Holocene and Late Pleistocene Bat Fossils (Mammalia:
Chiroptera) from Hamilton County, TN, and their
Timothy J. Gaudin, Ashley N. Miller, Jeremy L. Bramblett,
and Thomas P. Wilson
Southeastern Naturalist, Volume 10, Issue 4 (2011): 609–628
Full-text pdf (Accessible only to subscribers.To subscribe click here.)
2011 SOUTHEASTERN NATURALIST 10(4):609–628
Holocene and Late Pleistocene Bat Fossils (Mammalia:
Chiroptera) from Hamilton County, TN, and their
Timothy J. Gaudin1,*, Ashley N. Miller1, Jeremy L. Bramblett1,
and Thomas P. Wilson1
Abstract - Chiropteran mandibles from late Pleistocene/Holocene fossil cave localities
in Hamilton County were identified in order to examine changes in bat species diversity
and population trends over extended periods of time, providing insight into how bats
in Southeast Tennessee have responded to major environmental changes over the past
10,000–20,000 years. Generic and species identifications were based on an unpublished
key developed by the authors. Measurements of alveolar length (c1–m3) and total length
measurements from the symphysis to the condyle were taken for all specimens identifi
ed as members of the genus Myotis in an attempt to identify species in this genus. The
results of this study failed to confirm those of previous univariate morphological studies,
suggesting that multivariate morphometric analyses may be needed to establish a means
to differentiate among the species in this genus. Diversity data indicated two patterns of
species abundance, with Eptesicus fuscus (Big Brown Bat) dominating some sites and
Myotis sp. dominating others. The data suggest, but do not conclusively demonstrate, that
a temporal replacement of older Eptesicus faunas by younger, Myotis-dominated faunas
has occurred, connected with post-Pleistocene global warming. In addition, a correspondence
between human disturbance and bat populations levels was observed. It is very
likely that human disturbance has caused bat populations to become extinct in the caves
under study, reinforcing the claim of previous researchers that bat population decline is
a recent phenomenon that is tightly linked to human disturbance.
The transition between the late Pleistocene Epoch and the early Holocene Epoch
is marked by a dramatic change in climate which caused the glacial ice sheets
that covered large portions of the continent to gradually retreat (Corgan 1996,
Pielou 1991). The warming period at the Pleistocene/Holocene boundary caused
major changes in habitat distributions (Pielou 1991). Slowly, the diverse habitats
that were common in the Pleistocene were altered as the hypsithermal periods
of the early Holocene swept across the continent, with some biogeographical
realms shifting northward and others disappearing entirely (Pielou 1991). These
ecological changes caused many animal species to change their distribution and
many large mammal species to go extinct at this time (Barnosky et al. 2004, Graham
et al. 1996, Kurtén and Anderson 1980, Pielou 1991, Schubert et al. 2003).
Two major hypotheses exist to explain this extinction pattern: 1) that the climate
1Department of Biological and Environmental Sciences, University of Tennessee at Chattanooga,
615 McCallie Avenue, Chattanooga, TN 37403-2598. *Corresponding author
610 Southeastern Naturalist Vol. 10, No. 4
changes at the end of the Wisconsinan glaciation caused the large mammal extinction,
or 2) that prehistoric overkill by humans caused mammal extinctions
(Barnosky et al. 2004, Martin 2005, Pielou 1991).
Caves play an essential role in our understanding of the Pleistocene Epoch
in North America, as they represent the source of the fossils representing the
largest percentage of known North American Pleistocene faunas (Kurtén and
Anderson 1980, Schubert et al. 2003). They have therefore been critical in allowing
paleontologists to document biogeographic and evolutionary patterns
in a great variety of organisms (Corgan 1996, Schubert et al. 2003). Cave deposits
often preserve Holocene fossils as well, but these are rarely studied by
paleontologists because they do not contain extinct taxa (Schubert et al. 2003).
However, Holocene sites can provide useful information on the evolution
of current ecosystems (Schubert et al. 2003). Tennessee, with its multitude of
caves, provides an excellent environment for exploring fossils from caves in
both the Pleistocene and Holocene (Corgan 1996). Hamilton County contains
a plethora of caves, several of which have been shown to contain Pleistocene
and Holocene fossil remains (Bramblett 1998, Corgan 1996, Gaudin and
Bramblett 1999, Gaudin et al. 1998, Parmalee 1961).
Historically, nearly all of our information concerning the vertebrate fauna
of Hamilton County during the Pleistocene and Holocene is based on the
fossils of megafaunal and medium-sized vertebrates unearthed in Lookout
Mountain Cave by Dr. Henry C. Mercer in 1893 (Corgan 1996, Mercer 1894).
Indeed, most of the initial paleontological research on the Pleistocene of North
America focused on extinct mammalian megafauna (Kurtén and Anderson
1980). It was not until the 1920s that the number of mammalian microfaunal
taxa began to increase substantially (Kurtén and Anderson 1980). Due to the
wide biogeographic distribution and broad environmental tolerances of the species
found in Mercer’s megafaunal sample (Corgan 1996, Mercer 1894), they
are less than ideal indicators of environmental change. Microvertebrates, with
their smaller geographic ranges and narrower ecological niches, could provide
a better understanding of how vertebrate communities responded to environmental
changes that occurred during the Pleistocene and Holocene.
