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2015 SOUTHEASTERN NATURALIST 14(3):506–516
Small-Mammal Mortality Caused by Discarded Bottles
and Cans along a US Forest Service Road in the Cherokee
National Forest
M. Kevin Hamed1,* and Thomas F. Laughlin2
Abstract - Discarded containers along primary and secondary roadways trap and kill small
mammals, and recently, small-mammal remains were found in containers along roadside
pull-offs in more remote areas. We investigated the effects of containers along 7.9 km of
a graveled, 2-lane forest service road in a remote area of the Cherokee National Forest,
TN. We examined 2997 containers, of which 107 containers had 202 small-mammal skulls
representing 8 species of mammals including Sorex fumeus (Smoky Shrew), Sorex longirostris
(Southeastern Shrew), and Synaptomys cooperi (Southern Bog Lemming), which are
deemed species of greatest conservation need and in need of management by the Tennessee
Wildlife Resource Agency. Our observation of Southern Bog Lemming mortality due to
container debris is the first report of collection of this species from bottles. We recorded the
first observation of shrew mortality caused by aluminum cans, where 1% of all aluminum
cans contained shrew skulls. Unlike previous studies, we quantified all possible containers
available to trap small mammals and found glass disproportionately trapped more small
mammals than plastic or aluminum. Additionally, we determined the orientation of bottle
and can openings for all available containers and found that containers oriented upslope
(>15°) were significantly more likely to be associated with the mortality of small mammals
than containers in other orientations. We estimated that a mean of 25.6 small mammals/km
were killed in discarded containers. By using bottling dates on containers, we also estimated
containers were in place along the road an average of 2.16 ± 0.37 years before discovery.
Only using modern bottles with dates, we conclude that the minimal potential impact on
small-mammal populations was at least 973 small mammals killed per year in container
debris along graveled category 3 and 4 forest service roads in the Cherokee National Forest.
Introduction
Roads may markedly affect small-mammal populations by creating barriers
to movement, increasing mortality from vehicles, and increasing opportunities
for predation (Oxley et al. 1974). Discarded bottles along roadways and roadside
pull-offs are a source of additional mortality by acting as traps for small mammals
(Benedict and Billeter 2004, Brannon et al. 2010). Bottles containing rodent
and shrew remains were first found along British roadways in the 1960s (Morris
and Harper 1965), and similar findings were reported for discarded bottles in Italy
(Debernardi et al. 1997). Numerous studies in the US have also demonstrated smallmammal
mortality based on the presence of skulls in bottles (Benedict and Billeter
1Virginia Highlands Community College, PO Box 828, Abingdon, VA 24212. 2Department
of Biological Sciences, East Tennessee University, Johnson City, TN 37614. *Corresponding
author - khamed@vhcc.edu.
Manuscript Editor: Roger W. Perry
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2004, Brannon et al. 2010, Gerard and Feldhamer 1990, Pagels and French 1987).
Small mammals most likely become trapped in bottles and die by starvation or
drowning (Benedict and Billeter 2004).
Previous studies investigated the impact of bottles along well-traveled primary
and secondary highways (Benedict and Billeter 2004, Gerard and Feldhamer 1990,
Pagels and French 1987). Discarded containers killed up to 183 vertebrates/km
along primary roads (Benedict and Billeter 2004). Recently, containers near roadside
pull-off sites along primary and secondary roads in mountainous areas of the
Blue Ridge Mountains were identified as sources of mortality, with small-mammal
remains found in 4.7% of all open bottles (Brannon and Bargelt 2013). Ten percent
of all US roadways are located within national forest lands and over 2500 km are
within the Cherokee National Forest (CNF), but mortality associated with discarded
containers along national forest roadways has not been investigated, and the potential
impact to small mammals is unknown (Forman and Alexander 1998).
