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Title
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Eng
Challenging Times for North American Bats: Planning for the Future of a Myotis yumanensis and M. lucifugus Maternity Colony at The Evergreen State College Organic Farmhouse, The Evergreen State College, Olympia, Washington
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Date
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2012
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Creator
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Eng
Ferguson, Noel P
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Subject
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Eng
Environmental Studies
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extracted text
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CHALLENGING TIMES FOR
NORTH AMERICAN BATS:
Planning for the Future of a Myotis yumanensis
and M. lucifugus Maternity Colony
at
The Evergreen State College Organic Farmhouse
The Evergreen State College, Olympia, Washington
by
Noel Ferguson
A Thesis: Essay of Distinction
Submitted in partial fulfillment
of the requirements for the degree
Master of Environmental Studies
The Evergreen State College
March 2012
i
© 2012 by Noel Ferguson. All rights reserved.
ii
This Thesis for the Master of Environmental Study Degree
by
Noel Ferguson
has been approved for
The Evergreen State College
by
_____________________________
Steven G. Herman, PhD.
Member of the Faculty
_____________________________
Date
iii
ABSTRACT
CHALLENGING TIMES FOR NORTH AMERICAN BATS:
Planning for the Future of a Myotis yumanensis
and M. lucifugus Maternity Colony
at
The Evergreen State College Organic Farmhouse
Noel Ferguson
Many threats face North American bats. Highlighting the urgent need for bat
conservation efforts, a microcosmic example of the current degradation of North
American bat habitat exists on the campus of The Evergreen State College, in Olympia,
WA. There, a hand-built, rough-timbered farmhouse has provided roosting shelter for a
maternity colony of Little Brown (Myotis lucifugus) and Yuma Bats (Myotis yumanensis)
for many years. The farmhouse is slated for extensive remodeling activities that will
likely cause interruption of reproductive activities and abandonment of the site. During
the summer of 2011, emergence counts were conducted to determine the number of bats
present, reproductive success, and seasonal timing of departure from the roost.
Additionally, a literature review was conducted to determine the best mitigation measures
available in preparation for the farmhouse remodeling. Emergence count surveys
established that the farmhouse is extensively used by the breeding bats, with two intracolony groups that regularly change roosting locations on the building. The farmhouse
offers many options for roosting locations, with roost crevices on 3 sides of the structure
at varying heights. Although bat-houses have been used successfully as maternity colony
roosts by Little Brown Bats, attempting to replicate the abundance of roost crevices
available on the farmhouse with a bat-house would be very difficult. Installing multiple
bat-houses at varying heights and exposures may offer a similar range of roost
temperatures and conditions as the farmhouse does now. Not carrying out remodeling on
the farmhouse would offer the greatest assurance of continued bat reproduction at the
site. Out of concern for the bat colony’s uncertain future, continued monitoring should be
undertaken and well-designed and placed bat-houses installed to provide roosting
alternatives at the site.
TABLE OF CONTENTS
CHAPTER 1: YUMA BATS, LITTLE BROWN BATS, AND MATERNITY COLONIES
1
CHAPTER 2: NATURAL HISTORY OF MYOTIS YUMANENSIS AND M. LUCIFUGUS
4
BEHAVIOR
REPRODUCTIVE ECOLOGY
5
6
CHAPTER 3: BATS IN PERIL- THREATS TO BAT POPULATIONS
8
CHAPTER 4: MYOTIS AT TESC ORGANIC FARMHOUSE
10
CHAPTER 5: WHAT’S KNOWN ABOUT THE FARMHOUSE COLONY- SURVEYS AND
OBSERVATIONS
12
EMERGENCE COUNT PROTOCOL
EMERGENCE COUNT RESULTS 2011
12
13
CHAPTER 6: CONCLUSION AND RECOMMENDATIONS
RECOMMENDATIONS
FURTHER RESEARCH
AUTHOR’S NOTE
18
19
21
23
REFERENCES:
24
APPENDICES
30
APPENDIX A: MAP OF ORGANIC FARMHOUSE LOCATION
APPENDIX B: EMERGENCE COUNT SURVEY FORMS
APPENDIX C: SAMPLE SPREADSHEET FOR SUMMARIZING SURVEY DATA
APPENDIX D: EXAMPLES OF BAT DETECTORS
iv
30
31
36
39
LIST OF FIGURES
FIGURE 1
Juvenile Myotis observed roosting in central portion of west wall of farmhouse Aug. 4&5
13
FIGURE 2
Juvenile Myotis observed roosting under metal roof flashing on south wall of farmhouse Aug. 13
14
FIGURE 3
Roosting locations on north wall of farmhouse
14
FIGURE 4
Roosting locations on south wall of farmhouse
15
FIGURE 5
Roosting locations on west wall of farmhouse
15
FIGURE 6
Bat condo designed for 10,000 Little Brown Bats in Spokane, WA
18
FIGURE 7
Seven-chamber bat house
19
LIST OF TABLES
TABLE 1
Summary of total bats counted at farmhouse 2011
13
TABLE 2
Bats counted emerging from north wall of farmhouse 2011
15
TABLE 3
Bats counted emerging from south and west walls of farmhouse 2011
16
v
ACKNOWLEDGEMENTS
For support in the completion of this work, I have many people to thank. First, thank you
to my reader Dr. Steve Herman, whose patient guidance was invaluable. Thank you also to Dr.
