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Acoustic Surveys Reveal Hoary Bat (Lasiurus cinereus) and
Long-Legged Myotis (Myotis volans) in Yukon
Author(s): Brian G SloughThomas S JungCori L Lausen
Source: Northwestern Naturalist, 95(3):176-185. 2014.
Published By: Society for Northwestern Vertebrate Biology
DOI: http://dx.doi.org/10.1898/13-08.1
URL: http://www.bioone.org/doi/full/10.1898/13-08.1
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ACOUSTIC SURVEYS REVEAL HOARY BAT (LASIURUS CINEREUS)
AND LONG-LEGGED MYOTIS (MYOTIS VOLANS) IN YUKON
BRIAN GSLOUGH
35 Cronkhite Road, Whitehorse, YT Y1A 5S9 Canada; slough@northwestel.net
THOMAS SJUNG
Yukon Department of Environment, PO Box 2703, Whitehorse, YT Y1A 2C6 Canada
CORI LLAUSEN
Birchdale Ecological Ltd, PO Box 606, Kaslo, BC V0G 1M0 Canada
ABSTRACT—The bat fauna of Alaska and northwestern Canada remains poorly known,
principally due to a lack of dedicated surveys. To better assess the diversity of bats in the region,
we conducted full-spectrum acoustic surveys at several sites in Yukon, Canada. During our
surveys we obtained the 1st acoustic records of Hoary Bat (Lasiurus cinereus) and Long-Legged
Myotis (Myotis volans) in Yukon. Neither species had been documented previously in the territory,
but one or both species were known from adjacent Alaska, British Columbia, and Northwest
Territories. Characteristics of certain echolocation calls of Hoary Bats and Long-legged Myotis are
difficult to confuse with other species that might also occur in the region. In addition, we made
other noteworthy recordings; however, species identification for these other echolocation calls was
ambiguous. These 1st records significantly increase our knowledge of the ranges of these bat
species in Yukon, Canada. Further acoustic surveys, coupled with live captures, will help us
further understand the diversity and distribution of bats in Yukon.
Key words: acoustic survey, biodiversity, Canada, distribution, Hoary Bat, Lasiurus cinereus,
Long-legged Myotis, Myotis volans, Yukon
The bat fauna of Alaska and northwestern
Canada remains poorly known. Lack of dedi-
cated bat surveys using appropriate methods
and technology, and limited voucher specimens
in research museums have constrained our
knowledge regarding the diversity and distri-
bution of bats in this vast region (Parker and
others 1997; Jung and others 2006; Boland and
others 2009). This knowledge is essential in
understanding the role of bats as indicators of
ecosystem health (for example, Jones and others
2009), monitoring the spread and concern about
the impact of introduced disease linked with
white-nose syndrome (for example, Frick and
others 2010), and documenting changes in
geographic ranges that might occur as a result
of climate change (for example, Humphries and
others 2002).
In Yukon, until recently only the Little Brown
Myotis (Myotis lucifugus) was confirmed as
occurring in the territory (Slough and Jung
2007). However, dedicated bat surveys using
echolocation monitoring and live captures have
recently revealed the 1st records of the Northern
Long-eared Myotis (Myotis septentrionalis) in the
Liard River watershed (Jung and others 2006;
Lausen and others 2008), and the 1st record of
a bat with echolocation calls similar to the
ambiguous calls of the Big Brown Bat (Eptesicus
fuscus) or the Silver-haired Bat (Lasionycteris
noctivagans; Betts 1998), in southcentral Yukon
(Slough and Jung 2008). Similar recent discov-
eries have been reported from other parts of
Alaska and northwestern Canada due to in-
creased interest and survey efforts (for example,
Parker and Cook 1996; Boland and others 2009;
Grindal and others 2011; Lausen and others
2014). Slough and Jung (2008) reviewed the
diversity and distribution of bats in areas
adjacent to Yukon and determined that several
other species possibly occur in Yukon, including
Keen’s Myotis (M. keenii), Long-eared Myotis
NORTHWESTERN NATURALIST 95:176–185 WINTER 2014
176
(M. evotis), Long-legged Myotis (M. volans),
Silver-haired Bat (Lasionycteris noctivagans),
Eastern Red Bat (Lasiurus borealis), and Hoary
Bat (L. cinereus).