Several years ago microfaunal paleontological fieldwork was initiated in
caves at Lookout Mountain, TN (Bramblett 1998; Bramblett and Gaudin 2001;
Gaudin and Bramblett 1999; Gaudin et al. 1998, 1999) and in nearby parts of
Hamilton County (Ooltewah High School, Ooltewah, TN), and a large and diverse
sample of Pleistocene microvertebrate remains were recovered. Included
in these faunas were over 10,000 skeletal elements from bats, including partial
skulls, mandibles, and isolated postcranial remains (Bramblett and Gaudin
2001, Gaudin and Bramblett 1999). A sample of these bat fossils were identified
(Bramblett and Gaudin 2001, Gaudin and Bramblett 1999), demonstrating
the presence of at least six extant species of bats, most of which are cave-dwelling
for at least part of the year: Myotis septentrionalis (Trouessart) (Northern
Long-eared Bat), M. grisescens A.H. Howell (Gray Bat), Perimyotis subflavus
2011 T.J. Gaudin, A.N. Miller, J.L. Bramblett, and T.P. Wilson 611
(F. Cuvier) (Tricolored Bat), Corynorhinus rafinesquii Lesson (Rafinesque’s
Big-eared Bat), Eptesicus fuscus (Beauvois) (Big Brown Bat), and Lasiurus
sp. (L. borealis (Müller) [Eastern Red Bat] or L. seminolus (Rhoads) [Seminole
Bat]) (Bramblett and Gaudin 2001, Gaudin and Bramblett 1999). Among these
species, C. rafinesquii is currently uncommon and of special concern in parts of
its range, and M. grisescens is a federally listed endangered species (Choate et
al. 1994, Harvey et al. 1999).
Although a small population of P. subflavus persists in Ooltewah High School
Cave, we found no evidence that bat colonies are currently dwelling in any of
the Lookout Mountain caves in which fossils were discovered (Bramblett 1998).
The presence of extensive bat colonies in these caves in the Pleistocene and Holocene,
and their absence today, raises intriguing questions regarding the causes
of their disappearance. Obvious human disturbance is evident at all our Lookout
Mountain Cave localities. These disturbances range from a railroad track that
runs through one entrance to guided tours at another entrance. Human perturbation
is thought to be a major contributor to declines in cave bat populations by
disturbing hibernation or nursery sites (Tuttle 1979).
Tuttle (1979) used the size and color of stains from bat guano (or other bodily
secretions) on the ceilings of caves as an indicator of the size of historical bat
populations roosting in the caves. The estimates of current population size were
obtained by taking the number of square meters covered by new guano and multiplying
it by the mean clustering density of 1828/m2 (Tuttle 1975, 1976, 1979).
Historic colony size was calculated from the area covered by old guano deposits
or the area of staining on the cave roof (Tuttle 1979). Tuttle’s work suggested
that M. grisescens, a species of bat found among the fossil bats from the Lookout
Mountain caves, had recently experienced a dramatic population decline (Tuttle
1979). We note that this inference depends on the assumption of roost fidelity,
i.e., that colonies roost in the same part of the cave ceiling each year (Tuttle
1979). Though Tuttle may have observed roost fidelity during the six years of his
study (Tuttle 1979), it is possible that over centuries or millennia the bats slowly
migrated across the cave ceiling, using different parts as roosting areas. If the
latter were true, Tuttle’s (1979) inferences about the long-term population trends
in this species might need to be reconsidered.
Paleontology may offer an alternative method for examining long-term
population trends by providing data over a longer time frame than guano stains
will allow. Furthermore, paleontological studies offer an independent source
of data via the preservation of actual remains. Because most bat species from
the Pleistocene and Holocene of North America are still extant (Kurtén and
Anderson 1980), comparison of information on the known taxonomic diversity
and ecological characteristics of the modern bat fauna (Barbour and Davis
1969; Best and Jennings 1997; Caceres and Barclay 2000; Choate et al. 1994;
Decher and Choate 1995; Fujita and Kunz 1984; Harvey 1992; Harvey et al.
1999; Jones 1977; Kunz and Martin 1982; Kurta and Baker 1990; Shump and
Shump 1982a, b) to paleontological cave assemblages has the potential to yield
612 Southeastern Naturalist Vol. 10, No. 4
insight into a number of interesting questions. For example, such comparisons
can give us insight into how changes in biogeographic distributions and population
levels over time are correlated with environmental changes. The goal of the
present study is to use paleontology as a tool to contribute to our knowledge of
the historical ecology of bats. We identified chiropteran mandibles from known
fossil localities in order to examine changes in population and species diversity
over extended periods of time. This information in turn should provide insight
into how bats in Southeast Tennessee have responded to major environmental
changes, including climate change, habitat change, and human disturbance over
the past 10,000–20,000 years.