Tom O’Shea of the USGS Ft Collins, CO and Patty Briggs of the Hertfordshire Biological
Records Centre, UK who both eagerly contributed to my project. At Evergreen, many people
helped me along the way as well, thank you to Dr. Martha Henderson, Gail Wooten, and MES
faculty who have supported my learning and growth throughout the thesis process. Thank you to
Sarah Pedersen, Carlos Diaz, and Stacey Brewster at the Evergreen library for tons of research
assistance and a cool internship! Thank you to the C.E.L.L. committee and Facilities Services for
approving my plan to build bat houses. I also owe much gratitude to my Mom and Dad and
brothers Alex and Barry for steadfast support and encouragement. Last but most, thank you to
Arielle Pauling for keen bat observations and dedicated help with emergence counts and thesis
brainstorming.
vi
Chapter 1: Yuma Bats, Little Brown Bats, and Maternity Colonies
Bats are an integral part of Earth’s ecosystems on all continents except for
Antarctica. The vital roles bats play range from primary pollinators of fruit trees and cacti
to insect control, sweeping many tons of insects out the air every night (Evelyn et al.,
2004; Fleming et. al, 2003; O’Shea and Bogan, 2003; Tuttle, 2005). In Texas alone,
Brazilian Free-Tailed Bats (Tadarida brasiliensis) consume an estimated two million
pounds of insects nightly (Keeley, 1999). The economic value of the insect control
services provided by bats to farm crops across the United States is approximately $23
billion annually (Boyles et al., 2011; Altringham, 1996).
The State of Washington is host to many bat species during the summer months.
Some species are migratory, such as the Hoary Bat (Lasiurus cinereus), which spends
only a few months in the Pacific Northwest while bearing young and then migrating to
wintering grounds in Southern California and further south (Findley and Jones, 1964).
Others, such as Yuma Bats (Myotis yumanensis) and Little Brown Bats (Myotis
lugcifugus) migrate locally from their winter hibernacula in the Cascade Mountains,
heading to the lowlands of Western Washington during the summer (Falxa, 2008).
While Little Brown Bats are distributed throughout North America, Yuma Bats
are endemic to the West (Hall, 1981). Additionally, Yuma Bats are listed as a Species of
Concern, one step below being listed as endangered under the U.S. Fish and Wildlife
Service’s Endangered Species Act (O’Shea and Bogan, 2003). Like other North
American bats, Yumas are found in pockets; locally abundant in places, but otherwise
absent, due perhaps to habitat alteration or other human influences (Evelyn et al., 2004).
1
Two large combined breeding colonies of Little Brown and Yuma Bats are known to
exist in Thurston County, near the city of Olympia, WA. Both colonies are wellestablished, at times being composed of hundreds to thousands of individuals (BAOT,
2011; Falxa, 2008).
One colony is located in the Woodard Bay area, in a non-serviceable deteriorating
pier over Chapman Bay on the Puget Sound. The pier structure is occupied by up to 5,000
Yuma Bats during the breeding season (BAOT, 2011). The area is under the jurisdiction
of the Washington State Department of Natural Resources (WSDNR) and is monitored
by staff biologists and maintained as a Natural Resource Conservation Area (WSDNR,
2002). The second colony of Yuma Bats is found in a large, older, hand-built wooden
farmhouse1 on the campus of The Evergreen State College (TESC). A 2009 species
composition census found this colony to be comprised of approximately 600 Yuma Bats
and Little Brown Bats, plus individual California Myotis (Myotis californicus ), Big
Brown Bats (Eptesicus fuscus), and Silver-Haired Bats (Lasionycteris noctivagans)
(Davis, 2009). These large gatherings of Little Brown and Yuma Bats are known as
‘maternity colonies’, composed entirely of females bearing and raising young
(Altringham, 1996; Davis, 2009; Falxa, 2008). The males and non-productive females of
these species disperse in small groups and individually, and are not found with
reproductive females at this time (Christy and West, 1993).
The Woodard Bay colony maternity roost has been recognized by the DNR as an
important ecological site and the structure has been recently modified to prevent human
access to the bat breeding area and is expected to receive protection for the foreseeable
future (WSDNR, 2010). The colony at TESC, on the other hand, will be subject to a
1
See Appendix A for map of Farmhouse location
2
major disruption in the near future. Facilities Services of TESC has proposed a
remodeling project for the farmhouse, involving removal and replacement of all siding
materials (Paul Smith, 2011: personal communication; Davis, 2009; Falxa, 2008). The
rough-hewn, aged cedar siding that covers the building provides abundant and varied
habitat for roosting bats and rearing young. The breeding bats regularly move en masse to
different areas on the structure, probably due to varying temperatures within the siding,
weather conditions, and other factors (Davis, 2009). A disturbance to the roost structure,
even during the winter months when the bats are not present, could cause abandonment
of the site, thus greatly disadvantaging several species of endemic wildlife critical to local
agriculture and insect control within urban areas. English Nature, the national ecological
agency for the U.K., has found that modifications to roost structures such as changes in
size of roost space, changes to entrances, and changes to airflow can significantly impact
bats’ use of a roost and lead to desertion (Mitchell-Jones, 2004).