Shrews from the genus Sorex prefer mature forested habitat or edges and may
be especially vulnerable to becoming trapped in discarded, open containers along
forest service roads that often pass through forest stands (Brannon and Bargelt
2013, Ford et al. 1997, Laerm et al. 1999). Additionally, the southern Appalachian
Mountains support one of the most diverse Soricidae faunas in North America
(Berman et al. 2007, Ford et al. 2005, Laerm et al. 1999). Six species of small
mammals reported from the CNF and previously captured in bottles from areas
within the southern Appalachian Mountains have conservation status as designated
by the Tennessee Wildlife Resource Agency (TWRA), Tennessee Natural
Heritage Program (TNHP), and/or US Forest Service (USFS; Table 1; TNHP
2009, TWRA 2005, USDA 2004). Sorex cinereus (Masked Shrew), S. longirostris
(Southeastern Shrew), and S. fumeus (Smoky Shrew) are classified each as a
species of greatest conservation need and deemed in need of management by the
TWRA as well as an S4 species (uncommon, but not rare) species by the TNHP
Table 1. Conservation status of rare small mammals collected from bottles within the southern Appalachian
Mountains that also occur within the CNF (Brannon and Bargelt 2013, Brannon et al. 2010).
TWRA GCN = Tennessee Wildlife Resource Agency designation of species of greatest conservation
need, TWRA D = TWRA deemed in need of management, X = status granted. TNHP SRANK = Tennessee
Natural Heritage Program (TNHP) state rank. USFS FRANK = US Forest Service (USFS)
forest ranking (USFS 2004). S2 = very rare and imperiled, S3 = vulnerable, S4 = uncommon, but not
rare, F1 = extremely rare on the forest unit, and F3 = rare and uncommon on the forest unit. The present
study documented the first bottle mortality for the Southern Bog Lemming.
TWRA TNHP USFS
Species Common name GCN TWRA D SRANK FRANK
Sorex fumeus (Miller) Smoky Shrew X X S4 -
S. cinereus (Kerr) Masked Shrew X X S4 F3
S. longirostris (Bachman) Southeastern Shrew X X S4 -
S. hoyi (Baird) Pygmy Shrew X - S2 -
Parascalops breweri (Bachman) Hairy-tailed Mole - X S3 F1
Synaptomys cooperi (Baird) Southern Bog Lemming X X S4 F1
Ochrotomys nuttalli (Harlan) Golden Mouse X - - -
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(Table 1; TNHP 2009, TWRA 2005). Bottles have been identified as a source of
mortality for both Smoky Shrews and Southeastern Shrews, with trap rates as
high as 46.4/km along primary roads (Benedict and Billeter 2004, Brannon et al.
2010). Mortality associated with discarded containers along forest service roads
could impact populations of uncommon small mammals. Our objective was to
determine the impact of bottle and can debris on small mammals along a graveled
double-lane forest service road in the CNF. Additionally, we quantified bottle and
can attributes to determine if material type or color, orientation, or distance from
the road influenced small-mammal mortality from discarded containers.
Field-site Description
Our study site was located in the CNF (Sullivan County, TN) along Flatwoods
Road (USFS Road 87) at elevations of 618–695 m. We sampled a total road length of
7.9 km beginning 0.6 km from the national forest property boundary (36.46824ºN,
82.12302ºW) and ending 100 m past the junction with Big Creek Road (USFS Road
87D; 36.4918ºN, 82.0689ºW). This road section had 2 lanes and a graveled surface
and shoulders, with a mean (± 1 SE) width of 7.0 ± 0.3 m. It is classified as a USFS
category 4 road (moderate degree of user comfort at moderate travel speeds) for 7.5
km, with a few sections (total 0.4 km) classified as category 3 road (maintained for
travel by prudent drivers in standard passenger cars; USFS 2005). The mean width
of the herbaceous vegetated area between the road shoulder and forest edge was 4.2
± 0.7 m. The majority of the study area was forest-edge habitat, and the time since
last logging was ~50 years. The forest was mixed deciduous and southern Appalachian
oak (Quercus spp.) forest. A powerline right-of-way created additional edge
habitat along Flatwoods Road at a single crossing.