Chiropteran mandibles were identified based on a taxonomic key for lower
jaws of Holocene bats from the southeastern United States prepared by three of
us (T.J. Gaudin, J.L. Bramblett, and A.N. Miller) (see Supplemental Appendix
1, available online at https://www.eaglehill.us/SENAonline/suppl-files/s10-4
-882-Gaudin-s1, and, for BioOne subscribers, at http://dx.doi.org/10.1656/
S882.s1). This key allowed for identifications of most specimens to the species
level. However, only one species (Myotis septentrionalis) within the genus Myotis
was distinguishable using meristic characteristics. A quantitative method for
determining species identifications within the genus Myotis was used by Guilday
et al. (1977) to identify specimens belonging to the species Myotis grisescens and
Myotis leibii (Audubon and Bachman) (Eastern Small-footed Bat). Their method
involved measuring alveolar length between alveolus of the lower canine and the
last lower molar (c1 to m3). These measurements were plotted on a histogram,
revealing distinct peaks associated with the smallest (M. leibii) and the largest
(M. grisescens) species of Myotis (Guilday et al. 1977). We repeated Guilday et
al.’s (1977) measurements for all specimens identified as members of the genus
Myotis. Total mandibular lengths from the symphysis to the condyle were also
taken on all Myotis specimens for purposes of comparison. All measurements
were obtained using Mitutoyo® dial calipers, and recorded to the nearest 0.01
mm. The measurement data were then used to construct histograms using Microsoft
Excel®. No current method can be used to unambiguously identify skeletal
remains of the other southeastern US species of Myotis to the species level
(M. sodalis Miller and Allen [Indiana Bat], M. austroriparius (Rhoads) [Southeastern
Bat], and M. lucifugus (LeConte) [Little Brown Bat]). Therefore, we were
unable to distinguish these species in this study.
Taxonomic identifications and provenance of over 900 unidentified fossil bat
mandibles from four localities were recorded in a database at the University of
Tennessee at Chattanooga Natural History Museum. Two of the localities lie in
separate portions of Lookout Mountain Cave (herein designated as RR, RF) (Barr
1961, Corgan 1996). Another unnamed locality was designated Cave Without
Name (CWN) by Gaudin et al. (1998, 1999). All of these localities lie at the north
2011 T.J. Gaudin, A.N. Miller, J.L. Bramblett, and T.P. Wilson 613
end of Lookout Mountain near Chattanooga, TN. The final locality is Ooltewah
High School Cave (OHS) in Ooltewah, TN (Table 1). After all bat fossils were
identified and cataloged, the diversity at specific recovery sites within each cave
locality was determined using pie charts created in Microsoft Excel®. Minimum
number of individuals (MNI) (based on right mandibles) were initially calculated
in order to estimate population sizes for the various bat species at each site (Benton
et al. 1994). However, total number of elements ultimately was used because
MNI yielded sample sizes that were too small for analysis.
The total number of elements for each species at a given site was then used to
calculate heterogeneity and evenness measures from each site using Simpson’s
measure of evenness (Simpson 1949), Camargo’s index of evenness (Carmargo
1993), and Smith and Wilson’s index of evenness (Smith and Wilson 1996) using
the computer program Methods® (Krebs 2000). The Methods® program was
also used to generate Euclidean distances, a Bray-Curtis metric (Bray and Curtis
1957), a Canberra metric (Lance and Williams 1967), and percent similarities
(Renkonen 1938) for each locality except OHS cave. These latter tests require
data from at least three sites. Unfortunately, OHS cave did not have enough sites
to run these analyses. Evenness measurements should indicate the degree to
which relative abundances of individuals among the different species are comparable
(Krebs 2000). Euclidean distance, Bray-Curtis metric, Canberra metric,
and percent similarity give information about the degree of relative similarity
among the sites at a given locality with regards to species composition. Several
sites were omitted from analysis for the Euclidean distance, Bray-Curtis metric,
Canberra metric, and percent similarity measures from both the RF (site 5) and
RR (sites 7 and 8) localities. The small number of species recovered from these
sites interfered with the function of the pertinent equations.
Table 1. Cave locality information.
