Relationships of Three Species 

of Bats Impacted by White-Nose 

Syndrome to Forest Condition 

and Management

Alexander Silvis, Roger W. Perry, and W. Mark Ford

United States Department of Agriculture

Forest Service

Research & Development

Southern Research Station

General Technical Report SRS–214
Authors:

Alexander Silvis, Research Assistant Professor, Department of 

Fish and Wildlife Conservation, 310 W. Campus Drive, Virginia 

Polytechnic Institute and State University, Blacksburg, VA 24061; 

Roger W. Perry, Research Wildlife Biologist, U.S. Department of 

Agriculture, Forest Service, Southern Research Station, Hot Springs, 

AR 71902; and W. Mark Ford, Research Wildlife Biologist, U.S. 

Geological Survey, Virginia Cooperative Fish and Wildlife Research 

Unit, Blacksburg, VA 24061.

August 2016

Southern Research Station

200 W.T. Weaver Blvd.

Asheville, NC 28804

www.srs.fs.usda.gov

Product Disclaimer

The use of trade or firm names in this publication is for 

reader information and does not imply endorsement by the 

U.S. Department of Agriculture of any product or service.

Cover Photo

A female northern long-eared bat (Myotis septentrionalis) captured on the Fort Knox Military Reservation, 

Kentucky, USA. (Photo by Sean Langley, Apogee Environmental and Archaeological, Inc.)
Relationships of Three Species 

of Bats Impacted by White-Nose 

Syndrome to Forest Condition 

and Management

Alexander Silvis, Roger W. Perry, and W. Mark Ford

iii

CONTENTS

Acknowledgments iv

Abstract iv

Introduction 1

Bats and Forests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

White-Nose Syndrome 2

Purpose 3

Northern Long-Eared Bat (Myotis septentrionalis) 5

Introduction 5

Growing Season Roost Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Acoustic Activity Patterns and Foraging Ecology 13

Response to Forest Management 16

Threats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Research Questions and Needs 17

Regulations 17

Indiana Bat (Myotis sodalis) 19

Introduction 19

Growing Season Roost Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Acoustic Activity Patterns and Foraging Ecology 25

Response to Forest Management 26

Threats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

Research Questions and Needs 28

Regulations 29

Tri-Colored Bat (Perimyotis subflavus) 31

Introduction 31

Growing Season Roost Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Acoustic Activity Patterns and Foraging Ecology 34

Response to Forest Management 35

Threats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Research Questions and Needs 36

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Literature Cited 41

Page

Contents
iv Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

ACKNOWLEDGMENTS

This work was supported by a grant from the National Council for Air and Stream 

Improvement. Additional support was provided by the U.S. Department of Agriculture, 

Forest Service, Southern Research Station, the U.S. Geological Survey Cooperative 

Research Unit Program, and the Department of Fisheries and Wildlife Conservation 

at Virginia Polytechnic Institute and State University. We thank T. Bently Wigley, 

Craig Loehle, Darren Miller, and Dennis Krusac for their helpful comments on this 

manuscript. 

ABSTRACT

Forest management activities can have substantial effects on forest structure and 

community composition and response of wildlife therein. Bats can be highly influenced by 

these structural changes, and understanding how forest management affects day-roost and 

foraging ecology of bats is currently a paramount conservation issue. With populations 

of many cave-hibernating bat species in eastern North America declining as a result of 

white-nose syndrome (WNS), it is increasingly critical to understand relationships among 

bats and forest-management activities. Herein, we provide a comprehensive literature 

review and synthesis of: (1) responses of northern long-eared (Myotis septentrionalis) and 

tri-colored (Perimyotis subflavus) bats—two species affected by WNS that use forests 

during summer—to forest management, and (2) an update to a previous review on the 

ecology of the endangered Indiana bat (Myotis sodalis).

Keywords: Bat conservation, forest management, forestry, habitat relationships, Indiana 

bat (Myotis sodalis), North America, northern long-eared bat (Myotis septentrionalis), 

roost, tri-colored bat (Perimyotis subflavus), white-nose syndrome.
Introduction 1

INTRODUCTION

Bats and Forests

Well-managed forests are those managed for long-term 

sustainability using a variety of management tools that 

include harvesting and thinning, burning, replanting, and 

other similar practices. These forests provide valuable 

solid wood, fiber and biomass products; ecosystem 

services; green space; and recreational opportunities such 

as hunting, fishing, bird-watching, biking, and hiking.

Managed forests also provide habitat for a wide array of 

vertebrate and invertebrate species. However, not all forest 

management objectives are simultaneously compatible.

Most individual forest stands in the private sector and 

many in the public sector are managed to meet specific 

objectives, which may include promoting recreational 

opportunities, reducing wildfire risk, producing wood 

products, restoring ecosystems, and providing habitat for 

endangered species. Managed forest landscapes often 

provide a mosaic of forest structural conditions that allow 

many competing objectives to be accomplished at larger 

landscape scales. Understanding the effects on wildlife of 

different forest management techniques that are used to 

accomplish any given objective is considered a keystone of 

good forest stewardship.

Although the public largely associates bats with cave 

environments, many species of bats in the Eastern United 

States and Canada use caves only during hibernation 

(approximately October–April, depending on latitude) 

(fig. 1), and spend the remainder of the year in forests.

Figure 1—Generalized life cycle diagram of roosting for eastern North American cave bats. This 

diagram does not apply to gray bats (Myotis grisescens), Ozark big-eared bats (Corynorhinus townsendii

ingens), or Virginia big-eared bats (C. townsendii virginianus) that occupy caves year round.
2 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Depending on the species, bats rely on forests for day and 

night roosting, either in foliage, in tree cavities, or under 

loose bark of live and dead (snag) trees. Similarly, bats in 

these landscapes rely on different-aged forests and riparian 

zones within forests for foraging. Individual bat species 

vary tremendously in their ecology, but it is apparent that 

forest condition at the stand to landscape scale affects bat 

community composition, distribution, resource selection, 

and individual behavior (Bobrowiec and Gribel 2010, 

Borkin and Parsons 2014, Chaverri and others 2007, 

Chaverri and Kunz 2010, Ford and others 2005, Johnson 

and others 2010a, Smith and Gehrt 2010, Titchenell and 

others 2011).

Forest structural characteristics, particularly vegetation 

density, stand volume, tree heights, and stratification, 

are important factors determining local bat community 

composition, and these factors directly influence patterns 

of activity (Adams and others 2009, Fukui and others 2011, 

Hodgkison and others 2004, Menzel and others 2005b, 

Smith and Gehrt 2010). Similarly, forest composition and 

structural characteristics influence composition, density, 

and availability of bat invertebrate prey, and consequently 

bat activity (Dodd and others 2012b). Specific structural 

components, such as snags, are required by many forestroosting bats, and bats select roosts in part based on local 

and surrounding landscape features, both physical and 

biotic (Kunz and Lumsden 2003). Both landscape and 

local stand characteristics are important in roost selection 

(Miles and others 2006, Perry and others 2008), and 

availability of and proximity to water is an important 

criteria for many species. Stream corridors not only 

provide critical drinking areas, they also provide excellent 

foraging habitat for most bats, and these areas frequently 

have greater levels of activity than surrounding areas 

(Carter 2006, Ford and others 2006a, Johnson and others 

2010a, Menzel and others 2005b, Ober and Hayes 2008).

White-Nose Syndrome

Since its discovery in the winter of 2006–2007 in New 

York State, white-nose syndrome (WNS) has led to the 

deaths of millions of bats across much of the Eastern 

United States and southeast Canada, resulting in local to 

regional extirpation of once common bat species (Frick 

and others 2010). Now known to be caused by the coldadapted fungus Pseudogynmoascus destructans (Lorch 

and others 2011), WNS impacts physiology, water balance, 

and arousal patterns of hibernating bats in lethal ways 

(Cryan and others 2010, Reeder and others 2012, Willis 

and others 2011). To date, 11 species or subspecies in the 

Eastern United States have shown signs of P. destructans

fungal growth (table 1). Although mortality rates for many 

of the species that display clinical signs of WNS are high 

(Frick and others 2015), persistence of impacted species 

in some infected caves appears to be related in part to 

group size and microclimate factors (Langwig and others 

2012). Likewise, although the spread of WNS is correlated 

with distribution of caves and climate (Maher and others 

2012), the risk of infection for individual caves and timing 

of mortality appears to be related to distance to nearest 

WNS-positive cave and colony size (Wilder and others 

2011).

White-nose syndrome is now widespread across the 

Eastern United States, and the U.S. Fish and Wildlife 

Service (USFWS) has listed the once common northern 

long-eared bat (M. septentrionalis) as threatened under the 

Endangered Species Act (2015 Federal Register § 80(63): 

17974-18033). Given significant declines in populations 

of tri-colored (Perimyotis subflavus) and little brown 

(M. lucifugus) bats, it is possible these species may also 

be listed. Ecological impacts of bat population declines 

on forests remain unclear. It is apparent WNS impacts 

reproductive activity and annual recruitment of surviving 

bats (Francl and others 2012), thereby rendering impacted 

species more vulnerable to additive mortality. Moreover, 

WNS has altered community composition and foraging 

habitat use of WNS-impacted and nonimpacted species 

(Jachowski and others 2014a).

As populations of northern long-eared bats and other 

WNS-impacted species continue to decline, managers 

increasingly will be tasked with managing forests for 

bats and/or considering them in forest management 

and development plans, particularly as Federal listings 

potentially increase scope and extent of regulatory 

constraints. Decreased population sizes may render 

traditional mist-net sampling largely ineffective in many 

WNS-impacted regions (Coleman and others 2014).

Therefore, documenting and studying bat ecology and 

distribution to guide management will require increasing 

reliance on acoustical surveys and/or observations of 
Introduction 3

past landscape- and stand-level habitat associations that 

were developed pre-WNS (Jachowski and others 2014a, 

Silvis and others 2014a). Efforts to continue refining our 

understanding of relationships between these species and 

forest disturbance/stand development are currently limited 

by lack of comprehensive syntheses and assessments 

that can be used as the basis for proactive management 

of day-roosting sites and foraging areas. Because 

information from acoustic surveys is limited with regard 

to understanding roost selection and other aspects of bat 

ecology (Hayes 2000, Miller and others 2003), it is also 

increasingly important that historical data be thoroughly 

examined and synthesized.

Purpose

Three species of bats are particularly susceptible to 

WNS; these bats hibernate in caves and abandoned mines 

during winter but spend the growing season roosting and 

foraging in forests. The tree-roosting northern long-eared 

and tri-colored bats are at risk of extinction or regional 

extirpation due to WNS. To facilitate conservation of these 

species, we provide a review and synthesis of the literature 

addressing relationships among forest management, 

disturbance and successional processes, and responses 

of these species. Additionally, we provide an update to a 

previous review (Menzel and others 2001) on the ecology 

of the endangered Indiana bat (Myotis sodalis).

Table 1—White-nose syndrome bat species in the Eastern United States with population 

trend post-WNSa

Species Pre-WNS status WNS-related population trend Extinction risk

Northern long-eared bat 

(Myotis septentrionalis) Common Extreme decline High

Indiana bat 

(Myotis sodalis) Endangered Mild decline Moderate

Tri-colored bat 

(Perimyotis subflavis) Common Extreme decline Moderate

Eastern small-footed bat 

(Myotis leibii)

Uncommon, 

locally abundant Unknown Moderate

Big brown bat 

(Eptesicus fuscus) Common Slight decline Low

Little brown bat 

(Myotis lucifugus) Common Extreme decline Moderate

Gray bat 

(Myotis grisescens) Endangered Unknown/slight decline Unknown

Southeastern bat 

(Myotis austroriparius) Uncommon Unknown Unknown

Rafinesque’s big-eared bat 

(Corynorhinus rafinesquii)

Uncommon, 

locally abundant No apparent impact Unknown

Ozark big-eared bat 

(C. townsendii. ingens) Endangered Unknown Unknown

Virginia big-eared bat 

(C. t. virginianus) Endangered No apparent impact Unknown

a Local extinction risks were calculated by Frick and others (2010, 2015).

Northern Long-Eared Bat (Myotis septentrionalis) 5

Introduction

The northern long-eared bat is a small to medium-sized 

colonial species of forest-dwelling bat in the family 

Vespertilionidae. Considered a subspecies of Keen’s 

myotis (Myotis keenii) until 1979 (van Zyll de Jong 

1979), northern long-eared bats occupy a distinct, 

non-overlapping range in eastern North America and now 

are described as a monotypic species (Caceres and Barclay 

2000). The northern long-eared bat is distributed from 

Manitoba to Newfoundland, south through the Midwest to 

Georgia and Louisiana (fig. 2). Northern long-eared bats 

are distinct among Myotis bats in eastern North America 

based on their long ears and long, pointed tragus. Body 

mass ranges from 5 to 9 grams, and total length may be 

as much as 95 mm, with forearms between 34 and 38 mm 

(Caceres and Barclay 2000). Sympatric species over much 

of the species’ range include the Indiana bat, little brown 

bat, big brown bat (Eptesicus fuscus), and tri-colored bat.

Growing Season Roost Ecology

Northern long-eared bats are infrequent users of 

anthropogenic structures such as buildings and bat boxes 

(Burke 1999, Krynak 2010). The species is primarily 

considered a forest-dwelling bat because most recorded 

roosts are in live trees or snags (Broders and others 2006, 

Foster and Kurta 1999, Johnson and others 2012, Lacki and 

Schwierjohann 2001, Menzel and others 2002b, Morris 

and others 2010, Perry and Thill 2007a). During summer 

(May–July), females form maternity colonies within 

cavities of snags or declining live trees (fig. 3), under 

exfoliating bark of live trees and snags, or in crevices 

in trees (fig. 4) (Carter and Feldhamer 2005, Lacki and 

Schwierjohann 2001, Menzel and others 2002b, Silvis and 

others 2012). Colonies of approximately 100 individuals 

have been documented in both forest (Owen and others 

2002) and anthropogenic settings such as buildings and bat 

houses (Burke 1999, Krynak 2010), but smaller colonies 

containing 10–30 individuals appear to be more typical 

(Badin 2014, Johnson and others 2012, Owen and others 

2002, Patriquin and others 2013, Perry and Thill 2007a, 

Sasse and Pekins 1996, Silvis and others 2014a). Individual 

maternity colonies have been documented using up to 

42 different roost trees in a single year (Silvis and others 

2015a). Colony size may vary throughout the maternity 

season in conjunction with the reproductive condition 

of bats within a colony (Lacki and Schwierjohann 2001, 

Sasse and Pekins 1996).

NORTHERN LONG-EARED BAT

(Myotis septentrionalis)

Figure 2—Approximate range of northern long-eared bats (Myotis 

septentrionalis). Range data modified from National Atlas of North 

American bat ranges (U.S. Geological Survey 2014).
6 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Figure 3—A bottom-up view of a northern long-eared bat (Myotis septentrionalis) maternity roost snag and associated 

canopy gap in a mixed-mesophytic forest on the Fort Knox Military Reservation, Kentucky, USA. White arrow identifies 

roost tree. (Photo by Alexander Silvis, Virginia Polytechnic Institute and State University).

Maternity colonies of northern long-eared bats are socially 

structured, with bonds between individuals showing 

some temporal structuring (Garroway and Broders 2007).

Adult females within maternity colonies appear to be 

related, but genetic relatedness is only weakly correlated 

with patterns of social relationships (Patriquin and others 

2013). It is noteworthy that prior to WNS, northern longeared bats had high genetic diversity and considerable 

gene flow across their range (Johnson and others 2013).

