Southeastern Naturalist
S.T. Samoray, S.N. Cotham, and M.W. Gumbert
2019 Vol. 18, No. 3
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Spring Migration Behavior of a Perimyotis subflavus (Tri-colored
Bat) from Tennessee
Stephen T. Samoray1,*, Shelby N. Cotham1, and Mark W. Gumbert1
Abstract - On the nights of 27, 28, and 29 April 2018, we used aerial radio-telemetry to track a female
Perimyotis subflavus (Tri-colored Bat) as she migrated a straight-line distance of 243 km from a cave
in southern Tennessee to a roost in Peachtree City, GA. To our knowledge, this represents the longest
and most detailed spring migration track recorded for this species and places the Tri-colored Bat in
the category of regional migrant.
Introduction. In the eastern US, Perimyotis subflavus (Cuvier) (Tri-colored Bat) was
once considered a common species throughout its range (Barbour and Davis 1969, Damm
and Geluso 2008, Fujita and Kunz 1984) and therefore was less researched than federally
endangered species such as Myotis sodalis Miller and Allen (Indiana Bat) or M. grisescens
Howell (Gray Bat). However, populations of Tri-colored Bats have declined significantly
since the discovery of White-nose Syndrome (WNS) in 2006 (Powers et al. 2015, Turner
et al. 2011). WNS is caused by the fungus Pseudogymnoascus destructans and causes
mortality in hibernating bats (Ingersoll et. al 2016). Due to drastic population declines
from WNS, the Tri-colored Bat is currently petitioned for listing (USFWS 2017) under
the Endangered Species Act (ESA 1973, as amended). Researchers are now attempting to
answer many life-history questions about Tri-colored Bats including understanding migratory
behavior.
Methods. We captured Tri-colored Bats from a solution cave in the Cumberland Plateau
physiographic region of Franklin County, TN, ~5.5 km south of the city of Pelam. Biologists
from Copperhead Environmental Consulting, Inc., Arnold Air Force Base, and The
University of the South entered the cave on 27 April 2018 and hand-captured 2 Tri-colored
Bats. They recorded biological and morphometric data (e.g., sex, age class, reproductive
condition, mass, and forearm length; Table 1) and banded each bat with a Tennessee
Wildlife Resources Agency (TWRA) 2.4-mm, uniquely numbered, aluminum-lipped band
(Porzana Ltd, Icklesham, East Sussex, UK). They also fitted the bats with model LB-2X-T,
14-d radio-transmitters (Holohil Systems Ltd., Carp, ON, Canada) weighing 0.30 g. Researchers
captured bats under US Fish and Wildlife Service permit number TE94849B-0
following the American Society of Mammologists’ guidelines for the safe/proper handling
1Copperhead Environmental Consulting, Inc., 471 Main Street, Paint Lick, KY 40461. *Corresponding
author - ssamoray@copperheadconsulting.com.
Manuscript Editor: David Jachowski
Table 1. Data collected for 2 adult female Perimyotis subflavus (Cuvier) (Tri-colored Bat) hand-captured
and radio-tagged on 27 April 2018 from a cave in Franklin County, TN. NR = non-reproductive,
RFA = right forearm, and TWRA= Tennessee Wildlife Resource Agency. Reference for wing damage
index is Reichard and Kunz (2009).
Reproductive Wing damage
status Mass (g) RFA (mm) index Band prefix Band # Frequency
NR 6.50 35.0 0 TWRA A03130 172.152
NR 6.25 34.0 0 TWRA A03136 172.213
Notes of the Southeastern Naturalist, Issue 18/3, 2019
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2019 Vol. 18, No. 3
of wild animals (Sikes 2016). To track the bats during spring migration, we used a Cessna
172 Skyhawk fitted with FAA-approved (Form FAA 337–Major Repair and Alteration) aircraft
strut-mount assemblies (Advanced Telemetry Systems Inc., [ATS] 1997, Isanti, MN)
with two 172-3FB 4-element ATS Yagi directional antennas (model #13886; ATS). The
aerial crew consisted of a pilot and a navigator. The pilot maintained an altitude of ~455 m
above ground level, while the navigator monitored the transmitter signal through an ATS
programmable datalogging receiver (model R4500S) and recorded bat locations on mapping
software (DeLorme Topo North America 9.0, Yarmouth, ME) approximately every 5
min. A 2-person ground crew used a 5-element Yagi directional antenna (Wildlife Materials,
Inc., Murphysboro, IL) mounted to an extendable pole to track migrating bats in conjunction
with the aerial team, or independent of the aerial team when the plane was grounded
due to inclement weather or during refueling stops. Researchers tracked bats nightly until
spring migration was considered completed. Based on past experience tracking Indiana Bats
(Roby et al. 2019), we considered the spring migration completed after an individual bat
foraged in the same general area for 1 full night during acceptable migration weather (i.e.,
temperatures above 10 °C, wind speeds less than 10.3 m/s, and no precipitation) and returned to a
previously used roost tree. We plotted time-stamped bat location fixes in ArcGIS v10.5.1
(ESRI, Redlands, CA) to determine the distance and speed of bat flight.