Cave Elevation Latitude and longitude Site Site age (YPB) Sediment type size (n)
CWN 660’ 35.024°N, 85.342°W 1 14,459 ± 786 Yellow sand 26
2 14,459 ± 786 Yellow sand 13
4 14,459 ± 786 Yellow sand 32
RF 660’ 35.021°N, 85.338°W 1 14,811 ± 682 Orange clay 25
2 14,811 ± 682 Orange clay 9
4 14,811 ± 682 Orange clay 6
5 14,811 ± 682 Orange clay 1
6 25,458 ± 2100 Orange clay 21
RR 700’ 35.021°N, 85.338°W 1 16,148 ± 483 Orange clay 614
2 Unknown Dark silty clay 86
3 >10,000 Orange clay 20
4 Unknown Dark silty clay 12
5 less than 500 Orange clay 18
7 Unknown Dark silty clay 1
8 Unknown Dark silty clay 4
OHS 800’ 35.095°N, 85.066°W 1 less than 10,000 Brown sandy silt 4
614 Southeastern Naturalist Vol. 10, No. 4
Ages of sites within each locality were determined by radiocarbon dating and
faunal analysis. AMS Radiocarbon dating was performed by Rafter Radiocarbon
Laboratory (Lower Hutt, New Zealand). Elements used for the radiocarbon
analysis were selected from Pleistocene species, where possible, in an attempt
to approximate the maximum ages for each site. Dates were obtained for three
sites in RR: RR1 at ≈16,000 ybp, based on radiocarbon dating (16,148 ± 483 ybp,
date based on dermal scute from the extinct Dasypus bellus (Simpson) [Beautiful
Armadillo], sample ID number R 24720/1); RR3 at >10,000 ybp, based on the
presence of D. bellus (Kurtén and Anderson 1980); and RR5 at less than 500 ybp, based
on the presence of Mus musculus L. (House Mouse). The site at the OHS cave
locality was dated at less than 10,000 ybp based on the presence of Blarina carolinensis
(Bachman) (Southern Short-tailed Shrew), which, according to Klippel and Parmalee
(1982), likely arrived in middle Tennessee in the Holocene. Radiometric
dates were obtained for two sites in RF: RF1 at ≈15,000 ybp (14,811 ± 682 ybp,
date obtained from molar of extinct peccary Mylohyus sp., R 24888/2); and RF6
at ≈25,500 ybp (25,458 ± 2100 ybp, date obtained from radius of Marmota monax
L. (Woodchuck), R 24888/3). However, sites RF1–5 were part of the same
streambed, and fossils at all five localities are recovered only in the upper few
centimeters of sediment. We therefore believe that all five sites can be treated as
effectively contemporaneous. Similarly, a radiometric date was obtained for only
one site in CWN (CWN1 dated at 14,459 ± 786 ybp, date obtained from upper
molar of Mylohyus sp., R 24888/1), but because CWN2 and CWN4 were part of
the same streambed, with fossils found only in the upper few centimeters of sediment,
they too were treated as contemporaneous. Note the deposits from the RR
(16,000 ybp to less than 500 ybp) and RF (25,500 ybp to 15,000) localities likely exhibit
a relatively small temporal overlap, and that both encompass a broad range in
time, from 10 to 15 thousand years (Table 1).
A total of 909 bat mandibles were identified from the four cave localities. The
most common genus within the sample was Myotis, with 439 elements. The most
common species identified was Eptesicus fuscus, with 268 elements. Other taxa
that occurred in smaller numbers included species within the genus Corynorhinus
(68 elements: C. sp., 42 elements; cf. C. sp., 20 elements; C. rafinesquii, 6
elements), Perimyotis subflavus (29 elements), and Lasiurus borealis or L. seminolus
(6 elements; cf. L. borealis or L. seminolus, 1 element). A portion of the
sample was unidentifiable at the genus or species level (97 elements).
Of those 439 specimens belonging to the genus Myotis, 309 elements were
sufficiently preserved to obtain mandibular measurements. Total mandibular
lengths (symphysis to condyle) for this sample ranged from 9.38 mm to 11.60
mm (Fig. 1). Alveolar length (c1 to m3) ranged from 4.72 mm to 7.50 mm
(Fig. 2). The histograms created based on these measurements show several distinct
peaks (Figs. 1, 2). For total mandibular length, six peaks are noted at 9.4
2011 T.J. Gaudin, A.N. Miller, J.L. Bramblett, and T.P. Wilson 615
mm, 9.7– 9.8 mm, 10.1 mm, 10.4 mm, 11.1 mm, and 11.4 mm (Fig. 1). A total of
five peaks are present among the alveolar length data. These occur at 5.0 mm, 5.5
mm, 5.7–5.8 mm, 6.2 mm, and 6.5 mm respectively (Fig. 2).
Because Myotis septentrionalis was the only species in this genus that could
be identified with a meristic (i.e., size-independent) characteristic, specieslevel
variation in total mandibular and alveolar length measures was examined
separately. M. septentrionalis exhibited broad variation in both measurements,
overlapping much of the range of the total data sample, with mandibular lengths
ranging from 10.3–11.4 mm (mode of 10.9 mm), and alveolar lengths (c1–m3)
ranging from 5.5–6.9 mm (mode of 6.5 mm). When M. septentrionalis was
removed from the total sample (Figs. 3, 4), the peak at 11.4 mm in the total
mandibular length data was eliminated, whereas the other five original peaks remained
intact (Fig. 3). For the alveolar length data, removal of M. septentrionalis
left all peaks intact, but resulted in a decrease in the magnitude of the peaks at 5.5
mm, 6.2 mm, and 6.5 mm (Fig. 4).
The total number of individuals, site diversity, and site age are summarized
in Tables 1 and 2. Charts illustrating the abundance of species recovered at each
Figure 1. Histogram showing distribution of mandibular lengths (measured from symphysis
to the condyle) among all Myotis specimens measured in the present study (n = 120).
Figure 2. Histogram showing distribution of alveolar lengths (measured from c1 to m3)
among all Myotis specimens measured in the present study (n = 309).