Social structure of maternity colonies is defined by a 

fission-fusion dynamic in which individuals and small 

groups within the colony periodically “fuse” together into 

a single roosting group and then “diffuse” into smaller 

roosting groups (Garroway and Broders 2007, Johnson and 

others 2012, Silvis and others 2014a). Social bonds among 

females are manifested through roost switching movements 

wherein individuals with close associations share roosts 

more than expected by chance. Social connections among 

bats based on switching and sharing roosts are known as 

“roost networks” (Johnson and others 2012, Silvis and 

others 2014a).

Using roost network maps, both Silvis and others (2014a) 

and Johnson and others (2012) showed that, similar to 

Indiana bats (Silvis and others 2014b), northern long-eared 

bat maternity colonies used “primary” and “secondary” 

roosts; primary roosts are characterized by intense use 

relative to all other roosts, and secondary roosts by 
Northern Long-Eared Bat (Myotis septentrionalis) 7

Figure 4—Northern long-eared bat (Myotis septentrionalis) maternity 

colony (crevice near top of tree) in a 20-cm d.b.h. pine snag, located in 

a recently thinned and burned pine stand. (Photo by Roger W. Perry, 

U.S. Forest Service)

limited use. Number of bats using secondary roost trees 

on individual nights may be similar to the number that 

use primary trees (Johnson and others 2012). It has been 

suggested that the social structure of bats may be related 

to roost availability (Chaverri 2010), but this may not be 

the case for northern long-eared bats when a large number 

of potential roosts are available (Silvis and others 2014a).

Most research suggests roost switching occurs every few 

days (table 2) (Badin 2014, Carter and Feldhamer 2005, 

Foster and Kurta 1999, Garroway and Broders 2007, 

O’Keefe 2009, Silvis and others 2014a).

Conversely, relatively little is known about roosting 

ecology of male northern long-eared bats. Males tend to 

roost alone (Broders and Forbes 2004, Perry and Thill 

2007a) but have been found to occasionally share roosts 

with other males (Ford and others 2006b). It is likely that 

juvenile males use maternity roosts during the year of their 

birth, as has been documented for Indiana bats (Silvis and 

others 2014b). Arnold (2007) suggested that dispersal from 

maternity sites is male-biased. The number of individual 

roosts used by males appears to be relatively small over 

any given period of time (2.3 ± 0.4 SE, Ford and others 

2006b) with roost switching every few days (1.2–3.1 days; 

O’Keefe 2009, Jung and others 2004) (table 2).

Stand and landscape condition—Distribution of 

northern long-eared bats covers a substantial proportion 

of the Eastern United States, including southeastern and 

southcentral Canada. Consequently, the species has been 

documented roosting in many different forest types outside 

of hibernation. Forest types include: boreal coniferous and 

mixed pine (Broders and Forbes 2004, Henderson and 

Broders 2008), Laurentian mixedwood (Jung and others 

2004), northern hardwood (Broders and others 2006, 

Sasse and Pekins 1996), aspen-mixedwood (Crampton and 

Barclay 1998), mixed mesophytic-Allegheny hardwood 

(Ford and others 2006b, Menzel and others 2002b, Owen 

and others 2002), mixed mesophytic (Krynak 2010, Lacki 

and Schwierjohann 2001), western mixed-mesophytic 

(Silvis and others 2014a), upland hardwood (Badin 

2014, Timpone and others 2010), bottomland hardwood 

(Carter and Feldhamer 2005, Timpone and others 2010), 

Appalachian upland oaks (Quercus spp.) (O’Keefe 2009), 

and mixed shortleaf pine (Pinus echinata)-hardwood 

(Perry and Thill 2007a). As expected with such a wide 

distribution, roosts have been found in a wide variety of 

forest stand and landscape conditions. Still, there appear 

to be some clear patterns in habitat use at the stand and 

landscape level.

Generally, studies have documented roosts in deciduous 

forest stands, but preference for deciduous forest over 

other forest types based on roosts reported in the literature 

is biased due to the majority of studies occurring 

in deciduous-forest landscapes. Within coniferousdominated landscapes, roost-stand selection results differ 

between semi-boreal and austral locations. In Arkansas, 

northern long-eared bats (both sexes combined) preferred 

roosting in mature pine-dominated stands and mixed 

pine-hardwood forests (Perry and others 2007). In New 

Brunswick, Broders and Forbes (2004) reported selection 

for deciduous forest stands over coniferous stands by 

female northern long-eared bats.
8 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Roost-stand selection appears to occur at multiple spatial 

scales, with small-scale selection (250 m) in pinedominated landscapes indicating increased roosting 

probability in areas with abundant, thinned mature pine 

forest and group-selection cuts, but decreased amounts of 

immature pine (Perry and others 2008). Examination of 

large-scale selection (1 km) found increased probability 

of roosting in areas with abundant older (>100 years old) 

pine-hardwood stands and seed tree stands, and lower 

amounts of closed-canopy pine plantations; fewer but 

larger patches; more edge; and greater interspersion of 

patch types than random (Perry and others 2008). In 

northerly latitudes, male northern long-eared bats appear 

to either select for coniferous stands (Broders and Forbes 

2004) or use coniferous stands in proportion to their 

abundance (Jung and others 2004). Despite selection 

preference for deciduous stands in some areas, occurrence 

records make it clear that northern long-eared bats will 

roost and reproduce in pine-dominated forest stands (Jung 

and others 2004, Lausen and others 2008, Morris and 

others 2010, Perry and Thill 2007a). However, young, 

closed-canopy pine plantations (prior to thinning) are 

rarely used for roosting (Perry and Thill 2007a, Perry 

and others 2008), likely because of their dense, cluttered 

conditions, small tree sizes, and relatively low abundance 

of snags/dying trees.

Forest stands where northern long-eared bats roost 

typically have continuous canopy (Badin 2014, Johnson 

and others 2012, Lacki and Schwierjohann 2001, Menzel 

and others 2002b, Perry and Thill 2007a, Sasse and Pekins 

1996). Nonetheless, comparisons of roost stands and 

roosting areas with potential roost stands or random stands 

are variable, with some studies finding contrary results.

For example, Carter and Feldhamer (2005), Menzel and 

others (2002b), and Perry and Thill (2007a) found that 

some stands used for tree roosting had relatively complex 

canopies with greater or lesser canopy closure. In contrast, 

Owen and others (2002) found no difference in forest 

complexity between roosts and potential roosts, and Sasse 

and Pekins (1996) found less canopy closure in roost 

stands than in available stands. It is likely that roost-stand 

Table 2—Studies characterizing roost switching by northern long-eared bats (Myotis septentrionalis)

Study Location

Number

of bats

studied

Number 

of 

roosts Sex

Roost switching frequency

Mean SE

Badin (2014) Indiana 23 71 ♀ 3.1 switches/5.3 daysa —

Carter and

Feldhamer (2005) Illinois 10 19 ♀ 2.5 switches/3.9 daysa —

Ford and others (2006b) West Virginia 10 16 ♂ 2.3 roosts/3 daysc 0.4 roosts/0.4 days

Foster and Kurta (1999) Michigan 12 32 ♀ 2.8 switches/5.6 daysa —

Garroway and

Broders (2007) Nova Scotia 17 36 ♀ 1.6 daysb 0.5 days

Johnson and

others (2009) fire West Virginia 25 30 ♀ 1.4 daysb 0.2 days

Johnson and others

(2009) no fire West Virginia 44 40 ♀ 1.3 daysb 0.1 days

Jung and others (2004) Ontario 10 16 ♂ 3.1 daysb 0.3 days

Lacki and others (2009) Kentucky 18 54 ♀ 3.8 roosts/— 0.4 roosts/—

Menzel and others (2002b) West Virginia 7 12 ♀ 5.3 daysb 2.0 days

O'Keefe (2009) North Carolina 18 52 ♀ 1.8 daysb 0.3 days

O'Keefe (2009) North Carolina 16 50 ♂ 1.2 daysb 0.2 days

Owen and others (2002) West Virginia 61 43 ♀ 3.0 daysb 1.5 days

Patriquin and others (2010) Nova Scotia 40 99 ♀ 1.4 daysb 0.6 days

Sasse and Pekins (1996) New Hampshire 32 47 ♀ 2.2 roosts/4.5 daysa —

Silvis and others (2014a) Kentucky 54 108 ♀ 2.4 daysb 0.3 days

Timpone and others (2010) Missouri 13 39 — 3.1 roosts/4.9 daysa 0.4 roosts/2.9 days

aAverage number of times bat switched roosts/number of days tracked. 

bRoost switching frequency (mean number of days bat spent in each roost).

cMean number of roosts used/mean number of days tracked. 

SE = Standard error; ♀ = female; ♂ = male; — = values not available.
9

selection is related to local landscape history, use, and 

configuration, as well as climate, elevation, and regional 

forest and ecosystem type. Despite differences in these 

factors, northern long-eared bats appear to be consistent 

throughout much of their distribution in preferring forest 

stands and points within stands with overstory trees 

generally larger than those at random points (Badin 2014, 

Johnson and others 2012, Lacki and Schwierjohann 2001, 

Menzel and others 2002b, Perry and Thill 2007a, Sasse 

and Pekins 1996). As a caveat, many studies comparing 

roost and random trees have included overstory, midstory, 

and understory trees in the random set. Therefore, 

preference for “largest trees on the landscape” may be 

biased by inclusion of nonoverstory trees in comparisons 

of tree diameter at breast height (d.b.h.) and tree height.

Similarly, because random trees used for comparisons 

often are selected from within the same stand as roost 

trees, the scale of inference for many studies is limited to 

the roost stand.

Little information is available on basal area (BA) or stem 

density of stands used for roosting; therefore, it is difficult 

to determine thresholds to predict roosting. However, 

conditions used by northern long-eared bats for roosting 

range from forested pasture (Foster and Kurta 1999) to 

heavily thinned stands in industrial hardwood forests 

(Menzel and others 2002b, Owen and others 2002), to 

mature forest arising from old-field successional processes 

(Silvis and others 2012), which suggests that the species is 

tolerant of a wide range of basal area. In one well-studied 

population in Arkansas, the largest proportion of northern 

long-eared bat roosts were in stands with overstory BAs 

around 16 m2

/ha (70 square feet per acre) with little or no 

midstory (Perry and Thill 2007a). Overstory BA at roosts 

in that study ranged from 2.8 to 21.6 m2/ha (12–94 square 

feet per acre), with stand BA ranging up to 32 m2/ha 

(140 square feet per acre).

1

 Use of industrial and otherwise 

harvested forests for roosting (Johnson and others 2009, 

Menzel and others 2002b, Owen and others 2002, Sasse 

and Pekins 1996) indicates tolerance both for disturbance 

and heterogeneous landscapes. Persistence in landscapes 

where forest distribution is highly fragmented also has 

been documented, as both Henderson and others (2008) 

and Kniowski and others (2012) captured northern longeared bats in woodlots and forest stands within largely 

agricultural landscapes.

Although the species is capable of existing in fragmented 

landscapes, Henderson and others (2008) reported 

that probability of forest stand use was best predicted 

by amount of deciduous forest area within 2 km, with 

an increase in odds of 1.6 for every additional 100 ha 

of deciduous forest. Likewise, Carter and Feldhamer 

(2005) found that roosts were best distinguished from 

random trees by distance to forest, with roosts closer to 

contiguous forests. However, males and females may 

react to fragmentation differently, as Henderson and 

others (2008) found probability of use by males was 

better predicted by amount of deciduous forest within 

2 km, and probability of use by females was predicted 

by amount of deciduous forest within a patch. Minimum 

forest patch sizes where bats have been captured vary 

among studies, with minimums of 17.1 and 15.9 ha for 

females and males, respectively, on Prince Edward Island 

(Henderson and others 2008) and 86 ha in northeastern 

Ohio (Krynak 2010).

Roost characteristics—Maternity colonies of northern 

long-eared bats are primarily found in snags and decaying 

or declining live trees, as are solitary males and females.

Because maternity roosts have been the main focus of 

research, hereafter “roosts” will be used to mean maternity 

roost unless otherwise specified. Although roosting 

under loose bark and in crevices is common, use of tree 

cavities accounts for greater proportions of roosts used 

in hardwood forests (Badin 2014, Foster and Kurta 1999, 

O’Keefe 2009, Silvis and others 2015b). Decay stage 

of roost trees commonly ranges between 2 and 6 on the 

Cline and others (1980) scale, and decay stage generally is 

greater than that of other trees in forest stands (Badin 2014, 

Broders and Forbes 2004, Krynak 2010, Silvis and others 

2015b). However, tree decay stage may not necessarily 

differ between snags used as roosts and potentially 

available snags (Menzel and others 2002b).

Roost tree height and d.b.h. are highly variable among 

and within studies (Badin 2014, Krynak 2010, Lacki and 

others 2009a, Silvis and others 2015b) (table 3). Based on 

consolidated data from across the range of the northern 

long-eared bat, roost trees were most commonly 15 to 

55 cm in diameter, and some studies have found roost 

trees larger than random (Lacki and Schwierjohann 2001, 

Owen and others 2002, Sasse and Pekins 1996). The 

level of observed variability in these measures suggests 

that the species is not dependent upon trees of specific 

characteristics for roosting. Rather, because roost trees 

tend to be larger than nearby or random trees and occupy 

larger canopy gaps (Jung and others 2004, O’Keefe 2009, 

Northern Long-Eared Bat (Myotis septentrionalis)

1Perry, R.W. [N.d.]. Unpublished data. On file with: R.W. Perry, U.S.

Department of Agriculture, Forest Service, Southern Research Station, 

Hot Springs, AR 71902.
10 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Owen and others 2002, Silvis and others 2015b), specific 

roost characteristics relative to other trees in the forest 

stand are important. However, roost trees are not always 

larger than neighboring trees (Menzel and others 2002b, 

O’Keefe 2009). Larger canopy gaps surrounding roost 

trees than gaps around random trees may be an artifact of 

using snags and senescing live trees as roosts. Conversely, 

these trees may be used to maximize solar exposure by 

females during the maternity period; female tree-roosting 

bats may select warmer roosts during parturition (Kerth 

and others 2001), which speeds development of young 

(Racey and Swift 1981, Zahn 1999). Additionally, variation 

in roost selection by North American bats may be related 

to regional climate (Fabianek and others 2015). Because 

no manipulative studies using northern long-eared bats 

have been conducted, it is difficult to determine whether 

selection of snags is for solar exposure or simply based 

on roost availability (i.e., cavities and loose bark). Roosts 

often are located on ridge tops and south-facing aspects 

(Johnson and others 2009, Jung and others 2004, Lacki 

and Schwierjohann 2001, Silvis and others 2012). Use of 

ridgetops and south-facing aspects may provide better solar 

exposure and therefore decrease costs of thermoregulation 

to reproductive females (Garroway and Broders 2008, 

Johnson and others 2009, Kunz and Lumsden 2003).

