Campbell River Bat Project: Bat House Mitigations
Bridge Coastal Fish and Wildlife Restoration Project #06.W.CBR.03
Prepared for:
BC Hydro Bridge Coastal Fish and Wildlife Restoration Program
6911 Southpoint Drive (E14)
Burnaby, BC V3N 4X8
Prepared by:
David Nagorsen
Mammalia Biological Consulting
4268 Metchosin Road
Victoria, BC V9C 3Z4
Prepared with the financial support of BC Hydro Bridge Coastal Fish
and Wildlife Restoration Program
January 2009
Executive Summary
The Ladore and Strathcona generating stations in the Campbell River watershed
have had a long history of bat occupation in summer and human-bat conflicts. Because of
their many access points, totally excluding bats from these two structures has proven
difficult. Four bat houses installed at the generating stations in February 2002 supported bat
colonies and suggested the potential of installing more bat houses for mitigation. The goal
of this project was to reduce the number of bats roosting inside the two generating stations
and mitigate for the loss of natural roost trees from dam construction and associated
flooding by providing human-made bat roosts.
Twenty new bat houses were constructed for the project: 16 four-chamber, standard
sized maternity houses and 4 two-chamber rocket boxes based on the designs
recommended by Bat Conservation International. On 25-26 April 2007, eight new
maternity boxes and a double-wide maternity house from 2002 were attached to the a
concrete retaining wall at Strathcona. Two rocket boxes (one from 2002 that was attached
to the building on an old flag pole) were placed on aluminum poles concrete pads near the
retaining wall. On 26-27 April 2007, eight new maternity boxes, the double-wide maternity
box from 2002, and two new rocket boxes were installed at on a metal frame attached to
the south end wall at Ladore. Onset temperature loggers (StowAway Tidbits) were installed
in each bat house to record temperatures and a single logger was attached outside the bat
houses at each site to record ambient temperature. Temperatures were recorded from 15
May 2007-1 October 2008. The bat houses were examined for evidence of bat use on three
sessions in 2007 and 2008.
Maximum bat counts at Strathcona were ~900 in 2007 and ~ 1,470 in 2008.
Maximum bat counts at Ladore were ~130 in 2007 and ~ 150 in 2008. Its unknown if the
bat colonies associated with the bat houses are stable or will continue to increase. Bat
houses were occupied from late April to 1 November with maximum numbers in late
summer and early autumns. No bats were captured or handled to determine species or
reproductive condition, but the houses likely support maternity colonies of female the Little
Brown Myotis and Yuma Myotis. Temperatures inside the bat houses were warmer than
ii
ambient temperatures; maximum temperatures inside the standard maternity boxes and
rocket boxes occasionally reached or exceeded the lethal temperature of 44° C, whereas
temperatures recorded in the double-wide maternity boxes never exceed 40° C. Because
bats moved among the bat houses at a site in response to seasonal and daily temperature
effects, using multiple bat houses of several designs is most effective. The higher bat
numbers in the Strathcona bat houses can be attributed to microclimate and location
creating warmer temperatures than Ladore.
This project clearly achieved its two goals- 1) reduce bat occupancy of the
generating stations and 2) mitigate for the loss of natural tree roosts with bat houses. I
recommend that BC Hydro continue to maintain the bat houses now installed at the
Strathcona and Ladore stations. It is also essential that the monitoring program (bat counts
and temperature monitoring) continue. I recommend data gaps that could be explored with
more research. BC Hydro should establish a partnership with a local educational institution
such as North Island College, Campbell River or the University of Vancouver Island,
Nanaimo to continue the bat house project. I list several site specific recommendations.
iii
Table of Contents
Executive Summary ............................................................................................................... ii Introduction............................................................................................................................ 1 Goals and Objectives ............................................................................................................. 2 Study Area ............................................................................................................................. 2 Methods ................................................................................................................................. 3 Bat house design and construction..................................................................................... 3 Bat house installation ......................................................................................................... 4 Data loggers ....................................................................................................................... 7 Monitoring ......................................................................................................................... 8 Results.................................................................................................................................... 9 Bat Counts.......................................................................................................................... 9 Temperature Data ............................................................................................................ 11 Discussion ............................................................................................................................ 15 Recommendations ................................................................................................................ 18 General recommendations ............................................................................................... 18 Site Specific recommendations ........................................................................................ 19 Acknowledgements .............................................................................................................. 20 References ............................................................................................................................ 20 Appendix 1. Financial Statement Form ............................................................................... 22 Appendix 2. Performance Measures .................................................................................... 23 Appendix 3. BCRP Recognition .......................................................................................... 24 List of Figures
Figure 1. Locations of the Ladore and Strathcona BC Hydro generating stations in the
Campbell River watershed. .................................................................................................... 3 Figure 2. Nine bat houses mounted on the south retaining wall at Strathcona. Box 1 is the
double-wide maternity box, boxes 2-9 are the standard maternity boxes ............................. 5 Figure 3. Metal frame with bat houses attached to the west perimeter wall at Ladore ........ 5 iv
