myotis habitat case study
TRANSCRIPT
Myotis Habitat Protection and Enhancement for Endangered Indiana bat, Gray bat, and
Northern long-eared bat.
Blake Ellett
April 27, 2015
I. Introduction
The Indiana bat (Myotis sodalis), Northern long-eared bat (Myotis septentrionalis), and gray bat
(Myotis grisescens) are all Myotis species of bats that are listed as threatened or endangered
throughout their range in the United States. These bat species provide several ecosystem services
including insect control through predation (Mamm, 1981). These species have a broad
geographic range, stretching from Canada, Florida, and Missouri. There are two classes of bats,
cave dwelling bats, which inhabit caves all of the year or only in the winter hibernation months,
and tree dwelling bats, which reside specifically in forested habitats (Trani, M). The species
addressed in this report pertain to the cave dwelling Myotis species. These species have been
influenced by anthropogenic practices such as habitat clearing and urbanization along with
species declines associated with White Nose Syndrome (WNS), caused by the fungus Geomyces
destructans, which was introduced into the United States at Howes Cave, New York in 2006
(georgiawildlife.com/WNS, Gargas et. Al. 2009). The spread of WNS has decimated populations
of Indiana bats, Northern long-eared bats, gray bats, and several other indigenous species across
the U.S. With habitat loss increasing, and confronted with the new realities of high mortality
rates stemming from WNS, it is increasingly important to protect and enhance habitats for these
species as we are seeing drastic declines in population numbers (Photo 4, Appendix A). In the
following sections, discussion will include species description and life histories, discussion of
issues relating to the threatening and endangerment of the selected Myotis species, and policy
suggestions for recovering the indigenous populations.
II. Species Descriptions
Indiana bat
Indiana bat formally attained endangered species status through the USFWS (United States Fish
and Wildlife Service) on March 11, 1967 (Photo 1, Appendix A). Its distribution includes most
of the eastern United States from Oklahoma to Wisconsin, east to Vermont, and south to
northern Florida (Barbour and Davis 1969).
Indiana bats are best identified by a distinctively keeled calcar, toe hairs that do not extend past
the toe nails, a pinkish nose, and blunt tragus (georgiawildlife.com). The fur is short, grayish,
and typically duller than other Myotis species. Dorsal fur is darker at the base than the tip.
Forearm length is 35 to 41 millimeters, and weight ranges from 5 to 10 grams. While in flight,
the wing span is approximately 9 to 11 inches (fws.gov).
Indiana bats use caves and abandoned mine portals as hibernacula. During winter, they have
very specific hibernation requirements and occupy areas that maintain a consistent temperature
range (39-46 degrees F) and humidity range (>74%) (georgiawildlife.com). As such, very few
caves provide adequate microclimate for these bats (USFWS 2007). After hibernation, females
leave the hibernacula and fly to nursery sites to raise their young. Although some males may
leave with the females, others stay in or near the hibernacula throughout the summer months
(Barbour and Davis 1969).
At their summer roosts, Indiana bats typically live under the exfoliating bark of trees and in dead
snags of trees (Kurta and Kennedy 2002). It has been recognized that floodplain forests were the
significant habitat for Indiana bat utilization for foraging (Humphrey et al. 1977), but recent
studies indicate that this species also uses upland habitats (Sewell et al. 2006). Most known
maternity roosts have been located in or near wooded areas where some light gap is present
allowing full or partial solar exposure to the roost site. Maternity colonies typically roost under
the exfoliating bark of dead or live trees, and utilize dead snags as roosting sites (Gardner et al.
1991).
Indiana bats leave their maternity grounds mid-August to September and migrate toward their
hibernacula where they swarm near cave openings until they enter hibernation (Barbour and
Davis 1969). During the fall, mating occurs and females store sperm through their hibernation
until they inseminate themselves in the spring prior to spring migration (Barbour and Davis
1969).
Gray bat
The gray bat (Photo 2, Appendix A) is a medium-sized bat with a forearm length of 40 to 46
millimeters (1.6 to 1.8 in.) and a wingspan of 275 to 300 millimeters while in flight (10.8 to 11.8
in.) (Barbour and Davis 1969). The weight of the gray bat ranges from 7 to 16 grams it usually
falls between 8 and 10 grams (0.28 to 0.35 oz.) during the summer but may increase to 16 grams
(0.56 oz.) just before migration (georgiawildlife.com). The wing membrane is attached to the
foot at the ankle, this is one of the distinguishing traits for this species (Gore 1992). The fur is
gray immediately following the molt in midsummer but may bleach to chestnut-brown or bright
russet by the following May or June, especially in reproductive females (fws.gov).