However, ridgetops also have the highest natural 

Table 3—Roost parameters from studies characterizing day-roosts used by northern long-eared bats (Myotis septentrionalis)

Study Location

Number 

of

bats

Number 

of 

roosts Sex

Roost tree 

d.b.h. (cm)

Roost tree

height (m)

Roost

height (m)

Canopy

openness (%)

Dominant

location (%)

Mean SE Mean SE Mean SE Mean SE Bark Cavity

Badin (2014) Indiana 23 71 ♀ — — — — 8.4 — — — 26.8 64.7

Carter and 

Feldhamer (2005) Illinois 10 19 ♀ 37.3 4.7 15.8 2.0 9.2 1.4 56.0 7.2 58.0 42.0

Cryan and 

others (2001) South Dakota 9 21 ♀ 39.0 1.8 9.1 1.1 4.2 0.9 — — — —

Ford and others (2006b)

Snags West Virginia 3 6 ♂ 16.6 1.5 — — 10.3 1.2 — — — —

Live trees West Virginia 7 10 ♂ 53.4 6.3 — — 31.5 1.7 — — — —

Foster and Kurta (1999) Michigan 11 32 ♀ 65.0 1.0 23.3 0.2 10.5 0.9 56.0 7.0 48.3 51.7

Garroway and 

Broders (2008)

Pre/post-lactation Nova Scotia — 22 ♀ 41.0 3.2 13.4 1.4 8.0 0.9 26.0 6.8 — —

Lactation Nova Scotia — 22 ♀ 43.0 3.6 22.1 1.0 16.4 0.7 48.0 7.9 — —

Johnson and

others (2009)

Burned West Virginia 36 25 ♀ 24.3 3.2 14.0 1.3 8.6 1.0 17.6 1.9 — —

Unburned West Virginia 36 44 ♀ 30.9 2.6 16.3 1.2 8.8 0.7 9.4 0.2 — —

Jung and others (2004) Ontario 10 16 ♂ 42.6 3.8 20.1 1.1 — — 64.0 3.5 84.6 15.4

Krynak (2010) Ohio 8 21 ♀ 55.8 4.7 — — 19.5 1.2 21.0 2.7 81.0 19.0

Lacki and

others (2009b)

Pre-burn Kentucky 18 16 ♀ — — — — 10.0 3.6 — — 50.0 50.0

Post-burn Kentucky 18 35 ♀ — — — — 9.1 1.4 — — 21.7 78.3

Lacki and 

Schwierjohann (2001)

Bark roosts Kentucky 15 57 Mixed 32.0 2.9 — — 6.5 0.7 16.6 0.3 100.0 0.0

Cavity roosts Kentucky 15 57 Mixed 16.8 2.3 — — 3.5 0.5 7.2 0.1 0.0 100.0

Menzel and

others (2002b) West Virginia 7 12 ♀ 29.2 1.6 18.7 1.5 10.8 1.0 — — 8.3 91.7

O'Keefe (2009)

Females North Carolina 18 52 ♀ 45.6 4.3 18.4 1.8 — — — — — —

Males North Carolina 16 50 ♂ 31.9 4.5 15.7 1.6 — — — — — —

Owen and others (2002) West Virginia 61 43 ♀ 27.2 1.0 17.8 0.7 10.8 0.6 — — 34.9 65.1

Perry and Thill (2007a)

Males Arkansas 17 43 ♂ 15.0 1.3 7.9 0.7 4.9 0.6 — — 60.0 40.0

Females Arkansas 23 49 ♀ 18.7 1.0 8.7 6.0 5.2 0.5 — — 43.0 57.0

Sasse (1995) New Hampshire 26 48 ♀ 30.9 2.8 14.8 1.0 — — 83.0 1.4 — —

Silvis and

others (2015b) Kentucky 121 215 ♀ 31.8 1.6 15.9 0.7 — — 4.5 0.5 1.4 98.6

Timpone and

others (2010) Missouri 13 37 — 43.0 2.3 15.7 2.9 9.6 2.9 44.0 — 59.0 41.0

— = Values not available; d.b.h. = diameter at breast height; SE = standard error; ♀ = female; ♂ = male.
Northern Long-Eared Bat (Myotis septentrionalis) 11

disturbance frequency and severity (Lorimer and White 

2003), and as suggested by Silvis and others (2012), may 

provide a greater number of potential roosts.

Little is known about characteristics of cavities used 

by northern long-eared bats. Measurements on the 

internal characteristics of a small number of cavities 

used by females in Kentucky suggest that cavities vary 

tremendously in length, volume, and diameter, but that 

cavity volume may be positively related to number of 

entrances (Silvis and others 2015c).

It is important to consider that bats likely do not select 

roosts based on a single roost characteristic, but rather 

on overall characteristics of potential trees, forest stands, 

and surrounding landscape. Studies on roost selection 

by northern long-eared bats make it clear that roosts 

are generally in overstory trees and in later stages of 

decay than neighboring or random trees, and are located 

in canopy gaps (Johnson and others 2009, Lacki and 

Schwierjohann 2001, Menzel and others 2002b, Perry and 

Thill 2007a). However, the process behind selection of 

individual roosts on any given occasion remains unclear.

Gender, reproductive condition, weather and climate, and 

social bonds may all play a role in selection, with relative 

weight of each factor in roost selection varying. Garroway 

and Broders (2008) found that lactating females in Nova 

Scotia selected taller trees in more open forest conditions 

than non-lactating females, possibly to provide juvenile 

bats with easy practice for flying and foraging. Silvis and 

others (2012) also found that lactating bats selected sites 

with greater canopy openness, but in contrast to Garroway 

and Broders (2008), the model differentiating roosts 

used during this reproductive period was only weakly 

supported. In Arkansas, females selected significantly 

larger diameter trees than males and roosted at sites with 

significantly fewer midstory trees than males, likely 

because of different physiological and environmental 

requirements of reproductive females (gestation) versus 

males (increased torpor depth) (Perry and Thill 2007a).

Geographic location, particularly latitude, also may affect 

roost selection, as bats at the extremes of the species’ range 

will have different thermal stresses to overcome. Roost 

characteristics and likelihood of roost switching may be 

related to changing daily weather conditions (Patriquin and 

others, in press). Presence of non-random social groups 

and roost networks (Johnson and others 2012, Silvis and 

others 2014a) and temporally structured social bonds 

(Garroway and Broders 2007) would not be observed if 

social factors did not influence roost selection.

Tree species used/preferred—Species of trees used 

for roosting varies greatly (Garroway and Broders 2008, 

Johnson and others 2009, Lacki and Schwierjohann 2001, 

Perry and Thill 2007a), and a tremendous number of 

tree species have been documented as roosts (table 4).

Table 4—Tree species used for roosting by northern long-eared bats (Myotis septentrionalis)

Species Preferred Species Preferred

American beech (Fagus grandifolia) Pignut hickory (Carya glabra)

American elm (Ulmus americana) Pin oak (Quercus palustris)

American sycamore (Plaatus occidentalis) Ponderosa pine (Pinus ponderosa)

American basswood (Tilia americana) Red maple (Acer rubrum). . . . . . . . . . . . . . . . X

Big-tooth aspen (Populus grandidentata) Red oak (Quercus rubra)

Black cherry (Prunus serotina) Red spruce (Picea rubens)

Black gum (Nyssa sylvatica) Sassafras (Sassafras albidum) . . . . . . . . . . . X

Black locust (Robinia pseudoacacia). . . . . . . . . . . . X Scarlet oak (Quercus coccinea)

Black oak (Quercus velutina) Shagbark hickory (Carya ovata) . . . . . . . . . . X

Black walnut (Juglans nigra) Shortleaf pine (Pinus echinata). . . . . . . . . . . X

Blue ash (Fraxinus quadrangulata) Silver maple (Acer saccharinum). . . . . . . . . . X

Boxelder (Acer negundo) Slippery elm (Ulmus rubra)

Chestnut oak (Quercus prinus) Sourwood (Oxydendrum arboreum). . . . . . . X

Chinkapin oak (Quercus muehlenbergii) Sugar maple (Acer saccharum). . . . . . . . . . . X

Common persimmon (Diospyros virginiana) Sweet gum (Liquidambar styraciflua)

Eastern hemlock (Tsuga canadensis) Tree of heaven (Ailanthus altissima)

Eastern redbud (Cercis canadensis) Trembling aspen (Populus tremuloides)

Eastern redcedar (Juniperus virginiana) White ash (Fraxinus americana)

Flowering dogwood (Cornus florida) White birch (Betula papyrifera)

Green ash (Fraxinus pennsylvanica) White oak (Quercus alba)

Hackberry (Celtis occidentalis) White pine (Pinus strobus). . . . . . . . . . . . . . . X

Hawthorn (Crataegus spp.) Winged elm (Ulmus alata)

Loblolly pine (Pinus taeda) Yellow birch (Betula alleghaniensis) . . . . . . . X

Mockernut hickory (Carya tomentosa) Yellow-poplar (Liriodendron tulipifera)

Northern red oak (Quercus rubra)

X = Preference or intense use was observed.
12 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Roost-tree species is clearly tied to the local tree-species 

assemblage, and conditions resulting from past disturbance 

regimes (e.g., insect and fungal outbreaks, ices storms, 

fire, etc.) that created structural characteristics suitable for 

roosting in a particular tree species. Preference for certain 

tree species often occurs (Ford and others 2006b, Lacki 

and Schwierjohann 2001, Perry and Thill 2007a, Silvis 

and others 2012), which may be related to past disturbance 

events. Nonetheless, the process of selection for individual 

species is poorly understood. Silvis and others (2012) 

and Ford and others (2006b) suggested that selection for 

tree species may be related to successional trajectories of 

individual forest stands; both studies observed selection 

for an early successional tree species that atypically 

occurred in the overstory in mature second-growth forests.

In both cases, the early successional species largely were 

overtopped by larger trees and were in late stages of decay/

decline. Despite noted selection preferences, the wide 

variety of tree species used indicates that this bat may 

be a generalist and is not dependent upon an individual 

species or genus for roosting. Likewise, selection for 

atypical species or circumstantial availability of species 

(Ford and others 2006b, Perry and Thill 2007a, Silvis and 

others 2012) indicates that the species is flexible enough 

to be considered opportunistic in selecting tree species.

At a broad level, there appears to be few commonalities in 

characteristics of tree species used as roosts; used species 

range from shade tolerant to shade intolerant, and position 

from overstory to understory. In some cases, limited roost 

availability may drive northern long-eared bats to use 

anthropogenic structures (Henderson and Broders 2008).

Roosting area space use—Northern long-eared bats 

demonstrate some inter-annual fidelity to roost areas, 

with use of capture sites up to 5 years after initial capture 

(Perry 2011), but all individuals within maternity colonies 

may not return each year (Silvis and others 2015a).

No reliable estimates for inter-annual survival rates, 

particularly post-WNS, are available, making it unclear if 

low inter-annual return rates observed by Silvis and others 

(2015a) were due to low survival post-WNS or dispersal.

Stronger matrilineal relationships among individuals 

within maternity colonies than with individuals from 

neighboring maternity colonies (Patriquin and others 2013) 

suggest long-term site fidelity to areas, if not individual 

roosts, across generations. Intra-annual roost fidelity is 

apparent and related to social structure (Garroway and 

Broders 2007, Johnson and others 2012, Silvis and others 

2014a). It is unclear how far northern long-eared bats move 

from summer maternity grounds to hibernacula, as well as 

vice versa.

Estimates of area used for roosting are complicated by 

different methods used to estimate area and variable 

sample sizes among studies, but roosting area of maternity 

colonies in contiguous forest have been reported between 

1.3 and 58.3 ha (mean 38.05 ± 20 SD ha) by Silvis 

and others (2015a), with associated subgroups using 

1.45–35.33 (mean 12.6 ± 9.9 SD ha) (Johnson and others 

2012). In a fragmented agricultural landscape, Henderson 

and Broders (2008) found roosting areas of 0.3 ha and 

4.13 ha for two separate colonies, with the larger area 

used by a colony in a more-forested landscape. Individual 

roosts may be considerable distances apart (e.g., 2.55 km) 

(Foster and Kurta 1999), but clustering of roosts appears 

to be common (Johnson and others 2009, Sasse and 

Pekins 1996, Silvis and others 2014a). Colonies also 

may use “core” areas that coincide with primary roosts 

and especially dense clusters of roosts (Silvis and others 

2014a). Colony-level roosting areas appear to be distinct 

and non-overlapping (Silvis and others 2014a) and persist 

across years (Silvis and others 2015a).

Roosting areas used by individual females appear to be 

relatively small in most cases, with reported averages 

of 8.6 (± 9.2 SD) ha (Broders and others 2006) and 

5.4 (± 1.1 SE) ha (Badin 2014). Perry and Thill (2007a) 

found individuals typically moved among roost trees in an 

area <5 ha. Few studies have reported habitat composition 

of home ranges, but roosting areas reported by Silvis 

and others (2015c) and Henderson and Broders (2008) 

consisted entirely or primarily of closed canopy forest.

Roosting areas do not appear to be located closer to water 

or openings than random locations (Badin 2014), although 

Perry and others (2008) found roosts were more likely 

to be located near group-selection stands with numerous 

openings. Although use of interior forests seems to be the 

norm in landscapes fragmented by agriculture, some roosts 

may be located in close proximity to a variety of types of 

forest edges (Krynak 2010). In more-forested landscapes, 

use of interior forests, including those mechanically 

thinned, appears to be frequent (Johnson and others 2009, 

Menzel and others 2002b, Silvis and others 2015b).

Movement distances between summer roosts generally 

average <0.8 km (Badin 2014, Broders and others 2006, 

Foster and Kurta 1999, Gumbert and others 2002, O’Keefe 

2009, Silvis and others 2015a), but maximum distances of 

up to 2 km have been recorded (Foster and Kurta 1999).

Broders and others (2006) and O’Keefe (2009) reported 

longer distance movements by females than males, which 

may be due to stricter roost requirements for females 

(Broders and others 2006). Some evidence suggests that 

female reproductive condition also may impact movement 
13

distances (Silvis and others 2015a). Individual bats are 

believed to use a small number of roosts (~3) (Krynak 

2010, O’Keefe 2009, Silvis and others 2014a), but as 

many as seven different roost trees have been used by 

an individual during a 2-week radio tracking period.

1

Jackson (2004) found the number of roost trees used by 

individual females averaged 8.6 (range 2–11). Silvis and 

others (2015a) found that tracking period was positively 

related to roost discovery rate, so estimates may be biased 

low by the reported tracking periods of only a few days.

Reproductive condition does not appear to influence 

number of roosts used by individual bats (Silvis and others 

2015a). For a colony, tracking 10 bats for 5 days will 

identify a substantial proportion of the roosts used (fig. 5).

2

Average distances to roosts from point of capture is <0.7 

km (Broders and others, 2006, Ford and others 2006b, 

Henderson and Broders 2008, Johnson and others 2009, 

Krynak 2010, O’Keefe 2009, Sasse and Pekins 1996).

2

The maximum reported distance from capture site to roost 

location in the literature is 2,649 m (Badin 2014), but bats 

may go farther, as R.W. Perry (unpublished data) located 

roosts 9.8 km from the capture site in Arkansas.

1

Acoustic Activity Patterns and Foraging Ecology

Using acoustic detectors to monitor bat activity is 

becoming increasingly common. Unfortunately, acoustic 

detectors are unable to distinguish between individuals 

or sexes, and often cannot separate species based on 

quantitative characteristics of their echolocation calls 

(Britzke and others 2011, Clement and others 2014, 

Hayes 2000). Nonetheless, acoustic detectors are useful 

for monitoring purposes and understanding bat ecology 

(e.g., Weller 2008). Acoustic detectors cannot differentiate 

specific bat behaviors (e.g., searching for a new roost 

vs. commuting or foraging), with the exception of “feeding 

buzzes.” Because acoustic detectors cannot differentiate 

individuals, differences in number of calls recorded 

among areas do not necessarily indicate differences in 

bat numbers among those areas. Consequently, data from 

acoustic detectors often are analyzed under a detection/

non-detection framework or activity patterns, with the 

latter often considered foraging behavior. Obviously, bats 

will be detected using echolocation calls at their roosts, 

but acoustic detection does not indicate they roost at that 

location.

2 Silvis, A. [N.d.]. Unpublished data. On file with: A. Silvis, Department 

of Fish and Wildlife Conservation, Virginia Polytechnic Institute and 

State University, Blacksburg, VA 24060.New roosts discovered

Number radio-tagged bats

Figure 5—Smoothed mean (standard error in gray) number of new roosts discovered for every radio-tagged bat 

tracked. Data from three northern long-eared bat (Myotis septentrionalis) colonies collected over 2 years (Source: 

Silvis and others 2015a).