Figure 4. Eleven bat houses installed west perimeter wall frame at Ladore. Boxes 1, 2 are
rocket boxes, box10 is the double-wide maternity box, other boxes are standard maternity
boxes. Note that boxes 2, 4, 6 and 9 are mounted directly behind boxes 1, 3, 6, and ........... 6 Figure 5. Onset tidbit temperature logger installed on back of logger holder ....................... 6 Figure 6. Data logger holder attached to standard maternity house ..................................... 6 Figure 7 Hourly temperatures recorded in Box 8 (standard maternity box) at Ladore 1 June30 September 2008 .............................................................................................................. 14 Figure 8 Hourly temperatures recorded in Box10 (double-wide maternity box) at Ladore 1
June-30 September 2008 ...................................................................................................... 14
List of Tables
Table 1 Data loggers installed in bat houses.......................................................................... 8 Table 2 Bat counts in the 11 bat houses at Strathcona generating station... ........................ 10 Table 3 Bat counts in the 11 bat houses at Ladore generating station ................................. 11 Table 4 Temperature data for selected bat houses at Strathcona generating station recorded
2007 and 2008……………………………………………………………………………...12 Table 5 Temperature data for selected bat houses at Ladore generating station recorded
2007 and 2008……………………………………………………………………………...13 v
Introduction
Hydro generating stations with their warm stable temperatures and many ventilation
openings provide ideal conditions for pregnant and nursing female bats during the summer
maternity period. The loss of natural tree roosts such as large snags or wildlife trees
(Vonhof and Barclay 1996; Kellner and Rasheed 2002) from dam construction and
associated flooding probably increases the attractiveness of these human-made structures
for roosting bats. Bats in generating stations create human bat interactions and guano
deposits in the active workplace. The Ladore and Strathcona generating stations in the
Campbell River watershed (Fig. 1) have had a long history of bat occupation in summer
(Kellner and Rasheed 2002). Because of their many access points, totally excluding bats
from these two structures has proven difficult. As part of their BC Hydro Campbell River
bat project funded by the Bridge Coastal Restoration program (BCRP), Kellner and
Rasheed (2002) installed six bat houses at the John Hart, Ladore, and Strathcona generating
stations in February 2002. The purpose was to provide alternate roosts to reduce the
numbers of bats roosting inside the BC Hydro buildings and mitigate for the loss of natural
roosting habitat.
Kellner and Rasheed (2002) monitored their bat houses for one season from 10
June-1 August 2002. They observed only three bats in the maternity boxes at Ladore and
Strathcona, but the presence of guano and temperature profiles recorded over the summer
inside the bat boxes suggested that the bat houses had considerable potential as summer
roosts. Kellner and Rasheed (2002) recommended follow up monitoring each summer over
several years to assess their effectiveness. However, no monitoring was done until 6 July
2005, when D. Nagorsen was contracted by BC Hydro to examine the sites and assess the
houses for evidence of bat occupation. Large guano deposits under several bat boxes and
observations of bats inside, revealed that at least four of the six bat houses were being used.
A report (Nagorsen 2005) recommended the installation of more bat houses at Ladore and
Strathcona stations and increased monitoring to measure the effectiveness of bat houses as
alternate roosting habitat. In 2006, a proposal requesting funds for the construction and
installation of additional bat houses with follow up monitoring over 2 years was funded by
BCRP.
1
Goals and Objectives
The project was narrowly focused on bat house mitigation at Ladore and Strathcona
stations. The goal of the project was to reduce the number of bats roosting inside the two
generating stations and mitigate for the loss of natural roost trees by providing humanmade bat roosts.
Objectives were:
1. Relocate three existing bat houses installed in 2002 that were considered a problem
by BC Hydro staff because of guano deposits and stains in high traffic areas.
2. Construct and install 20 new bat houses at the Ladore and Strathcona stations to
increase the number of available human-made roosts.
3. Monitor the bat houses for two summers to determine their effectiveness.
4. Monitor bat box and ambient temperatures with data loggers.
Study Area
The project was located at the Ladore and Strathcona BC Hydro generating stations
(Fig. 1) in the Campbell River watershed, Vancouver Island. They were the two stations
with bats roosting inside the stations. John Hart station was excluded from the project
because it had no bat occupancy issues (Kellner and Rasheed 2002; Nagorsen 2005). At
Strathcona, all bat houses were located inside the fenced secure perimeter of the generating
station. At Ladore, the bat houses were located on outside of the west perimeter wall. The
installation sites were anthropogenic habitats (retaining walls near buildings); natural
habitat in close proximity to the stations was riparian and second growth forest bordering
dams.
2
Figure 1. Locations of the Ladore and Strathcona BC Hydro generating stations in
the Campbell River watershed.
Methods
Bat house design and construction
Twenty new bat houses were constructed for the project with construction
completed in January 2007. They consisted of 16 four-chamber maternity houses and 4
two-chamber rocket boxes based on the designs recommended by Bat Conservation
International (see Tuttle et al. 2004). Outer parts of the houses were constructed from
plywood; the inner partitions that formed the chambers were cedar. Horizontal grooves
were cut into the inside partitions and landing board of each house to provide rough
surfaces for bats to grip. The roof of each house was covered with Duraseal roofing
3
material for waterproofing. All bat houses were painted black and uniquely numbered with
red paint to cross-reference bat observations and temperature loggers with the
corresponding bat house. In addition to the 20 new bat houses, three existing bat houses
from the Kellner and Rashheed (2002) BCRP project were used in this project. Two were
double wide, four-chamber maternity boxes; one was a rocket box.
Bat house installation
Logistics and locations for the installing the bat houses given in the original BCRP
proposal were based on casual observations from the 6 July 2005 assessment. Various
buildings and concrete walls within Ladore and Strathcona that were proposed as possible
sites to mount bat boxes were determined to be unsuitable because of potential bat guano
issues with BC Hydro staff. Onsite visits with BCH VIG and BCRP staff 13 February 2007
and 12 April 2007 were conducted to establish suitable locations at Ladore and Strathcona
for locating the existing and new bat houses and determine any BCH involvement in the
installation.
