Discarded Bottles as a Source of Shrew Species Distributional Data along an Elevational Gradient in the Southern Appalachians
M. Patrick Brannon, Melissa A. Burt, David M. Bost, and Marguerite C. Caswell
Southeastern Naturalist, Volume 9, Issue 4 (2010): 781–794
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2010 SOUTHEASTERN NATURALIST 9(4):781–794
Discarded Bottles as a Source of Shrew Species
Distributional Data along an Elevational Gradient in the
M. Patrick Brannon1,*, Melissa A. Burt1, David M. Bost1,
and Marguerite C. Caswell1
Abstract - Discarded bottles were inspected for skeletal remains at 220 roadside sites
along the southeastern Blue Ridge escarpment of North Carolina, South Carolina, and
Georgia as a technique to examine the regional distributions of shrews. Vertebrate
remains were found at approximately 63% of our study sites and in 4.5% of the open
bottles we examined. Bottles collected a total of 553 specimens of small mammals
representing 5 species of shrews and 6 species of rodents. The Northern Short-tailed
Shrew (Blarina brevicauda) and the Smoky Shrew (Sorex fumeus) were abundant and
distributed throughout the region, although Smoky Shrews were more strongly associated
with mesic environments and higher altitudes (x̅ = 940.1 m ± 25.4 m). The Masked
Shrew (S. cinereus) and the Southeastern Shrew (S. longirostris) exhibited contiguous
allopatry, with Masked Shrews occurring exclusively in mesic forest habitats at high
elevations (x̅ = 1126.7 ± 27.4 m), and Southeastern Shrews occurring only in xeric
habitats at lower elevations (x̅ = 503.7 ± 64.9 m). Our study demonstrates the utility
of discarded bottles as a quick and effective alternative method for surveying shrews,
without the added mortality that occurs from pitfall- or snap-trapping.
Diversity of North American Soricidae is greatest in geographic regions
such as the southern Appalachians where precipitation is high and where
topography results in a variety of forested habitats (Berman et al. 2007,
Ford et al. 2006). The southeastern region of the Blue Ridge escarpment
marks the edge of the Appalachians through southwestern North Carolina,
northwestern South Carolina, and northeast Georgia. Elevation in this region
decreases abruptly over a relatively short geographic distance north to south
approaching the mountain-piedmont interface (Ford et al. 2001, Laerm et al.
1999). For example, elevations in the Highlands region of North Carolina,
the southernmost high plateau of the Appalachian mountains (Johnston
1967), shift from about 1255 m to 313 m in Walhalla, South Carolina over
an approximate distance of only 35 km.
This steep altitudinal gradient is characterized by considerable diversity in
habitat type and moisture regimes and the associated patterns of soricid species
richness (Ford et al. 2006, Laerm et al. 1999, McCay et al. 2004). In the
Blue Ridge region, assemblages of northern boreal species, including Sorex
cinereus (Kerr Masked Shrew), S. fumeus (Miller) (Smoky Shrew), S. hoyi
(Baird) (Pygmy Shrew), and Blarina brevicauda (Say) (Northern Short-tailed
1Highlands Biological Station, 265 North Sixth Street, Highlands, NC 28741. *Corresponding
author - email@example.com.
782 Southeastern Naturalist Vol. 9, No. 4
Shrew), and southern Piedmont and Coastal Plain species, including S. longirostris
Bachman (Southeastern Shrew), B. carolinensis (Bachman) (Southern
Short-tailed Shrew), and Cryptotis parva (Say) (Least Shrew), converge (Berman
et al. 2007, Ford et al. 2006, Johnston 1967, Laerm et al. 1999, Mengak
et al. 1987). At transitional elevations, members of the two assemblages may
co-occur (Greenberg and Miller 2004), but they are generally segregated by
habitat type (Ford et al. 2001, McCay et al. 2004).