With the tremendous hurdles presented to the bats including habitat destruction
and alteration, wind turbine developments, and the White Nose Syndrome epidemic, it is
necessary that steps be taken on bats’ behalf to ensure their populations do not go extinct
within our lifetime. This thesis examines in-depth the current usage of the farmhouse by
bats, the species using the farmhouse, as well as proposes long-term monitoring of the
bats at TESC Farmhouse. In the following section, a description the biology of the bats
comprising the Farmhouse’s maternity colony is explored.
3
Chapter 2: Natural History of Myotis yumanensis and M. lucifugus
In the Pacific Northwest of North America, Little Brown Bats are similar in
appearance to the more regional Yuma Bat, and can only be reliably identified either by
examination in the hand or using electronic bat detectors2 (Greg Falxa, 2010: personal
communication). In areas where the bats’ ranges overlap, such as the Pacific NW, the
animals can be distinguished at close range by examination of the fur. Yuma Bats have
glossy fur while Little Brown Bats have dull fur- though not always the most reliable
method of identification, as intermediate individuals have been observed (Fenton, 1980).
Most bat echolocation calls are inaudible to the human ear; however, with the use of an
electronic bat detector, echolocation calls can be used to reliably identify species
(Johnston, 2002).
Both species belong to the genus Myotis, or mouse-eared bats. Yuma Bats are of
similar dimensions, sometimes a bit smaller than Little Brown Bats with total length of
37-49 cm and forearm length of 32-38 cm (Hall, 1981). Little Brown Bats are cinnamon
to dark-brown on the upper parts and buffy to pale grey on the underparts. The upper
parts of Yuma Bats are buffy-tawny to brown while the underparts are pale buffy to
yellowish white (Fenton, 1980). Yuma Bats, occur only on the west coast of North
America with six subspecies spread throughout their range. The subspecies that lives at
Evergreen’s farmhouse is Myotis yumanensis saturates. Saturatus occurs approximately
from San Diego, California north along the Pacific and west of the Cascade Mountains to
the northern end of Vancouver Island, British Columbia, including a population on the
island itself (Hall, 1981).
2
See Appendix D for examples of bat detectors
4
Behavior
As with all Pacific Northwest bats, Little Brown and Yuma Bats are nocturnal and
have insectivorous diets (Christy and West, 1993; Fenton, 1980). They set out from their
roost sites during an approximate one hour window from ½ hour before to ½ hour after
sunset on their nightly hunting forays (Butchkowski, 2009; Kunz, 2003). The bats are
opportunistic, catching and eating an array of insects on the wing. Interestingly, Little
Brown Bats capture insects directly with their mouths but also by scooping a flying insect
into their tail or wing membranes and then directing the insect into their mouth while
flying (Saunders, 1988).
All bats extensively use echolocation calls during flight. Bats echolocate to detect
insect prey, gain detail on the surface structure of the prey, and avoid obstacles
(Altringham, 1996; Fenton, 1980; Gould, 1955). There is evidence that the bats
additionally use echolocation calls to detect con-specifics at roost sites. The only nonecholocation calls used during flight are “honks” which Little Brown Bats use when on a
collision course with another bat. The “honk” call involves lowering the end portion of
their frequency modulated calls from 40 to about 25 kHz (Fenton, 1980).
Little Brown and Yuma Bats are seasonal visitors at their breeding and summer
feeding sites. Although they may awaken occasionally during the winter months to forage
on warmer nights, most of the cooler months are spent in hibernation (Altringham, 1996).
The bats hibernate in cave areas, preferring very specific locations with certain
temperature and humidity conditions (Christy and West, 1993; Davis and Hitchcock,
1965, Kunz and Reynolds, 2003). Although it is not known for certain, biologists
speculate that the Olympia populations hibernate in caves on the west slope of the
Cascade Mountains (Greg Falxa, 2010: personal communication). Yumas begin their
5
summer seasonal activities by awakening from hibernation in early to late April,
depending on weather trends. Upon arousal from hibernation, the female bats gather at
maternity roost sites and the males disperse individually or in small groups (Altringham,
1996; Christy and West, 1993). The TESC Organic Farmhouse bats normally return to
the maternity colony site in late April (Davis, 2009).
Reproductive Ecology
Many bats of temperate regions, including Yuma and Little Brown, share a
mechanism for maximizing the time available during summer to rear young. The bats,
male and female, gather for a mating swarming period during late summer and early fall
to copulate and vigorously feed to put on weight for the upcoming hibernation
(Altringham, 1996; Kunz and Reichard, 2010). With this strategy, the bats do not need to
spend precious time in the spring mating before beginning gestation (Altringham, 1996).