Methods
We sampled containers along Flatwoods Road from 2 April to 30 April 2004 (4.2
km) and from 25 March to 22 April 2005 (3.7 km). We examined all open containers
within 10 m of the road edge and excluded closed containers that prevented bottle
access by small mammals. To locate containers, we walked along the road edge
and searched for containers visually and also examined containers we stepped on
that were hidden by leaf litter. We recorded the container material, color, size, and
distance from the road shoulder. We listed container size as the volume printed on
the container (e.g., 355 ml/12 oz), and classified container material as glass, plastic,
aluminum, or steel. We also noted the orientation of the container opening in relation
to a level plane (i.e., an upslope bottle was at an angle with the opening ≥15°
higher than the bottom of the bottle and was facing upslope). In order to separate
skulls and skull fragments from fur and other debris, we poured container contents
through a sieve and removed bones. We returned skulls to the laboratory for identification,
but left all other container contents (e.g., water, invertebrates, debris, fur,
and other natural material) at the collection site.
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To determine container parameters, we retrieved a random subset of glass bottles
(n = 10; 355-ml glass bottles) and all aluminum cans (n = 3; 355 ml) that contained
small-mammal remains. We used SPI dial calibers (Wiha model 31-415-3, Schonach,
Germany) to measure the widest opening of the container and an Ohaus Scout
Pro scale (model SPE 123, Parsippany, NJ) to determine empty container mass. To
estimate the length of time bottles and cans were present in the forest, we recorded
production dates found on container labels with small-mammal remains and took
the difference from when we found the container. We quantified the number of
small mammals/km/year by using dated bottles and cans containing small-mammal
skulls. Our estimate of container longevity was somewhat greater than the actual
period because bottles were not placed in the forest on the production date, nor did
small mammals enter the bottle on the discovery date, but we utilized this approach
to standardize our approximation of deposition dates and species-mortality rates.
Also, dates were only available on bottles produced since the mid-1990s; older
bottles lacked production dates. Thus, our mortality-rate estimates should be considered
the minimum possible mortality without the impact of older bottles.
We identified skulls in the laboratory under a Nikon SMZ-2T stereomicroscope
(Melville, NY). Some skulls required removal of tissue by Dermestes maculatus De
Geer (Dermestid Beetles), but most were clean. We utilized small-mammal dichotomous
keys developed to identify animals with whole bodies and skulls (Barbour
1974, Linzey 1998). Additionally, we used information from previous morphological
studies and species descriptions to identify skulls or skull fragments with teeth
(French 1980, George et al. 1986, Owens 1984, Smolen 1981).
We employed chi-square goodness-of-fit tests to examine potential associations
of small-mammal mortality with material composition, color, or the positioning of
the container opening (IBM 2011). We used each km searched as our sampling unit
to determine both containers and skulls/km. We established the mean number of
individual species/bottle using only containers with skulls of each species. Finally,
we used linear regression to determine if observed mortality was a function of distance
from the road (IBM 2011).
Results
We examined a total of 2997 containers (381.6 ± 33.1 containers/km), and material
composition was 84.8% glass, 10.3% aluminum, 4.8% plastic, and 0.1% steel
(Table 2). Container volumes ranged from 162.7 ml (5.5 oz) to 1182.9 ml (40 oz).
Brown glass was the most common container type (64.9%), clear glass comprised
14.9%, and green glass comprised 4.9% of all containers found ( Table 2).