616 Southeastern Naturalist Vol. 10, No. 4
site (Figs. 5–8) appear to fall into two categories. Half the sites are dominated by
Eptesicus fuscus, with E. fuscus comprising at least 50% of the total number of
recovered specimens (Figs. 5, 6). These E. fuscus-dominated sites include all the
sites at the Cave without name (CWN) locality and the Ruby Falls entrance to
Lookout Mountain Cave (RF) locality. The remaining bat faunas are dominated
by members of the genus Myotis (Figs. 7–9). Faunas where Myotis comprised
Table 2. Summary of similarity metrics at each locality. BC = Bray-Curtis metric, CM = Canberra
metric, ED = Euclidean distance, and PS = percent similarity.
Locality Sites BC CM ED PS
1 vs. 2 0.46 0.15 4.55 69.2
1 vs. 4 0.86 0.91 1.93 95.0
2 vs. 4 0.40 0.21 6.31 69.2
1 vs. 2 0.51 0.31 6.81 80.0
1 vs. 4 0.33 0.42 7.35 92.0
1 vs. 6 0.83 0.57 2.45 76.8
2 vs. 4 0.67 0.57 1.50 80.0
2 vs. 6 0.45 0.49 7.09 64.8
4 vs. 6 0.38 0.83 8.00 84.8
RR 1 5
1 vs. 2 0.23 0.21 81.83 68.3
1 vs. 3 0.06 0.13 94.82 77.3
1 vs. 4 0.04 0.13 96.59 59.8
1 vs. 5 0.06 0.14 95.30 57.0
2 vs. 3 0.38 0.43 14.93 79.4
2 vs. 4 0.24 0.41 16.60 64.0
2 vs. 5 0.35 0.46 15.09 73.6
3 vs. 4 0.56 0.63 2.41 65.0
3 vs. 5 0.68 0.61 2.10 65.0
4 vs. 5 0.80 0.94 1.61 86.1
Figure 3. Histogram showing distribution of mandibular lengths (measured from symphysis
to the condyle) among all Myotis specimens, except M.septentrionalis, measured
in the present study (n = 101).
2011 T.J. Gaudin, A.N. Miller, J.L. Bramblett, and T.P. Wilson 617
at least 50% of recovered specimens are found at all the sites from the railroad
entrance to Lookout Mountain Cave (RR) and the Ooltewah High School Cave
locality (OHS). Among all the sites excavated, RR1 had the largest number of
Figure 4. Histogram showing distribution of alveolar lengths (measured from c1 to m3)
among all Myotis specimens, except M. septentrionalis, measured in the present study
(n = 258).
Figure 5. Species diversity based on total number of individuals recovered per species
at each of the various sites within the Cave without Name (CWN) locality: a. Site 1, b.
Site 2, and c. Site 4.
618 Southeastern Naturalist Vol. 10, No. 4
Figure 7 (opposite page). Species diversity based on total number of individuals recovered
per species at each of the various sites within the Lookout Mountain Cave, Railroad
entrance (RR) locality; a. Site 1 and b. Site 2.
Figure 6. Species diversity based on total number of individuals recovered per species at
each of the various sites within the Lookout Mountain Cave, Ruby Falls (RF) locality: a.
Site 1, b. Site 2, c. Site 4, and d. Site 6.
individuals, the highest level of species diversity, and included all species of
Chiroptera found within the total sample (Fig. 7a, Table 1).
Information on the similarity among sites (excluding OHS) obtained using
Euclidean distance (ED), Bray-Curtis metric (BC), Canberra metric (CM) and
percent similarity (PS) indicate varying degrees of similarity (Table 2). Among
the sites within CWN, sites 1 and 4 appear to be the most similar, with a 95%
similarity. Sites 1 and 4 also have BC and CM values that approach 1, and a markedly
smaller ED than other site-by-site comparisons. This similarity can also be
observed by comparing the species list for these sites (Fig. 5).
Strong PS are seen throughout all sites in RF, with the lowest being ≈65% for
site RF2 versus RF6. Site RF6 exhibits a stronger PS value when compared with
site RF4 (≈85%) than it does when compared to site RF2, which is similar in age
to site RF4 (Table 1). The ED values for site RF6 are relatively high when compared
with sites RF2 and RF4 (7.09 and 8.00, respectively), but markedly lower
2011 T.J. Gaudin, A.N. Miller, J.L. Bramblett, and T.P. Wilson 619
620 Southeastern Naturalist Vol. 10, No. 4
when compared with site RF1 (2.45). Some inconsistencies can be noted when
comparing results across indices. CM seemed to indicate that site RF4 and RF6
are the most similar. Values from BC showed sites RF1 and RF6 as most similar,
whereas PS indicated sites RF1 and RF4 are most similar. Sites RF2 and RF4 had
the smallest ED values.
Figure 8. Species diversity based on total number of individuals recovered per species
at each of the various sites within the Lookout Mountain Cave, Railroad entrance (RR)
locality: a. Site 3, b. Site 4, c. Site 5, and d. Site 8.
Figure 9. Species diversity based
on total number of individuals
recovered per species at each of
the various sites within the Ooltewah
High School Cave (OHS)
2011 T.J. Gaudin, A.N. Miller, J.L. Bramblett, and T.P. Wilson 621
The railroad entrance to Lookout Mountain sites also exhibited fairly high
PS values (57% or greater). ED, CM, and BE indicate similarity among all sites
except site RR1, although PS values for site RR1 are well within the range of the
other site-by-site comparisons. The most similar sites appear to be RR4 and RR5,
with the smallest ED (1.61), BC and CM values very close to 1, and a very high
PS (86.1%). This observation is reinforced by a comparison of species abundance
patterns for those sites (Fig. 8b, c).