Females store spermatozoa throughout the winter and fertilization occurs upon arousal
from hibernation in the spring (Altringham, 1996; Racey, 1979).
After a 40-50 day gestation period, females give birth to one flightless and blind
pup (Altringham, 1996; Kunz and Reichard, 2010). The young remain flightless and
totally reliant on their mothers until about 18 days old, at which time they fledge and can
forage for insects on their own, however pups’ diets are supplemented with milk until
around 26 days old (Kunz and Anthony, 1996; Kunz and Reichard, 2010; Kurta et al.,
1989).
The colonial strategy for rearing young provides benefits to the mothers and
young alike. By participating in such a colony, the bats share body heat, easing the
energetic burden of maintaining a high body temperature during gestation in order to
6
promote rapid embryo development (Barclay, 1982). Young bats, not yet volant (capable
of flight), can also benefit from colonial living. By having many nursing mothers around,
nursing duties are occasionally shared by unrelated mothers in the event that young are
separated from their own mother (Altringham, 1996)
During the spring and summer months, males and non-productive females
disperse individually at separate sites from gestating and lactating females (Kurta and
Kunz, 1988). Occasionally males are found at maternity colony sites, but in these
situations the males roost separately from the females (Davis and Hitchcock, 1965).
7
Chapter 3: Bats in Peril- Threats to Bat Populations
In 1998, Altringham noted “there is now considerable evidence that bat
populations in many parts of the world are in decline, and that the range of many species
has contracted”. Bat populations in North America are threatened on various fronts
including continuing habitat destruction, increasing numbers of wind turbines, and very
recently, a newly discovered fungus (Boyles, 2011; Tuttle et al., 2009). Aptly named
White Nose Syndrome (Geomyces destructans), the disease is evident by a velvety white
fungus found on the snout, ears, wings and other exposed skin on infected bats (Blehert et
al., 2009).
White Nose Syndrome (WNS) is, at present, causing the most accelerated,
precipitous decline of North American wildlife in recorded history (Bat Conservation
International, 2009). WNS is a disease that was first recognized in New York State in
February 2006 (Frick et al., 2010). By 2009, within three years of its discovery, WNS
was confirmed to have spread to at least 9 states along the eastern seaboard, inland to
Kentucky, and north to Ontario, decimating colonies of 6 species of hibernating bats
along the way and in many cases causing 100% mortality (Tuttle et al. 2009; USFWS et
al. 2010).
The disease alters bats’ hibernation cycle and bats use up fat reserves and perish
(Foley et al., 2010; Reichard, 2009). Infected bats will often take flight in mid-winter,
perhaps attempting to forage and replace body fat reserves, and then often die near cave
entrances or inside the hibernacula cave (Fascione, 2010; Foley et al., 2010). Little
Brown Bats appear to be particularly vulnerable to White Nose Syndrome. Kunz and
Reichard (2010) noted that since 2006, WNS has killed at least one million Little Brown
8
Bats in the Northeastern U.S. Should WNS reach the Washington State, the challenges
facing Olympia’s maternity colonies will be greatly increased.
Several factors put the Woodard Bay and TESC colonies at risk to catastrophic
decline in population numbers. Little Brown Bats and Yuma Bat only bear one young per
reproductive female per year, but these bats are long-lived with cases of individual bats
living 30+ years in the wild (Keen and Hitchcock, 1980; Wilkinson and South, 2002). In
optimum conditions, the bats’ longevity assures that the species continues to maintain
population stability despite low numbers of young reared during each breeding season,
however low reproductive rates also leave bat populations vulnerable to drastic declines
(Christy and West, 1993). A disease, such as WNS, could rapidly spread through a
colony wiping out large numbers of bats and accordingly, disturbance or destruction of
maternity roosts could have a similar effect (Frick, 2010; Williams and Brittingham,
2006). Only two colonies of Yuma and Little Brown Bats are known to exist in Thurston
County. Because these colonies are composed of the only reproductive individuals known
in the county, these colonies are at high risk for catastrophic impact on entire species
regionally.
9
Chapter 4: Myotis at TESC Organic Farmhouse
Caretakers at the Farmhouse first noticed bats using the cedar siding for shelter in
1987 (Greg Falxa, 2010: personal communication). Since that time, members of the local
community have enjoyed the summer evening emergence of the bats on the flight out to
their nightly feeding grounds.
While the Farmhouse has proven to be a secure maternity roost site for many
years, as demonstrated by the bats’ continued fidelity to the site, it may not remain a
reliable breeding location in the future. As explained by the director of Facilities Services
at TESC, the Farmhouse structure is slated for a major overhaul (Paul Smith, 2011:
personal communication). The remodeling project will include complete removal and
replacement of all siding materials. The plans will likely not include replicating the
rough, hand-split cedar siding currently on the building (Paul Smith, 2011: personal
communication).