A total of 107 bottles and cans (3.6% of all containers found) contained the
remains of 202 small mammals, with a mean of 1.9 ± 0.2 small mammals per container
with remains (Table 3). We detected most skulls (95.5%) in glass containers
(Table 3). We collected the largest number of skulls found in a single container—8
skulls: 7 Blarina brevicauda Say (Northern Short-tailed Shrew) and a single Smoky
Shrew—from a 650.5-ml brown-glass bottle. We recorded skulls of the smallest
shrews (Smoky and Southeastern Shrews) in aluminum cans, which is the first
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reported mortality in this container type. Aluminum cans contained 2.5% of all
skulls, and 1.0% of all aluminum cans found contained skulls (Table 2). Mortality associated
with all containers resulted in an average of 25.7 ± 5.2 small mammals/km.
We identified 8 species (3 shrews and 5 rodents; Table 3) among the 202
small-mammal skulls collected. The largest percentage of skulls found (66.3%;
n = 134) were Northern Short-tailed Shrews, the majority (69.4%) of which were
in brown-glass bottles (Table 3). Of bottles that contained Northern Short-tailed
Shrew skulls, there was a mean of 1.8 ± 0.2 skulls/container, and containers often
trapped more than 1 individual (range = 1–7 individuals/bottle). The second most
commonly detected species was the Smoky Shrew (n = 29; 14.4% of all skulls;
Table 3). Brown-glass bottles contained the majority of the Smoky Shrews (58.6%),
whereas aluminum cans trapped 13.8%. There were 1.3 ± 0.1 skulls/container in
cans and bottles containing Smoky Shrews, also reflecting the common occurrence
of multiple captures within a single container for this species. Southeastern Shrew
skulls were relatively uncommon (2.5% of skulls), and mortality of these animals
had no apparent associations with container type or coloration. We infrequently
Table 3. Number of mammals found per container type along 7.5 km of class 4 and 0.4 km of class 3
US Forest Service roads in the Cherokee National Forest, Sullivan County, TN, from 2 April–30 April
2004 and 25 March–22 April 2005.
Glass Plastic Aluminum
Species Brown Clear Green Clear Green Cans Total
Northern Short-tailed Shrew 93 33 6 2 - - 134
Smoky Shrew 17 5 3 - - 4 29
Southeastern Shrew 2 1 1 - - 1 5
White-footed Mouse 14 3 - 1 1 - 19
Deer Mouse 4 - - - - - 4
Woodland Vole 7 - - - - - 7
Southern Bog Lemming - 2 - - - - 2
House Mouse 1 - - - - - 1
Unidentified - 1 - - - - 1
Total 138 45 10 3 1 5 202
Table 2. Characteristics of containers found along 7.5 km of class 4 and 0.4 km of class 3 US Forest
Service roads in the Cherokee National Forest, Sullivan County, TN, from 2 April–30 April 2004 and
25 March–22 April 2005. Al. = aluminum.
Glass Plastic Al.
Brown Clear Green Blue Total Clear Green White Total Cans Steel
# of containers found 1945 445 147 2 2539 95 47 4 146 310 2
Containers with skulls 73 22 6 0 101 2 1 0 3 3 0
# of skulls/container type 138 45 10 0 193 3 1 0 4 5 0
% of all containers found 64.9 14.9 4.9 0.1 84.8 3.2 1.5 0.1 4.8 10.3 0.1
% with skulls 3.8 4.9 4.1 0.0 - 2.1 2.1 0.0 - 1.0 0.0
% of all skulls found in 68.3 22.2 5.0 0.0 - 1.5 0.5 0.0 - 2.5 0.0
each container type
# of skulls/container type/km 21.90 7.14 1.59 0.00 - 0.48 0.16 0.00 - 0.79 0.00
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found remains of Peromyscus leucopus Rafinesque (White-footed Mouse) in containers
(n = 19; 9.5% of all skulls; Table 3). Of containers with White-footed Mice,
73.7% were in brown-glass bottles (Table 3). We recorded smaller numbers of
P. maniculatus Wagner (Deer Mouse; n = 4), Microtus pinetorum Le Conte (Woodland
Vole; n = 4), and Mus musculus L. (House Mouse; n = 1), and all were all found
in brown-glass bottles. Clear-glass bottles contained Southern Bog Lemmings (n =
2; Table 3) and an unidentified skull, which appeared to be a Peromyscus sp.