Information on the heterogeneity and evenness within each locality was
obtained using Smith and Wilson’s index (SW), Carmargo’s index (C), and
Simpson’s measure of evenness (S) (Table 3). These indices indicated that
most localities had a moderate level of biodiversity. High levels of biodiversity
were noted using SW, C, and S for RR1 (SW = 0.204, C = 0.379, S =
0.390) and RR2 (SW = 0.316, C = 0.292, S = 0.241). Results from SW also
indicated that RF6 (SW = 0.267, C = 0.548, S = 0.55) had high levels of biodiversity,
whereas the other indices indicated average levels of biodiversity at
this site. Relatively low biodiversity was evident using SW, C, and S for RF4
(SW = 0.924, C = 0.833, S = 0.9) and OHS1 (SW = 0.813, C = 0.75, S = 0.8).
The value of 1.0 for RR8 using SW, C, and S reflected the fact that sample
size for all species were equal at this site.
Although, as noted previously, only Myotis septentrionalis could be distinguished
from other Myotis species based on meristic characters, we were
able to recognize some Myotis grisescens and M. leibii specimens based
on morphological measurements. However, the size distribution within our
sample differs dramatically from that of Guilday et al. (1977). Guilday et al.
Table 3. Summary of heterogeneity and evenness at each site. S = Simpson's measure of evenness,
C = Carmago's index, and SW = Smith and Wilson's index.
Sites S C SW
CWN1 0.691 0.590 0.569
CWN2 0.494 0.577 0.696
CWN4 0.603 0.563 0.341
RF1 0.590 0.573 0.566
RF4 0.900 0.833 0.924
RF5 0.667 0.667 0.743
RF6 0.550 0.548 0.267
RR1 0.390 0.379 0.204
RR2 0.241 0.292 0.316
RR3 0.476 0.500 0.515
RR4 0.600 0.600 0.680
RR5 0.476 0.511 0.576
RR8 1.000 1.000 1.000
OHS1 0.800 0.750 0.813
622 Southeastern Naturalist Vol. 10, No. 4
(1977) identified any specimen with an alveolar length of 5.5 mm or less as
pertaining to M. leibii and any specimen with an alveolar length of 6.6 mm or
greater as belonging to M. grisescens (Guilday et al. 1977). In contrast, in our
study, the lower alveolar peak occurred at 5.0 mm, and no clear upper alveolar
length peak was present, except for a peak at 6.5 mm (Fig. 2) that fell within
the range of M. septentrionalis (5.5–6.9 mm) and therefore could not be attributed
to M. grisescens. When the total length data were examined, a clear
upper peak could not be seen once M. septentrionalis was removed from the
histogram (Fig. 4). Nevertheless, we were able to assign specimens above the
range for total mandibular length in M. septentrionalis (11.5 mm or greater) to
M. grisescens. Specimens occurring at or below the lower peaks in both total
mandibular length (9.5 mm or less) and alveolar length (5.0 mm or less) were
assigned to M. leibii.
Although differences in the age or the mode of formation of the deposits may
exist between the present study and that of Guilday et al. (1977), it is not readily
apparent how these differences would translate into differences in the distribution
of measurements found in both studies. The range in locality age (<500 ybp
to 25,500 ybp) is much greater in our study than in that of Guilday et al. (1977).
Guilday et al. (1977) estimate that the Clark’s Cave deposit is somewhere between
20,000 and 11,000 ybp. Thus, their fauna may be older than some of our
remains. Therefore, it is conceivable that the relevant species of Myotis have
changed size over time, as is known to occur in other mammalian lineages, which
often become smaller in the warming post-Pleistocene climate (Kurtén and Anderson
1980). This hypothesis would explain the apparent reduction in the size
of M. leibii mandibles, but would not account for the lack of a clear upper peak
for M. grisescens in our analysis. It is also possible that both analyses have erred
in assuming that Holocene species represent a reasonable proxy for Pleistocene
diversity. It is certainly possible that different Myotis species, either extinct varieties
or Recent species with a different modern geographic distribution, inhabited
these areas at various times in the Pleistocene, skewing the measurement distribution
of one or both analyses. Whatever the cause, taken together, the results of
the two studies imply that simple length measures may not be sufficient even for
identification of the largest and the smallest Myotis species. Moreover, neither we
nor Guilday et al. (1977) were able to distinguish between the medium-size Myotis
species from the southeast [M. austroriparius, M. sodalis, and M. lucifugus].
It seems clear that multivariate morphological studies are needed to establish a
means to differentiate among the species in this genus. Such multivariate analyses
are beyond the scope of this study.