Habitat generalists such as Northern Short-tailed Shrews and Smoky
Shrews have been found to be common and have wide distributions throughout
the southern Appalachians (Laerm et al. 1999). Species with narrower
niche breadths such as Masked Shrews and Southeastern Shrews, on the
other hand, appear to exhibit contiguous allopatry based on elevation and
habitat moisture (Ford et al. 2001, Pagels and Handley 1989). Although
these two species may overlap in their latitudinal distribution in the Blue
Ridge (Ford et al. 2006, Johnston 1967, McCay et al. 2004), with one exception
(Greenberg and Miller 2004), they have not been recorded at the
same site (Ford et al. 2001, Laerm et al. 1999, Mengak et al. 1987, Pagels
and Handley 1989). Masked Shrews have been collected as far south as the
Walhalla Fish Hatchery in Oconee County, SC (Laerm et al. 1995a) and Tray
Mountain, White County, GA (Laerm et al. 1999) and at elevations as low as
615 m in mesic hemlock (Tsuga spp.)-hardwood forests (Ford et al. 2001).
Southeastern Shrews have been reported in North Carolina from Coweeta
Hydrological Laboratory in Macon County (Laerm et al. 1999) and Bent
Creek Experimental Forest in Buncombe County (Greenberg and Miller
2004, Johnston 1967) and at altitudes as high as 923 m, but only in xeric oak
(Quercus spp.)-pine (Pinus spp.) habitats (Ford et al. 2001).
Previous studies of shrew species distribution and diversity in the southeastern
region of the Blue Ridge have relied upon traditional sampling
methodologies such as snap- and pitfall- trapping (e.g., Ford et al. 1997,
2001; Greenberg and Miller 2004; Laerm et al. 1995a, 1997a, 1997b, 1999,
2000b; McCay et al. 1998; Mengak et al. 1987). Such techniques are generally
effective, but are extremely labor-intensive (Handley and Kalko 1993,
Kalko and Handley 1993, Kirkland and Sheppard 1994). However, the
presence of shrews also can be determined by examining skeletal remains
extracted from discarded bottles, a relatively underused method of collecting
small mammals (Clegg 1966, Morris and Harper 1965). Frequently, an
animal will enter a bottle when foraging or in search of shelter and become
entrapped because of the slope and slippery interior surface, or will drown
if the bottle is partially filled with rainwater (Benedict and Billeter 2004).
Data collected from discarded bottles have been used effectively to delineate
the ranges of Northern Short-tailed, Southern Short-tailed, and Southeastern
Shrews in Virginia (Pagels and French 1987, Pagels and Handley 1989).
Our objective was to similarly use roadside bottles to examine the general
distribution of shrews, and to better demarcate the altitudinal and habitat
segregation between Masked and Southeastern Shrews along the southeastern
region of the Blue Ridge escarpment.
2010 M.P. Brannon, M.A. Burt, D.M. Bost, and M.C. Caswell 783
We examined bottles for skeletal remains along primary and secondary
roads throughout Macon, Jackson, and Transylvania counties in North Carolina,
Oconee and Pickens counties in South Carolina, and Rabun County in
Georgia (Fig. 1) periodically from September 2007 to November 2009. To
maximize the efficiency of our search effort, we limited our study sites to
established pull-offs, scenic overlooks, and parking areas where large numbers
of bottles and other items of trash have accumulated. Although we were
restricted by the availability of such sites at different locations, we attempted
to sample from as many elevations and habitats as possible throughout the
region. Our study sites were clustered at a few localities because of these
constraints, but were counted as independent sites if separated by a minimum
distance of 0.8 km, which exceeds the home range of most shrews (Whitaker
and Hamilton 1998).
Surrounding or adjacent forest stands generally were ≥50 years old at
our survey sites, though stand age appears to have little influence on shrew
Figure 1. Map of the southeastern Blue Ridge escarpment illustrating locations of
study sites. Discarded bottles were examined for small-mammal skeletal remains at
220 localities in regional counties of North Carolina (123 sites), South Carolina (66),
and Georgia (31) from September 2007 to November 2009.
784 Southeastern Naturalist Vol. 9, No. 4
abundance (Ford et al. 1997, 2002). We recorded latitude, longitude, and
elevation at each site and mapped data using ArcGIS® 9.3 software (ESRI,
Inc.; Redlands, CA). Because soricid distribution is greatly influenced by
environmental moisture (Brannon 2002a, Getz 1961), we also ranked the
vegetational community at each site into one of the five habitat moisture
classes described by Ford et al. (2001). We assigned values from xeric to
mesic of 1 to pine communities, 2 to mixed pine-hardwood communities,
3 to upland hardwood and riverine communities, 4 to northern hardwood
communities, and 5 to cove hardwood and montane streamside communities
(Ford et al. 2001).