Glass containers trapped the largest number of small mammals. More glass
containers and fewer aluminum or plastic containers were related to mortality than
expected based on container availability (χ2 = 18.48, P = 0.004). Thus, glass appears
to be disproportionately associated with trapping and mortality of small mammals.
However, glass color was not related to small-mammal mortality (χ2 = 4.05, P =
0.26). Only Northern Short-tailed Shrews, Smoky Shrews, and White-footed Mice
were found in sufficient numbers to determine if their occurrence was associated
with a container type and color. Northern Short-tailed Shrew mortality was associated
with brown-glass and clear-glass bottles but not with aluminum cans (χ2 =
20.15, P = 0.0002). However, mortality of Smoky Shrews and White-footed Mice
was not associated with any particular type of container (χ2 = 2.23, P = 0.47; χ2 =
3.26, P = 0.35, respectively). We did not detect an association of container type for
all Peromyscus spp. combined (χ2 = 5.42, P = 0.37).
Containers with skulls averaged 4.24 ± 0.19 m from the road. There was a significant
positive relationship between distance from the road shoulder and the presence
of small-mammal remains (r = 0.76, P < 0.01). Containers found with the opening
oriented upslope contained significantly more skulls (77.8%) than those that were
perpendicular to the slope (18.5%) or those pointing downslope (3.7%; χ2 = 360.31,
P < 0.01). The estimated mean time that a subsample of bottles and cans were present
in the forest was 2.16 ± 0.37 years, based on containers that had production dates
(n = 13). We found a total of 21 skulls in 13 dated bottles and cans. Given the age
of the bottles, the number of remains found in them, and the distance surveyed, we
estimated a minimum of 1.21 small mammals killed/km/year in containers that had
small-mammal remains in them.
The mean weight of ten 354.9-ml (12 oz) brown-glass bottles that contained
skulls was 188.65 ± 2.55 g. The mean diameter of brown-glass bottle openings was
19.39 ± 0.01 mm. The mean weight of three 354.9 ml aluminum cans was 14.13 ±
0.19 g, and the mean opening diameter was 11.23 ± 0.01 mm.
Discussion
Small-mammal mortality from discarded containers has been observed on
well-traveled paved roads and pull-off areas (Benedict and Billeter 2004, Brannon
and Bargelt 2013, Brannon et al. 2010, Morris and Harper 1965). We found
that containers along a graveled national forest road (Flatwoods Road) also contributed
to small-mammal mortality. Past studies did not detect small-mammal
remains in aluminum cans (Benedict and Billeter 2004, Gerard and Feldhamer
1990, Pagels and French 1987); thus, aluminum cans were excluded from more
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recent studies (Brannon and Bargelt 2013, Brannon et al. 2010). However, we
documented both Smoky and Southeastern Shrews in aluminum cans, indicating
this refuse may be an important source of mortality. Containers along Flatwoods
Road captured uncommon mammals of conservation concern. In this study, approximately
18% of all captures were uncommon small mammals, including the
first record of container-caused mortality of Southern Bog Lemming. Comparatively,
a previous study along primary roads found less than 5% of all captures
were uncommon species (Benedict and Billeter 2004). This difference is likely
because most of Flatwoods Road passes through forested habitat and the roadassociated
edge habitat, both of which are appropriate to support these species.
Shrews in the southern Appalachians are habitat generalists or prefer either forest
or edge habitats (Ford et al. 1997, Laerm et al. 1999, Linzey 1998). The species
richness we observed in containers along a forest service road (8 species) was
similar to findings along primary roads (7 species; Benedict and Billeter 2004).
However, compared to our study, roadside pull-offs had greater species richness
(11 species; Brannon et al. 2010), which was most likely due to a greater elevational
range (255–1336 m) surveyed, encompassing ranges of both higher- and
lower-elevation species (i.e., Sorex cinereus Kerr [Masked Shrew] and Southeastern
Shrew; Brannon et al. 2010, Ford et al. 2005).