The purpose of this study was to increase our
knowledge regarding the diversity and distri-
bution of bats in Yukon, Canada. We used full-
spectrum ultrasound recording devices to
acoustically survey bats at several sites through-
out the territory. Acoustic surveys have been
useful in providing a more complete assessment
of bats, and may be a powerful technique for
detecting uncommon species (for example,
O’Farrell and Gannon 1999; MacSwiney and
others 2008; Furey and others 2009), particularly
those with distinctive echolocation calls (for
example, Hayes and others 2009). In addition,
bat densities appear to be low in the region
(Boland and others 2009), thus acoustic surveys
provide an efficient means to record presence of
species where capture per unit effort in mist-
nets or harp traps is low.
METHODS
Acoustic surveys were conducted at several
locations in the boreal forest of southern and
central Yukon, Canada in April–October, 2010
to 2012 (Table 1; Fig. 1). All of our survey sites
were at relatively low elevations (approximately
300–600 m ASL), and near local water bodies.
Dominant vegetative cover consisted of forests,
with stands dominated by White Spruce (Picea
glauca), Lodgepole Pine (Pinus contorta), Trem-
bling Aspen (Populus tremuloides), or Balsam
Poplar (P. balsamifera). Wetlands and various
types and sizes of water bodies were abundant
in survey areas. Human infrastructure in the
area surrounding survey locations varied but
was generally sparse. The City of Whitehorse
was the largest urban center in the region. Most
survey sites were road-accessible; however,
some remote sites were accessed by boat. To
increase our chances of recording regionally
uncommon species, we avoided sampling with-
in 10 km of known maternity colonies of Little
Brown Myotis.
At each survey site, we used 1 to 2 ultrasound
detectors to passively record full-spectrum
echolocation calls of bats. Full-spectrum record-
ings of bat calls provide complete time-frequen-
cy data, including minimum frequencies, call
duration, slope of call, and harmonics (Ahle
´n
and Baagøe 1999). They also provide time-
amplitude components including frequency
of maximum amplitude and relative energy
among calls and harmonics. Full-spectrum
acoustic parameters may allow better species
TABLE 1. Information on the sites acoustically sampled for bat echolocation calls in summer and fall 2010–
2012 in Yukon, Canada, and summary information on the number of bat echolocation calls recorded at each site.
Site Region – Location
Years
surveyed
Coordinates
No. of
survey
nights
No. of
detector
nights
B
No. of
bat calls
Mean no. of
bat calls per
detector
night
Latitude
(6N)
Longitude
(6W)
CENTRAL YUKON
1 McQuesten Airstrip 2011 63.601 2137.561 4 4 158 39.5
SOUTHWESTERN YUKON
2 Dalton Post 2011 60.117 2137.034 15 15 457 30.5
SOUTHEAST YUKON
3 Tom Creek 2010 60.301 2129.006 4 4 18 4.5
4 Rantin Lake 2010 60.028 2129.042 1 3 22 7.3
5 Cosh Creek 2012 60.009 2127.824 15 15 98 6.5
6 Smith River
A
2010 60.078 2127.342 9 18 89 4.9
SOUTHCENTRAL YUKON
7 Nisutlin River
A
2010–2011 60.599 –132.635 15 25 26 1.0
8 Nisutlin Bay 2012 60.162 –132.700 7 7 139 19.9
9 Bennett Lake 2010–2011 60.043 –135.168 5 9 41 4.6
10 Windy Arm 2010–2011 60.093 –134.510 11 29 43 1.5
11 Wolf Creek Cliff 2010–2012 60.584 –134.961 93 107 548 5.1
12 Crater Lake Cliff 2011 60.642 –135.035 8 8 609 76.1
TOTALS 187 244 2248 9.2
A
Coordinates are approximate for Smith River and Nisutlin River, where multiple sites were sampled along a .20 km stretch of river.
B
1 detector-night 51 detector sampling for bat echolocation calls for 1 night. In several instances more than 1 detector was used per
night at a site.