Strathcona
On 25 April 2007, eight new maternity (numbered 2-9) boxes were attached with
Hilti bolts to the concrete retaining wall at Strathcona. The double-wide maternity box
originally mounted on the crane rail wall was relocated to the same retaining wall adjacent
to the eight new boxes (Fig. 2). The double-wide box was occupied by a large number of
bats. However, most remained inside the bat box during the move and installation. On
April 26, the rocket box attached to the building on an old flag pole was relocated to a
concrete pad south of the retaining wall where it was attached to an aluminum pole. It also
contained bats. A new rocket box on a pole was also placed at this location on an adjacent
concrete pad.
Ladore
On 26-27 April 2007, eight new maternity boxes and two new rocket boxes were
installed at Ladore. The double-wide maternity box originally mounted on a pole attached
to the building was relocated to the site with the new boxes. It was occupied by a large
number of bats; however, similar to Strathcona most remained inside the bat box during the
move and installation. Bat houses were mounted on a metal frame attached to the south end
wall that faces the spillway (Fig. 3) . Seven bat houses (numbered 1, 3, 5, 7, 8, 10, 11)
4
faced out from the wall; four houses (numbered 2, 4, 6, 9) were mounted on the back side
of the frame facing the wall (Fig. 4).
Figure 2. Nine bat houses mounted on the south retaining wall at Strathcona. Box 1 is
the double-wide maternity box, boxes 2-9 are the standard maternity boxes
Figure 3. Metal frame with bat houses attached to the west perimeter wall at Ladore
5
Figure 4. Eleven bat houses installed west perimeter wall frame at Ladore. Boxes 1, 2
are rocket boxes, box10 is the double-wide maternity box, other boxes are standard
maternity boxes. Note that boxes 2, 4, 6 and 9 are mounted directly behind boxes 1, 3,
6, and
Figure 5. Onset tidbit
temperature logger installed on
back of logger holder
Figure 6. Data logger holder attached
to standard maternity house
6
Data loggers
Onset temperature loggers (StowAway Tidbits) were installed in each bat house to
record temperatures and a single logger was attached outside the bat houses at each site to
record ambient temperature. A 8.5 cm circular piece of wood cut from the upper front
section of each house was used to hold the data logger attached by a single screw. A rubber
gasket glued to the inner surface of logger holder was used to weather seal the holder (Fig.
5). The logger holder was attached to the bat house with two screws (Fig. 6). Loggers were
inserted in the new bat houses when they were installed 25-27 April 2007 and left in place
throughout the study. Loggers were removed from the bat houses 1 October 2008 as part of
the last monitoring session of the project.
Because the three bat houses from 2002 unexpectedly contained large number of
bats when they were relocated 25-27 April, logger holders could not be cut from the bat
boxes without disturbing bats. No temperature profiles were recorded for these boxes in
2007. During the first monitoring session in 2008 (4 June), a logger was attached to the
lower part of an inside partition of each of the double-wide maternity boxes.
Temperature loggers were programmed to begin to record temperatures at 30 min
intervals beginning 15 May 2007; data were downloaded 28 September 2007, 4 June 2008,
and 1 October 2008 (Table 1). Loggers were re-launched immediately after downloads. On
1 October 2008, the final monitoring session, all temperature loggers were removed from
the bat houses. Temperature data were downloaded to a lap top computer using BoxCar Pro
4.3 software (Onset Computer Corporation, Bourne, MA). BoxCar files were exported to
Excel 2007 and Systat 12 software (Systat Software Inc., San Jose, CA) for analyses.
7
Table 1 Data loggers installed in bat houses
Dates Downloaded
Bat
Logger
Begin
End
28 Sept 07 4 June 08 1 Oct 08
House
SN
Strathcona
1
1087209 4 June 08 1 Oct 08
-1
X
2
1087206 15 May 07 1 Oct 08
X
X
X
3
1087205 15 May 07 1 Oct 08
X
X
X
4
1087204 15 May 07 1 Oct 08
X
X
X
5
1087201 15 May 07 1 Oct 08
X
X
X
6
1087203 15 May 07 1 Oct 08
X
X
X
7
1087200 15 May 07 1 Oct 08
X
X
X
8
1087207 15 May 07 1 Oct 08
X
X
X
9
1087202 15 May 07 1 Oct 08
X
X
X
2
ambient 1087208 15 May 07 1 Oct 08
X
X
Ladore
1
1087223 15 May 07 1 Oct 08
X
X
X
2
1087224 15 May 07 1 Oct 08
X
X
X
3
1087212 15 May 07 1 Oct 08
X
X
X
4
1087222 15 May 07 1 Oct 08
X
X
X
5
1087220 15 May 07 1 Oct 08
X
X
X
6
1087221 15 May 07 1 Oct 08
X
X
X
7
1098153 15 May 07 1 Oct 08
X
X
X
8
1087214 15 May 07 1 Oct 08
X
X
X
9
1087216 15 May 07 1 Oct 08
X
X
X
10
1087216 4 June 08 1 Oct 08
-1
X
11
1087218 15 May 07 1 Oct 08
X
X
X
3
ambient 1087216 15 May 07 4 June 08
X
X
ambient 1087211 4 June 08 1 Oct 08
-4
X
1
logger installed 4 June 2008
2
ambient logger was accidentally left attached to the wall when the loggers were removed