According to the Facilities Services director, construction activities could take
place during the winter months while the bats are away at hibernacula sites. Additionally,
measures to allow for continued bat access could possibly be incorporated into the
design. However, there are no guarantees that the returning bats, in a low state of health
from sustained fat-loss during hibernation, and in early stages of gestation, would
recognize their historic breeding roost or find the remodeled structure suitable.
Even if the remodeled structure will allow for continued bat access, a major
construction project on one of only two known Myotis maternity colony roosts in
Thurston County holds great potential for causing reproductive interruption, possibly
resulting in a catastrophic local impact on Yuma and Little Brown Bat populations
10
(Briggs, 2000; Evelyn et al., 2004; Mitchell-Jones, 2004). Not disturbing the farmhouse
structure at all would be the best assurance that the colony continues to survive, but that
does not appear to be an option (Paul Smith, 2011: personal communication).
11
Chapter 5: What’s Known about the Farmhouse Colony- Surveys and
Observations
In 2009, Davis et al. used bat detectors and SonoBat software (SonoBat, Arcata,
CA) coupled with mist netting for five evenings early in the breeding season (April 16 to
May 24) to determine the ratio of bat species present at TESC’s Organic Farmhouse. Ms.
Davis found a ratio of 6.07 : 1.04 Yuma Bats to Little Brown Bats exiting the Farmhouse
roost. During Davis’ acoustic sampling surveys, the lowest combined count of Yuma and
Little Brown Bats emerging was 8 and the survey with the highest count resulted in 78
bats.
Bat detectors are complex however, and require that the observers be thoroughly
familiar with their operations, limitations, and potential biases (Johnson, 2002; Kunz,
2003). For on-going monitoring efforts, low-tech but effective evening ‘emergence
counts’ are the standard and most accurate method for censusing bats that depart from
buildings, mine tunnels, and trees (Kunz, 2003; Kunz and Anthony, 1996; Rydell et al.,
1996; Sedgeley and O’Donnell, 1998). Emergence counts consist of placing observers at
strategic locations near a bat roost and counting the bats as they emerge for evening
departure from the roost.
Emergence Count Protocol
Emergence counts consist of visual observations of bats exiting their roost site. In
order to effectively conduct counts, observers should be assigned specific exits or fields
of view (at TESC’s Organic Farmhouse, the north and south sides of the building), and
should be present at their stations prior to the start of emergence to ensure that the earliest
departing bats are counted (Kunz, 2003). Counts should begin ½ hour before official
12
sunset and conclude at ½ hour after official sunset following guidelines suggested by
Johnson (2002) and Butchkowski (2009) for Myotis yumanensis and M. lucifugus
emergence counts. If availability of observers is limited, evening emergence surveys
should be conducted during at least 3 consecutive nights during periods of maximum
adult colony size; for maternity colonies, this is the period of late pregnancy and early
lactation- approximately the 3rd week of June (Butchkowski, 2009; Kunz, 2003).
If observers are available for ongoing emergence counts, information such as
intra-colony variation in the number of bats present and seasonal change in colony size
associated with reproductive activity can be garnered (Kunz, 2003; Ransome, 1990). For
ongoing emergence counts, observers should conduct their first count during the last
week of May and continue to survey at least every two weeks through July 31
(Butchkowski, 2009). Two or more counts on consecutive evenings should be conducted
to obtain error parameters (Butchkowski, 2009). If counts are conducted after young
begin to fly (approximately late June, early July), it is important to bear in mind that
newly volant young may depart later in the evening than adults, thus making it necessary
to extend the census period until past the time when the adults have emerged, or make
visual counts of roosting young if possible (Butchkowski, 2009; Kunz, 2003; Kunz and
Anthony, 1996).
Emergence Count Results 2011
In summer 2011, the author, with the help of a research assistant, conducted eight
evening emergence counts at the farmhouse during the lactation and fledging period (6
July to 14 August). The counts were completed on a weekly basis except during the week
of 11 July through 17 July, due to heavy rainfall. The emergence counts resulted in
13
findings detailing the number of bats utilizing the Organic Farmhouse as well as the bats’
roosting behavior at the site. The first evening emergence count on 6 July, 2011, resulted
in the highest count of all the surveys. 330 bats were observed exiting the Farmhouse on
that date (Table 1).
Bats counted
248
220
210
161
158
13-Aug-11
11-Aug-11
9-Aug-11
7-Aug-11
5-Aug-11
3-Aug-11
1-Aug-11
30-Jul-11
28-Jul-11
26-Jul-11
24-Jul-11
22-Jul-11
20-Jul-11
18-Jul-11
16-Jul-11
14-Jul-11
12-Jul-11
10-Jul-11
55
29
8-Jul-11
6-Jul-11
350 330
300
250
200
150
100
50
0
Table 1. Summary of the total number of bats counted during weekly emergence
counts at TESC Organic Farmhouse 2011. The final 4 counts were paired to obtain
error parameters.
The number of emerging bats counted declined over the next few weeks until 4
August, when 110 juvenile Myotis spp were observed roosting together underneath siding
material on the west face of the
Organic Farmhouse (Fig. 1).
Approximately the same number of
juveniles was observed at the same
location the following night as well.