Community-level numeric analysis seems to suggest close similarity
among sites within CWN (Table 2). This similarity makes sense considering
that sites in CWN occur within a single dry streambed. The fact that sites
CWN1 and CWN4 are physically the two most distant sites at the locality
but are ecologically the most similar seems to confirm that all sites at this locality
are uniform in age and composition, and may once have been part of a
2011 T.J. Gaudin, A.N. Miller, J.L. Bramblett, and T.P. Wilson 623
larger metapopulation. Interestingly, similar intra-site homogeneity is evident
for RF, even though there appears to be a 10,000-year age difference between
RF1–4 and RF6. Some RF sites appear to be more similar to RF6 than other
RF sites of similar age, and all sites are dominated by Eptesicus fuscus. Therefore,
based on this sample, site age does not appear to have a strong effect on
species composition for RF sites. The RR locality also exhibits substantial
similarity among sites for some, but not all, measurements. Though species
composition among sites was similar (Figs. 7 and 8), ED, CM, and BC indicated
a sizable difference between site 1 and the other sites (Table 2). This
difference may be due to the large sample size from site 1 (614 elements)
when compared to other sites (4–86 elements). The large sample sizes of RR1
and RR2 may also help explain the higher level of biodiversity noted for both
localities using SW, C, and S. Similarly, the relatively small sample size (4–6
elements) of RF4, RR8, and OHS1 likely explains the low levels of diversity
seen using SW, C, and S for these localities.
The variation in the abundance of particular bat genera and species among
localities is apparent from the species distributions pie charts shown in Figures
5–9. These figures indicate that E. fuscus dominates sites within CWN and RF,
whereas Myotis sp. dominates sites at RR and OHS. The reason for this difference
in abundance is not clear. RF and RR are both part of the same cave system
and share similar external environments, indicating that external environments
probably do not play a role in the pattern of dominance observed. Cave size also
does not seem to be a factor in determining species abundance. RF and RR are
part of a single large cave system, but have distinctly different species abundance
patterns. OHS and CWN are relatively small caves, but are also dominated by
Habitat preference of extant bat species might help explain species distributions
within our sample. Some bat species, like Myotis grisescens, roost only in
caves (Barbour and Davis 1969, Choate et al. 1994, Harvey 1992, Harvey et al.
1999). Other species like M. leibii, E. fuscus, and Perimyotis subflavus, occur in
a wider range of habitats that include abandoned mines, man-made structures,
rock crevices, trees, etc. (Barbour and Davis 1969, Choate et al. 1994, Harvey
1992, Harvey et al. 1999). Although one species, L. seminolus, will occasionally
roost in caves, and individuals of several other species of southeastern Lasiurus
are sometimes found in and around cave entrances, the preferred roosting habitat
for most southeastern Lasiurus are trees (Barbour and Davis 1969, Choate
et al. 1994, Harvey 1992, Harvey et al. 1999), which almost certainly explains
why Lasiurus sp. represents only a small portion of the sample. Interestingly,
exclusively cave-dwelling species do not make up a majority of our sample.
However, with the exception of Lasiurus, there is no clear correlation between
habitat preferences and the pattern of species abundance in our sample. In fact,
Myotis sp. and E. fuscus were found to dominate cave localities that appear to
conflict with their general habitat preferences. Many species of Myotis prefer
cool but not freezing winter hibernacula, and tend to be more abundant in
624 Southeastern Naturalist Vol. 10, No. 4
deeper portions of the caves they inhabit (Barbour and Davis 1969, Best and
Jennings 1997, Choate et al. 1994, Decher and Choate 1995, Harvey 1992, Harvey
et al. 1999)—M. leibii is an exception to this generalization, but this rare,
cold-tolerant species apparently represents only a small portion of our sample.
On the other hand, E. fuscus is very cold tolerant and prefers cooler, even freezing
hibernacula (Barbour and Davis 1969, Choate et al. 1994, Harvey 1992,
Harvey et al. 1999). It is therefore often found near the entrances of caves. Yet
in our own sample, Myotis were prevalent from the front of the Lookout Mountain
cave system (RR locality), whereas E. fuscus were abundant at the back of
the same cave system (RF locality).
Colony size may also contribute to the observed pattern in species abundances.
Several bat species present in our sample are characterized by large
colony sizes of 100 to over 1000 individuals. This pattern is typical for
M. grisescens, M. lucifugus, M. sodalis, and E. fuscus (Barbour and Davis
1969, Choate et al. 1994, Decher and Choate 1995, Harvey 1992, Harvey et al.
1999, Kurta and Baker 1990). It is perhaps not surprising then that these two
genera, Myotis and Eptesicus, dominate the overall sample, although it does
not explain why particular faunas are dominated by one genus or the other. Our
remains also incorporate species (Corynorhinus sp., Lasiurus sp., Perimyotis
subflavus, M. septentrionalis, and M. leibii) that roost singly or in small
colonies less than 100 individuals (Barbour and Davis 1969; Best and Jennings
1997; Caceres and Barclay 2000; Choate et al. 1994; Fujita and Kunz 1984;
Harvey 1992; Harvey et al. 1999; Kunz and Martin 1982; Shump and Shump
1982a, b). One might expect these taxa to dominate the small samples obtained
from smaller caves because small caves cannot accommodate large colonies.
However, this was not the case in our study. One small cave system, CWN,
was dominated by E. fuscus remains, whereas the other small cave system,
OHS, yielded mostly remains from Myotis sp., although none of the OHS Myotis
specimens could be identified to species.