1 October 2008. Data for summer 2008 needs to be downloaded from this logger.
3
logger failed from 28 Sept 07-4 June 08; removed and replaced with 1087211
4
installed 4 June 2008
Monitoring
The original proposal recommended that each bat house be monitored at least once
a month in June, July and August. However, monitoring had to be coordinated with the
availability of BC Hydro staff for access and it was not possible to follow a fixed schedule
for monitoring. Three monitoring sessions were done in 2007 (2 August, 28 September,
8
and 7 November) and 2008 (4 June, 23 July, 1 October). The 7 November 2007 monitoring
was only done at Strathcona. Because of weather conditions on this day, the wall at Ladore
could not be safely accessed by ladder. To inspect for bats, the open bottom of each bat
house was accessed by a ladder placed on the cement retaining walls and the chambers
were examined briefly with a flashlight. It was not possible to observe the entire roosting
area inside a bat house especially when the box contained numbers of bats; therefore, the
counts of bats inside each box are rough estimates and likely underestimate the total
numbers. To avoid disturbance, no bats were handled or removed from the bat houses. The
ground and wall surface under each bat house was inspected for the presence of guano
another indicator of bat use. At Strathcona, the two rocket boxes mounted on poles could
not be safely accessed by ladder for examination of the chambers and bat use could only be
assessed by the presence of guano under the boxes.
Results
Bat Counts
Strathcona
In 2007, the highest count was 22 August with ~900 bats (Table 1). Most of the
bats on this date were concentrated in the new maternity boxes on the eastern end of the
wall (boxes 7-9). The double-wide bat house (box 1) contained only ~50 bats; however, a
large accumulation of guano under this bat house indicated that was occupied by 100s of
bats earlier in the summer. On 28 September, the bat count was reduced with most bats in
boxes 7-9 similar to September. By November, the bats had abandoned the bat houses.
Only one of the rocket boxes (box 11) had evidence of bats, but the guano under this box
consisted of a few scattered pellets suggesting only a few bats. In 2008, the highest count
was ~1,470 bats on 1 October (Table 2) with most bats occupying the bat houses on the
western side of the wall (boxes 1-6). In contrast, in the June and July monitoring sessions,
the bats were concentrated in the double-wide maternity box (box 10). Similar to 2007, the
two rocket boxes showed no evidence for heavy bat use.
9
Table 2 Bat counts in the 11 bat houses at Strathcona generating station 2007 and
2008
1
2
2
Bat House Number
4
52
62
72
82
2
Date
1
2
3
92
103 113 Totals
2007
22 Aug
50
2
0 11 20 35 110 300 420 n
n
~900
28 Sept 20
1
2
7 25 70 40 120 150 n
g
~620
7 Nov
0
0
0
0
0
0
0
2
0 n
n
~2
2008
4 June 400
1
4
4
6 10 15 20 40 n
g
~500
23 Jul
700
1
0
0
0
0
0
0
0 n
g
~700
1 Oct
250 250 250 100 300 250 10 60
0 n
g
~1470
1
double-wide maternity box
2
standard maternity box
3
rocket boxes on poles, could not be accessed to count bats; n=no guano under box,
g=guano under box
Ladore
In 2007, the highest count was 28 September with ~130 bats (Table 3). In both
2007 sessions bats mostly occupied the double-wide maternity box (box 10). The bat
houses could not be accessed during the 7 November monitoring but its likely the bats had
left the bat houses by this date. Highest count in 2008 was ~150 on 1 October. In contrast
to 2007, bats were not confined to the double-wide maternity box and were more evenly
distributed among the bat houses attached to the front of the metal frame. For the paired
front-to-back houses ( rocket boxes 1-2 and maternity boxes 3-4, 5-6, 8-9), the houses
attached at the back of the metal frame closer to the retaining wall (boxes 2, 4, 6, and 9)
clearly supported fewer bats than the boxes attached on the front side of the frame (Table
2).
Species in the Bat Houses
No bats were captured or removed from the houses to verify their identification from traits
that could be examined in the hand (Nagorsen and Brigham 1993). Nevertheless, from
visual observations the bats occupying the bat houses were species of Myotis, likely the
Yuma Myotis (Myotis yumanensis) and/or Little Brown Myotis (Myotis lucifugus).
10
Table 3 Bat counts in the 11 bat houses at Ladore generating station 2007 and 2008
1
1
Bat House Number
3 42 52 62 72 82
2
Date
1 2
92 103 112
2007
22 Aug
6 0
0 0
1 0
1
2 0 100 0
28 Sept
0 0
0 0
4 0
2
5 0 120 0
7 Nov
-------not monitored wall too wet for ladder-----2008
4 June
6 0
0 1
0 0
0
0 0 12
0
23 Jul
0 0
3 0 10 0 12
1 0 12
1
1 Oct
0 0 20 0 50 0 20 40 6 12
0
1
rocket boxes
2
standard maternity box
3
double-wide maternity box
Totals
~110
~130
~20
~40
~150
Temperature Data
General Patterns
May-September temperatures recorded at both sites (Tables 4, 5) showed a similar
pattern with mean and maximum temperatures increasing through May and June, reaching
a peak in July, followed by declines in August and September. Mean temperatures
recorded in the bat houses were typically 1-3° C warmer than ambient temperatures
recorded outside the bat houses on the retaining walls.
Mean ambient and bat house temperatures were consistently 1-3° C higher at
Strathcona than Ladore in 2007 (Tables 4, 5). Comparative ambient temperatures for both
sites are not available for 2008, but temperatures recorded in the bat houses at Strathcona
were warmer than those recorded in the Ladore bat houses as in 2007.
Variation Among Years
For Strathcona, yearly differences in ambient temperatures can only be compared
for May. The data suggest cooler temperatures in 2008, a trend reflected in the mean
temperatures recorded in the bat houses. There are no obvious yearly differences in the
mean temperatures recorded in the bat houses from June-September at Strathcona. May
ambient temperatures for 2008 are not available for Ladore, but temperatures recorded in
the bat houses suggest cooler temperatures in May 2008 similar to Strathcona. Mean
ambient temperatures recorded June-September at Ladore showed no yearly differences.