On both nights, the juvenile bats
were observed at the end of the
survey period, after the departure of
Figure 1: Juve. Myotis observed roosting in large group
in central
adult
bats.portion west wall of farmhouse August 4&5.
14
On the following survey, 13 August,
the juvenile bats were not seen under the siding on the west side of the farmhouse.
However, bats were observed emerging from the south side of the Farmhouse, this time
from underneath metal flashing material along the edge of the roof (Fig. 2). Upon closer
inspection, we determined that many juvenile bats were roosting under the flashing, but
an accurate count was not possible due to obscured viewing. On the following night, 14
Figure 2. Juve. Myotis were observed roosting under
metal roof flashing on the south side of the Farmhouse
August 13.
Figure 3. Two roosting locations were observed on the
north wall of the Farmhouse. The area near the roof
peak was used the most frequently.
August, bats were again observed roosting under and exiting from the south side roof
area.
Throughout the survey season, bats were observed emerging from several locations in
addition to sites where juveniles were observed roosting. Two groups of bats were
noticed during emergence counts. One group consistently emerged from the Farmhouse
on the north end of the building, while another group moved en masse to several different
locations on the south and west sides of the structure. The north side group emerged from the
location on the lower section of the wall on the first evening survey, 6 July (Fig. 3). On all
subsequent emergence counts, bats emerged from the higher location near the roof peak. The
15
number of bats emerging from the northern wall peaked on 18 July with 130 bats and declined
throughout following surveys (Table 2).
Emergence Count North Side of Farmhouse
130
114
94
80
68
8/13/2011
8/11/2011
8/9/2011
8/7/2011
8/5/2011
8/3/2011
8/1/2011
7/30/2011
7/28/2011
7/26/2011
7/24/2011
7/22/2011
7/20/2011
7/18/2011
7/16/2011
7/14/2011
7/12/2011
7/10/2011
30
22
7/8/2011
7/6/2011
140
120
95
100
80
60
40
20
0
Table 2. Number of bats counted emerging from north side of TESC Organic
Farmhouse 2011.
\ Roosting locations on south wall of
Figure 4.
Farmhouse on July 6, 18 & 22.
Figure 5. Roosting locations on west wall of Farmhouse
on July 28, and Aug 4 & 5.
The group of Little Brown and
Yuma Bats that was first observed emerging from the south wall of the Farmhouse on 6
July changed roosting locations regularly throughout the surveying period. On July 6, 18
and 22, the group was observed emerging from three different locations on the south wall
of the Farmhouse (Fig. 4). On 28 July and 4 & 5 August, the group was observed
emerging from two different locations on the west wall of the Farmhouse (Fig. 5) and no
bats were observed emerging from the south wall. As previously noted, juvenile bats
16
were observed roosting under slats on the west wall on 4 & 5 Aug. One week later, 13 &
14 August, most bats had apparently departed for the season and the few remaining bats
emerged from the north wall and the metal flashing along the roof on the south wall (Fig.
2). No bats were observed emerging from or roosting on the west wall.
The peak number of bats counted emerging from the south and west walls
occurred on the first count, 6 July (Table 3). The count numbers declined greatly until 4
August when the group of approximately 110 juvenile bats was discovered on the west
wall of the Farmhouse.
Emergence Counts South and West Sides of Farmhouse
250 235
180
200
140
150
96
100
67
28
50
7
25
Table 3. Number of bats counted emerging from south and west sides of
TESC Organic Farmhouse 2011.
17
8/13/2011
8/11/2011
8/9/2011
8/7/2011
8/5/2011
8/3/2011
8/1/2011
7/30/2011
7/28/2011
7/26/2011
7/24/2011
7/22/2011
7/20/2011
7/18/2011
7/16/2011
7/14/2011
7/12/2011
7/10/2011
7/8/2011
7/6/2011
0
Chapter 6: Conclusion and Recommendations
Observations of the TESC Organic Farmhouse colony in 2011 clearly established
that the annual gathering of bats is indeed a maternity colony bearing young at the
Farmhouse. Additionally, observations demonstrated that the colony is quite mobile,
using many surfaces of the structure for roosting and rearing young. The bats move
around to different locations often, likely due to varying roost temperatures and weather
conditions (Mitchell-Jones, 2004). Frequent moves to different roosting locations may
also help the bats evade parasites (Tuttle, 1993).
If TESC Facilities Services does proceed with remodeling the Farmhouse,
a habitat with varied and abundant areas for Myotis bats to roost and raise young will be
lost. Bats are notoriously selective about the habitats in which they carry out life
functions such as feeding, mating, hibernating, and bearing young (Evelyn et al., 2004;
Mitchell-Jones, 2004; Tatarian, 2006; Williams and Brittingham, 2006). Attempting to
mimic the variety of roosts available on the Farmhouse with a structure such as a bat
house would be difficult due to the wide range of nooks available for roosting on the
current farmhouse structure. As observed during the 2011 emergence counts, bats can
roost low to the ground in cooler areas, high up on the structure under the roof, and on
three different sides of the building. The variety of roosts provides bats with a range of
temperatures, humidity’s, and gradient of safety from ground predators that would be
very difficult to replicate.