The gray bat occurs over a limited geographic range in limestone karst areas of the southeastern
United States, as this species is primarily a cave dwelling species (Tuttle 1976). The majority of
known gray bat populations occur in Alabama, Northern Arkansas, Kentucky, Missouri, and
Tennessee (Brady et al. 1982), with small maternity populations as far north as southern Indiana
(Barbour and Davis 1969), and as far west as southeastern Kansas (Brady et al. 1982). The
species was listed under the ESA in 1976 as endangered throughout its range.
Gray bats are true “cave bats” and typically use caves as both winter and summer roosts. Less
than 5% of known caves systems provide suitable habitat for gray bats across its range (Mitchell
and Martin 2002). During the summer maternity season, gray bats typically roost in relatively
warm caves with temperatures ranging from 13.9° to 26.3°C (57° to 79°F). During the summer
maternity season, gray bats roost in caves within 2.5 mi of a stream or reservoir which are then
used as foraging corridors (Brady et al. 1982).
As riparian specialists, gray bats frequent streams, lakes, and wetlands during foraging and
distribute themselves 17 km upstream and downstream of their roost cave (LaVal et al. 1977).
The species will often travel great distances during nightly movements to and from roosts and
foraging areas and have been found to move up to 48 kilometers from their roost cave (Brady et
al. 1982). Gray bats have been shown to preferentially feed on aquatic insects such as
Trichoptera, Plecoptera, Ephemeroptera, and Diptera (Brady et al. 1982).
Northern long-eared bat
Northern long-eared bats can be distinguished from other Myotis species in their range by their
long ears (extended past their nose when pressed down over their face) and longer more pointed
tragus (Photo 3, Appendix A). The Northern long-eared bat’s forearm lengths range from 32 to
39 millimeters (Barbour and Davis 1969). The Northern long-eared bat has been historically
considered to be a common bat within forests throughout most of its range. However, with the
introduction of WNS and the subsequent population decline, as well as habitat loss and
degradation, this is no longer true as this species is now listed under the ESA as threatened
(USFWS, 2015). The southern extent of the range of the Northern long-eared bat begins in
northern Georgia and Alabama and expands north into southern British Columbia, Canada
(fws.gov).
Northern long-eared bats spend the summer months in forested habitats and forage through
riparian corridors. Maternity colonies of this species usually occur under exfoliating bark of
trees (Lacki and Schwierjohann 2001), although roosting use of bat boxes and human made
structures like shutters and bridge decks has been documented (Broders et al. 2004). During the
winter months, from late October through April, Northern long-eared bats can be found
hibernating in caves and abandoned mines (Krynak, 2010).
As with other Myotis in their range, Northern long-eared bats breed in the fall during swarming,
prior to hibernation. Females store sperm over hibernation and eggs are fertilized in the spring
shortly after awakening from hibernation. Pups are born in spring and become volant in under a
month. In late summer, maternity colonies begin to break up and both sexes begin to move to
swarming and hibernation sites.
III. Issues Related to Threatening/Endangerment of Myotis species
These Myotis species face a number of anthropogenic and biological issues related to the success
of the species moving forward. Due the nature of these species being cave dwellers through their
wintering ranges and requiring specific conditions within these caves for survival, they only have
a few suitable cave systems for roosting habitation within their range. Protecting these important
ecosystems from human disturbance is extremely important due to the sensitivity of these species
during hibernation and how easily they can become awakened/aroused during their hibernation
which causes them to use up vital energy (fws.gov).
WNS creates a biological disturbance to the bats through a fungal growth on the wings and face
during hibernation. WNS is decimating populations of cave dwelling bats across North America
(Blehert 2009). It is hypothesized that WNS affects bats while hibernating by arousing the
infected individual more frequently and for longer amounts of time as opposed to an un-exposed
individual, burning through fat reserves stored for the winter hibernation (USFWS 2011). WNS
also affects the wing membrane, creating scarring and physical holes within the membrane.
Direct degradation of wing membrane can decrease physiological functionality and cause issues
such as reduced thermoregulation, dehydration, and physical scarring affecting the physical
mechanisms of flight (USFWS 2011).
Direct habitat loss and degradation also affect bat species throughout North America. Through
urbanization projects, roadway construction/expansion, and development, large amounts of
forested habitat, exhibiting summer roosting habitat, are removed or degraded. Along with the
physical removal of summer roosting trees, decreased water quality can affect these species by
not allowing riparian insect species to reproduce due to issues with water quality and habitat
availability. Indiana bat, gray bat, and Northern long-eared bat use riparian and stream corridors
to feed in aquatic-based habitats where specific types of insect prey are abundant (Brack 2006).
Protecting these important forested areas are key in providing suitable habitat for summer
ranging Myotis species.
IV. Policy Suggestions
In this section, policy suggestions are discussed for protecting and enhancing Indiana bat, gray
bat, and Northern long-eared bat habitats and hibernacula across their known ranges. Suggestions
for protecting and enhancing these habitats include public education, mitigation of snags for
potential roosting sites, increases habitat protection, and monitoring of species populations
throughout the ranges.