WINTER 2014 SLOUGH AND OTHERS:NEW BAT RECORDS IN YUKON 177
FIGURE 1. Locations of sites sampled for echolocation calls of bats in Yukon, Canada, 2010–2012. Site numbers
correspond to those provided in Table 1.
178 NORTHWESTERN NATURALIST 95(3)
discrimination than other methods such as zero-
crossing (Fenton 2000; Fenton and others 2001).
At each survey site (except before August
2010; Table 1) we used a direct recording
Pettersson D500x ultrasound detector (Petters-
son Elektronik AB, Uppsala, Sweden) to pas-
sively detect, record, and store full-spectrum bat
echolocation calls. In 2010, detectors were
placed on a tripod $1 m above the ground in
uncluttered flyways that were often adjacent to
forest edges near streams or lakes. The detectors
were tilted at an angle of incidence of 30 to 456,
to maximize the chance of recording high-
quality search-phase calls. Survey effort was
continuous throughout the night, and units
were deployed for up to one week at a time at
a survey site. In 2011 and 2012, we attempted to
improve the quantity and quality of bat echo-
location call recordings made by using an
external microphone placed 6 m above the
ground at a 06angle of incidence. Placing the
microphone higher in the air increased the
likelihood of recording high-flying bats and
also further reduced echoes and high-clutter call
recordings from bats flying near the ground.
Prior to August 2012, we used 2 Pettersson
D240x time-expansion ultrasound detectors
to supplement recordings obtained with the
D500x. For all D240x deployments, detectors
were coupled to a digital recorder (Edirol R-09;
Roland Corporation, Hamamatsu, Shizuoka,
Japan) and placed on a tripod in the same
fashion as the D500x. These recorders were also
situated in uncluttered flyways. Calls were
sampled for 1.7 s and time-expanded (10x).
The D240x units recorded for about 2 h after
sunset, by which time the digital storage
medium was full.
Digitally recorded echolocation calls were
viewed and processed in SonoBat (versions
2.9.7 and 3.05) and Kaleidoscope Pro (version
1.1.21; classifier 1.04) acoustic analysis software.
Only search-phase calls of sufficient quality
(non-fragmented) were used in species identifi-
cation. We used 3 methods of identifying
recorded echolocation calls: visual identification
by bat acoustic identification experts; measure-
ment of call parameters and comparison of these
measurements to North American acoustic iden-
tification keys; and automated identification.
Visual identifications were made independently
by 3 analysts with experience determining bats
species from full spectrum recordings (BGS, CLL
and DW Nagorsen). We used two programs for
automated identification (SonoBat and Kaleido-
scope Pro), and we also applied a multivariate
approach (Discriminant Function Analysis,
DFA) to a suite of call parameters, measured in
SonoBat, as an independent species identifica-
tion (for example, Broders and others 2004). Call
parameters (n515) extracted from each call
included: call duration and interval; maximum
and minimum frequency; frequency with the
most energy and frequency of the knee; domi-
nant, steepest, lowest, and total slope of the call;
and frequency of the 1st and 2nd harmonics.
Sonograms of recorded calls were digitally and
visually compared with reference calls and
tabulated echolocation call characteristics from
a call library of identified bats from the western
United States (J Szewszak, Humboldt State
University, unpubl. data). We performed DFA
using SAS 9.2 (Proc DISCRIM; SAS Institute Inc.,
Cary, NC).
RESULTS
During 3 years of acoustic survey, we
recorded 2249 bat echolocation call sequences
during 187 nights (244 detector-nights; 1 detec-
tor monitoring for 1 night 51 detector night).
Many of the surveys (47.1%; 115 detector nights)
were in the vicinity of the City of Whitehorse
(Table 1). Three sites contributed 71.8% of the
echolocation call sequences (Table 1): the largest
percentage of our echolocation calls (n5609;
27.1%) came from the Crater Lake basalt cliffs,
followed by the Wolf Creek basalt cliffs (n5
548; 24.4%) and Dalton Post (n5457; 20.3%).
The Wolf Creek basalt cliffs were sampled more
intensively than other sites, constituting 43.9%
(107 detector nights) of survey effort. Crater
Lake basalt cliffs and Dalton Post contributed
3.3% and 6.2% of the total number of detector
nights, respectively. Most detections (about
99%) were of unidentified species of Myotis,
with the vast majority presumably being Little
Brown Myotis (Table 2).