Northern Long-Eared Bat (Myotis septentrionalis)
14 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Currently, identifying Myotis bats in eastern North 

America is a contentious issue for some, as the 

echolocation calls of species within this genus in North 

America are similar with considerable overlap in 

echolocation metrics. Recent analysis of the performance 

of bat call identification software by the U.S. Geological 

Survey found that accuracy rates of automated 

identification software generally are >75 percent at the 

individual file level, and even better at a presence-absence 

level when maximum-likelihood values are considered 

(Ford 2014, U.S. Fish and Wildlife Service 2015a).

Although many studies reviewed herein have not used 

the software approved by USFWS for Indiana bat surveys 

(http://www.fws.gov/midwest/Endangered/mammals/

inba/surveys/inbaAcousticSoftware.html), many have 

provided estimates for call classification accuracy 

(derived from discriminant function analysis). It is beyond 

the scope of the current review to assess accuracy of 

all reviewed studies, and we accept results of acoustic 

studies as presented with the above caveats noted.

Northern long-eared bat echolocation calls range in 

frequency from 40 kHz to 120 kHz, but average call 

frequency is typically 49–53 kHz (fig. 6). Echolocation 

calls of this species are of low intensity relative to many 

other species in their frequency range. Nothing currently 

is known about characteristics of social vocalizations 

made by this species or whether call characteristics vary 

across its range. Little acoustic work has focused directly 

on the northern long-eared bat. However, it does appear 

that intra-night patterns of acoustic activity differ among 

reproductive periods and may vary among habitat types 

(Johnson and others 2011).

Stand and landscape condition—At the landscape level, 

presence of northern long-eared bats may be positively 

related to amount of forest cover and negatively related to 

amount of urban/rural cover (Johnson and others 2008, 

Starbuck and others 2015) and small stem density 

(Starbuck and others 2015), with activity levels higher in 

forested than urban and rural landcover types (Johnson 

and others 2008). However, these results are equivocal, as 

Figure 6—Echolocation calls recorded from a captured and hand-released northern 

long-eared bat (Myotis septentrionalis) showing both full spectrum and zero-crossing 

data. (File courtesy of M.B. Fenton; edited for space)
Northern Long-Eared Bat (Myotis septentrionalis) 15

fragmentation amount has been found to have no negative 

impact on presence in forest stands (Ethier and Fahrig 

2011). Independent of forest amount, forest fragmentation 

may have positive effects by reducing travel times between 

foraging and roosting sites (Ethier and Fahrig 2011); 

several studies have found high levels of activity at forest 

edges in fragmented forest-agricultural landscapes (Jantzen 

and Fenton 2013, Mills and others 2013).

Forest type (deciduous, coniferous, mixed) may not impact 

presence or activity levels (Patriquin and Barclay 2003), 

but it is clear that forest conditions and local landscape 

features are related to activity patterns (Brooks 2008, 

Brooks and Ford 2005, Dodd and others 2012b, Ford and 

others 2005, Loeb and O’Keefe 2006). In forests, activity 

levels appear to be greater in more open than cluttered 

conditions (Brooks 2008, Loeb and O’Keefe 2006).

Activity may be greater in open stands, including partially 

harvested single-tree, shelterwood, and seed-tree harvested 

stands (Dodd and others 2012b). However, decreased 

activity levels in fields (Jantzen and Fenton 2013) suggest a 

limit to the level of openness tolerated for foraging. Using 

radiotelemetry, Owen and others (2003) found northern 

long-eared bats selected for partially harvested stands 

(30–40 percent of BA removed), but avoided leave-tree, 

two-aged harvests, and young clearcuts. Accordingly, 

contiguous canopy conditions appear to be somewhat 

important (Brooks and Ford 2005, Ford and others 2005).

Forested wetlands, riparian areas, and vernal pools often 

are considered important landscape features for bats, 

particularly the Indiana bat (Carter 2006, Fulton and 

others 2014). Several studies have investigated activity 

patterns of northern long-eared bats in such locations.

Henderson and Broders (2008) found foraging areas were 

concentrated along forested riparian zones. Other studies 

have indicated that pools and streams under closed canopy 

conditions are preferred to more open streams and pools 

(Brooks and Ford 2005, Johnson and others 2010a), but 

pool size alone is unimportant (Ford and others 2005).

Activity levels in riparian corridors have been found to 

be similar (Ford and others 2005) or greater than that 

of uplands (Owen and others 2004); use of forests with 

contiguous canopy but a relatively uncluttered and open 

midstory suggests a relatively complex relationship with 

forest stand characteristics.

Foraging area and habitat—Data from radio-tagged 

individuals indicate that foraging areas used by northern 

long-eared bats are larger than roosting areas. Broders and 

others (2006) report minimum mean foraging areas of 

46.2 (± 44.4 SD) ha for females and 13.5 (± 8.3 SD) ha for 

males, and Owen and others (2003) report average home 

ranges of 65 (± 5.2 SE) ha for females. In fragmented 

agricultural landscapes, foraging and movement were 

limited to forest-covered corridors and tree-lined 

hedgerows, with open areas used less and forested areas 

used more than expected (Henderson and Broders 2008).

In forested landscapes, foraging preference has been 

reported for diameter-limit harvests, intact forests, and 

road corridors (Owen and others 2003), and it does not 

appear that bats preferentially forage in either deciduous 

or coniferous forests (Broders and others 2006). Relative 

to roosting areas, foraging areas may be closer to forested 

riparian zones, and have lower canopy heights and higher 

structural complexity (Henderson and Broders 2008).

Foraging areas appear to be located close to or contain 

roosting areas (Broders and others 2006), with maximum 

movement distances of up to 1770 m (Broders and others 

2006, Henderson and Broders 2008).

Prey selection—Northern long-eared bats are insectivores 

that forage both by gleaning and aerial hawking (Ratcliffe 

and Dawson 2003). Dietary analyses have indicated that 

northern long-eared bats prey on at least seven orders of 

insects and Arachnida (Carter and others 2003, Dodd and 

others 2012a). Lepidoptera are a preferred prey resource 

as indicated by total volume and frequency of occurrence 

in fecal samples from a variety of locations throughout 

the species’ range (Brack and Whitaker 2001, Dodd and 

others 2012a, Whitaker 2004). Coleoptera and Diptera also 

appear to be commonly consumed (Brack and Whitaker 

2001, Carter and others 2003, Dodd and others 2012a, 

Feldhamer and others 2009, Whitaker 2004). Pre-WNS, 

bats provided an estimated $3.7 billion per year in insect 

control of agricultural pests (Boyles and others 2011); 

northern long-eared bats are known to consume a variety 

of forest-insect pests including eastern tent caterpillar 

(Malacosoma americanum); a variety of leaf rollers and 

tiers; and fruit, stem, and root borers (Dodd and others 

2012a).
16 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Response to Forest Management

A variety of forest management activities may occur 

across a landscape, including treatments to forest 

stands (e.g., thinning, midstory reduction, clearcutting, 

shelterwood harvest, single- and group-tree select harvest, 

and prescribed fire) and other activities such as road 

construction and right-of-way clearing. Management 

regimes can be widely divergent, ranging from custodial 

management with minimal disturbances to intensive 

management with frequent disturbances. Few studies have 

conducted controlled experiments to determine the effects 

of forest management on northern long-eared bats, and 

where information is available, it does not adequately cover 

the full range of forest management techniques available 

to forest landowners. However, sufficient work has been 

completed to infer broad patterns in the response of this 

species to both timber harvest and prescribed fire.

Timber harvest—As noted earlier, northern longeared bats roost (Johnson and others 2009, 2012; Owen 

and others 2002; Perry and Thill 2007a) and forage in 

harvested or otherwise thinned forest stands (Badin 2014, 

Ford and others 2005, Grindal and Brigham 1998, Owen 

and others 2004). Indeed, the species even has been 

documented to preferentially select partially harvested and 

burned forested conditions for roosting (Perry and others 

2008). Use of partially harvested stands for roosting does 

not answer questions about proximate effects of roost loss 

on maternity colonies, and unfortunately, little information 

is available on this topic. However, Silvis and others 

(2015a) conducted a small-scale, targeted roost-removal 

study that provided some insight into effects of roost loss 

on a short timescale. Their results suggest that loss of a 

primary roost has little impact on colony location, roost 

selection, social structure, fragmentation, or roost-use 

patterns, but a loss of ~17 percent of roosts may begin to 

cause colony fragmentation, a finding consistent with a 

previous simulation (Silvis and others 2014a). Although 

there is a considerable gap in understanding the effects 

of forest harvest on snag and roost loss rates across the 

species range (e.g., Perry and Thill 2013), it is evident that 

at least in the mid- to long-term, forest thinning may create 

suitable habitat for northern long-eared bats.

Fire—Three studies have investigated direct effects of 

prescribed fire on northern long-eared bats. These studies 

indicate that northern long-eared bats may move roosting 

areas into or closer to burned areas in both the immediate 

and short term (Dickinson and others 2009, Johnson and 

others 2009, Lacki and others 2009b). Further, changes in 

habitat conditions resulting from fire do not impact roost 

switching rates or overall roosting area size (Johnson and 

others 2009, Lacki and others 2009b). Adult northern 

long-eared bats apparently are able to arouse from torpor 

in late April and exit roost trees during prescribed fires 

before roost trees are surrounded or consumed by fire, and 

may resume roosting and foraging in burned areas within 

6 days after fire (Dickinson and others 2009). However, 

how non-volant bats and adults with offspring respond to 

fire is unknown. Foraging patterns after burning appear 

to be more related to stand type and topographic position 

than burn history (Dickinson and others 2009, Lacki and 

others 2009b).

Considerable proportions of roosts used by colonies after 

fire may be within burned areas, with Lacki and others 

(2009b) reporting 73 percent and Johnson and others 

(2009) reporting 38 percent of located roosts being in 

burned areas. Perry and Thill (2007a) found 73 percent of 

female roosts and 54 percent of male roosts in areas that 

had been burned 1–5 years previous. Similarly, colony 

sizes and nightly activity patterns at roosts also appear 

to be unaffected by burning (Johnson and others 2011).

Roost selection may be variable in response to changes in 

habitat structure, particularly canopy openness. Johnson 

and others (2012) found that in burned areas, bats were 

more likely to use cavity trees of smaller diameter where 

the canopy was interrupted by fire-related mortality. In 

contrast, roosts in unburned areas were nearer the tops 

of larger cavity trees. Lacki and others (2009b) similarly 

found that roost selection differed pre- and post-fire; 

roosts used post-fire were in trees with a greater number 

of cavities and a higher percentage of bark cover, whereas 

roosts used pre-fire were taller in height and in earlier 

stages of decay than random snags. Because inter-annual 

patterns in roost selection have been poorly studied, 

changes in roost-selection preference should be regarded 

with some caution (Silvis and others 2015b).

Based on the above, it appears that prescribed fire may 

benefit northern long-eared bats, despite actual (Dickinson 

and others 2009) or potential roost loss and habitat 

disturbance. This may be because increases in habitat 

quality following burning may provide an adequate 

trade-off for short-term roost loss. Although the exact 

mechanisms for tolerance to roost loss are unclear, flexible 

roost selection criteria (Silvis and others 2015b), frequent 

roost switching, and social structure (Silvis and others 

2015a), may play a role, as might landscape disturbance 

dynamics. Ford and others (2016) found that, although 

abundance of preferred roosting species may decline postfire, recruitment rate of alternate species may be three 

times greater than the loss of preferred species.
Northern Long-Eared Bat (Myotis septentrionalis) 17

Threats

Although relatively common and locally abundant before 

WNS, northern long-eared bats now are of conservation 

concern and listed as threatened under the Endangered 

Species Act. Population declines of this species following 

WNS have been substantial, and risk of local extinction is 

believed to be substantially greater for northern long-eared 

bats than other WNS-impacted species and unrelated to 

number of bats within hibernacula pre-WNS (Frick and 

others 2015). Consequently, the greatest threat to this 

species is WNS. Additive mortality resulting from habitat 

loss or disturbance during the maternity season should also 

be considered a threat to local populations. Habitat loss or 

disturbance resulting from forest management are probably 

not substantial threats per se, as numerous studies have 

found that northern long-eared bats will preferentially and 

opportunistically use managed forest stands for roosting 

and foraging (Ford and others 2006b, Johnson and others 

2012, Menzel and others 2002b, Owen and others 2003).

Moreover, because the decline in population size is due 

to WNS rather than habitat loss, it may be assumed that 

habitat availability is not a limiting factor for the species 

across most of its range, except in highly agricultural 

areas of the Midwestern United States and the forestprairie transition zone on the western periphery of its 

range. Avoidance of habitat manipulation and tree removal 

that affects known occupied roost trees during the active 

maternity season (mid-May through early August) could 

reduce risk of mortality related to tree-felling in maternity 

areas where northern long-eared bats are known to be 

present. The limited proportion of most landscapes that 

are harvested in any given year makes it unlikely that loss 

of a small number of roost trees would cause negative 

population-level impacts.

Research Questions and Needs

Many questions remain unanswered relative to northern 

long-eared bat ecology. Research priorities include:

• Effective treatment for WNS infections. The greatest 

threat to survival of the species is WNS. Unless northern 

long-eared bats are capable of rapid adaptation to this 

disease, they could become functionally extinct over a 

large portion of their range without an effective treatment.

• More effective models to predict locations of potential 

roost trees. Current information is insufficient and not 

standardized to allow accurate prediction over managed 

forest landscapes. In particular, more information is needed 

on how parameters often recorded by forest managers 

(i.e., basal area, midstory density) relate to potential roost 

locations.

• Effects of roost-site disturbance, including roost 

loss, during all life history phases. Studies are needed 

to document specific effects of roost loss due to harvest, 

both short- and long-term. Understanding the effects 

of roost-site disturbance will benefit land managers for 

forest planning. Potential for disturbance to roosting bats 

from management activities, such as harvest or burning 

during the summer maternity season, also needs further 

investigation.

• Effects of long-term changes in habitat conditions.

Given the wide breadth of habitats used by this species 

and relatively stable forest ownership and management 

trends in the United States (Oswalt and others 2012), 

significant loss of habitat for this species from ongoing 

forest management operations seems unlikely. A greater 

concern is how long-term changes in habitat structure 

and forest community composition, and changes in cave 

hibernacula conditions resulting from climate change, may 

shift distribution of the species.

• How northern long-eared bats use forested landscapes near hibernacula during spring staging and fall 

swarming. Preparation for hibernation and emergence 

from hibernation are critical for ensuring survival.

Regulations

Due to declines from WNS, northern long-eared bats 

were listed as federally threatened in April 2015 (50 CFR 

17 FWS–R5–ES–2011–0024). Using a provision under 

section 4(d) of the Endangered Species Act of 1973 

(hereafter, Act), the USFWS has enacted measures that are 

“necessary and advisable to provide for the conservation 

of the northern long-eared bat...” (hereafter, 4(d) rule; 

50 CFR 17 FWS–R5–ES–2011–0024; 4500030113).

Invocation of section 4(d) of the Act allows specific 

management actions to be exempt from the regulatory 

prohibited “take.” “Take” is defined as “to harass, harm, 

pursue, hunt, shoot, wound, kill, trap, capture or collect” 

individuals of the species (50 CFR part 17). “Take” may 

be purposeful (e.g., intentional killing, harassing, harming, 

capture or handling of individuals) or incidental (take 

is incidental to, and not the purpose of, an otherwise 

lawful activity, such as tree harvest). The final 4(d) rule, 

published in January 2016, makes several provisions 
18 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

to exempt forest management from “take” within the 

designated WNS zone. Outside the designated WNS 

zone, incidental take is allowed, but purposeful take 

is prohibited. In the WNS zone, incidental take of bats 

is prohibited in and around the hibernacula, including 

activities that may alter the hibernacula at any time of 

the year, such as alterations of the entrance or interior 

environment that may adversely affect bats. Prescribed fire 

and timber harvesting are exempted from incidental take, 

provided that:

(1) Known, occupied, maternity roost trees may 

not be destroyed, and no other tree removal may 

take place within a 45-m radius of known occupied 

maternity roosts during the pup season. As defined in 

the 4(d) rule, the pup season is June 1 through July 31.