M. septentrionalis represents a sizable portion of the sample from the Lookout
Mountain cave system (RR and RF), yet it has colonies of no more than 100
individuals (Barbour and Davis 1969, Caceres and Barclay 2000, Choate et al.
1994, Harvey 1992, Harvey et al. 1999). The prevalence of M. septentrionalis
may be an indication that several of these cave sites preserve a mixed-age assemblage.
The large sample of M. septentrionalis elements is likely the result
of the accumulation of elements over a long period of time. Although the sites
themselves do not provide detailed stratigraphic information, time averaging of
M. septentrionalis specimens could be demonstrated through AMS radiocarbon
dating of multiple specimens, but this is expensive and is beyond the scope of
It is possible that the differential pattern of species abundance at different
sites can be explained as the result of temporal changes associated with
overall climate change in the area. Most of the E. fuscus-dominated localities
(CWN1, 2, and 4 and RF1, 2, 4, and 6) are similar in age, having been dated
2011 T.J. Gaudin, A.N. Miller, J.L. Bramblett, and T.P. Wilson 625
to an age of about 14,000 ybp (14,811 ± 682 ybp [RF1, 2, and 4] and 14,459 ±
786 ybp [CWN sites]). However, site RF6, which is also E. fuscus dominated,
is ≈10,000 years older (25,458 ± 2100 ybp) than the other sites. The age range
for Myotis-dominated sites (RR and OSH) is even more substantial. Within two
RR localities alone, there are sites radiocarbon dated to >16,000 ybp (16, 148
± 483 ybp [RR1]) and sites dated faunally to <500 ybp (RR5). The OHS cave
was faunally dated to <10,000 ybp. The Eptesicus-dominated faunas are by and
large older than the Myotis-dominated faunas. Moreover, the oldest site, RF6,
has the highest percentage representation of E. fuscus of any of our sites (20/21
specimens), although the sample size is modest. The youngest site (RR5) has
the highest proportion of Myotis remains (14/18 specimens), and the other post-
Pleistocene site (OHS1) is 75% Myotis (3/4 specimens), although the sample
sizes at both sites are small. In the Pleistocene sites from the RR locality, Myotis
comprises closer to 50% of the respective faunas (e.g., 11/20 specimens at
RR3, 303/614 at RR1). It is tempting to interpret this pattern as a temporal
replacement of E. fuscus by species in the genus Myotis. Furthermore, this temporal
change would be consistent with changes in climate that are occurring
simultaneously. The substantial climatic warming that has occurred since the
mid-Pleistocene (Pielou 1991) could be construed as favoring the less-coldtolerant
species of Myotis over the more-cold-tolerant E. fuscus. However, it
is important to note that the Myotis-dominated faunas overlap the E. fuscusdominated
faunas by at least two thousand years, and that only four sites in the
study have been carbon dated. Therefore, at this point, we cannot conclude with
certainty that the patterns of species abundance are created by temporal changes
While global warming might explain faunal changes in the distant past, and
may be inferred as a continuing source of faunal change in the near future, it
has been suggested that recent changes in bat species diversity and abundance
are attributable to human-related disturbances. The results of our study would
seem to reinforce this conclusion. Our fossils provide evidence that the Lookout
Mountain cave system supported large bat populations for over 25,000 years.
Bat remains are recovered from deposits formed as recently as <500 ybp (RR5),
indicating that the disappearance of bats from this system is a very recent phenomenon.
It is known that as human population levels rapidly increased in the
area over the past 500 years, human disturbance of the caves has increased. In
the Lookout Mountain cave system, these disturbances include saltpeter mining,
the building of a railroad tunnel through the RR locality, and even the
use of the RF locality as a tourist site. These data therefore strongly implicate
anthropogenic disturbance as a major source of bat disappearance in the Lookout
Mountain cave system. Thus, these results reinforce Tuttle’s (1979) claim,
based on different lines of evidence (guano stains), that bat population decline
in southeast Tennessee is a recent phenomenon that is tightly linked to human
disturbance. It also reemphasizes the need to decrease human disturbance in order
to prevent further declines in extant bat abundance and diversity.
626 Southeastern Naturalist Vol. 10, No. 4
We wish to thank the CSX Corporation for facilitating access to several of the
cave sites where these bat specimens were collected. We thank P. Millener, K. Ballew,
P. van Alstyne, W. Stevens, M. Stevens, M. Konertz, J. England, and many of T. Gaudin’s
former students for assistance in collecting and processing specimens. AMS
radiocarbon dating of specimens from several cave sites was performed by Rafter
Radiocarbon Laboratory (Lower Hutt, New Zealand), and we thank Dr. Phil Millener
for his assistance in obtaining these dates. For access to specimens used in creating
our taxonomic key and identifying our bat specimens, we thank W. Klippel, University
of Tennessee at Knoxville, M. Kennedy of the University of Memphis, D. Ekkens of
Southern Adventist University, and E. McGhee of the University of Georgia. For their
comments on a previous draft of this manuscript, we thank E. Carver and M. Santiago.
A. Miller’s research was supported by a Provost Student Research Award from the University
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