On 4 August 2010, a high-quality Hoary Bat
echolocation-call sequence was recorded (Fig. 2)
on the Smith River, approximately 135 km east
of Watson Lake, Yukon. The recording location
was at 598 m elevation, in a small sedge
meadow partially surrounded by a closed-
canopy mature White Spruce forest, adjacent to
WINTER 2014 SLOUGH AND OTHERS:NEW BAT RECORDS IN YUKON 179
TABLE 2. Summary of species detected (Yes) and potentially detected (Possibly) at various sampling sites in Yukon. Species that were possibly detected refers to
our inability to determine species identification with certainty, due to absence of species-specific diagnostic traits in the recorded calls. Information on the sites
acoustically sampled for bat echolocation calls in summer and fall 2010–2012 in Yukon, and summary information on the number of bat echolocation calls recorded
at each site are provided in Table 1.
Region-location
Little Brown
Myotis
Northern
Myotis
Long-eared
Myotis
Long-legged
Myotis
Big Brown
Bat
Silver-haired
Bat
Eastern
Red Bat
Hoary
Bat
CENTRAL YUKON
McQuesten Airstrip Yes – Possibly – – – – –
SOUTHWESTERN YUKON
Dalton Post Yes Possibly Possibly – – – – –
SOUTHEAST YUKON
Tom Creek Yes Possibly – – – – – –
Rantin Lake Yes – – – – – – –
Cosh Creek Yes Possibly Possibly – – – – –
Smith River Yes Possibly Possibly – Possibly Possibly Possibly Yes
SOUTHCENTRAL YUKON
Nisutlin River Yes – – – – – – –
Nisutlin Bay Yes Possibly – – Possibly Possibly – –
Bennett Lake Yes – – – – – Possibly –
Windy Arm Yes Possibly – – – – – –
Wolf Creek Cliff Yes – – Yes – – Possibly –
Crater Lake Cliff Yes – – – – – – –
180 NORTHWESTERN NATURALIST 95(3)
FIGURE 2. Spectrograms and oscillograms of echolocation calls from a Hoary Bat (Lasiurus cinereus) recorded
at Smith River on 4 August 2010 (top), and a Long-Legged Myotis (Myotis volans) recorded at the Wolf Creek
basalt cliffs on 16 September 2011 (bottom).
WINTER 2014 SLOUGH AND OTHERS:NEW BAT RECORDS IN YUKON 181
the Smith River. Kaleidoscope Pro identified this
file as Hoary Bat. SonoBat showed consensus
identification (by vote and by sequence classifi-
cation) as Hoary Bat, as did visual analysis by all
3 experts. The shape of the echolocation calls was
of a shallow FM (frequency modulation) type,
and measured parameters were consistent with
those noted by Fenton and others (1983) from
elsewhere in western Canada. Specifically, pulse
durations were 10.7 msec, and the characteristic
and low frequencies ranged from 23.5 to
22.4 kHz, and 21.7 to 21.0 kHz, respectively.
Additionally, the second pulse was visibly lower
in frequency than the first in the sequence, a trait
also common in Hoary Bats. This file was then
analyzed in a DFA. Using step-wise DFA, the
above 3 parameters plus slope were used to
differentiate low-frequency bats in a reference
library collected by CLL. Due to a lack of
homogeneity within covariance matrices, qua-
dratic DFA was performed (Tabachnick and
Fidell 2001). Overall cross-validation error for
Hoary Bat was 14% (7% misidentified as Silver-
haired Bat and 7% misidentified as Big Brown
Bat). The potential Hoary Bat recording was
classified in the DFA as Hoary Bat with 99.94%
probability.
On 13 to 19 September 2010 and 16 September
2011, we recorded echolocation call sequences
of Long-legged Myotis (Fig. 2) at the Wolf Creek
basalt cliff site, 16 km southeast of Whitehorse,
Yukon. The recording location was at 774 m
elevation, adjacent to an approximately 150-m-
long by 20-m-high southeast-facing rock cliff
that was surrounded by closed-canopy mature
White Spruce forest adjacent to Wolf Creek.