11
Table 4 Temperature data for selected bat houses at Strathcona generating station
recorded 2007 and 2008. For relative location and type of bat house for each bat box
see Figure 2.
2007
2008
Box1 Box2 Box9 Ambient Box1 Box2 Box9 Ambient
May
Mean
-1
19.3 19.3
18.1
-1
16.9 17.2
15.8
Maximum
46.3 45.4
42.8
43.0 45.0
41.5
Minimum
4.8
5.0
6.5
3.1
3.0
4.1
SD
9.5
9.2
8.1
8.4
8.6
7.4
CV
0.49 0.48
0.45
0.50 0.50
0.47
June
2
Mean
18.9 18.9
18.0 16.5 18.6 19.3
Maximum
46.8 45.9
44.6 40.3 47.3 48.5
Minimum
7.7
7.6
9.4 6.2
5.4
5.0
SD
7.5
7.3
6.2 6.0
8.3
8.8
CV
0.40 0.38
0.35 0.36 0.45 0.46
July
Mean
23.7 23.7
22.4 20.4 22.7 23.1
Maximum
52.1 51.7
51.3 36.6 44.8 45.4
Minimum
10.3 10.2
11.4 10.0
9.5
9.4
SD
8.4
8.3
7.1
5.7
8.3
8.5
CV
0.36 0.35
0.32 0.28 0.36 0.37
August
Mean
21.9 24.2
20.7 19.8 22.5 24.3
Maximum
48.8 53.5
45.1 40.3 51.5 52.3
Minimum
10.3 11.1
12.7
8.8
8.3
7.9
SD
9.0
9.9
7.3
6.5
9.6 10.6
CV
0.41 0.40
0.35 0.33 0.43 0.44
September
Mean
17.4 19.8
17.5 17.2 19.8 19.8
Maximum
49.9 51.7
45.6 38.2 49.4 47.4
Minimum
4.6
4.7
5.6
6.5
5.1
5.0
SD
9.9 10.7
8.2
6.3 10.0
9.9
CV
0.55 0.54
0.47 0.36 0.51 0.50
1
temperature logger installed in this box 4 June 2008
2
ambient logger was accidentally left attached to the wall when the loggers were removed
1 October 2008. Data for summer 2008 needs to be downloaded from this logger.
12
Table 5 Temperature data for selected bat houses at Ladore generating station recorded
2007 and 2008. For relative location and type of bat house for each bat box see Figure 4.
Box
1
May
Mean
Maximu
m
Minimum
SD
CV
June
Mean
Maximu
m
Minimum
SD
CV
July
Mean
Maximu
m
Minimum
SD
CV
August
Mean
Maximu
m
Minimum
SD
CV
September
Mean
Maximu
m
Minimum
SD
CV
1
2
Box
2
Box
8
2007
Box
9
Box1
0
Ambien
t
Box
1
Box2
Box
8
2008
Box
9
Box1
0
Ambien
t
16.8
36.7
16.9
35.1
15.6
36.8
15.8
32.1
-1
-
14.7
37.5
16.2
40.0
14.6
37.8
14.3
40.1
14.3
33.6
-
-2
-
6.0
7.9
0.47
7.1
6.7
0.40
5.9
7.2
0.46
6.8
6.0
0.38
-
5.6
6.3
0.43
3.1
8.0
0.49
2.8
6.8
0.47
2.4
7.2
0.53
3.9
6.1
0.43
-
-
16.8
39.6
17.0
38.8
15.8
39.3
16.1
35.1
-
14.8
40.3
16.8
42.6
16.3
37.9
15.9
42.8
16.1
39.1
15.1
34.0
15.0
42.0
7.1
6.1
0.36
8.6
5.2
0.34
7.0
5.5
0.35
8.3
4.6
0.29
-
6.8
4.9
0.33
6.0
7.2
0.43
6.6
6.0
0.37
5.9
6.9
0.43
7.1
6.0
0.37
6.5
5.7
0.37
5.9
6.2
0.41
21.7
21.8
20.4
20.7
-
19.4
20.5
19.7
20.1
18.7
18.6
46.4
46.4
47.1
43.4
-
49.6
41.7
20.3
6
35.6
40.6
37.0
31.8
40.3
9.2
7.3
0.33
10.6
6.2
0.29
9.4
6.5
0.32
10.3
5.4
0.26
-
9.4
6.0
0.30
9.7
7.1
0.35
11.2
5.4
0.27
9.6
6.7
0.34
10.9
5.6
0.28
10.2
5.0
0.27
9.7
5.7
0.31
20.6
43.5
20.2
40.4
19.3
43.7
19.1
36.6
-
17.9
43.1
20.1
46.4
19.3
37.1
19.6
47.1
19.1
37.8
18.0
36.3
17.9
44.8
9.7
8.0
0.39
11.2
6.1
0.30
9.6
7.2
0.37
10.9
5.1
0.27
-
9.4
5.9
0.33
8.6
8.3
0.41
9.2
6.0
0.31
7.9
8.2
0.42
8.9
6.2
0.32
8.5
5.8
0.32
7.7
6.7
0.37
18.1
48.9
16.4
39.2
16.0
49.8
15.4
33.6
-
14.9
42.2
18.4
50.0
16.7
30.4
17.7
48.7
16.5
30.7
15.5
29.3
15.5
39.8
5.4
9.3
0.51
6.0
6.5
0.40
5.0
8.4
0.53
5.9
5.5
0.36
-
5.3
6.0
0.41
6.6
9.2
0.50
7.4
5.2
0.31
5.9
9.0
0.51
7.1
5.4
0.33
6.2
5.1
0.33
5.9
5.9
0.38
temperature logger installed in this box 4 June 2008
logger failed from 28 Sept 07-4 June 08, replaced with new logger
13
Figure 7 Hourly temperatures recorded in Box 8 (standard maternity box) at Ladore
1 June-30 September 2008
Figure 8 Hourly temperatures recorded in Box10 (double-wide maternity box) at
Ladore 1 June-30 September 2008
14
Variation Among Bat Houses
At Strathcona maternity box 9 recorded higher mean temperatures in August and
September 2007, and from May-August in 2008 than maternity box 2 located at the west
end of the wall. The double-wide maternity box (box 1) consistently had mean
temperatures ~2° C cooler than the smaller maternity boxes. At Ladore the paired boxes
mounted back-to-back (box1 vs box2, box8 vs box9) generally showed no differences in
their mean temperatures except in September when the boxes facing the wall were cooler.
