources of mortality: Although no significant population declines have been observed due to the sources of mortality listed below alone, they are now important factors affecting this bat’s viability until we find ways to address white-nose syndrome.

  • Wind energy-related mortality: Wind turbines can kill bats by direct collision with turbine blades. Mortality has been documented for northern long-eared bats, although a small number have been found to date. However, there are many wind farms operating within a large portion of the species’ range, and many more projects are planned in the future.
  • Summer habitat loss: Highway construction, commercial development, surface mining and wind facility construction permanently remove habitat and are activities prevalent in many areas of this bat’s range. Summer habitat loss may result in longer flights between suitable roosting and foraging habitat, fragmentation of maternity colonies and direct injury or mortality.
  • Winter habitat loss and disturbance: Gates or other structures intended to exclude people from caves and mines, but do not consider bat needs, may not only restrict bat flight and movement, but also change airflow and internal cave and mine microclimates. A change of even a few degrees can make a cave unsuitable for hibernating bats. Also, cave-dwelling bats are vulnerable to human disturbance while hibernating. Arousal during hibernation causes bats to use up their already reduced energy stores, which may lead to individuals not surviving the winter.
  • Climate change: Changes in temperature and precipitation may influence the species’ available suitable roosting and foraging habitat and prey availability.

What is being done to help the northern long-eared bat?

  • Disease management: Actions have been taken to try to reduce or slow the spread of white-nose syndrome through human transmission of the fungus into caves and mines, including cave and mine closures and advisories and national decontamination protocols. A national plan was prepared by the U.S. Fish and Wildlife Service and other state and federal agencies that details actions needed to investigate and manage white-nose syndrome. Many state and federal agencies, universities and non-governmental organizations are researching this disease to try to control its spread and address its effect. 
  • Addressing wind turbine mortality: The U.S. Fish and Wildlife Service and others are working to minimize bat mortality from wind turbines on several fronts. The agency funds and conducts research to determine why bats are susceptible to turbines, how to operate turbines to minimize mortality and where important bird and bat migration routes are located. The agency has and continues to work with many wind energy project proponents in developing habitat conservation plans that provide wind farms a mechanism to continue operating legally while minimizing and mitigating mortality of federally endangered or threatened bats.
  • Hibernacula protection: Many federal and state natural resource agencies and conservation organizations have protected caves and mines that are important hibernacula for cave-dwelling bats.

Scientific Name

Myotis septentrionalis
Common Name
Northern Long-eared Bat
Northern Myotis
Northern Bat
FWS Category

Location in Taxonomic Tree

Identification Numbers



Characteristic category

Life Cycle

Life Cycle

Breeding begins in late summer or early fall when males begin to swarm near hibernacula. After copulation, females store sperm during hibernation until spring. In spring, they emerge from their hibernacula, ovulate and the stored sperm fertilizes an egg. This strategy is called delayed fertilization.

After fertilization, pregnant females migrate to summer areas where they roost in small colonies and give birth to a single pup. Maternity colonies of females and young generally have 30 to 60 bats at the beginning of the summer, although larger maternity colonies have also been seen. Numbers of individuals in roosts typically decrease from pregnancy to post-lactation. Most bats within a maternity colony give birth around the same time, which may occur from late May or early June to late July, depending on where the colony is located within the species’ range. Young bats start flying by 18 to 21 days after birth.

Life Span

The maximum northern long-eared bat life span is estimated to be up to 18 and a half years, as noted by J.S. Hall and others in 1968.

Characteristic category



Like most bats, northern long-eared bats emerge at dusk to feed during their active time period. They primarily fly through the understory of forested areas feeding on prey, which they catch while in flight using echolocation or by gleaning motionless insects from vegetation. 

Characteristic category



Winter Habitat

Northern long-eared bats spend winter hibernating in caves and mines, called hibernacula. They use areas in various sized caves or mines with constant temperatures, high humidity and no air currents. Within hibernacula, surveyors find them hibernating most often in small crevices or cracks, often with only the nose and ears visible.

Spring, Summer and Fall Habitat

During the summer and portions of the fall and spring, northern long-eared bats may be found roosting singly or in colonies underneath bark, in cavities or in crevices of both live trees and snags, or dead trees. Males and non-reproductive females may also roost in cooler places, like caves and mines. Northern long-eared bats seem to be flexible in selecting roosts, choosing roost trees based on suitability to retain bark or provide cavities or crevices. The species has also been found, although less commonly, roosting in structures, such as barns and sheds. Northern long-eared bats use forested areas not only for roosting, but also for foraging and commuting between summer and winter habitat.


A dense growth of trees and underbrush covering a large tract.

Cave or Karst

A natural chamber or series of chambers in the earth or in the side of a hill or cliff. An irregular limestone region with sinkholes, underground streams and caverns.

Characteristic category



The northern long-eared bat has a diverse diet including moths, flies, leafhoppers, caddisflies, beetles and arachnids.

Characteristic category

Physical Characteristics

Size & Shape

Average body length: 77 to 95 mm (3 to 3.7 in)
Tail length: 35 to 42 mm (1.3 to 1.6 in)
Forearm length: 34 to 38 mm (1.3 to 1.5 in)
Wingspread: 228 to 258 mm (8.9 to 10.2 in)


The northern long-eared bat’s adult body weight averages 5 to 8 grams (0.2 to 0.3 ounces), with females tending to be slightly larger than males.

Color & Pattern

The northern long-eared bat’s fur color can be medium to dark brown on the back and tawny to pale-brown on the underside. As its name suggests, this bat is distinguished by its long ears, particularly as compared to other bats in its genus Myotis.

Characteristic category

Similar Species

Similar Species

Within its range, the northern long-eared bat can be confused with the little brown bat, Myotis lucifugus, or the western long-eared myotis, Myotis evotis.



The species’ range includes all or portions of the following 37 states and the District of Columbia: Alabama, Arkansas, Connecticut, Delaware, Georgia, Illinois, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Maryland, Massachusetts, Michigan, Minnesota, Mississippi, Missouri, Montana, Nebraska, New Hampshire, New Jersey, New York, North Carolina, North Dakota, Ohio, Oklahoma, Pennsylvania, Rhode Island, South Carolina, South Dakota, Tennessee, Vermont, Virginia, West Virginia, Wisconsin and Wyoming. The northern long-eared bat’s range also includes eight Canadian provinces.

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