In comparing small-mammal mortality along Flatwoods Road to other primary
roads and pull-offs, the number of possible containers available to trap
small mammals varied. Primary roads, including interstate ramps, averaged 2461
bottles/km (Benedict and Billeter 2004), secondary roads averaged 577 bottles/
km (Pagels and French 1987), and roadside pull-offs averaged 239.2 bottles/km
(Brannon and Bargelt 2013). Flatwoods Road had considerably fewer bottles
(381.6/km) than primary roads and was somewhat comparable to secondary roads
and roadside pull-offs. Greater numbers of bottles provide more opportunities to
trap small mammals, and any comparisons of mortality/km could be skewed for
primary roads. Additionally, containers at roadside pull-offs were often clustered,
which could also lead to an unequal comparison (Brannon et al. 2010). We believe
the percentage of containers with small-mammal remains provides a better
comparison between different road types. Along primary roads, 4% of containers
were found with remains (Benedict and Billeter 2004) and 4.5% of containers at
roadside pull-offs had remains (Brannon et al. 2010). Slightly fewer containers
along Flatwoods Road contained remains (3.6%). However, we included aluminum
cans, which reduced our percentage compared to other studies. Just counting
bottles, 3.9% contained remains, which was still slightly less than primary roads
and roadside pull-offs.
As with primary roads and roadside pull-offs, containers along Flatwoods Road
often trapped multiple individuals (mean 1.9 ± 0.2/container with small-mammal
remains); mean skulls/bottle ranged from 1.9 to 3.7 in past studies (Benedict
and Billeter 2004, Brannon and Bargelt 2013, Brannon et al. 2010, Gerard and
Feldhamer 1990). The maximum number of skulls found in a single bottle along
Flatwoods Road (8) was less than from bottles along primary roads (19; Benedict
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and Billeter 2004), secondary roads (39; Gerard and Feldhamer 1990), and roadside
pull-offs (22; Brannon et al. 2010). Large bottles often contained greater numbers
of skulls than smaller bottles (Benedict and Billeter 2004). Differences in studies’
findings could be due to fewer numbers of larger containers at our study site, but a
comparison was not possible because other studies did not quantify container size
(Brannon et al. 2010, Brannon and Bargelt 2013).
There are 805.5 km of category 3 and 4 roads in the CNF. Assuming our mean
mortality rate of 1.21/km/year in containers along these road types, containers have
the potential to kill 973 small mammals/year in the CNF. We established our yearly
estimate using only bottles and cans with dates. Older bottles have the potential to
trap and kill large numbers of small mammals (Brannon et al. 2010), but without
dates we were unable to estimate their impact. Thus, we acknowledge our estimates
are conservative, but provide resource managers an approximation that may inform
their conservation planning.
Similar to Benedict and Billeter (2004), we found glass disproportionately killed
small mammals versus other container types. The size of the container opening
could be excluding larger species (Morris and Harper 1965), and we found aluminum-
can openings to be 8.1 mm narrower than glass bottles. Smaller species, such
as Smoky and Southeastern Shrews, can fit through aluminum-can openings, but
Northern Short-tailed Shrews are too large for aluminum-can openings. Aluminum
cans weighed only 7% of the mean weight of glass containers, potentially allowing
shrews to reposition containers from the upslope position and escape (Benedict and
Billeter 2004). Additionally, the height of bottle openings also might explain fewer
remains of smaller shrews in glass bottles because their openings are much higher
(25 mm) above the forest floor than those of aluminum cans (15 mm) (Gerard and
Feldhamer 1990). Lastly, shrews have a behavior of squeezing through small holes
and would be more likely than rodents to attempt to enter an opening just slightly
larger than their skull width, which could explain a lack of rodents in aluminum
cans (Morris and Harper 1965).