The rocket boxes (boxes 1,2) recorded mean temperatures ~1° C warmer than temperatures
in the standard maternity boxes (boxes 8, 9). Similar to Strathcona, the double-wide
maternity box (box 10) consistently had mean temperatures ~2° C cooler than the other bat
houses (Figs. 6, 7).
Discussion
The results from 2007 and 2008 demonstrate that this project achieved its two
goals- 1) reduce bat occupancy of the generating stations and 2) mitigate for the loss of
natural tree roosts with bat houses. Kellner and Rasheed (2002) estimated minimum
populations of about 97 bats roosting in Strathcona and 73 bats roosting in Ladore in the
summer of 2001. No bat counts or estimates of guano accumulation were done inside the
generating stations in 2007 and 2008 because of access issues. However, anecdotal
statements from various BC Hydro staff suggest that the number of bats roosting inside the
two generating stations during 2007 and 2008 was significantly reduced. With >1400 bats
occupying the bat houses at Strathcona and ~150 bats occupying the bat houses at Ladore,
the populations associated with the bat houses exceed the numbers of bats that roosted in
the generating stations. Clearly the bat houses are attracting bats that roosted elsewhere in
the lower Campbell River watershed in addition to those that occupied the generating
stations. Although no bats were captured and examined for reproductive condition, the
numbers suggest that the bat houses support maternity colonies of female bats and their
young. The increase in the number of bats occupying the bat houses from 2007 to 2008
may be the result of more bats discovering the bat houses or individuals born in the bat
15
houses in 2007 returning the following year. Monitoring should be continued for several
more seasons to determine if the bat house colonies have reached their maximum size.
Long et al. (2006) found that bat houses were usually occupied by a bat colony within two
years of placement, but the colony may slowly increase in numbers if it was colonized
initially by a few individuals.
The species of bats occupying the bat houses was not determined but they are
presumably Yuma Myotis (Myotis yumanensis) and/or Little Brown Myotis (Myotis
lucifugus). From captures, Kellner and Rasheed (2002) determined that the colony inside
the Strathcona generating station was a mixed population of Little Brown Myotis and
Yuma Myotis, whereas the colony at Ladore consisted of only Yuma Myotis. They are the
two commonest bat species in the lower Campbell River watershed and accounted for 88%
of the captures by Kellner and Rasheed (2002). Both species have been demonstrated to
use bat houses (Tuttle et al. 2004) and a population of some 340 Little Brown Myotis
occupy six bat houses installed on old power poles at the old Camp 8, TimberWest site
near Strathcona station (Cortese and Thacker 2006).
Although the number and types of bat houses installed at Strathcona and Ladore
were similar, the Strathcona houses supported many more bats. Bat populations inhabiting
the natural habitats in the vicinity of the two sites are unknown, but both sites are close to
water with potential foraging habitat. Kellner and Rasheed (2002) estimated similar bat
numbers roosting in the generating station buildings at the two sites. The greater success of
the Strathcona bat houses can be attributed to location and microclimate. The retaining wall
at Strathcona is south facing and well protected from winds. In contrast, the wall at Ladore
faces northwest and is exposed to winds from the river. Temperature profiles recorded in
the Strathcona bat houses were consistently warmer than those at Ladore.
Bats were observed in the bat houses from late April until 7 November. Because of
differences in monitoring, occupancy dates cannot be compared among the two years.
Highest counts were in late summer-early autumn (August to 1 October) when the bat
houses would contain adults and volant young-of-the-year. Kellner and Rasheed (2002)
first observed juvenile bats in the generating stations on July 12. The 1 November
monitoring revealed only 2 bats remaining in Strathcona bat houses. No winter monitoring
was done, but the Little Brown and Yuma Myotis would be expected to abandon the bat
16
houses and migrate to local caves or mine adits for hibernation. The discovery in late April
2007 of bats residing in the two original double-wide maternity boxes and rocket box was
unexpected. Fresh guano pellets under these houses suggested they had been occupied for
several weeks. Maternity colonies in buildings typically form from mid May to late August
on the south coast (personal observation). Temperature regimes in bat houses mounted in a
warm stable microclimate associated with cement walls evidently will support bat colonies
for a more extended period from early spring to early autumn.
At Strathcona, bats appeared to concentrate in the double-wide maternity box in
June and July; in August to early October they were more dispersed among the bat houses.