Known occupied maternity roost trees are “trees that 

have had female northern long-eared bats or juvenile 

bats tracked to them or the presence of female or 

juvenile bats is known as a result of other methods.” 

A tree will remain a known, occupied maternity roost 

“as long as the tree and surrounding habitat remain 

suitable for northern long-eared bats” (page 1,911).

(2) No removal of trees may take place within a 

0.4-km radius of known northern long-eared bat 

hibernacula if take may occur. However, timber 

management may be allowed if it is conducted at a 

time when bats are unlikely to be roosting in trees 

within the buffer (e.g., winter), the activity does not 

adversely affect the hibernacula’s climate, or the 

activity does not change the suitability of the area 

for bat foraging. Local USFWS Ecological Services 

Field Offices (http://www.fws.gov/offices) should be 

consulted prior to activities to evaluate the potential 

for incidental take of northern long-eared bats.
Indiana Bat (Myotis sodalis) 19

Introduction 

The Indiana bat is a small to medium-sized 

colonial species of forest-dwelling bat in the family 

Vespertilionidae. Although listed as endangered, Indiana 

bats are distributed widely from eastern Oklahoma and 

Kansas to New Hampshire, south from the Great Lakes to 

Tennessee, with apparently limited numbers in northern 

Mississippi, northern Georgia, and the upper Coastal Plain 

of Alabama (fig. 7). As of 2015, maternity colonies also 

have been identified in the Coastal Plain of Virginia,3 and 

it is possible that populations may exist in the Coastal 

Plain of northeastern North Carolina. Indiana bats are 

distinguished from the physically similar little brown bat 

by their keeled calcar and short toe-hairs. Adult body 

mass averages 7.1–7.5 grams. Total wingspan may be as 

much as 240–267 mm, with forearms between 36.0 and 

40.6 mm (Thomson 1982). Sympatric species include the 

northern long-eared bat, little brown bat, big brown bat, 

and tri-colored bat.

Menzel and others (2001) provided a comprehensive 

review of the ecology of the Indiana bat. Herein, we 

provide a review of literature published since 2001, with 

particular focus on research in more diverse landscapes 

and on topics not addressed in the Menzel and others 

(2001) review.

Growing Season Roost Ecology

Similar to northern long-eared bats, Indiana bats rarely 

use anthropogenic or artificial structures such as bat boxes 

(Belwood 2002, Butchkoski and Hassinger 2002, Whitaker 

and others 2006), although they readily use artificial 

bark roosts (Adams and others 2015). During summer 

(May–July), females form maternity colonies under loose 

bark or in crevices or cavities of snags or declining live 

trees, whereas males roost solitarily (fig. 8) (Britzke and 

others 2003, 2006; Kurta and others 1993, 2002; Timpone 

and others 2010). Colonies larger than 100 are reported 

(Kniowski 2011, Kurta 2005), but average colony size 

is probably between 50 and 90 (Adams and others 2015, 

Britzke and others 2006, Callahan and others 1997, Harvey 

2002, Kurta and others 2002). Individual colonies may use 

numerous roosts, with reports of over 30 roosts (Bergeson 

and others 2015, Silvis and others 2014b). In some cases, 

number of roosts used by a colony appears to be relatively 

small (Johnson and others 2009), but it is unclear if this 

is an artifact of sampling. Although maternity colonies by 

definition contain mother-offspring pairs, no studies have 

identified whether colonies themselves follow matrilines 

across years, how nearby colonies are related, or the 

population genetic structure in general.

3 Germain, M. St. [N.d.]. Unpublished data. On file with: M. St.

Germain, Department of Fish and Wildlife Conservation, Virginia 

Polytechnic Institute and State University, Blacksburg, VA 24060.

Figure 7—Approximate Indiana bat (Myotis sodalis) range. Range 

data modified from National Atlas North American bat ranges (U.S.

Geological Survey 2014).

INDIANA BAT

(Myotis sodalis)
20 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Roost switching occurs an average of every 2 to 6 days.

There is some evidence that roost switching may be less 

frequent in more challenging environments, like those at 

relatively high elevations in mountainous terrain (Britzke 

and others 2003), but this has not been thoroughly tested.

Although only addressed in a single study, maternity 

colonies of Indiana bats exhibit a fission-fusion social 

dynamic associated with roost switching, which may 

also carry over during foraging (Silvis and others 2014b).

Social structure of maternity colonies appears to be 

variable among years, but factors that drive this variability 

are unclear. It is commonly accepted that maternity 

colonies of Indiana bats use multiple roosts, with some 

being “primary” and others “secondary.” Primary roosts 

receive consistent use, use by a large number of bats 

relative to other roosts used by the colony, or both (Britzke 

and others 2003, Callahan and others 1997, Miller and 

others 2002). However, network analysis suggests that bats 

probably do not view roosts in binary fashion (primary 

or alternate), but rather on a continuum. Moreover, roost 

importance within colony networks may change across 

years, and former primary roosts may decrease in status 

or may not be used (Britzke and others 2006, Silvis and 

others 2014b). Not all individuals within a maternity 

colony will hibernate together (Kurta and Murray 2002), 

which raises questions about how maternity colonies form 

and how migration routes are chosen.

Overall annual adult survival was estimated to be 

64.2 percent pre-WNS, with little difference between males 

and females, although caution is urged when interpreting 

this estimate given biases inherent to the study design 

(Boyles and others 2007, Humphrey and Cope 1977).

It is unknown what inter-annual survival rates are now 

that WNS is causing decreased over-winter survival.

Stand and landscape condition—In the agricultural 

Midwestern United States, roosts of Indiana bats 

commonly are found in bottomland hardwood forests, 

riparian forests, and otherwise hydric forest types 

(Bergeson and others 2013, Carter 2006, Kniowski 2011, 

Timpone and others 2010). In the Appalachian Mountains 

and the periphery of their range, Indiana bats have been 

found in more upland areas (Britzke and others 2006, 

Hammond 2013, Johnson and others 2010b, Johnson and 

Gates 2009) and in somewhat xeric forest types despite 

Figure 8—Solitary male Indiana bat (Myotis sodalis) roosting under loose bark of a 20-cm d.b.h. pine snag 

during the fall. (Photo by Stephen Brandebura, Arkansas State University)
Indiana Bat (Myotis sodalis) 21

availability of hydric forests (Jachowski and others 2016).

As noted by Carter (2006), location of suitable roosts 

in relation to other habitat features probably is more 

important than habitat type alone in determining roosting 

locations. Indeed, landscape-scale analyses have found 

that forest area and configuration are better predictors of 

roosting than distance to stream or water alone (Jachowski 

and others 2016, Pauli and others 2015a, Watrous and 

others 2006, Weber and Sparks 2013). However, distance 

to stream and area in hydric forest still may be important 

predictors (Bergeson and others 2015, Carter and others 

2002, Pauli and others 2015a, Watrous and others 2006).

Across studies, reported landscape composition ≥1 km 

around roosts ranges from 8 to 62 percent forested, 33 to 

55 percent agricultural and open field, 8 to 19 percent 

wetland, 6 to 23 percent urban and residential, and 0.9 to 

3 percent open water (Bergeson and others 2015, Kurta 

and others 2002, Miller and others 2002, Sparks and 

others 2005, Watrous and others 2006). Proportion of 

forest within local landscapes has been found to have 

positive effects (Watrous and others 2006, Weber and 

Sparks 2013), negative effects (Pauli and others 2015a), or 

no relationship (Farmer and others 2002) with likelihood 

of Indiana bat presence. A positive relationship between 

amount of forest on the landscape and presence of Indiana 

bat roosts is consistent with the overall requirement for 

forest roosts, but the negative relationship between forest 

amount and presence identified by Pauli and others 

(2015a) is difficult to explain. It is possible that landscape 

configuration has differential effects on habitat selection 

by Indiana bats, as the best predictors of summer habitat 

have been found to differ between forested and agricultural 

areas (Weber and Sparks 2013). The apparent positive 

effect of moderate amounts of forest edge in agricultural 

areas also could be suggestive that Indiana bats actually 

prefer moderately forested landscapes (Watrous and others 

2006, Weber and Sparks 2013). This may help explain why 

roost switching is relatively less common and colony sizes 

are smaller in the mostly forested Appalachian Mountains 

and other sites on the periphery of their distribution 

(Britzke and others 2006, Carter 2006). Preference for 

only moderately forested landscapes at large scales is 

consistent with selection for diverse land cover types 

(Watrous and others 2006), but may also be an artifact 

of landscape configuration within the core of the species 

range. Reproductive maternity colonies are known to 

persist in habitat fragments across years (Silvis and others 

2014b) (fig. 9), suggesting that even if moderately forested 

landscapes are not preferred, colonies are able to persist 

and reproduce therein.

Forest stands used by Indiana bats in the Midwestern 

and Northeastern United States are typically deciduous 

(Brack 2006, Britzke and others 2006, Carter and others 

2002, Carter and Feldhamer 2005, Johnson and others 

2010b, Johnson and Gates 2009, Kniowski 2011, Kurta 

and others 2002, Timpone and others 2010, Watrous and 

others 2006), possibly because of limited availability 

of mixed or pine-dominated stands. In more southerly 

areas, the species roosts in mixed pine-hardwood 

stands3

 (Britzke and others 2003) or stands otherwise 

containing pine trees (Brack 2006, Gumbert and others 

2002, Hammond 2013, Perry and others 2016). There 

is apparent selection preference for larger forest stands 

in fragmented landscapes (Jachowski and others 2016).

Among stands, density of suitable roost trees (Farmer and 

others 2002), basal area, and density of large trees may 

be better predictors of roost-site selection than distance 

to hydric features (Jachowski and others 2016, Miller 

and others 2002), with increased likelihood of presence 

with increased availability of large trees and potential 

roosts. However, forest patches in the Midwestern United 

States used by Indiana bats for roosting often contain 

considerable percentages of bottomland hardwoods and 

wetlands (Carter and others 2002, Watrous and others 

2006).

Roost characteristics—Indiana bats have consistently 

been found to roost in trees larger than surrounding trees 

and in moderate to large canopy gaps; nearly all studies 

have found statistically significant differences in these 

factors between roosts and random trees (Bergeson and 

others 2015; Brack 2006; Britzke and others 2003, 2006; 

Carter and Feldhamer 2005; Johnson and others 2010b; 

Johnson and Gates 2009; Kniowski 2011; Kurta and others 

2002; Miller and others 2002; Timpone and others 2010; 

Watrous and others 2006) (fig. 10). Loose or exfoliating 

bark is by far the primary roost type, with only limited 

crevice and cavity roosting reported (Bergeson and others 

2015; Brack 2006; Britzke and others 2003, 2006; Carter 

and Feldhamer 2005; Jachowski and others 2016; Johnson 

and others 2010b; Kniowski 2011; Kurta and others 

2002; Miller and others 2002; Timpone and others 2010; 

Watrous and others 2006). Roost tree decay stage is 

generally advanced, but availability of roosting substrate 

appears to be more important (Bergeson and others 2015; 

Brack 2006; Britzke and others 2003, 2006; Carter and 

Feldhamer 2005; Jachowski and others 2016; Johnson 

and others 2010b; Kniowski 2011; Kurta and others 

2002; Miller and others 2002; Timpone and others 2010; 

Watrous and others 2006).
22 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Figure 9—Indiana bat (Myotis sodalis) roost locations in a highly fragmented agricultural landscape in Pickaway County, Ohio 

(Source: Kniowski 2011).
Indiana Bat (Myotis sodalis) 23

Figure 10—Representative Indiana bat (Myotis sodalis) roost. Note size 

relative to surrounding trees and canopy gap. (Photo by Andrew Kniowski, 

Virginia Polytechnic Institute and State University)

Virtually all studies suggest that selection for canopy 

gaps is beneficial for increasing solar exposure, but no 

studies have assessed whether solar exposure increases 

recruitment or juvenile growth rate. Furthermore, benefits 

of increased solar exposure to non-reproductive females 

and males are unknown. Roosts may be located on 

south-facing aspects and mid-slope, which also provides 

increased solar exposure (Britzke and others 2003, 

Jachowski and others 2016), although this is not universal 

and may be offset by other factors (Johnson and others 

2010b). In North Carolina, Indiana bats selected roosts 

on the upper portion of ridges on south-facing slopes in 

mixed pine-hardwood forests (Hammond 2013). However, 

Gardner and others (1991) found that roost temperatures 

at sites with intense solar radiation may reach potentially 

lethal levels (e.g., 44 °C) in mid- to late-summer, forcing 

bats to move to less-exposed and better insulated roosts, 

and Indiana bats may use sites with more shade during 

warm weather (Callahan and others 1997). Perry and 

others (2016) found males during the fall roosted mostly 

in lower slope positions in the higher elevation portions of 

study areas. Cooler temperatures resulting from cold air 

drainage into lower slopes (Perry 2013) may have allowed 

deeper torpor and greater energy conservation during the 

critical pre-hibernation period (Perry and others 2016).

There does not appear to be a substantial difference in 

roost selection among reproductive conditions or sexes, 

although this has not been thoroughly studied. Similarly, 

although some studies have found that “primary” roosts 

are larger and receive more solar exposure than “secondary 

roosts” (Britzke and others 2003, Kniowski 2011), this is 

not always the case (Miller and others 2002).

Diameter of live trees and snags used for roosting varies 

from 4.3 to 86.6 cm d.b.h. (Britzke and others 2003, 

Menzel and others 2001, Perry and others 2016), which 

suggests flexibility in tree sizes used. Although studies 

suggest many species of bats (including Indiana bats) 

prefer trees larger than random for roosting, these studies 

are biased by minimum sizes used to calculate random 

trees. For example, when minimum diameter of random 

trees are set ≤15 cm d.b.h., Indiana bats preferred trees 

larger than random, but did not prefer trees larger than 

random when minimum size of random trees included in 

analysis are set at ≥18.5 cm d.b.h. (U.S. Fish and Wildlife 

Service 2007). Therefore, Indiana bats likely prefer 

overstory trees, but not necessarily the largest overstory 

trees. Males during fall may use trees ≥20 cm d.b.h.

at a higher proportion than their availability, and trees 

smaller than this at less than their availability (Perry and 

others 2016). Overstory age of forest stands is an important 

factor for roost selection by Indiana bats (and other bat 

species), as trees must be large enough (older) to provide 

adequate rooting substrate. In Arkansas, 98 percent of 

male roosts were in stands with an overstory ≥38 years 

old, suggesting this may be an important age threshold for 

roost selection, likely due to the development of adequate 

tree size and surrounding forest structure (Perry and 

others 2016).
24 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Tree species used/preferred—Indiana bats have been 

reported using at least 31 species or genera of trees 

(Kurta 2005) (table 5), and likely use many more.