Public education is an important component of raising awareness and support for protecting vital
ecosystems and individuals of Indiana bat, gray bat, and Northern long-eared bat. Providing
interactive discussions between conservation professionals and the general public can provide a
personal experience that can better educate and inform private landowners and citizens.
Providing interpretive signs at utilized hibernacula caves can inform the general public of issues
related to WNS and impacts related to disturbance. Along with interaction and proper sign
utilization, continuing to provide useful literature and scientific documentation can further build
support of the science behind these threatening issues and build a factual base of evidence to
support conservation efforts.
Mitigating snags for potential roosting sites of Myotis species can be implemented on various
projects, including Department of Transportation projects (DOT). Mitigation banking is already
a lucrative and important component of stream and wetland protection and enhancement across
the U.S (mitigationbanking.org). Many states require direct mitigation purchases of credits when
jurisdiction waters or wetlands are impacted in any way through construction, maintenance, and
development projects. These mitigation banks all have different values of credits that can be
purchased, depending on the quality of the watershed, location in regards to tidal influenced
waters of the U.S., and wetland system extent within the project corridors closest bank. This
policy was put in place to enact a no net loss policy to wetlands and jurisdictional waterways in
the United States and to protect our vital biological systems. Myotis bat species roost in dead
snags and under sloughing bark. Mitigation of dead snag removal in DOT projects could ensure
that endangered and threatened Myotis species are provided ample summer roosting habitat. This
creates an entire new part of mitigation and encourages individuals to protect snags for Myotis
utilization by providing a monetary incentive. Ecological surveys can estimate the quality of the
habitat and quantity of suitable roost sites to be mitigated at a certain ratio (i.e. 1:1) depending on
quality.
Direct protection of suitable habitat for Myotis species can increase the amount of suitable
roosting and hibernacula sites across the species range. Forested habitats are becoming
increasingly fragmented, isolated, and degraded. Protecting these forested areas is integral in
providing the suitable summer roosts and foraging habitats for bat species. Myotis species utilize
upland and riparian habitats for foraging. Riparian corridors can be protected through buffer
zones adjacent to streams. Buffer zones vary in width, ranging from 10 ft. to 300 ft., depending
on the required service of the buffer (Hawes and Smith 2015). Cave hibernacula can be protected
through the installation of gates and restrictive devices that limit the access to those who receive
written permission from a designated protection agency, i.e. the USFWS.
Monitoring Myotis species is important for quantifying survival rates, range distributions, and
overall health of the species. Winter caves surveys for WNS should be conducted at all known
infected sites, counting affected and dead individuals for year to year correlations of survival
rates within the hibernacula. Along with cave surveys, summer mist netting surveys should be
conducted to identify, evaluate, and count bat species across known ranges. These surveys are
conducted by USFWS endangered species permit holders. Mist nets are erected in foraging and
flyway corridors, physically netting bats as they emerge for nocturnal foraging. These mist
netting surveys can provide useful information on diversity and known ranges for specific
species.
We have just begun to understand the ecological significance of bats in North America. Indiana
bats, gray bats, and northern long-eared bats face a multitude of issues related to survival. WNS
and habitat degradation are the leading causes of mortality for Myotis species. Through careful
policy implementation and protection, we can provide avenues in which to increase the quality of
habitats, forested and cavernous, for threatened and endangered Myotis species in North
America.
PHOTOGRAPHIC LOG
Photo: 1
Description:
Indiana bat (Myotis
sodalis)
Source:
http://ecos.fws.gov/
speciesProfile
Photo: 2
Description:
Gray bat (Myotis
grisescens)
Source:
http://ecos.fws.gov/
speciesProfile
Photo: 3
Description:
Northern long-eared
bat (Myotis
septentrionalis)
exhibiting WNS
Source:
http://www.fws.gov/
midwest/
endangered/
mammals/nlba
Photo: 4
Description:
White nose positive
bats
Source:
http://www.in.gov/
dnr/fishwild/5404.htm
Appendix A. Photographic Log
Appendix B. Citation
Blehert, David S et al. "Bat white-nose syndrome: an emerging fungal pathogen?" Science 323.5911 (2009): 227-227.
Brack, Virgil. (2006) Diet of the Gray Myotis (Myotis grisescens)., “Variability and consistency, opportunism, and selectivity.” Department of Ecology and Organismal Biology, Indiana State University, Terre Haute, IN 47089, USA (VB) Apartado 24-5655, Monteverde, Puntarenas, Costa Rica (RKL)
Barbour, R. W. and W. H. Davis. 1969. Bats of America. The University Press of Kentucky, Lexington, Kentucky, 286p.