We located bottles visually at each site by walking along the sides of
roads and down embankments into adjacent forested areas, and by shuffling
our feet to uncover those buried in leaf litter (Benedict and Billeter 2004).
The size of the search area varied according to individual site conditions
such as steepness of the slope and thickness of the vegetation, but was generally
about 100 m in length and as far off the shoulder of the road into the
vegetation as bottles could be found. “Bottles” were defined as any plastic or
glass container of any size including beer and soda bottles, jars, milk jugs,
or other similar items of trash. Aluminum cans were examined initially but
were excluded from analyses because they were never found to contain any
vertebrate remains. In addition to the bottles that contained specimens, we
recorded both the number of open bottles (i.e., potential traps) and bottles
with caps during each search.
Bottles that appeared to contain skeletal remains usually were covered by
leaf litter, and often held water, dirt, and dead invertebrates and had a foul
odor. The presence of fur, frequently dried to the side of the bottle’s interior,
was our primary indicator. Contents were extracted and then carefully
teased apart to find bones (Benedict and Billeter 2004). Skulls, mandibles,
and other bones including any skull fragments were labeled for each site and
placed into plastic bags to be deposited at the Highlands Biological Station.
We identified small mammals to species by dentition and other distinctive
cranial characteristics (Caldwell and Bryan 1982, Pivorun et al. 2006). In
many cases, shrew skulls were missing diagnostic unicuspid teeth, but we
were able to make positive identifications through comparisons with reference
Species were characterized as present or absent at each study site. We
used correlation analysis to examine relationships of elevation and habitat
moisture with the relative abundance of each shrew species (Zar 1999).
Segregation of Masked Shrews and Southeastern Shrews were analyzed
using Student’s t-tests for elevation, and Mann-Whitney U-tests for habitat
moisture class (Zar 1999). To assess patterns of soricid diversity, we grouped
the total number of captures and site occurrences for each species by habitat
moisture class and by 300-m intervals (Ford et al. 2001), and differences between
these groups in overall shrew capture rates (# shrews / # open bottles)
and species richness (S) were examined using chi-square (χ2) goodness-of-fit
tests (Zar 1999).
2010 M.P. Brannon, M.A. Burt, D.M. Bost, and M.C. Caswell 785
We examined a total of 10,461 bottles at 220 sites throughout the region
(Fig. 1). Of this total, 6145 (58.7%) of the bottles were open and served as
potential traps for small mammals, with an average of 27.9 open bottles per
site. Skeletal remains were found at 138 (62.7%) of the sites and in 4.5% of
the open bottles we examined, with a mean (± 1 SE) of 2.6 ± 0.3 specimens
per site (range = 0–30).
Bottles contained a total of 553 specimens of small mammals, representing
5 species of shrews and 6 species of rodents (Table 1). Unlike Benedict
and Billeter (2004), we collected skeletal remains in abundance from both
glass and plastic bottles. Multiple specimens (x̅ = 2.1 ± 0.2) were frequently
extracted from individual bottles, especially from ones positioned at steep
angles or those containing rainwater (Morris and Harper 1965, Pagels and
French 1987). The most collected from a single bottle was 22 skulls, representing
3 species of small mammals. Overall capture rate for small mammals
(total # animals / total number of open bottles) was 9.0% across all sites
(Table 1), but was more than 12.3% at elevations >900 m and in mesic habitats
(moisture classes 4 and 5). Bottles also captured 1 Desmognathus ocoee
Nicholls (Ocoee Salamander), 4 Plethodon metcalfiBrimley (Gray-cheeked
Salamander), 2 P. serratus Grobman (Southern Red-backed Salamander),
and 1 Carphophis amoenus (Say) (Eastern Worm Snake). We also found in
bottles an abundance of invertebrates, consisting primarily of beetles, millipedes,
Individually, the small-mammal species with the highest incidence of
capture (5.4%) was the Northern Short-tailed Shrew (n = 332, 59.9% of
Table 1. Summary of small-mammal captures and site occurrences based on 6145 open bottles
and 220 sites. Skeletal remains were collected from discarded bottles along the southeastern
Blue Ridge escarpment of North Carolina, South Carolina, and Georgia from September 2007 to
November 2009. % = percentage of captures. Overall capture rate (CR) was defined as # animals
/ total # open bottles and is given as %. Site = site occurrence.