Observations. Both radio-tagged bats foraged within the staging area (i.e., within 5 km;
Roby et al. 2019) of the cave after release. After ~45 minutes, the bat carrying transmitter
172.213 (Bat 213) began moving south. The plane could only track 1 bat at a time; thus,
the tracking crews focused on this bat for the remainder of the study. We tracked Bat 213
for 4.5 h until weather and fuel restrictions forced the plane to land. During this period, Bat
213 traveled ~90.4 km at an average speed of 19.9 km/h. On the morning of 28 April, the
aerial crew flew a search pattern along the bat’s last known trajectory and located her day
roost in Dekalb County, AL, on the shore of Weiss Lake, a straight-line distance of 127 km
from the cave. On the evening of 28 April, Bat 213 foraged in the vicinity of her roost for
40 min and then traveled southeast for a total of 124 km at an average speed of 29.7 km/h
to a location ~7 km south of Peachtree City, GA. She foraged here from 23:30 h to 01:00 h.
Tracking stopped at 01:00 h when Bat 213 appeared to be stationary. On the night of 29
April, the aerial crew tracked her while she foraged for 2 h, and they considered this the end
point of the spring migration. We feel confident about this conclusion, as the bat was found
by the ground crew on 30 April just 210 m northwest of the final foraging point recorded by
the plane on 29 April. This roost was in a clump of dead hardwood leaves hanging from a
branch of a 68.8-cm diameter-at-breast-height Pinus echinata Mill. (Short-Leaf Pine). The
roost was 13 m high and ~1.5 m from the trunk of the tree. A team from the US Fish and
Wildlife Service Georgia Field Office and the Georgia Department of Natural Resources
conducted a follow-up survey of this tree on 7 May and determined that the bat had dropped
the transmitter. Although the transmitter was not recovered, the strongest signal was from
the ground ~30 m east of the roost tree. Bat 213 traveled a total straight-line distance of 243
km from the cave to this roost tree (Fig. 1).
Discussion. Fleming and Eby (2003) defined 3 categories of bat migration based on
migration distance. Sedentary species move less than 50 km, regional migrants travel 100–500
km, and long-distance migrants may move over 1000 km. While seasonal movements of
Tri-colored Bats throughout the year are unclear (Cryan and Barclay 2009, Fraser et. al
2012, Fujita and Kunz 1984), early banding studies recorded movements as far as 136 km
(Griffin 1940). Other literature has classified the Tri-colored Bat as a regional migrant that
visits swarming sites as early as August, hibernates over winter in a central hibernaculum,
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and disperses to summer maternity colonies (Davis 1966, Fujita and Kunz 1984, Schwartz
and Schwartz 2001). In a more recent study, Fraser et. al (2012) used stable isotope analysis
to conclude that some male Tri-colored Bats in Ontario followed a latitudinal migration
pattern more typical of long-distance migrants such as Lasiurus cinereus Beauvois (Hoary
Bats) and L. borealis Müller (Eastern Red Bats). Therefore, Tri-colored Bats should be
considered a partial (some, but not all, members of the species migrate) and a differential
(migratory patterns vary by sex or age) migrant (Hobson and Norris 2008). However, Fraser
et al. (2012) did not report migration distances; in fact, the only previously reported study
to actively track a migrating Tri-colored Bat took place in Wisconsin in 2017 using groundbased
telemetry only. Contact with the bat was not maintained over the entire migration
track, but a final roost area was located ~44 km (straight-line distance) from the release site
(J.P. White, Wisconsin Department of Natural Resources, Madison, WI, pers. comm.).
The Tri-colored Bat has been described as a weak flier (Barbour and Davis 1969) and
the bat’s relatively small size and wing aspect ratio are more suited for maneuverability
than speed (Findley et. al 1972, Fleming and Eby 2003, Norberg and Rayner 1987). Based
on this characterization, we expected that this species would migrate distances closer to the
136 km distance described by Griffin (1940). However, we found that Tri-colored Bats are
capable of traveling as far as 243 km during a 2-night period at average speeds similar to
those found in Tadarida brasiliensis Geoffroy (Brazilian Free-Tailed Bat; McCracken et. al
2016). Our data are consistent with previous findings (Davis 1966, Fujita and Kunz 1984,
Griffin 1940, Schwartz and Schwartz 2001) and indicate that Tri-colored Bats should be
classified as regional migrants.
Figure 1. The migration track of Bat 213 during the nights of 27, 28, and 29 April 2018. Bat 213 was
a female Perimyotis subflavus (Tri-colored Bat) fitted with a radio-transmitter at a cave in Franklin
County, TN, and tracked 243 km to a roost near Peachtree City, GA.
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Acknowledgments. This work was funded by Arnold Air Force Base with assistance from
Shannon Allen (AAFB) and John Lamb (AECOM). We thank Amy Turner (The University of The
South) for landowner coordination, Pete Pattavina and Laci Pattavina for field assistance in Georgia,
and all the Copperhead Consulting field crews who assisted with this research. We also thank
Copperhead Consulting’s Piper Roby and Richard Borthwick for their editorial comments and the
reviewers and editors for their time and expertise. The views and conclusions contained in this document
are those of the authors and should not be interpreted as representing the opinions or policies
of the US Government.
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