Broders, H. G. and G. J. Forbes. 2004. Interspecific and Intersexual Variation in Roost-site Selection of Northern Long-eared and Little Brown Bats in the Greater Fundy National Park Ecosystem. Journal of Wildlife Management 68(3):602-610.
Brady, J.T., T.H. Kunz, M.D. Tuttle, and D.E. Wilson. 1982. Gray bat recovery plan. U.S. Fish and Wildlife Service, Denver, CO
Gardner, James E, James D Garner, and Joyce E Hofmann. "Summer roost selection and roosting behavior of Myotis sodalis (Indiana bat) in Illinois." (1991).
Gargas, Andrea et. al. "Geomyces destructans sp. nov. associated with bat white-nose syndrome." Mycotaxon 108.1 (2009): 147-154.Lorch, Jeffrey M et al.
Gore, J. A. 1992. Gray bat. Pages 63-70 In S. R. Humphrey (ed.). Rare and endangered biota of Florida. University Presses of Florida, Gainesville.
Hawes, Ellen and Smith, Markelle. “Riparian Buffer Zones: Functions and Recommend Widths.” 2015. Yale School of Forestry and Environmental Studies.
Humphrey, Stephen R, Andreas R Richter, and James B Cope. "Summer habitat and ecology of the endangered Indiana bat, Myotis sodalis." Journal of Mammalogy (1977): 334-346.
Krynak, Timothy J., "Bat Habitat Use and Roost Tree Selection for Northern Long-eared Myotis (Myotis septentrionalis) in North Central Ohio" (2010). Masters Theses. Paper 2.
Kurta, A. and J. Kennedy. 2002. The Indiana bat: biology and management of an endangered species. Bat Conservation International, Austin, Texas. 253 pp.
Lacki, M. J., and J. H. Schwierjohann. 2001. Day-Roost Characteristics of Northern Bats in Mixed Mesophytic Forest. Journal of Wildlife Management. Volume 65 (3): 482-488.
LaVal, Richard K et al. "Foraging behavior and nocturnal activity patterns of Missouri bats, with emphasis on the endangered species Myotis grisescens and Myotis sodalis." Journal of Mammalogy (1977): 592-599.
Mamm, J. (1981). “Correspondence of food habits and morphology in insectivorous bats.” Journal of Mammalogy.
Mitchell, W. A., and Martin, C. O. (2002). “Cave- and crevice-dwelling bats on USACE projects: Gray bat (Myotis grisescens),” EMRRP Technical Notes Collection (ERDC TN-EMRRP-SI-25). U.S. Army Engineer Research and Development Center, Vicksburg, MS. www.erdc.usace.mil/el/emrrp
National Mitigation banking Association. “ http://mitigationbanking.org/mitigationbanks/index.html ” (accessd 2/26/2015)
Sewell, P., P. Roby, and M. W. Gumbert. 2006. Rare bat survey on the Cherokee National Forest, Tennessee. Final Report, U.S. Forest Service, Cleveland, Tennessee.
Trani, K. Margaret. “Maintaining Species in the South” USDA Forest Service. (http://www.srs.fs.usda.gov/sustain/draft/terra5/terra5.pdf)
Tuttle, M.D. 1976. Population ecology of the gray bat (Myotis grisescens): factors influencing growth and survival of newly volant young. Ecology, 57:587-595. (USFWS) United States Fish and Wildlife Service. 2013. 2013 Revised Range-wide Indiana Bat Summer Survey Guidelines.
U.S.F.W.S., (2011). “A National Plan for Assisting States, Federal Agencies, and Tribes in Managing White-Nose Syndrome in Bats.” US Fish and Wildlife Service, 300 Westgate Center Drive, Hadley, MA 01035.
U.S.F.W.S., (2015) “U.S. Fish and Wildlife Service Protects Northern Long-eared Bat as Threatened Under Endangered Species Act.” Midwest Region, 5600 American Blvd W, Suite 990, Bloomington MN 55437.
Website sources
White Nose syndrome reference page
http://www.georgiawildlife.com/WNS , accessed 4/23/2015
Myotis Septentrionalis reference page: http://www.fws.gov/midwest/endangered/mammals/nlba/nlbaFactSheet.html (Updated January 2015)
Myotis sodalis reference pages:
http://www.fws.gov/Midwest/Endangered/mammals/inba/index.html (Updated November 20, 2014) http://georgiawildlife.com/sites/default/files/uploads/wildlife/nongame/pdf/accounts/mammals/
myotis_sodalis.pdf (Updated September 2009)
Myotis grisescens reference pages:
http://www.georgiawildlife.com/sites/default/files/uploads/wildlife/nongame/pdf/accounts/mammals/ myotis_grisescens.pdf (Updated September 2009)
http://www.fws.gov/midwest/endangered/mammals/grbat_fc.html (Last updated: July 16, 2014)