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Monograph 22
A Noteworthy Hibernation Record of Myotis leibii (Eastern
Small-footed Bat) in Massachusetts
Jacques Pierre Veilleux*
Abstract - A study of the hibernating bats present in select western Massachusetts hibernacula
was initiated during the winter of 2005–2006. During the surveys, five state-threatened Myotis
leibii (eastern small-footed bats) were observed within one hibernaculum (Bat’s Den Cave).
These five individuals were the first eastern small-footed bats observed in Massachusetts since
1999, and represent a new county distribution record (Berkshire County).
Six species of bats currently hibernate or have historically hibernated in caves
and/or mines in Massachusetts. Four species are commonly observed within hibernacula,
including Eptesicus fuscus Beauvois (big brown bat), Pipistrellus subflavus
Cuvier (eastern pipistrelle), Myotis lucifugus LeConte (little brown bat), and M.
septentrionalis Trouessart (northern myotis). The last record, and the only record
considered reliable, of the federally endangered M. sodalis Miller and Allen (Indiana
bat) hibernating in Massachusetts was in 1939, when approximately 60 individuals
were observed in the Chester Emery Mine, located in the town of Chester, Hampden
County (T. French, MassWildlife, Westboro, MA, pers. comm.). Similarly, only two
locality records exist for the state threatened M. leibii Audubon and Bachman
(eastern small-footed bat) in Massachusetts (T. French, pers. comm.). These records
are from two mines, the Macia Mine and the Old Chester Emery Mine, which are also
located in the town of Chester. A single eastern small-footed bat was observed in the
Macia Mine in 1981, and between 1 and 5 individuals have been observed in the Old
Chester Emery Mine during 6 of 20 winter surveys conducted between 1937 and
1999. Records for this species are usually rare throughout its range. This paper
presents a new record of the eastern small-footed bat hibernating in Massachusetts,
and represents a new county record for this species in the state.
A study to determine the current status of hibernating bat populations in western
Massachusetts hibernacula (focusing on Berkshire and Franklin counties) was initiated
in December of 2005 and continued through February of 2006. A total of 17
caves and mines was visited.
Within each cave or mine, all observed bats were identified to species (unless the
bat location was not accessible for visual inspection, i.e., high ceilings). In most
cases, species identification was completed without handling the bats. Internal cave/
mine temperature measurements were obtained using a Kestrel 4000 weather instrument.
As part of the study, a suite of external and internal site characteristics was
measured, but are not further discussed in this paper.
A total of 921 hibernating bats was observed within 16 of the 17 hibernacula
surveyed. The most common species observed were the northern myotis (n = 350),
eastern pipistrelle (n = 211), big brown bat (n = 203), and little brown bat (n = 142).
Several bats hibernating on high ceilings were observed that could not be identified
to species due to inaccessibility.
On 22 January 2006, we surveyed Bat’s Den Cave, located in Egremont, Berkshire
County. Bat’s Den Cave is a relatively extensive cave system (relative to other
Massachusetts caves), with greater than 100 m of passage. Ceiling height in the
largest room reaches approximately 4 m, while the side passages mainly range from
0.5 to 1.5 m in height and width. Internal cave temperatures ranged from 4.5 ºC
within the initial “main room” past the main entrance, to 8.3 ºC within an upper-level
attic. Outside ambient temperature was 0.6 ºC at the time of the survey.
Ninety-four bats were observed, mainly comprised of eastern pipistrelles
(n = 67), big brown bats (n = 9), and little brown bats (n = 8). In addition to these
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three species, five eastern small-footed bats were observed within the cave. Two
individuals were hibernating singly on the rear wall of the “main room,” approximately
10 m from the main entrance to the cave. Air temperature recorded
immediately near the hibernating bats was 4.5 ºC (the coldest temperature recorded
in the cave). One individual was handled for voucher photographs. The
individual was a female, and besides the characteristic black facial mask, had a
forearm measuring 32 mm and a very well-developed keel on the calcar. This
combination of characters is the main diagnostic feature for this species. Three
additional eastern small-footed bats were clustered on the ceiling of the “basement”
area, a small side passage branching from the “main room,” which was
approximately 9 m from the cave entrance. Air temperature recorded immediately
near this group of hibernating bats was 6.5 ºC.
Although their hibernation ecology has not been extensively researched, eastern
small-footed bats have been reported to prefer colder hibernation temperatures compared
to other Myotis bats (Best and Jennings 1997, Butchkoski 2003, Hitchcock et al.
1984, Tuttle 2003), and this preference appears to influence both their roost selection
and winter activity. For example, they are often found in the coldest sections of a cave
or mine, either using short (less than 150 m in length) cave or mine adits (Best and
Jennings 1997) or choosing roost locations near the entrance of larger hibernacula
(Tuttle 2003). The five individuals observed in Bat’s Den Cave were found roosting at
temperatures of 4.5 and 6.5 ºC, and relatively near the main entrance. The lowest
temperature observed within the cave was 4.5 ºC, and the maximum cave temperature
observed was 8.3 ºC. Therefore, it appears that the eastern small-footed bats were
following the general pattern of temperature and position preference described by
previous investigators. It is also believed that they roost in narrow crevices (Best and
Jennings 1997), although all of the individuals documented from Bat’s Den Cave were
found on exposed surfaces of the cave wall or ceiling.
The five individuals observed within Bat’s Den Cave represent a new county record
for this species in Berkshire County, MA. Bat’s Den Cave has been surveyed for bats in
the past, with no eastern small-footed bats being observed. It would be interesting to
survey this cave periodically, perhaps once per two or three years, to determine whether
additional eastern small-footed bats locate and use this cave as a hibernaculum.
Acknowledgements. I wish to thank Eleanor Tillinghast of Green Berkshires, Inc.
for initiating this study and providing financial support. Michael Eaton provided
caving expertise and Susan Benoit, Susie Fowle, and James Ferris provided help in
the field. Tim Simmons and Tom French, of MassWildlife, provided information
about historical bats records, as well as approved the permit to conduct the surveys.
Lastly, this work would not have been possible without the many landowners that
granted us permission to enter their property to examine their caves or mines.
Literature Cited
Best, T., and J.B. Jennings. 1997. Myotis leibii. Mammalian Species. American Society of
Mammalogists 547:1–6.
Butchkoski, C. 2003. Indiana bat hibernacula surveys. Annual report submitted to the Pennsylvania
Game Commission, Harrisburg, PA. 10 pp.
Hitchcock, H.B., R. Keen, and A. Kurta. 1984. Survival rates of Myotis leibii and Eptesicus
fuscus in southeastern Ontario. Journal of Mammalogy 65:126–130.
Tuttle, M.D. 2003. Estimating population sizes of hibernating bats in caves and mines. Pp. 31–
39, In T.J. O’Shea and M.A. Bogan (Eds.). Monitoring Trends in Bat Populations of the
United States and Territories: Problems and Prospects. US Geological Survey, Information
and Technology Report USGS/BRD/ITR-2003-0003. National Technical Information Service,
Springfield, VA. 274 pp.
*Department of Biology, Franklin Pierce College, Rindge, NH 03461; veilleuxj@fpc.edu.