These calls were of a moderately steep FM-type
(Fig. 1), with moderate pulse duration ($4 msec)
and a characteristic frequency of approximately
40 kHz. Such calls are superficially typical of
those produced by various sympatric species of
Myotis in western Canada. However, Long-
legged Myotis calls tend to be somewhat longer
in pulse duration and less steep than most other
species of Myotis in western Canada (Fenton
and others 1983; Saunders and Barclay 1992).
More importantly, we used a key diagnostic
trait that is occasionally present in Long-legged
Myotis echolocation calls: a short upward
sweep prior to the downward sweep from the
maximum frequency (J Szewczak, Humboldt
State University, unpubl. data; compiled echo-
location call characteristics and reference call
files of identified Long-legged Myotis). We
observed an upsweep in 4 call sequences of this
species (Fig. 1). SonoBat identified this species
with consensus (by vote and sequence classifi-
cation), and the calls were independently
classified as a Long-legged Myotis by all 3
experts. Additionally, Kaleidoscope Pro provid-
ed a positive identification for this species. The
pulse duration was 2.7 to 4.4 msec (n58) and
the characteristic, and low frequencies were 39.0
to 44.9 kHz, and 44.8 to 34.3 kHz, respectively.
DISCUSSION
Using echolocation calls from acoustic sur-
veys, we provide the 1st records of Hoary Bats
and Long-legged Myotis in Yukon, Canada.
Echolocation calls were reliably ascribed to
these 2 species because calls contained charac-
teristics not observed in calls of other bat species
present in northwestern North America (sensu
Hayes and others 2009). Moreover, our species
identifications relied on both qualitative assess-
ments (based on quantifiable parameters) by 3
biologists with several years of experience
identifying bats from full-spectrum echoloca-
tion calls, and a quantitative classification based
on statistical analysis of call measurements
(SonoBat, DFA) and shapes (Kaleidoscope
Pro). For Hoary Bats, the call duration, charac-
teristic frequency, variation in low frequency,
and call shape set the spectrogram for this
species apart from other bats. Indeed, the
species with a spectrogram most similar to the
uncluttered calls of a Hoary Bat is not a bat, but
the Northern Flying Squirrel (Glaucomys sabri-
nus), which emits a variety of frequency
modulated vocalizations (Gilley 2013; Murrant
and others 2013). However, arc-whistles of
Northern Flying Squirrels are much longer in
duration (171.2 ±3.9 msec), with a shallower
slope and a lower minimum frequency (15.3 ±
2.8 kHz; Gilley 2013). While Northern Flying
Squirrels are likely common in areas we
surveyed, it would be difficult to confuse a
spectrogram from a Hoary Bat with a Northern
Flying Squirrel based on call duration alone.
Northern Flying Squirrel arc-whistles were
recorded at the Cosh Creek site.
Most Long-legged Myotis echolocation calls
appear quite similar to those of other species of
Myotis, particularly Little Brown Myotis (Saun-
182 NORTHWESTERN NATURALIST 95(3)
ders and Barclay 1992). However, the call
duration is often longer (Fenton and others
1983), and they sometimes have an upsweep at
the beginning (J Szewczak, Humboldt State
University, unpubl. data, compiled echolocation
call characteristics and reference call files of
identified Long-legged Myotis), which is diag-
nostic. No other species of Myotis are reported
to have this upsweep, giving us a high level of
confidence that we ascribed these echolocation
calls to the correct species.
Our records of Hoary Bats and Long-legged
Myotis in Yukon are not surprising. Slough and
Jung (2007) hypothesized that both Hoary Bats
and Long-legged Myotis occurred in Yukon,
based on distributional records of one or both
species from Alaska, British Columbia, and
Northwest Territories and considering the pau-
city of bat surveys in Yukon. Hoary Bats have
been recorded from Nahanni National Park,
Northwest Territories (Lausen and others 2014),
approximately 200 km to the east of our
recording site. Additionally, individuals were
recorded and captured about 75 km south of
our location at Liard River Hot Springs Provin-
cial Park, British Columbia (Wilkinson and
others 1995; Bradbury and others 1997). We
suspect that Hoary Bats occur widely across
southeastern Yukon, albeit at low densities.