Family and Species Common name n % CR Site
Blarina brevicauda (Say) Northern Short-tailed Shrew 332 59.9 5.4 94
Sorex fumeus (Miller) Smoky Shrew 105 19.0 1.7 58
S cinereus Kerr Masked Shrew 30 5.4 0.5 26
S. longirostris Bachman Southeastern Shrew 6 1.1 0.1 6
S. hoyi (Baird) Pygmy Shrew 5 0.9 0.1 3
Peromyscus maniculatus Wagner Deer Mouse 36 6.5 0.6 22
P. leucopus (Rafinesque) White-footed Mouse 27 4.9 0.4 15
Microtus pinetorum (Le Conte) Woodland Vole 5 0.9 0.1 5
(Audubon and Bachman) Eastern Harvest Mouse 5 0.9 0.1 1
Myodes gapperi (Vigors) Southern Red-backed Vole 1 0.2 <0.1 1
Ochrotomys nuttalli (Harlan) Golden Mouse 1 0.2 <0.1 1
Totals 553 9.0
786 Southeastern Naturalist Vol. 9, No. 4
captures), which we found at 94 (42.7%) of our study sites (Table 1). It
was widely distributed across a variety of elevations (Table 2) and habitats
(moisture class range = 2–5; Table 3) throughout the region (Fig. 2a). Mean
elevation for this species was 815.5 ± 26.9 m (range = 361–1336 m). The
presence of Northern Short-tailed Shrews was not significantly correlated
with elevation (r = 0.01, df = 218, P = 0.85) or habitat moisture (r = 0.11,
df = 218, P = 0.10).
Table 2. Occurrence (site) and abundance (n) of individual shrew species at sites within each
300-m elevational range. Specimens were collected from discarded bottles along the southeastern
Blue Ridge escarpment of North Carolina, South Carolina, and Georgia from 2007 to 2009.
Capture rate was defined as # shrews / # open bottles.
<300 m 300–599 m 600–899 m 900–1199 m ≥1200 m
Species Site n Site n Site n Site n Site n
Northern Short-tailed Shrew 0 0 25 87 29 104 35 132 5 9
Smoky Shrew 0 0 3 6 16 25 36 67 3 7
Masked Shrew 0 0 0 0 3 4 16 18 7 8
Southeastern Shrew 1 1 3 3 2 2 0 0 0 0
Pygmy Shrew 0 0 0 0 1 1 2 4 0 0
No. of sites: 4 53 71 80 12
No. of open bottles: 187 1734 2142 1840 242
Total No. of shrews: 1 96 136 221 24
Overall capture rate (%): 0.5 5.5 6.4 12.0 9.9
Species richness (S): 1 3 5 4 3
Table 3. Occurrence and abundance of individual shrew species at sites in habitat moisture
classes 1 to 5, most xeric to most mesic. Specimens were collected from discarded bottles along
roads on the southeastern Blue Ridge escarpment of North Carolina, South Carolina, and Georgia
from 2007 to 2009. Capture rate was defined as # shrews / # open bottles.
1 2 3 4 5
Species Site n Site n Site n Site n Site n
Northern Short-tailed Shrew 0 0 15 38 23 100 28 97 28 97
Smoky Shrew 0 0 3 6 9 15 21 41 25 43
Masked Shrew 0 0 0 0 0 0 11 14 15 16
Southeastern Shrew 1 1 4 4 1 1 0 0 0 0
Pygmy Shrew 0 0 0 0 1 1 1 1 1 3
No. of sites: 6 45 51 56 62
No. of open bottles: 223 1606 1410 1388 1518
Total No. of shrews: 1 48 117 153 159
Overall capture rate (%): 0.5 3.0 8.3 11.0 10.5
Species richness (S): 1 3 4 4 4
Figure 2 (opposite page). Distributions of individual shrew species along the southeastern
Blue Ridge escarpment based on skeletal remains found in discarded roadside
bottles: (a) Northern Short-tailed Shrew, (b) Smoky Shrew, and (c) Masked Shrew
(dots), and Southeastern Shrew (triangles).