At Ladore in 2007 bats were mostly restricted to the double-wide maternity box; in 2008
they were more dispersed among the bat boxes. In a study of bat colonies in barn loft, Licht
and Leitner (1966a) observed that when temperatures reached 41° C, Yuma Myotis had to
move to cooler locations in the roost. Temperatures of 44° C are lethal for this species
(Licht and Leitner 1966b). Maximum temperatures occasionally reached and exceeded this
critical temperature in some of the standard maternity boxes (Fig. 6) and rocket boxes.
Presumably bats moved to a lower, cooler part of the bat house or relocated to another bat
house during these periods of temperature extremes. In contrast, maximum temperatures
recorded in the lower area of the two double-wide maternity boxes never exceeded 40° C
(Fig. 7). The larger double-wide maternity boxes may be preferred in spring and early
summer when females are pregnant or nursing because they offer a broader temperature
range. In late summer, when the young are volant, the smaller standard boxes may provide
more optimum temperature regimes. Temperature differences do not account for the
absence of bats in the four bat houses facing the wall at Ladore. With the upward slope of
the retaining wall, these houses may have provide insufficient height between the landing
board and the wall. Although the original rocket box on the flag pole at Strathcona
supported a number of bats, the new and relocated rocket box from 2002 were less
effective than the maternity boxes. Temperature profiles recorded in the two rocket boxes
at Ladore were similar to those in the standard maternity boxes. When exposed to a variety
of bat boxes in close proximity with similar temperature regimes, bats may prefer the
maternity boxes because they provide more roosting space.
17
This study has shown that human-made bat houses can successfully attract and
support large maternity colonies of the Little Brown Myotis and Yuma Myotis. Mounting
the bat houses on cement walls provides warm stable temperature regimes. Temperatures in
the bat houses exceeded ambient temperatures by several degrees. The ambient recorders
were mounted in a warm microclimate on walls and the temperature differential between
the bat houses and natural roosting sites in the watershed such as trees is likely far greater.
Bats moved among the various bat houses throughout the season in response to subtle
temperature changes and their reproductive status. It appears that employing a number of
bat houses that contain a mix of double-wide and standard sized maternity boxes is most
effective.
Recommendations
General recommendations
Given the success of the bat houses in reducing bat occupancy of the generating
stations and mitigating for the loss of natural tree roosts, I recommend that BC Hydro
continue to maintain the bat houses now installed at the Strathcona and Ladore stations.
The bat houses should last for several decades with minor repairs or maintenance. It is
essential that the monitoring program (bat counts and temperature monitoring) continue.
The monitoring should extend from April-October with bimonthly checks. The Onset tidbit
loggers purchased through this BCRP project could be reinstalled in the bat houses in 2009
and used to monitor temperature profiles for several more years. The major requirement is
the time and travel expenses for monitoring the bat houses and temperature loggers.
Data gaps that should be addressed with more research are:
•
the species of bats using the bat houses-DNA analysis of faecal pellet
samples collected under bat boxes could be used to address this.
•
the earliest spring dates when bats occupy the bat houses.
•
timing of reproduction in the bat house colonies and its correlation with
temperature.
•
long term trends in the bat house colony numbers and their association with
variation in local weather conditions.
18
BCRP does not support long term continuous monitoring; therefore, BC Hydro
should explore other potential partnerships to support the continuation of this project. A
local consulting firm could be found to continue the monitoring, but a more cost efficient
approach would be to partner with either a natural history club or an educational centre.
There is currently no active local natural history club in the Campbell River area. However,
North Island Community College in Campbell River or a university such as the University
of Vancouver Island in Nanaimo are possible partners. The biology program at the
University of Vancouver Island for example, requires fourth year students to complete an
undergraduate research project and the bat house monitoring could be yearly student
research project. Another option is a biology graduate student at the University of Victoria.
A detailed study of the bat houses would make an ideal Masters thesis project.
Site Specific recommendations
Strathcona
The nine maternity houses on the retaining wall at Strathcona should be left in their present
position. The two rocket boxes installed on poles on the cement pads are contributing little
and I recommend that they be moved to another location at Strathcona or relocated to a
suitable site at the Ladore station.
Ladore
The two rocket boxes (boxes 1, 2) and three standard maternity houses (boxes 4, 6, 9) that
face the retaining wall at Ladore are not being used by bats. I recommend they be removed
from the metal frame and relocated to another location at Ladore, preferably sites with a
south facing aspect and long sun exposure. Unfortunately, the best locations at Ladore for
installing bat houses are sites where there is potential for human-bat conflicts. However,
several locations proposed in the 15 February 2007 memo to BC Hydro such as the front of
audit tunnel inside fence and the rock outcrop across tail race should be explored. The use
of old power poles with two maternity boxes mounted back-to-back facing different aspects
was also recommended in the 15 February memo.
19
Acknowledgements
This project was funded by the BC Hydro Bridge Coastal Fish and Wildlife
Restoration Program. Mike Grant and Al Mclean (BC Hydro, John Hart Station) assisted
with the logistics of installation and monitoring and provided access to Strathcona and
Ladore stations. Scott Allen (BCRP) helped trouble shoot various issues including
contingency funding from BCRP to assist with costs of installing bat houses. I thank Nick
Golinski for his expertise and enthusiasm in constructing and installing the bat houses.
Bruce Walton assisted with the bat house installation. Deb Cowper (Latitude West
Consultants) and Robyn Budd (Moondog Consulting) monitored the bat houses. Dave
Lindsay (TimberWest) provided information on the bat houses at Camp 8.
References
Cortese, L, and C. Thacker. 2006. Inventory of Little Brown Bats (Myotis lucifugus).
Unpublished report, TimberWest, 4 pp.