There is a historic record of a Long-legged
Myotis captured in Atlin, British Columbia
(Swarth 1936), about 135 km southeast of where
the species was recorded in Yukon. We suspect
that Long-legged Myotis are restricted in their
distribution in Yukon to local areas in south-
central Yukon, particularly near rock cliffs.
More survey effort is needed to better under-
stand the distribution of Hoary Bats and Long-
legged Myotis in Yukon.
We also obtained recordings potentially rep-
resenting other bat species not previously
recorded in Yukon. Because knowledge of bat
diversity and distribution in northwestern
Canada is poorly known, these observations
may be useful for focusing further survey effort
targeted at recording these species through
captures. For instance, echolocation calls re-
corded at several sampling sites appeared to be
either Long-eared Myotis or Northern Myotis,
based on automatic classification by SonoBat
and Kaleidoscope Pro (Table 2). Detections of
Long-eared Myotis would represent 1st records
for these species in Yukon, and they are
expected to occur in Yukon (Slough and Jung
2007). Detection of Northern Myotis from west
of the Liard River would represent a significant
range extension. Unfortunately, it is difficult to
ascribe passively recorded echolocation calls
to these species with certainty (for example,
Fenton 2000; Fenton and others 2001). Little
Brown Myotis display variation in call charac-
teristics where they forage in clutter (Broders
and others 2004; Wund 2006; Talerico 2008), and
there is also geographic variation in Little
Brown Myotis call structure (Veselka and others
2013), factors which might contribute to mis-
identification by our automated procedures.
Similarly, we obtained recordings near Teslin
that appeared to be the echolocation calls of
either a Big Brown Bat or a Silver-haired Bat
(Table 2). However, Betts (1998) pointed out
that there is a high degree of overlap in the
echolocation calls of these species and potential
for misidentification. We have recorded at least
one of these species in Yukon, but more acoustic
records, and if possible, captures, will be
needed to conclusively determine whether one
or both of these species are found in Yukon.
Finally, at some sites we collected recordings
that were identified by automated software as
Eastern Red Bats (Table 2), but some of their
echolocation calls closely resemble Little Brown
Myotis (Fenton and others 1983; Obrist 1995).
Therefore, we cannot reliably conclude this bat
species occurs in Yukon based on echolocation
calls alone, although it is hypothesized to be
here based on visualization and suspected
acoustic record in the Northwest Territories
(Lausen and others 2014), and recent collection
of several carcasses under newly erected wind
turbines in northeastern British Columbia (Na-
gorsen and Paterson 2012).
Acoustic surveys can be useful in improving
our knowledge of the diversity and distribution
of bats in areas not previously well sampled
(Morrison and others 2010; Grindal and others
2011). For this purpose, however, their utility is
limited to those echolocation calls containing
diagnostic traits that lead to species identifica-
tions with a high level of certainty (Hayes and
others 2009). For calls lacking diagnostic traits
(for example, the Big Brown Bat or Silver-haired
Bat calls recorded during these surveys), audi-
tory evidence alone is not sufficient for deter-
WINTER 2014 SLOUGH AND OTHERS:NEW BAT RECORDS IN YUKON 183
mining species presence (sensu McKelvey and
others 2008). In most cases, acoustic records
need to be substantiated with more reliable
evidence, such as DNA or a specimen, before
presence can be confirmed (McKelvey and
others 2008).
ACKNOWLEDGMENTS
DW Nagorsen kindly reviewed a subset of the
recorded calls and aided in species identification. We
are grateful to L Ash, C Guillemette, PM Kukka, M
McFarlane, TD Pretzlaw, K Schmok and K Slough for
assistance with deploying equipment in the field. PM
Kukka kindly produced the map. Financial support
was provided by a Northern Research Endowment
Fund Grant from the Yukon Research Centre, Yukon
College, the Yukon Department of Environment,
and Environment Canada’s Habitat Stewardship
Program. K Blejwas, LE Olson, and an anonymous
reviewer provided helpful comments that improved
the manuscript.
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Submitted 26 April 2013, accepted 9 April 2014.
Corresponding Editor: Link E Olson.
WINTER 2014 SLOUGH AND OTHERS:NEW BAT RECORDS IN YUKON 185