2010 M.P. Brannon, M.A. Burt, D.M. Bost, and M.C. Caswell 787
788 Southeastern Naturalist Vol. 9, No. 4
Smoky Shrews also were collected in abundance (n = 105, 19.0% of
small-mammal captures) at many sites (n = 58 sites, 26.4%; Table 1). This
species was distributed across a wide range of elevations (Table 2) and moisture
classes (range = 2–5; Table 3) in the region, although more commonly
in North Carolina (Fig. 2b). The southernmost locality for Smoky Shrews in
our survey was near the Chattooga River at Hwy 76 in Oconee County, SC,
at an elevation of 486 m. Occurrence of this species was significantly greater
at higher elevations (r = 0.29, df = 218, P < 0.01) and in more mesic environments
(r = 0.31, df = 218, P < 0.01). Mean elevation for Smoky Shrews was
940.1 ± 25.4 m (range = 448–1238 m).
Fewer Masked Shrews were collected than larger species of shrews (n =
30; 5.4% of captures), and were found at fewer sites (n = 26 sites; 11.8%).
This species also was more restricted in its altitudinal (Table 2) and habitat
distribution (moisture class range = 4–5; Table 3) along the southeastern
Blue Ridge escarpment. Masked Shrews were collected only in North Carolina
(Fig. 2c) at high elevations (r = 0.43, df = 218, P < 0.01) and exclusively
in moist habitats such as northern hardwood and cove hardwood-montane
streamside communities (r = 0.32, df = 218, P < 0.01). Mean elevation for
Masked Shrews was 1126.7 ± 27.4 m (range = 812–1368 m).
Southeastern Shrews (n = 6; 1.1% of captures) were collected from 6
(2.7%) of our study sites (Table 1), but were significantly segregated from
Masked Shrews by both elevation (t = 9.60, df = 30, P < 0.01) and habitat
(U = 156, n1 = 6, n2 = 26, P < 0.01). This species was associated with lower
altitudes (r = -0.185, df = 218, p < 0.01; Table 2) in South Carolina and
Georgia (Fig. 2c) and with more xeric environments (r = -0.211, df = 218,
P < 0.01), such as mixed hardwood-pine communities (moisture class range
= 1–3; Table 3). Mean elevation for Southeastern Shrews was 503.7 ± 64.9
m (range = 255–728 m).
Pygmy Shrews are widely distributed in a diversity of vegetational
communities and elevations across the Blue Ridge, but appear to be locally
uncommon (Johnston 1967, Laerm et al. 2000b). Because in our surveys this
species was found at only 3 sites (Table 1), we excluded it from individual
statistical analyses. The few Pygmy Shrews that we did collect (n = 5; 0.9%
of captures) occurred at high altitudes (Table 2) in North Carolina and South
Carolina, and in mesic environments (range = 3–5; Table 3). Mean elevation
for Pygmy Shrews was 1049.0 ± 87.7 m (range = 882–1179 m).
Overall soricid capture rates differed significantly among both elevational
ranges (χ2 = 10.55, df = 3, P < 0.05) and habitat moisture classes (χ2 =
12.17, df = 3, P < 0.05). Capture rate for shrews was highest at altitudes
from 900–1199 m (12.0%; Table 2) and in mesic northern hardwood habitats
(moisture class 4; 11.0%; Table 3). No significant differences existed
for shrew species richness among elevational ranges (χ2 = 2.74, df = 3, P >
0.05) or moisture classes (χ2 = 2.12, df = 3, P < 0.05), although it was greatest
(S = 5) within the intermediate range of elevations (600–899 m) where
Masked Shrews and Southeastern Shrews co-occur near their altitudinal
demarcation (Table 2), albeit in different habitats (Table 3).
2010 M.P. Brannon, M.A. Burt, D.M. Bost, and M.C. Caswell 789
Increases in species richness along elevational gradients are a function
of many complex ecological interactions (Ford et al. 2006, Rickart 2001).
Soricid diversity is greatest at higher-elevation sites of the southern Appalachians,
where environmental conditions resemble those of more northern
forests (Laerm et al. 1999, Pagels et al. 1994). Shrews are more abundant in
mesic forests than in xeric habitats (Cudmore and Whitaker 1984, Kirkland
1991, Laerm et al. 1999), including those with streams or seeps (Laerm et al.