The position of the discarded container proved to be an important factor in
small-mammal mortality (Benedict and Billeter 2004, Brannon and Bargelt 2013,
Gerard and Feldhamer 1990, Morris and Harper 1965). We found that containers
with openings oriented upslope (≥15°) killed significantly more mammals (77.8%)
than all other orientations, which is similar to Benedict and Billeter’s (2004) observations.
Additionally, we observed that containers with multiple skulls were
almost always oriented upslope at step angles (>45°) with the mouth of the container
touching or close (<2.5 cm) to the ground. In captive trials, Cryptotis parva
Say (Least Shrews), Apodemus sylvaticus L. (Wood Mouse), and Myodes glareolus
Schreber (Bank Vole) could not escape a dry glass bottle if it was inclined at an
angle >15°, and the minimum angle needed to prevent escape decreased to slightly
above horizontal if the interior of the bottle was wet (Gerard and Feldhamer 1990,
Morris and Harper 1965). Bottles oriented upslope were more likely to collect water
and drown small mammals than those with other orientations (Benedict and Billeter
2004, Brannon and Bargelt 2013, Gerard and Feldhamer 1990).
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Relative frequencies of small mammals found in containers along Flatwoods
Road were similar to results from prior studies of containers along primary and
secondary roads (Benedict and Billeter 2004, Gerard and Feldhamer 1990). The
Northern Short-tailed Shrew was the most common mammal found in containers
(66.6%), and this observation was similar to those made during previous studies
in the eastern US (59.9–86.2%; Benedict and Billeter 2004, Gerard and Feldhamer
1990). The relative frequencies of both Smoky (14.4%) and Southeastern Shrews in
containers (2.5%) were also comparable to other studies (4.8–20.6% and 1.1–4.3%,
respectively; Brannon and Bargelt 2013, Gerard and Feldhamer 1990, Pagels and
French 1987). However, our study and previous studies did not estimate the relative
abundance of small mammals at study sites, which may have indicated if some
species are more susceptible to bottle mortality due to population densities at the
study site.
We acknowledge that our conclusions are based solely on a single road, and
sampling multiple roads would have provided a better understanding of the impact
of discarded containers on small mammals. Traffic volumes, proximity to
recreation facilities, and road-maintenance regimes could greatly impact the
number of potential containers available to trap small mammals along USFS
roads, and therefore multiple roads should be examined in the future. However,
we found that containers along a single section of a graveled forest service road
are trapping and killing small mammals at rates similar to those reported for developed
areas (Benedict and Billeter 2004). Many of the species trapped along
Flatwoods Road, such as Southern Bog Lemming, are considered rare; therefore,
the impact of these containers could have negative consequences for small-mammal
populations. Discarded containers along thousands of kilometers of national
forest roads in the southern Appalachians will likely cause mortality as long as
these containers are present. Small-mammal mortality created by discarded containers
is one of the few anthropogenic effects that could be easily mitigated, e.g.,
through litter clean-ups, proactive enforcement of litter-control regulations, and
education to reduce littering.
Acknowledgments
We are grateful to the CNF staff for project support and access to our study site. All
sampling was approved by the TWRA (Scientific Salvage Permit #1888). We also thank
students from Virginia Highlands Community College (VHCC) General Biology classes
in spring 2004 and 2005 for their assistance in collecting bottles. Special thanks to VHCC
students G. Blevins, A. McConnell, and J. Osborne for their help in collecting containers
and cleaning skulls. We are grateful to M. Kennedy (University of Memphis), D. Linzey
(Virginia Tech), R. Semlitsch (University of Missouri-Columbia), M. Chatfield (Unity College),
and R. May (VHCC) for their advice and assistance. We also thank K. Powers and
two anonymous reviewers for their suggestions on a previous version of this manuscript.
Roger Perry and two anonymous reviewers improved our current manuscript and deserve
thanks for their efforts.
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2015 Vol. 14, No. 3
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