Preference, or intense use, has been reported for silver 

(Acer saccharinum) and sugar maples (A. saccharum) 

(Kurta and others 2002, Timpone and others 2010), oaks 

(Bergeson and others 2015, Carter and Feldhamer 2005, 

Timpone and others 2010), shagbark hickory (Carya 

ovata) (Brack 2006, Britzke and others 2006), pines 

(Britzke and others 2003, Gumbert and others 2002, 

Hammond 2013), and green ash (Fraxinus pennsylvanica) 

(Carter and Feldhamer 2005). Regionally, deciduous 

species dominate across the Midwestern United States, but 

pines appear to be selected in southern areas, mountainous 

regions, and along the east coast (Brack 2006, Britzke and 

others 2003, Carter and Feldhamer 2005, Gumbert and 

Table 5—Tree species (or species groups) used as 

roosts by Indiana bats (Myotis sodalis)

a

Species Preferred

American beech (Fagus grandifolia)

Ash (Fraxinus spp.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X

American basswood (Tilia americana)

Birch (Betula spp.)

Black locust (Robinia pseudoacacia)

Eastern hemlock (Tsuga canadensis)

Elm (Ulmus spp.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X

Flowering dogwood (Cornus florida)

Green ash (Fraxinus pennsylvanica) . . . . . . . . . . . . . . . X

Hackberry (Celtis occidentalis)

Hickory (Carya spp.)

Hophornbeam (Ostrya virginiana)

Honey locust (Gleditsia triacanthos)

Maple (Acer spp.). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X

Mockernut hickory (Carya tomentosa)

Oak (Quercus spp.). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X

Pines (Pinus spp.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . X

Poplar (Populus spp.)

Quaking aspen (Populus tremuloides)

Sassafras (Sassafras albidum)

Shagbark hickory (Carya ovata) . . . . . . . . . . . . . . . . . . . X

Shortleaf pine (Pinus echinata). . . . . . . . . . . . . . . . . . . . X

Sourwood (Oxydendrum arboretum)

American sycamore (Platanus occidentalis)

Sweet birch (Betula lenta)

Tuliptree (Liriodendron tulipifera)

Walnut (Juglans spp.)

White ash (Fraxinus americana)

White pine (Pinus strobus)

Yellow birch (Betula alleghaniensis)

Yellow-poplar (Liriodendron tulipefera)

X = Preference or intense use was observed.

a List is not comprehensive due to lack of reporting in some 

studies.

others 2002, Hammond 2013, Menzel and others 2001, 

Perry and others 2016). Live shagbark hickory tends to 

be used whenever it is an available species (Menzel and 

others 2001), possibly due to its longevity (roost stability) 

compared to snags as well as its unique exfoliating bark 

characteristics (Perry and others 2016). Selection for 

tree species has not been thoroughly investigated, but 

all tree species preferred or intensely used are notable 

for being susceptible to developing loose bark. Regional 

preference for tree species is clearly constrained by the 

local assemblage of available tree species and likely with 

habitat type. For example, based on species reported as 

preferred or strongly used, it appears that in xeric sites, 

oaks, hickory, and pines may be selected, whereas in mesic 

sites, maples and ash are selected. In both cases, preference 

for tree species is also likely constrained by stand history 

and the resulting availability of suitable roosts.

Roosting area space use—Maternity colonies may be 

>500 km away from hibernacula (Kurta and Murray 2002, 

Winhold and Kurta 2006), with southerly hibernacula 

having greater catchment areas than northerly hibernacula 

(Britzke and others 2012). However, distances moved 

from hibernacula may also be quite small, with some 

recorded distances <40 km (Britzke and others 2006).

Indiana bats exhibit site fidelity to roosting areas (Gumbert 

and others 2002, Silvis and others 2014b), both within 

(Brack 2006, Butchkoski and Hassinger 2002, Gumbert 

and others 2002, Silvis and others 2014b) and between 

years (Gumbert and others 2002, Silvis and others 2014b).

It is unclear how long bats may continue to use roost 

areas, but some roost areas have been used up to 4 years 

(Kniowski 2011, Kurta and Murray 2002). Colony areas 

may shift slightly between years, possibly in response to 

roost suitability and survival (Gumbert and others 2002, 

Kurta and Murray 2002, Silvis and others 2014b). Overall 

inter-annual return rates for colony members are unknown 

and difficult to predict. Return rates could be high given 

relatively high pre-WNS yearly survival estimates, or low 

given that not all members of maternity colonies hibernate 

together (and thus may be free to join new colonies).

Roost area home range (not including foraging area) 

is inconsistently reported in the literature, and where 

reported, differences in method and sample size 

complicate cross-study comparisons. Nonetheless, 

whole-colony roost areas have been reported between 

174.9 and 1704.0 ha (Carter and Feldhamer 2005, Silvis 

and others 2014b). Silvis and others (2014b) reported 

that roost area may vary considerably in size between 

years and provided an observed difference of 1529.1 ha 

between consecutive years in the agricultural Midwest.
25

Maximum reported distance moved between a capture 

location and a roost is 40 km, but this was recorded 

during spring when bats were emerging from caves and 

may not be the norm; mean recorded distance moved 

during this time was 26.9 km (Britzke and others 2006).

In contrast, Johnson and Gates (2009) reported maximum 

distance between capture site and roost as 2.6 km during 

the maternity season. Rommé and others (2002) reported 

a mean maximum distance of 4.3 (± 2.8 SD) km, and 

Perry and others (2016) reported distances up to 11.6 km 

from capture sites (hibernacula) to tree roosts during fall.

Distances moved between sequentially used roosts may 

be considerable, as Carter and Feldhamer (2005) and 

Bergeson and others (2015) report maximum distances of 

4.6 and 8.2 km, respectively. However, average distance 

moved between roosts is probably considerably smaller 

with reported means of 686 and 1079 m (Bergeson and 

others 2015, Kurta and others 2002). There have been no 

formal comparisons of distances moved by bats in different 

reproductive conditions.

Acoustic Activity Patterns and Foraging Ecology 

USFWS guidance recently have allowed summer surveys 

for Indiana bats to use acoustic methodology (U.S. Fish 

and Wildlife Service 2015a). Indiana bat echolocation calls 

range in frequency from 40 kHz to 69 kHz, but average 

call frequency is typically 47-51 kHz (fig. 11). Although 

identification of Myotis bats from their echolocation calls 

is currently a contentious issue, particularly when done 

using automated identification software, empirical reviews 

of software suggest that echolocation calls of Indiana bats 

can be distinguished relatively reliably from those of other 

Myotis species, particularly when maximum likelihood 

values are used (Britzke and others 2002, 2011; U.S. Fish 

and Wildlife Service 2015a).

Stand and landscape condition—In a mostly forested 

landscape, occupancy of forest patches by Indiana bats 

has been found to be positively related to mean patch 

size but negatively related to proportion of landscape in 

Figure 11—Echolocation call recorded from a hand-released Indiana bat (Myotis 

sodalis) showing both full spectrum and zero-crossing data.

Indiana Bat (Myotis sodalis)
26 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

forested cover types (Yates and Muzika 2006); this is 

consistent with observations of roosting areas (Pauli and 

others 2015a). In largely forested landscapes, probability of 

presence has been found to be positively related to riparian 

stream order and canopy cover (Ford and others 2005), 

and basal area of snags (Yates and Muzika 2006). Among 

forest stands, activity levels are greater in riparian forests 

than upland forests (Owen and others 2004), with overall 

activity levels positively associated with canopy cover over 

waterways, smaller streams, and elevation (which may be 

correlated) (Johnson and others 2010a). In riparian areas, 

activity has been found to be negatively related to percent 

wetland and open water (Johnson and others 2010a).

Foraging area and habitat—Foraging areas used 

by maternity colonies of Indiana bats apparently are 

considerably larger than roosting areas, with Silvis and 

others (2014b) providing an estimate between 3555.3 

and 3609.0 ha; foraging areas appeared stable between 

years. Mean home range for individual Indiana bats 

is consistently reported between 200 and 400 ha, but 

may be variable within a given locality or among bats 

within a maternity colony (max reported SD = 994 ha) 

(Bergeson and others 2013, Brack 2006, Butchkoski and 

Hassinger 2002, Jachowski and others 2014b, Johnson 

and Gates 2009, Kniowski and Gehrt 2014, Menzel and 

others 2005a, Rommé and others 2002). Home range 

size may decrease throughout summer (Bergeson and 

others 2013), but there is no apparent difference in home 

range area among different reproductive conditions 

(Womack and others 2013a). Reported fall home ranges 

may be larger than summer home ranges (Rommé 

and others 2002), and the smallest reported average 

home range is 130.5 ha (Jachowski and others 2014b).

Home ranges of individuals roosting in buildings may 

be smaller than those of individuals roosting in trees 

(Butchkoski and Hassinger 2002). Largest reported 

average home range size is 1137 ha (Womack and 

others 2013a). Indiana bats may travel over 4 km from 

roosts while foraging (Butchkoski and Hassinger 2002, 

Murray and Kurta 2004, Rommé and others 2002).

At the landscape scale, Indiana bats consistently prefer 

hydric and forested habitat types, and avoid agricultural 

and developed land cover types (Bergeson and others 2013, 

Brack 2006, Butchkoski and Hassinger 2002, Johnson 

and Gates 2009, Kniowski and Gehrt 2014, Menzel and 

others 2005a, Sparks and others 2005, Womack and others 

2013b). Preferred habitat may change across seasons, with 

Brack (2006) noting increasing use of deciduous forest in 

the pre-hibernation period. Within home ranges, habitat 

use is similar to that of the landscape scale, with increased 

likelihood of use of forested wetland, and decreased use 

of shrub wetlands and developed lands (Jachowski and 

others 2014b). Depending on landscape configuration, 

Indiana bats may traverse agricultural areas using forest 

edges (Murray and Kurta 2004), or fly across fields 

(Kniowski and Gehrt 2014). The decision to fly across 

fields or traverse edges probably is tied to energetic costs 

and possibly exposure to predators, and use of forest edges 

probably is more likely when forest availability is greater.

Prey selection—Indiana bats are insectivores that are 

believed to forage primarily by aerial hawking. Dietary 

analyses have found that they prey on insects of the 

orders Lepidoptera, Coleoptera, Trichoptera, Diptera, 

Hymenoptera, Hemiptera, Homoptera, and Neuroptera; 

they also consume spiders (Caylor 2011, Feldhamer 

and others 2009, Lee and McCracken 2004, Tuttle and 

others 2006). Lepidopterans are a preferred food based on 

percent volume and frequency (Caylor 2011, Feldhamer 

and others 2009, Lee and McCracken 2004, Tuttle and 

others 2006).

Response to Forest Management

Perhaps due to complications of conducting manipulative 

experiments with endangered species, there are few direct 

studies on effects of forest management and no systematic 

investigation of effects of different forest management 

techniques on Indiana bats. Consequently, available 

information is derived from occasions when Indiana bats 

were found on managed landscapes.

Timber harvest—Indiana bats have been found in 

managed forest systems (Jachowski and others 2014b, 

Johnson and others 2010b) and may display a positive 

association between foraging and managed forest 

conditions (Womack and others 2013b). Indiana bats 

are often found roosting in a variety of managed forests 

during fall, including stands that have been selectively cut, 

clearcut, shelterwood cut, and burned (Brack 2006, Perry 

and others 2016). However, Indiana bat activity has also 

been found to be lower 2 to 4 years after forest thinning 

compared to pre-thinning, although activity levels may be 

greater in uneven-aged treatments than in either even-aged 

treatments or unharvested controls (Caylor 2011).

Dietary composition has been found to vary after forest 

management treatments, possibly related to changes in 

insect availability (Caylor 2011). Simulations of effects 
27

of timber harvest on Indiana bats suggest that creation of 

suitable foraging habitat may be maximized under low 

intensity timber-harvest scenarios such as single-tree and 

patch-cutting, with short-term availability of roosting 

habitat maximized using selection harvests (Pauli and 

others 2015b). However, single-tree selection over the 

long term (>1 cutting entry) leads to cluttered, unevenaged structure, and no studies have examined long-term 

effects of this silvicultural system on bats. Although 

evidence is limited, preference for managed forests, 

greater activity in partially harvested areas, and simulation 

results suggest that Indiana bats are at least tolerant to 

many forest management practices and may benefit from 

careful application of forest management techniques. It 

is possible that forest management activities that remove 

moderate amounts of basal area and promote development 

of potential roosting habitat may benefit Indiana bats, but 

robust documentation of potential positive effects would 

require considerable future study.

Fire—Few studies have investigated the effects of fire on 

Indiana bats. Johnson and others (2010b) found that in a 

landscape containing both burned and unburned forest, 

male Indiana bats readily used burned stands for roosting, 

and roost switching behavior did not differ between burned 

and unburned stands. In burned stands, Indiana bats 

roosted in fire-killed red and sugar maples, whereas in 

unburned stands, they roosted primarily in live hickories, 

oaks, and maples (Johnson and others 2010b). Selection for 

fire-killed maples corresponds with findings of Ford and 

others (2016) who suggested that prescribed fire increased 

overall availability of roosting opportunities for northern 

long-eared bats, which mitigated loss of roosts caused by 

fire. In 1 of 3 study areas in Arkansas, Perry and others 

(2016) found male Indiana bats during the fall preferred 

mature forest stands (≥50 years old) that had been recently 

burned and stands burned multiple times over the previous 

10 years for roosting, whereas mature forests that were 

not burned were used at a lower proportion than their 

availability (fig. 12). MacGregor and others (1999) found 

male Indiana bats during the fall roosted twice as often as 

expected in an area burned frequently for red-cockaded 

woodpeckers (Leuconotopicus borealis) during 1 of 

2 years of sampling. Johnson and others (2010b) found 

that roosts in burned stands occupied larger canopy gaps 

than roosts in unburned stands. Given the commonly held 

supposition that increased solar radiation is beneficial 

for bats, it may be that burning increases overall roost 

suitability in burned stands, at least for females during the 

summer maternity season.

Figure 12—Snag used by male Indiana bats (Myotis sodalis) during fall 

in an open pine stand burned frequently. (Photo by Stephen Brandebura, 

Arkansas State University)

Direct effects of growing-season burns on roosting bats 

are unknown, as no published studies have reported these 

effects. Average height of roost entrance for Indiana 

bats (summarized from 16 separate studies) was 5–16 m 

(U.S. Fish and Wildlife Service 2007), which may be high 

enough to avoid direct mortality during low-intensity fires.

Bats roosting under pieces of bark, which are typically 

closed at the top but open at the bottom, may be more 

affected by rising heat and smoke, whereas bats in cavities 

are likely more protected (Guelta and Balbach 2005). Bats 

roosting in well insulated cavities located relatively high 

in the trees are unlikely to be subjected to injury during 

low-intensity prescribed burns (Perry 2012).

Indiana Bat (Myotis sodalis)
28 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Dickinson and others (2010) created models predicting 

potential burns to ears, wings, or other non-furred parts of 

bats based on roost heights, fire intensity (flame length), 

and wind speed. Winds may reduce temperature and 

gas concentrations at roosting heights by distorting fire 

plumes. They suggest that bats roosting at heights above 

12 m (wind speeds of 2 m/sec [4.5 mph]) to 22 m (wind 

speeds of 0 m/sec) would not be injured during intense 

controlled burns (flame lengths approximately 1.6 m 

high). Furthermore, they suggested models used to predict 

foliage scorch during prescribed burns may potentially be 

useful as surrogates for predicting injury to bats. Carbon 

monoxide levels at roosting heights are unlikely a concern 

when flame lengths (fire intensity) are <1.6 m, which 

are typically the most intense fires observed during most 

prescribed burns (Dickinson and others 2010). Models 

for carbon monoxide suggest that critical levels of blood 

carboxyhemoglobin may be reached during intense 

fires, but only in close proximity to flames, which limits 

potential danger to lower-height roosts.

If applied outside of the active season, it seems likely 

that prescribed fires may affect bats similarly to timber 

harvest, creating appropriate conditions for both roosting 

and foraging. Studies suggest fire generally has beneficial 

effects on bats by creating snags, reducing understory and 

midstory clutter, creating more open forests, and possibly 

increasing abundance of flying insects (Perry 2012).