1997a). Forest communities such as cove hardwoods, northern hardwoods,
and mixed oak-hickory (Carya spp.) generally provide moist and dense
ground cover, high volumes of coarse woody debris in the latter stages of
decay, and abundant invertebrate faunas favorable to most shrews (Brannon
2002a, Gist and Crossley 1975, Greenberg and Forrest 2003).
The wide range of elevations and the varied topography of the Blue
Ridge escarpment provide aspects where xeric forests used by species such
as the Southeastern Shrew are in close proximity to mesic habitats that support
other shrew species such as the Masked Shrew (Brannon 2002a, Ford et
al. 2006). Environmental moisture is especially important to the distribution
of shrews such as the Masked Shrew and Smoky Shrew because it affects
not only their water balance and mobility (Chew 1951, Getz 1961), but also
the abundance and accessibility of invertebrate prey (Brannon 2002b, Gist
and Crossley 1975, McCay and Storm 1997). However, greater numbers
of shrews collected from bottles in moist forest habitats may only reflect
increased epigeal movement (Brannon 2002b, McCay 1996), and not actual
species abundance (Ford et al. 2002).
In mesic forests, soricid communities are not random but rather appear
to follow a pattern where ecological separation is achieved through differential
exploitation of common resources by species of dissimilar body size
(Brannon 2000, Fox and Kirkland 1992, Kirkland 1991). Most areas of the
Blue Ridge are dominated by large-sized (Northern Short-tailed Shrew) and
medium-sized (Smoky Shrew) habitat generalists, associated with a less
abundant and more specialized small-sized species (Masked Shrew) and
an uncommon smaller-sized habitat generalist (Laerm et al. 1999, Kirkland
1991, McCay et al. 2004) such as the Pygmy Shrew (Laerm et al. 2000b).
Other species such as Sorex dispar Batchelder (Rock Shrew) or S. palustris
Richardson (Water Shrew) sometimes also occur, but fill specialized niches
(Kirkland 1991) and are generally rare (Johnston 1967; Laerm et al. 1995b,
The Northern Short-tailed Shrew is the species of small mammal most
frequently trapped in bottles (Benedict and Billeter 2004, Pagels and
French 1987). It is one of the most common and widespread of all the small
mammals in the Blue Ridge (Johnston 1967, Laerm et al. 1999, Mengak et
al. 1987) and, like in our study, has been collected previously from a variety
of elevations and vegetational communities (George et al. 1986, Laerm
et al. 1999). Northern Short-tailed shrews are usually associated with areas
790 Southeastern Naturalist Vol. 9, No. 4
having dense ground cover such as rocks, logs, and a deep leaf-litter layer
(Getz 1961, Kitchings and Levy 1981), which most sites in our study area
provided. Smoky Shrews are most abundant in mesic forest communities
with considerable structural debris (Brannon 2000, 2002a; Cudmore and
Whitaker 1984; Owen 1984), but are occasionally present in more xeric
habitats such as dry south-facing slopes, ridgelines, and meadows (Laerm
et al. 1999). Although they generally have a more northern distribution,
Smoky Shrews have been reported previously from the mountainous regions
of South Carolina in suitable habitats (Johnston 1967, Mengak et
al. 1987), as in our study. River gorges in this region are refugia of more
typical northern forest communities (Laerm et al. 1995a), and may provide
corridors that also facilitate dispersal of Smoky Shrews southward to lower
altitudes (Johnston 1967).
The lower elevational distribution limit of 812 m for Masked Shrews and
the higher elevational distribution limit of 728 m for Southeastern Shrews
observed in our surveys are consistent with the findings of Ford et al. (2001),
and show an increasing north-to-south elevation cline demarcating segregation
between these two species (Ford et al. 2006). Masked Shrews have been
reported from isolated localities in the Blue Ridge region of Georgia and
South Carolina at elevations as low as 610 m (Laerm et al. 1995a, 1999),
but maintain a continuous distribution at higher elevations in North Carolina
(Ford et al. 2001, Johnston 1967). They are uncommon at low elevations
(Laerm et al. 1995a), and are generally restricted to mesic habitats with more
northern affinities and with substantial ground cover (Brannon 2002a, Laerm
et al. 1999, Pagels et al. 1994). The Masked Shrew appears to exhibit contiguous
allopatry with Southeastern Shrews based upon altitudinal and habitat
gradients (Ford et al. 2001, Pagels and Handley 1989), where its functional
role as a small-sized habitat specialist is replaced by the Southeastern Shrew
farther south at low elevations and in xeric habitats (Laerm et al. 1999).