Kellner, M., and S. Rasheed. 2002. Campbell River bat project: inventory and habitat
assessment. BC Hydro Bridge-Coastal Fish and Wildlife Compensation Program.
56 pp.
Licht, P., and P. Leitner. 1967a. Behavioural response to high temperatures in three species
of California bats. Journal of Mammalogy 48:52-61.
Licht, P., and P. Leitner. 1967b. Physiological responses to high environmental
temperatures with special reference to bats. Comparative Biochemical Physiology
22:371-397.
Long, R. F., W. M. Kiser, and S. B. Kiser. 2006. Well-placed bat houses can attract bats to
Central Valley farms. California Agriculture 60: 91-94.
Nagorsen, D. W., and R. M. Brigham. 1993. Bats of British Columbia. Royal British
Columbia Museum Handbook. University of British Columbia Press, Vancouver,
164 pp.
Nagorsen, D. W. 2005. Report on bat house assessment BC Hydro John Hart, Ladore, and
Strathcona Stations. Letter report submitted to BC Hydro, John Hart Station, 3 pp.
Tuttle, M. D., M. Kiser, and S. Kiser. 2004. The bat builder’s handbook. Bat Conservation
International. 34 pp.
20
Vonhof, M. J., and R. M. R. Barclay. 1996. Roost-site selection and roosting ecology of
forest-dwelling bats in southern British Columbia. Canadian Journal of Zoology
74:1797-1805.
21
Project # 06.W.CBR.03
Appendix 1. Financial Statement Form
BUDGET
BCRP
ACTUAL
Other
BCRP
Other
INCOME
Total Income by Source
Grand Total Income
19,215.00
18,425.37
(BCRP + other)
EXPENSES
Project Personnel
Wages
Consultant Fees
Note: Expenses must be entered as negative numbers (e.g. – 1000, etc.) in order for the
formulas to calculate correctly.
9200.00
-10291.50
6312.00
3303.00
-433.62
-5057.10
-2593.15
400.00
50.00
(List others as required)
Materials & Equipment
Equipment Rental
Materials Purchased
Travel Expenses
Permits
(List others as required)
Administration
Office Supplies
Photocopies & printing
Postage
(List others as required)
Total Expenses
Grand Total Expenses
19, 215.00
-18,425.37
The budget balance should equal $0
The actual balance might not equal $0*
(BCRP + other)
BALANCE
(Grand Total Income –
Grand Total Expenses)
0
789.63
* Any unspent BCRP financial contribution to be returned to: BC Hydro, BCRP
6911 Southpoint Drive (E16)
Burnaby, BC V3N 4X8
ATTENTION: SCOTT ALLEN
22
Project #
06.W.CBR.03
Appendix 2. Performance Measures
Using the performance measures applicable to your project, please indicate the amount of habitat
actually restored/enhanced for each of the specified areas (e.g. riparian, tributary, mainstream).
Performance Measures – Target Outcomes
Impact Mitigation
Fish passage technologies
Drawdown zone
revegetation/stabilization
Wildlife migration
improvement
Prevention of drowning of
nests, nestlings
Area of habitat made
available to target species
Area turned into productive
habitat
Area of habitat made
available to target species
Area of wetland habitat
created outside expected
flood level (1:10 year)
Habitat Conservation
Functional habitat
conserved/replaced
through acquisition and
mgmt
Functional habitat
conserved by other
measures (e.g.
riprapping)
Designated rare/special
Rare/special habitat
habitat
protected
Maintain or Restore Habitat forming process
Area of stream habitat
Artificial gravel recruitment
improved by gravel plmt.
Artificial wood debris
Area of stream habitat
recruitment
improved by LWD plcmt
Area increase in
Small-scale complexing in
functional habitat through
existing habitats
complexing
Prescribed burns or other
Functional area of habitat
upland habitat
improved
enhancement for wildlife
Habitat Development
New Habitat created
Functional area created
Habitat conserved –
general
23
Wetland
Upland
Lowland Coniferous
Lowland Deciduous
Riverine
Reservoir Shoreline Complexes
Primary
Target
Species
Riparian
Primary Habitat Benefit
Targeted of Project (m2)
In-stream Habitat – Tributary
Project Type
Estuarine
In-Stream Habitat – Mainstream
Habitat (m2)
None of the performance measures in the table are appropriate as the project was focused on a
small area within the generating stations. Three performance measures were:
1. Reduce bat populations and bat-human interactions in the generating station buildingsanecdotal information from interviews with BC Hydro staff indicate this was
accomplished.
2. Attract bats to the bat houses-90% of the 23 bat houses were used by bats.
3. Mitigate for loss of natural roosts habitat-bat house colonies of > 1,400 at Strathcona
and ~150 at Ladore are much larger than the populations (70-100) estimated in 2002 to
be roosting in the generating buildings; therefore, the bat houses are attracting bats
from both the generating station buildings and from other areas of the lower Campbell
River watershed.
Appendix 3. BCRP Recognition
Because the bat houses were located inside the restricted area of the Strathcona station and on
the outside perimeter of the Ladore station signage was not appropriate. Attracting the public
to the Ladore bat houses could result in vandalism. In four public lectures I gave on bats
(Vancouver Natural History Society, 25 January 2007; Saltspring Island Conservancy, 23
February 2007; Victoria Natural History Society, 13 March 2007; Parks Canada, Gulf Islands
National Park Reserve, 15 August 2009), the BCRP bat house project was discussed,
illustrated with slides, and used as an example of the effectiveness of bat house mitigation. An
article on the project will be submitted to the Winter Issue of the Western Canada Bat
Working Group.
24