However, as with effects of timber harvest, additional 

study is suggested.

Threats

Federally endangered before WNS, the Indiana bat 

has been a species of conservation concern since 1967.

Pre-WNS, populations of this species were increasing, 

largely as a result of comprehensive habitat management 

measures that protected both hibernacula and summer 

maternity habitat. Populations are once again on the 

decline as a result of WNS (Thogmartin and others 

2012, 2013). Given effectiveness of pre-WNS habitat 

conservation efforts, the greatest threat to this species is 

WNS. Additive mortality resulting from habitat loss or 

disturbance during maternity season may be a threat to 

local populations, but effective conservation measures 

already in place should limit risk. As with all species 

experiencing rapid declines, loss of genetic diversity 

following a potential WNS-related population bottleneck 

may lead to further population declines. Secondarily, over 

the next several centuries, changes in climate may also 

reduce total available habitat across the species’ range and 

shift populations to the Northeastern United States and 

the Appalachians Mountains (Loeb and Winters 2013).

Climate change also is likely to shift roost preference, as 

a recent analysis has shown that range-wide variation in 

bat roost selection is related to mean summer temperature 

(Fabianek and others 2015).

Research Questions and Needs

Much is known about the Indiana bat, but many questions 

remain unanswered. Research priorities include:

• Effective treatment for WNS infections. The greatest 

threat to survival of the species is WNS. Although declines 

in Indiana bats due to WNS have not been as dramatic as 

other bat species, unless this species can adapt to WNS, 

an effective treatment for the disease may be required to 

prevent it from becoming functionally extinct over much of 

its range.

• Effects of long-term changes in habitat conditions 

and availability. Maintaining adequate roosting habitat 

will continue to be a challenge for land managers.

However, given the wide breadth of habitat types used, 

loss of habitat seems unlikely except for fragmentation 

in the Midwestern United States. A greater concern is 

whether long-term changes in habitat structure and forest 

community composition will have additive impacts 

with WNS. Additionally, changes in cave hibernacula 

environments resulting from climate change may affect the 

species’ distribution.

• More effective models to predict locations of potential 

roost trees. Current information is insufficient and not 

standardized to allow accurate prediction over managed 

forest landscapes. In particular, more information is needed 

on how the parameters often recorded by forest managers 

(i.e., basal area, midstory density) relate to potential roost 

locations.

• Studies on effects of forest management on Indiana 

bats are few. Consequently, information is needed on 

effects of various silvicultural systems and prescribed 

burning on Indiana bat roosting and foraging.

• How Indiana bats use forested landscapes near 

hibernacula during spring staging and fall swarming.

Preparation for hibernation and emergence from 

hibernation are critical for ensuring subsequent survival.
Indiana Bat (Myotis sodalis) 29

Regulations

Under the National Environmental Policy Act, individual 

Federal projects must be assessed for potential effects on 

endangered species that may be present in an area. This 

act covers Federal lands and projects funded with Federal 

money. For example, on National forests and military 

installations where land and range management routinely 

occurs, each site has a comprehensive plan (e.g., forest 

plan) that outlines standards for management. In addition, 

most sites within the range of the Indiana bats have 

formally consulted with USFWS in development of their 

plans and have received non-jeopardy biological opinions 

and incidental take statements (Krusac and Mighton 

2002). These formal consultations are intended to balance 

the need to conduct land management activities and the 

need to minimize but not eliminate “take” of Indiana 

bats (Dickinson and others 2009). Because most Federal 

entities negotiate separately with their local USFWS 

field office, management standards (e.g., snag retention 

guidelines, smoke guidelines, buffers around hibernacula) 

for Indiana bats may differ among sites (Dickinson and 

others 2009). Activities that deviate from established and 

approved plans may require additional formal consultation 

with USFWS.

Similar to Federal lands, non-Federal and private landowners may negotiate with USFWS to develop habitat 

conservation plans (HCPs). Under an HCP, incidental take 

statements are issued by USFWS after consultation, again 

with the goal of balancing the need for land management 

and minimizing take.

31

Introduction

The tri-colored bat (Perimyotis subflavus), formerly 

known as the eastern pipistrelle (Pipistrellus subflavus), is 

a small forest-dwelling bat in the family Vespertilionidae 

(Fujita and Kunz 1984). This species is distributed from 

southeastern Canada to Honduras and reaches as far west 

as Oklahoma (fig. 13). Evidence suggests that its range is 

expanding westward (Armstrong and others 2006, Geluso 

and others 2005, Kurta and others 2007). Tri-colored 

bats are the second smallest bat species in eastern North 

America, with a body mass ranging from 3.3 to 8.0 grams, 

a total length of 77 to 89 mm, and a forearm length of 

31.4 to 34.1 mm (Fujita and Kunz 1984, Whitaker and 

Hamilton 1998) (fig. 14). Sympatric species over much 

of the species’ range in the Eastern United States include 

the Indiana bat, little brown bat, northern long-eared bat, 

and big brown bat. Due to a paucity of research, little is 

known about the ecology of the tri-colored bat in forests, 

especially when compared to the better-studied northern 

long-eared and Indiana bats.

Growing Season Roost Ecology

Brack and Mumford (1984) speculated that the tri-colored 

bat range is constrained by geographic distribution of 

hibernacula. However, there is little robust evidence for 

this as stable isotope data indicate that this species is a 

regional migrant (Fraser and others 2012) and acoustic 

data indicate their ability to cross long geographic 

distances such as the Great Lakes (Thorne 2014).

Furthermore, tri-colored bats are found hibernating in 

culverts, old bunkers, and other man-made structures in 

areas without caves from Texas across the Southeastern 

United States (Jones and Pagels 1968, Sandel and others 

2001), and its distribution extends into tropical regions of 

Central America and southern Mexico. Exact distances 

migrated are unknown, but it appears that males migrate 

longer distances than females (Fraser and others 2012).

Patterns of acoustic detection during the late summer and 

early fall suggest that migration may be in mid-August 

(Dzal and others 2009, Thorne 2014), with bats in the 

Midwestern United States entering hibernacula sometime 

between late-September through mid-October (Damm and 

Geluso 2008).

TRI-COLORED BAT

(Perimyotis subflavus)

Figure 13—Approximate tri-colored bat (Perimyotis subflavus) range.

Range data modified from National Atlas North American bat ranges 

(U.S. Geological Survey 2014).

Tri-colored bats may begin forming maternity groups as 

early as mid- to late April. During the summer maternity 

season (generally April–July), tri-colored bats are known 

to roost in buildings (Jones and Suttkus 1973), live and 

dead foliage, other vegetation (including lichens and 

Spanish moss), and exfoliating bark (Farrow and Broders 

2011, Poissant and others 2010, Veilleux and others 2004, 

Veilleux and Veilleux 2004). In southern locations, 

summer roosts may also serve as hibernacula (Jones and 

Suttkus 1973). Tri-colored bats form small maternity 

Tri-Colored Bat (Perimyotis subflavus)
32 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

colonies, with a maximum reported colony size of 29 

individuals (Whitaker 1998), and mean colony sizes of 

10–18 (Poissant 2009, Whitaker 1998). Although colonies 

are generally believed to contain primarily females, in at 

least one instance, adult males have been found in almost 

equal proportion to females within colonies (Jones and 

Suttkus 1973).

Although the social structure of maternity colonies has not 

been assessed, colonies appear to be distinct social groups 

with little to no interchange of individuals among groups 

(Poissant 2009). Roost switching may occur as often as 

every 2.5 days (Poissant 2009), but may occur less often1, 

with individual bats using multiple roosts (Perry and Thill 

2007a, Veilleux and Veilleux 2004). Compared to other 

temperate foliage-roosting species, tri-colored bats have 

greater roost-site fidelity during summer, with individuals 

remaining in the same roost for a maximum of 17–33 

consecutive nights (Perry and Thill 2007b, Veilleux and 

others 2003). Movement of all colony members is common 

(Poissant 2009, Whitaker 1998). Most of the time in roosts 

(77 percent) is spent resting, with 16 percent of time spent 

in an alert condition (Winchell and Kunz 1996).

Historic estimates suggest survival peaks at approximately 

3.5 years with males having greater survival than females 

(Davis 1966), although the method used to assess survival 

was not robust by current analytical standards. Litter size 

is larger than those of similarly sized bats in eastern North 

America, with a reported average litter size of 1.93–1.96 

(Hoying and Kunz 1998). Parturition occurs between 

late May and early July (Whitaker 1998). Juvenile body 

mass and growth are closely related to ambient and roost 

temperature, rainfall, and availability of insect prey 

(Hoying and Kunz 1998). Volancy generally is attained 

by approximately 4 weeks of age (Whitaker 1998). Adult 

females may abandon maternity roosts shortly after 

young are volant, although juveniles may remain longer 

(Whitaker 1998). Capture ratios in the Southeastern United 

States indicate a sex ratio of 0.4F:1M juveniles, and an 

adult sex ratio of 5.0F:1M (Miller 2003). It is unlikely that 

the adult population truly is skewed so strongly towards 

females, and it is relatively common in many locations to 

capture more males than females. Indeed, Perry and others 

(2010) found the opposite trend, with 1F:3M. In part, 

detection of skewed sex ratios may be biased by proximity 

of sampling to maternity colonies.

Stand and landscape condition—Range of the tri-colored 

bat encompasses a considerable portion of eastern North 

America. Although the species has been captured across 

diverse forest types, studies on forest associations of this 

species are limited. Roosting behavior of this species in 

forests has been documented in mixed pine-hardwood 

stands in the Ouachita Mountains in Arkansas (Perry and 

others 2007, 2008; Perry and Thill 2007a), deciduous 

hardwoods in western Indiana (Veilleux and Veilleux 

2004), and hardwood-boreal transition Acadian forest 

in Nova Scotia (Farrow and Broders 2011, Poissant 

2009). In the Ouachita Mountains, small-scale roost 

site selection (<250 m) was positively related to area of 

mixed pine-hardwoods >100 years old, group selection 

cuts, and thinned mature (>50 years old) stands. In 

contrast, landscape scale roost site selection (>1000 m) 

was negatively related to area of immature pine stands 

15–29 years old and area of mixed pine-hardwoods 

50–99 years old, but positively related to largest forest 

patch size and patch adjacency (Perry and others 2008).

Additionally, roosts reported by Perry and others (2007, 

2008) were farther from roads than random, and most were 

in unharvested 50–99 year old mixed pine-hardwood or 

hardwood stands. In the Acadian forests of Nova Scotia, 

small-scale roost site selection was positively related to 

number of trees with useable lichen substrate (Usnea 

trichodea), and percent softwood immediately surrounding 

roosts, and negatively related to distance from water.

Because studies of roosting behavior are limited, it is 

difficult to generalize these behaviors across regions.

Roost characteristics—Buildings reported as roosts 

include houses and abandoned military bunkers (Jones and 

Suttkus 1973, Whitaker 1998). Nonetheless, foliage roosts 

appear to be the preferred roost type in forests during 

summer (Perry and Thill 2007b, Poissant and others 2010, 

Veilleux and Veilleux 2004). In the Ouachita Mountains 

of Arkansas, all roosts were in foliage, with 50 percent 

of female and 91 percent of male roosts in dead leaves 

Figure 14—An adult tri-colored bat. (Photo by Andrew Kniowski, 

Virginia Polytechnic Institute and State University)
Tri-Colored Bat (Perimyotis subflavus) 33

suspended in deciduous trees; 43 percent of maternity 

colonies were in dead needle clusters suspended in large, 

live pines (fig. 15) (Perry and Thill 2007b). In Indiana, 

all roosts by females were in live or dead deciduous tree 

foliage (Veilleux and others 2004). In the Acadian forest of 

Nova Scotia, female tri-colored bats roosted exclusively in 

beard lichen (Usnea trichodea) found primarily in boreal 

conifers (Poissant and others 2010). Dead leaf clusters used 

for roosting can range from a single dead leaf to clusters 

>30 cm in diameter, and large dead limbs containing 

multiple clusters of dead leaves have been documented as 

maternity colonies (Perry and Thill 2007b).

Trees containing female roosts in Arkansas were larger 

than random trees, whereas trees containing male roosts 

did not differ from random (Perry and Thill 2007b). It 

seems likely that abundance of suitable substrate is an 

important criterion for roost selection, as trees containing 

tri-colored bat roosts in Nova Scotia had a greater amount 

of U. trichodea coverage than random trees (Poissant 

and others 2010). Reproductive condition impacts roost 

selection, with reproductively active females roosting at 

lower levels in the forest strata, closer to permanent water 

sources, and farther from the nearest forest/field edge than 

non-reproductive females (Veilleux and others 2004).

Figure 15—Tri-colored bat (Perimyotis subflavus) maternity colony located in suspended dead pine 

needles 20 m above the ground in a live 40-cm d.b.h. pine. (Photos by S. Andrew Carter, U.S. Forest 

Service)
34 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Tree species used/preferred—Few studies have 

assessed selection preferences for tree species used by the 

tri-colored bat. It is clear, however, that U. trichodea lichen 

is a preferred roost type in Nova Scotia (Poissant and 

others 2010). With regard to tree species used for roosting, 

spruce trees (Picea sp.) have been used extensively in Nova 

Scotia (Poissant and others 2010), and oaks were the most 

used species reported for reproductive females in Indiana 

(Veilleux and others 2004) and for males and females 

in Arkansas (Perry and Thill 2007b). Female maternity 

colonies in Arkansas were often found in clusters of dead 

pine needles in large overstory shortleaf pines (Perry and 

Thill 2007b).

Roosting area space use—Adult tri-colored bats exhibit 

inter-annual site fidelity, with juveniles exhibiting natal 

site fidelity (Veilleux and Veilleux 2004). However, 

temporal extent of this fidelity is unclear. Roosting area 

of individual bats appears to be relatively small (≤2.3 ha) 

(Veilleux and Veilleux 2004). Roosting area of maternity 

colonies is variable in size, with a reported range in Nova 

Scotia between 1.6 and 77.4 ha (mean = 22.8), and contain 

an average of 22.8 roosts (Poissant 2009).

Acoustic Activity Patterns and Foraging Ecology

Because acoustic detectors collect information across the 

bat species community, there is a relatively greater amount 

of acoustic information on tri-colored bats than capture 

and radio-tracking data. Additionally, it is worth noting 

that the echolocation calls of tri-colored bats are easy to 

distinguish from bats of the genus Myotis due to some 

diagnostic call characteristics. Echolocation calls from 

tri-colored bats range in frequency from approximately 

40 to 49 kHz (fig. 16).

Stand and landscape condition—At the landscape level, 

studies have found the amount of nonforest landcover 

to be negatively related to activity (Farrow and Broders 

2011), and the amount of forest to be negatively related 

with activity while fragmentation had no impact (Ethier 

and Fahrig 2011). In a savannah-woodland gradient in the 

Missouri Ozark Highlands, occupancy was found to have 

a weak negative relationship with both percent forest and 

percent urban landcover (Starbuck and others 2015). Thus, 

the particular effects of landscape condition on activity and 

presence remain unclear.

Figure 16—Echolocation call recorded from a captured and hand-released tri-colored bat (Perimyotis subflavus) showing 

both full spectrum and zero-crossing data.
Tri-Colored Bat (Perimyotis subflavus) 35

At the stand level, the exact relationship between activity 

and forest structure is moderately well understood. Several 

studies have indicated a positive association between 

activity and canopy cover and forest age (Ford and others 

2006a, Johnson and others 2010a), with activity in forests 

being greater at sites with low to moderate amounts of 

vegetation cover and density (Bender and others 2015, 

Ford and others 2006a, Johnson and others 2010a, Loeb 

and O’Keefe 2006, Yates and Muzika 2006). Activity 

levels were positively related to forest and corridor edge 

(Hein and others 2009, Morris and others 2010), and 

riparian areas (Broders and others 2003, Ford and others 

2005, Johnson and others 2008, Owen and others, 2004, 

Vindigni and others 2009). Activity was low over open 

waterways and pools (Broders and others 2003, Johnson 

and others 2010a, Menzel and others 2005b, Owen and 

others 2004).