Although diminutive species of Sorex may be less abundant naturally in
southern Appalachian forests than larger habitat generalists such as Smoky
Shrews and Northern Short-tailed Shrews (Laerm et al. 1999, 2000b), bottles
often underestimate their true population sizes (Gerard and Feldhamer 1990)
and may reduce reliability of analyses (Benedict and Billeter 2004). Tiny
bones may decompose or be scavenged more quickly, and fragments may
be more easily overlooked (Benedict and Billeter 2004). For example, we
collected 6 Southeastern Shrews at 220 sites, whereas Ford et al. (2001)
captured 217 at 101 sites using pitfalls. Similarly, we collected 30 Masked
Shrews compared to 2442 captured by Ford et al. (2001). It is also possible
that bottles may not as effectively trap smaller species of shrews (Gerard and
Nevertheless, our study demonstrates the utility of discarded bottles as
an alternate source of small-mammal distributional and taxonomic data,
and is one of the few to use bottles as a survey technique to delineate the
ranges of shrew species over a wide geographic region (Pagels and French
2010 M.P. Brannon, M.A. Burt, D.M. Bost, and M.C. Caswell 791
1987, Pagels and Handley 1989). This method was far less time- and laborintensive
than traditional methods such as pitfall-trapping (Ford et al. 1997,
Hanley and Kalko 1993, Kirkland and Sheppard 1994, McCay et al. 1998),
yet yielded results comparable to those of previous studies from a community
composition standpoint (Ford et al. 2001, Laerm et al. 1999). Because
discarded bottles are already in place and function continuously, distributional
gaps may be filled in a very short period and reduce the necessity of
overnight trapping (Pagels and French 1987). Furthermore, discarded bottles
sample small-mammal populations without the added mortality that occurs
from pitfall- or snap-trapping (Kalko and Handley 1993, Kirkland and
Sheppard 1994, Taulman et al. 1992). Although bottles may be an inferior indicator
of actual species abundances (Benedict and Billeter 2004, Gerard and
Feldhamer 1990) and are ineffective in short-term studies involving activity
patterns (Taulman et al. 1992), the geographic distributional information
obtained from bottles for general taxonomic surveys may be limited only by
the area sampled and the diversity of the small-mammal fauna (Pagels and
Although concentrations of bottles at our limited study sites may not
be representative of the entire region, our finding of 4.5% of open bottles
containing vertebrates is consistent with that of Benedict and Billeter (2004)
for areas with high levels of human disturbance. But because a single bottle
can entrap multiple animals, overall capture rates for small mammals may
be alarmingly higher, especially in areas with high soricid diversity. Pagels
and French (1987) estimated mortality as 24 to 71 small mammals per km
at sites across Virginia, but it may exceed 183 animals per km in areas with
larger accumulations of bottles (Benedict and Billeter 2004). Many rural localities
with vehicle parking, such as our study sites, serve as illegal garbage
dumps which may reduce the local abundance of individual shrew species
(Courtney and Fenton 1976), including some listed as threatened or of special
concern (Laerm et al. 2000a). In mountainous terrain, bottles often roll
down steep slopes where they remain undetected by road cleanup crews and
may function as traps for extremely long periods. Although we do not know
exactly when individual animals were captured (Gerard and Feldhamer
1990), we determined that many of the bottles in our study that contained
specimens were years or even decades old, based on their designs and label
information. With such a large number of potential trap-nights represented,
accumulations of open bottles along roadways in the southern Appalachians
pose a considerable mortality risk to small mammals (Benedict and Billeter
2004, Pagels and French 1987), especially shrews (Clegg 1966, Morris and
Portions of this study were conducted through the University of North Carolina at
Chapel Hill’s 2007 and 2008 Institute for the Environment program at the Highlands
Biological Station. We thank Brennan Bouma, James T. Costa, and Anya Hinkle for
792 Southeastern Naturalist Vol. 9, No. 4
their support of this project, and Gary Wein for his assistance in generating maps
from our GIS data. We also thank W.M. Ford and two anonymous reviewers for their
helpful suggestions for revisions to this manuscript.
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