18
Recommendations
As it appears inevitable that the Farmhouse structure will be remodeled, some
attempt at providing the maternity colony with alternative housing should be undertaken
lest the colony abandon the site, which would likely result in many casualties (Briggs,
2000; Evelyn et al., 2004; Mitchell-Jones, 2004).
In spring 2011, TESC’s Facilities Services and the Center for Ecological Living
and Learning (C.E.L.L.) granted the author permission to build a bat house near the
Organic Farmhouse. The author plans to construct bat housing and assist students with
further study of the maternity colony during summer of 2012.
Bat condos have been successfully used to provide maternity roost shelter for
Little Brown Bats (Fig. 6). Little information is available about Yuma Bats using bathouse structures for maternity roosts.
However, because Yuma Bats have
displayed long-lasting fidelity to the
Farmhouse site, one could expect that
the bats may be accepting of an
alternative roost structure at the same
location (Evelyn et al., 2004).
Figure 6. A bat-condo intended for relocation of a
colony of 10,000 Little Brown Bats near Spokane,
WA 2008. http://www.wa.nrcs.usda.gov
There are many uncertainties
with a bat house being the only available
shelter for roosting and parturition at the site should the Farmhouse become rendered
inaccessible to bats due to remodeling. The Little Brown and Yuma Bat colony may
readily accept an artificial bat house and begin using it, or, only a few bats may use it, or,
it may remain uninhabited. However, when a bat-house is designed specifically to meet
19
bats’ needs, with considerations such as location, exposure to sunlight, and dark-colored
stain for heat retention all taken into account, occupancy rates can be greatly increased
(Tuttle, 1993). Conditions such as temperature, humidity, air movement, location of the
structure, and height above ground are all determining factors in whether bats will occupy
a bat-house (Evelyn et al., 2004; Mitchell-Jones, 2004). A design such as that provided in
the Pennsylvania Game Commission’s “Bat Condo Directions”, by Butchkoski and
Hassinger (1997), takes into consideration many of the requirements of Myotis bats and
has been successful in attracting Little Brown Bat colonies.
Another option is the installation of several smaller sized bat houses in strategic
locations near the Farmhouse (Fig. 7). While smaller bat houses typically house only
100-200 bats, their smaller size allows for more placement options including different
heights, distances from buildings etc., and exposure to sunlight. Varied placements may
provide the bats with enough options for roosting to replicate the abundance of roosts
available at different heights and exposures on the Farmhouse. Additionally, smaller bat
houses are less expensive and less labor intensive to build than a large bat condo.
Figure 7. A sevenchamber bat house
from Bat
Conservation and
Management, Inc.
Houses up to 210
Myotis sized bats.
http://www.batmana
gement.com
20
Further Research
Continuing study of the Organic Farmhouse colony should include temperature
and humidity measurements in the bats’ preferred roosting locations in order to learn
more about the roosting and parturition requirements of local Little Brown and Yuma
Bats. As more information is gathered about the habits of the colony, continuing the
availability of optimum shelter should become more straightforward. In addition to
investigating the roosting habits on the farmhouse, yearly emergence counts should be
continued in order to monitor presence and fluctuations in the maternity colony
population (O’Shea and Bogan, 2003).
Emergence Count Data Forms and Surveyor Information Forms specifically made
for surveys at the Organic Farmhouse and Kifer Barn are available in Appendix B.
Additionally; the Emergence Count Protocol section of Chapter 5 provides a proven
methodology and straightforward means of carrying out seasonal monitoring of the
Farmhouse bat colony. A basic database, such as a Microsoft Excel®-style format, would
be very helpful for compiling yearly survey data and keeping all important information
about the colony together in one format. See Appendix C for sample Excel spreadsheet
summary of emergence counts for 2011.
Further research on the Farmhouse bat colony should also take into account the
rapid spread of White-Nose Syndrome among North American bats and the potential that
the disease may reach Washington State. As WNS appears to only be active in
hibernating bats, identifying the Farmhouse colony’s hibernacula site could be very
helpful in taking preventative measures against WNS infection (Reichard and Kunz,
2009). It is believed that the primary means of transmission of WNS is from bat to bat,
however, recreational activities in areas infected with WNS such as caving or hiking,
21
could lead to people inadvertently transmitting the disease great distances in a short
amount of time (USFWS, 2011). As a side-note, currently there is no evidence that
Geomyces destructans is pathogenic to humans (USFWS, 2011).
If the hibernacula site for the Farmhouse bat colony can be identified, protection
from disturbance by humans, possibly including cavers carrying WNS, could be
established for the site. One possible method for following the colony members to their
hibernacula is radio telemetry, involving attaching small transmitters to several colony
members while at the Farmhouse site at then tracking them to their wintering grounds.
Radio tracking a bat over long distances would require an intensive effort to maintain
contact with the traveling bat, as radio telemetry transmitters have a limited effective
range that is reduced substantially by vegetation and geographical features such as hills
(Holland and Wikelski, 2009).