Foraging area and habitat—No studies have documented 

foraging patterns of radio-tagged tri-colored bats.

However, acoustic data from the upper Coastal Plain in 

South Carolina suggested that feeding activity (feeding 

buzzes) did not differ between canopy gaps and closed 

canopy forests; between gaps of different sizes; between 

harvested or unharvested forests; or among gap edges, gap 

centers, and adjacent forest (Menzel and others 2002a).

Prey selection—Dietary analysis indicates that 

Trichoptera, Coleoptera, Diptera, and Hymenoptera form 

a substantial proportion of the tri-colored bat diet (Caylor 

2011, Feldhamer and others 2009).

Response to Forest Management

Few studies have assessed response of tri-colored bats 

to forest management activities, although the species 

is known to occur in intensively managed landscapes 

throughout eastern North America (Bender and others 

2015, Brooks 2008, Caylor 2011, Morris and others 

2010, Owen and others 2004, Vindigni and others 2009).

Activity of tri-colored bats was apparently unaffected by 

prescribed burning in pine stands (Loeb and Waldrop 

2008), with no apparent relationship to time since burning 

(Armitage and Ober 2012).

In an actively managed forest landscape of Arkansas, 

tri-colored bats roosted only in stands with a hardwood 

component that retained an overstory ≥50 years old 

(Perry and Thill 2007b). In that study, 48 percent of male 

roosts were in partially harvested stands (group selection 

stands or stands with overstory reduction and midstory 

removal), but 88 percent of those roosts were located in 

unharvested greenbelts [including streamside management 

zones (SMZs) or riparian buffers] that were retained 

within harvested stands. No female roosts were found in 

partially harvested portions of stands (Perry and Thill 

2007b). The common denominator among roost sites 

used by tri-colored bats in that study was the presence 

of a well-developed, hardwood-dominated midstory.

Potential direct effects of fire on tri-colored bats are 

unknown. Mean roost heights in forests have been reported 

as 17.7 m in Indiana and 12.5 m in Arkansas (Perry and 

Thill 2007b, Veilleux and others 2004), suggesting bats 

may roost high enough to avoid negative direct effects 

during low-intensity burning. Given the highly flammable 

nature of their roost substrate (elevated dead leaves), 

direct effects of fire could be negative, but no studies have 

examined this relationship.

Threats

Although relatively common and locally abundant 

before WNS, the tri-colored bat is now of conservation 

concern across its temperate distribution. Population 

declines of this species following WNS have been great, 

and risk of local extirpation is believed to be substantial 

(Ford and others 2011, Frick and others 2015). Given 

the cosmopolitan nature of their distribution, including 

Mexico and Central America, extinction is unlikely, but 

extirpation from some areas in North America is possible.

The greatest threat to this species is WNS. Wind turbines 

also have killed significant numbers of tri-colored bats 

(Arnett and others 2008). Additional mortality resulting 

from habitat loss or disturbance during the maternity 

season may be a threat to local populations. In the long 

term, loss of genetic diversity following WNS may lead 

to further population declines. This may be a larger risk 

for the tri-colored bat than the northern long-eared bat as 

genetic evidence suggests that tri-colored bats survived a 

historically recent population bottleneck (Martin 2014).

Threats from habitat loss or disturbance resulting from 

forest management are unknown, but use of dead foliage 

roosts, which generally have shorter lifespans than snags, 

suggests that this species is highly plastic and adaptive 

in response to forest habitat management at small spatial 

scales. Moreover, because population decline is due to 

WNS rather than habitat loss, and because the species 

range was expanding pre-WNS (Kurta and others 2007), 

it may reasonably be assumed that habitat availability is 
36 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

not a limiting factor for this species. Avoidance of habitat 

manipulation and tree removal that affects roost trees 

during the active maternity season (mid-May through early 

August) should be sufficient to avoid mortality related to 

tree-felling in maternity areas. Moreover, given the habitat 

plasticity demonstrated by this species, it is unlikely that 

tree felling operations below the landscape scale will have 

population-level effects.

Research Questions and Needs

Many questions remain unanswered relative to the ecology 

of the tri-colored bat. Research priorities include:

• Effective treatment for WNS infections. The greatest 

threat to survival of the species is WNS. If tri-colored bats 

are unable to adapt to this disease, an effective treatment 

for WNS may be one of the few options to prevent tricolored bats from becoming functionally extinct over 

portions of their range.

• Forest-habitat relationships. Significant study is 

suggested to fully understand the life history and ecology 

of this species.

• Effects of forest management. Studies are needed to 

document the specific effects of forest management at both 

the short and long term. Understanding effects of roost-site 

disturbance could be highly beneficial to land managers for 

forest planning.

• Effects of long-term changes in habitat conditions and 

availability: Studies are needed to understand how longterm changes in habitat structure and forest community 

composition, and changes in cave hibernacula conditions 

resulting from climate change might shift the distribution 

of this species.

• Range-wide genetic diversity of the species. Limited 

genetic data are available on this species. Efforts to 

understand the genetic diversity of the tri-colored bat could 

be beneficial for long-term planning of population recovery 

and assessment of species extinction risk.

• How tri-colored bats use forested landscapes near 

hibernacula during spring staging and fall swarming.

Preparation for hibernation and emergence from 

hibernation are critical for ensuring subsequent survival.
Conclusions 37

CONCLUSIONS

Northern long-eared, tri-colored, and Indiana bats are 

forest-obligate species, but display different relationships 

within the forests they inhabit. Despite unique relationships 

between each species and forests, all display variability 

in behavior across their range, with great degrees of 

flexibility in habitat selection. Recent work with bat habitat 

selection and behavior indicates that some variability 

in roost selection (Fabianek and others 2015) and roost 

switching behavior (Patriquin and others, in press) may 

be related to local climatic conditions. At the larger, 

distribution-wide scale, differences in habitat selection are 

closely tied to local landscape configuration and forest 

structural condition.

Historically, ecology of northern long-eared bats has 

been considered similar to Indiana bats, primarily due 

to overlap in roost-tree characteristics. However, several 

factors have been found to differ between the two species.

First, although both species have defined social structures 

and both use roosts in a hierarchical fashion, it is not 

apparent that social structure and behavior are identical 

(Silvis and others 2014a, 2014b). Additionally, size of 

area used for roosting and foraging differs substantially 

between these two species, with Indiana bats using space 

at scales nearly an order of magnitude greater than those 

of northern long-eared bats (Silvis and others 2014a, 

2014b). Indiana bat roost selection also varies subtly from 

that of northern long-eared bats (Carter and Feldhamer 

2005, Foster and Kurta 1999, Timpone and others 2010).

Although both species typically select roost trees larger 

than surrounding trees and sites with canopy gaps, roost 

trees used by Indiana bats are generally larger than those 

used by northern long-eared bats. Roost type also varies, 

with Indiana bats using exfoliating bark as roosts more 

consistently than northern long-eared bats, which typically 

use cavities to a greater extent. Moreover, northern longeared bats may roost further away from aquatic areas 

than Indiana bats (Jung and others 2004). In general, 

roost selection and landscapes used by the Indiana bat 

are more consistent across the species’ range than that 

of the northern long-eared bat. Relative to the above 

characteristics, tri-colored bats are substantially different 

from both species. In particular, tri-colored bats use foliage 

roosts and form smaller and less intensely social groups 

than either northern long-eared or Indiana bats.

All three species reviewed are capable of persisting in 

fragmented landscapes that consist of variable mixtures 

of forest, agriculture, and to some extent, exurban 

development. Based on the studies reviewed, Indiana 

bats may be better suited to fragmented environments 

than tri-colored or northern long-eared bats. It is 

important to note that this perceived tolerance may 

be due to study-location bias, as many bat researchers 

studied Indiana bats in small woodlots in fragmented 

landscapes. Relatively little is known about how changing 

landscape configuration affects these three species of bats, 

particularly when changes consist of large-scale conversion 

of forests and mixed landscapes to more-intensive 

agricultural or developed land use. However, it is apparent 

from a number of studies that these three species may 

benefit from heterogeneous forest landscapes such as those 

created by active forest management, when heterogeneity 

encompasses forest type, age, and structural characteristics 

(fig. 17). Benefits of heterogeneous forest landscapes to 

bats may arise from beneficial juxtaposition of roosting 

and foraging areas.

Although northern long-eared bats do not appear as 

tolerant of landscape fragmentation as Indiana bats, this 

species is plastic in selection of forest stands and roosting 

habitat. They may capitalize on beneficial changes in 

habitat near existing roosts, as demonstrated by females 

shifting roosting and foraging areas to stands recently 

treated with prescribed fire (Ford and others, in press; 

Johnson and others 2009; Lacki and others 2009b).

Further, both simulations and experimental manipulations 

suggest that northern long-eared bats may be tolerant of 

some limited to moderate level of roost loss (Silvis and 

others 2014a, 2015a). Simulation results suggest that 
38 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

Figure 17—A 70-percent overstory retention shelterwood harvest in an oak-hickory forest, Richland Furnace State Forest, 

Ohio. (Photo by Alexander Silvis, Virginia Polytechnic Institute and State University)

Indiana bats also may be tolerant of roost loss, but that 

response to roost loss may be less predictable (Silvis 

and others 2014b). Differences in responses between 

northern long-eared bats and Indiana bats to roost loss 

are unsurprising because these species differ in social 

roosting behaviors, roost switching, and numbers of 

roosts used per individual. In contrast, virtually nothing is 

known about the effects of roost loss on tri-colored bats.

It seems reasonable to suspect that effects of roost loss 

on tri-colored bats are limited, given their preference for 

an abundant and highly ephemeral roosting resource (i.e., 

foliage that lasts for days to weeks rather than years). In all 

cases, tolerance to roost loss is predicated on avoidance of 

direct mortality resulting from roost loss or alteration.

Despite the ecological differences among these three 

species, there are a number of forest management 

approaches that could broadly benefit these and other 

bat species. Activities such as prescribed burning and 

harvesting are often constrained by numerous and 

sometimes conflicting objectives, including favorable 

burning parameters, public health and safety, site 

conditions, market conditions, and ecological objectives.

For example, maintaining habitat for endangered 

red-cockaded woodpeckers may require burning during 

periods that may be less favorable for bats. Nonetheless, 

the following approaches could be used to improve 

roosting and foraging habitat and to reduce potential 

negative impacts on bats. It should be noted that these 

management options are not regulatory and do not 

supersede local, State, and Federal regulations, but will 

likely improve habitat conditions for bats. However, some 

items, such as hazard tree removal and timing of timber 

harvest, are explicitly mentioned in the 4(d) rule. Also, as 

noted above, response of bats to most forest management 

actions has largely not been studied; these suggestions 

should be viewed with this in mind: 

• Where feasible during vegetation management 

operations, retain snags (especially those ≥20 cm d.b.h.) 

except where human safety or property may be jeopardized 

or when disease or insects associated with dead trees could 

pose a forest health threat.
Conclusions 39

• When possible, conduct hazard tree removal during the 

dormant season unless an immediate threat to human safety 

or property exists.

• Consider installing artificial roosts in areas lacking 

adequate roost structure, especially adjacent to ponds and 

along riparian areas. Artificial bark roosts have been found 

to be particularly effective for Indiana bats (Adams and 

others 2015).

• During timber marking and harvest, consider retaining 

some mature trees of species known to be preferred for 

roosting, such as live shagbark hickory. Retain trees that 

show signs of cavities, basal openings, or hollowing of the 

bole. Plan timber harvests to avoid the pup-rearing season 

(e.g., June–July as designated in the current 4(d) rule 

stipulations for northern long-eared bat), when feasible.

• Unless ecological or silvicultural objectives or limited 

burn windows require growing-season burns, consider 

conducting prescribed burns during the dormant season.

Avoid burning during the pup-rearing season (e.g., June–

July), when feasible.

• During spring and fall when bats are roosting in trees, 

consider minimizing prescription and use of intense burns 

when temperatures are <10 °C (50 °F) or when winds 

<8 kph (5 mph). To minimize potential impacts, conduct 

spring and fall burns during afternoons when ambient 

temperatures are greatest (fig. 18).

• In areas with continuous canopy cover, consider 

maintaining small (<2 ha) forest openings with abundant 

snags, especially in close proximity to hibernacula. 

• Protect and maintain forest cover and snags in riparian 

areas. Consider maintaining continuous canopy cover 

over water sources and create ponds in areas lacking water 

sources.

• Consider maintaining diverse landscapes that include 

early successional patches, abundant edges, woodlands, 

savannas, and mature to older forest stands. Within 

mature forests, maintaining or encouraging a diversity of 

composition and structure (e.g., variable overstory basal 

area and midstory densities) could provide for diverse bat 

communities and benefit a wide array of other taxa.

Figure 18—Low intensity prescribed fire being applied to a 50-percent overstory retention shelterwood harvest in Richland 

Furnace State Forest, Ohio, to promote oak regeneration. (Photo by Andrew Kniowski, Virginia Polytechnic Institute and 

State University)
40 Relationships of Three Species of Bats Impacted by White-Nose Syndrome to Forest Condition and Management

• Consider using thinning to limit length of time 

regenerating stands remain in dense, closed-canopy 

conditions and to accelerate stands from the stemexclusion to the understory re-initiation phase. Consider 

midstory reductions in some mature stands to improve 

foraging habitat conditions and to promote canopy gap 

heterogeneity. Planting rows of seedlings farther apart 

during reforestation operations may extend the time to 

canopy closure and thin as operationally and economically 

feasible.

• Consider protecting cave and abandoned mine 

hibernacula from entry during the fall swarm through 

hibernation and spring emergence to prevent disturbance.

Try to avoid activities such as dozer operations, tree 

felling, fire-line construction, or blasting in close proximity 

(within 0.4 km) to hibernacula during these periods.

Consider hibernacula as smoke-sensitive areas during 

winter prescribed burns. Try to avoid activities in any 

season that might alter or change hibernacula airflow.
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Silvis, A.; Perry, R.W.; Ford, W.M. 2016. Relationships of three species of bats impacted 

by white-nose syndrome to forest condition and management. Gen. Tech. Rep. SRS–214. 

Asheville, NC: U.S. Department of Agriculture Forest Service, Southern Research Station. 

48 p.

Forest management activities can have substantial effects on forest structure and community 

composition and response of wildlife therein. Bats can be highly influenced by these 

structural changes, and understanding how forest management affects day-roost and 

foraging ecology of bats is currently a paramount conservation issue. With populations of 

many cave-hibernating bat species in eastern North America declining as a result of whitenose syndrome (WNS), it is increasingly critical to understand relationships among bats 

and forest-management activities. Herein, we provide a comprehensive literature review 

and synthesis of: (1) responses of northern long-eared (Myotis septentrionalis) and tricolored (Perimyotis subflavus) bats—two species affected by WNS that use forests during 

summer—to forest management, and (2) an update to a previous review on the ecology of 

the endangered Indiana bat (Myotis sodalis).

Keywords: Bat conservation, forest management, forestry, habitat relationships, Indiana 

bat (Myotis sodalis), North America, northern long-eared bat (Myotis septentrionalis), roost, 

tri-colored bat (Perimyotis subflavus), white-nose syndrome.
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Relationships of Three Species of Bats Impacted by White-nose Syndrome to Forest Condition and Management August 2016