However, this is not to say that it would not be worth the effort to attempt to
radio-track individuals from the Farmhouse colony to their hibernacula site; Evelyn et al.
(2004) was successful in tracking 15 out of 16 radio-tagged Yuma Bats to roost sites in a
suburban California residential area. Additionally, Cochran and Kjos (1985) successfully
radio-tracked an individual Swainson’s Thrush (Catharus ustulatus) over 1,500 km, by
ground vehicle. Thus, with enough perseverance, it appears that one could radio-track
small bats to their hibernation sites as well. Unfortunately, as of yet, developing
technology has not reduced globally-effective Position Tracking Terminal (PTT) satellite
tracking transmitters to a light enough weight to use on Myotis sized bats (Holland and
Wikelski, 2009).
22
Author’s Note
Please feel free to contact the author with any questions about bat activity at the
Farmhouse or for support such as electronic copies of field survey forms, or
recommendations about setting up bat monitoring activities. Enjoy the bats!!
Noel Ferguson
NFerguson24@gmail.com
23
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29
APPENDICES
Appendix A: Map of Organic Farmhouse Location
Map of The Evergreen State College, Potasnik, GIS 2006
30
Appendix B: Emergence Count Survey Forms
31
The Evergreen State College Bat Colony
Summer Maternity Roost Monitoring-EMERGENCE COUNT Data Form
SURVEYOR NAME:_____________________________________
(Surveyor who is responsible for reporting, and has completed a SURVEYOR INFO data
form)
SKY
WIND
START
START
END
TOTAL
CODE
CODE
TEMP
TIME
TIME
BATS
NO
NO
ºF
(24 hr)
(24 hr)
COUNTED
DATE
Survey TECHNIQUE
USED:
VISUAL, VIDEO, or
OTHER
BAT
TALLY/
NOTES and
COMMENTS
SKY
CODE
WIND
CODE
DESCRIPTION
DESCRIPTION
~Speed
1
Clear-Clear to a few clouds
1
Calm-Leaves Still
0 MPH
2
Partly Cloudy-Clouds but variable sky conditions
2
Slight Breeze-Leaves slightly Rustling
1-7 MPH
3
Cloudy-Mostly cloudy or overcast
3
Gentile Breeze-Leaves and twigs in motion 8-12 MPH
4
Drizzle-Light intermittent rain
4
Mod. Breeze-Small branches begin to move 13-18 MPH
5
Showers-Steady soaking rain
5
Windy-Small Trees or more in canopy sway 19-24+ MPH
6
Thunderstorms-Rain with thunderstorms
6
Not Recorded-
7
Not Recorded-Not Recorded
Sky and wind codes of 1 – 3 are best. Code of 4 is marginal. Avoid surveying if code is higher than 4.
32
Not Recorded
Roost Site Surveyed:
Organic Farmhouse
Check box for side(s) of Farmhouse surveyed
N
S
E
W
(See photos for orientation)
Kifer Barn
Other:_____________________________
Location on Organic Farmhouse and/or Kifer Barn where bats were observed
emerging. (Mark location(s) on appropriate photos)
North
East
South
South II
33
West
Kifer Barn
34
The Evergreen State College Organic Farmhouse and Kifer Barn
Summer Maternity Roost Monitoring-SURVEYOR INFORMATION Data Form
SURVEYOR INFORMATION (CONFIDENTIAL):
NAME: _________________________________________________________________
ADDRESS: _________________________________________________________________
_________________________________________________________________
CITY: ___________________________________________
ZIP:
STATE: __________
_________________
PHONE: __________________________________________
EMAIL:
__________________________________________
SURVEYOR TYPE (circle what best describes you):
Volunteer
-You are surveying as a volunteer and have limited expertise in both bat
identification and ecology.
Student
-You are a student studying bats with a basic expertise in both bat identification and
ecology.
Researcher -You are actively involved in bat research on an academic and/or professional level.
COMMENTS: (Bat experience etc.)
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
______________________________________________________________________________________
35
Appendix C: Sample Spreadsheet for Summarizing Survey Data
36
37
38
Appendix D: Examples of Bat Detectors
Pettersson Elektronik
“The D1000X is a professional ultrasound detector, based on the latest technology. The detector
has heterodyne, frequency division and time expansion systems and also a built-in 16-bit
recording system using a Compact Flash card as storage medium. It is equipped with our wellknown, high-quality capacitance microphone which has been further improved to give lower
noise, wider dynamic range and lower distortion.” www.batsound.com last accessed 9-14-11
Approx $6,000
“The D 500X is an ultrasound recording unit intended for long-term, unattended recording of bat
calls. In contrast to time expansion bat detectors, the D500X records full-spectrum ultrasound in
real time with virtually no gaps between recordings. The recorder is equipped with four slots for
CF cards, which typically makes it possible to leave the unit in the field for more than a month.
The triggering system allows the device to automatically start recording as a sound is detected.”
www.batsound.com last accessed 9-14-11 Approx $2,400
39
