Diet and Abundance of Southern Two-lined Salamander
Larvae (Eurycea cirrigera) in Streams within an
Agricultural Landscape, Southwest Georgia
Tara K. Muenz, Stephen W. Golladay, Lora L. Smith, and George Vellidis
Southeastern Naturalist, Volume 7, Number 4 (2008): 691–704
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2008 SOUTHEASTERN NATURALIST 7(4):691–704
Diet and Abundance of Southern Two-lined Salamander
Larvae (Eurycea cirrigera) in Streams within an
Agricultural Landscape, Southwest Georgia
Tara K. Muenz1,*, Stephen W. Golladay1, Lora L. Smith1, and George Vellidis2
Abstract - We sampled five stream reaches within an agricultural landscape in southwestern
Georgia for benthic macroinvertebrates and larval amphibians from 2002 to
2003 to determine whether cattle grazing impacts these faunal components. Two of
the stream reaches had been fenced to exclude cattle (buffered), whereas the other
three were not, allowing cattle access to the streams (unbuffered). We captured larval
Eurycea cirrgera (Southern Two-lined Salamanders) incidentally in our benthic
samples and compared salamander capture rates between buffered versus unbuffered
streams. We also examined salamander stomach contents relative to the composition
and abundance of benthic macroinvertebrates, comparing these data by stream type
as well. Overall, capture success for larval salamanders was higher at buffered sites.
Midge larvae (family Chironomidae) were the most frequent invertebrate taxon detected,
both in the benthic and stomach content samples; however, we also observed
cladocerans, copepods, and ostracods in each sampling regime. A linear electivity
index revealed that larval Southern Two-lined Salamanders showed slight dietary
selection for midge larvae in the subfamily Tanypodinae. This finding, coupled with
the observation that chironomid larvae composed over half of Southern Two-lined
Salamanders stomach contents, suggests some preference or selection for this benthic
group. However, larval Tanypodinae were found at all sites, suggesting that their
identification to species level may be necessary to determine whether differences in
the prey base explained differences in salamander selectivity between buffered versus
unbuffered streams. Factors other than prey selectivity, such as instream habitat
quality, may also have infl uenced larval salamander abundance.
Agrarian activities pose a threat to streams by altering natural flow
regimes or disrupting instream and riparian habitat through chemical and
physical changes (Schultz et al. 1995). These changes can also alter benthic
macroinvertebrate assemblages that constitute a major prey base for larval
salamanders (Davis 2000, Muenz et al. 2006, Strand and Merritt 1999).
Although changes in the macroinvertebrate fauna resulting from agricultural
activities have been relatively well documented, the repercussions on
aquatic predators such as larval salamanders are largely unknown. Here we
report on the diet of larval Eurycea cirrgera Green (Southern Two-lined
Salamanders) collected in benthic macroinvertebrate samples from Coastal
Plain streams in southwest Georgia as part of a larger study examining the
1Joseph W. Jones Ecological Research Center, Newton, GA 39870. 2Biological and
Agricultural Engineering Department, University of Georgia, Tifton, GA 31793.
*Corresponding author - Tara.Muenz@jonesctr.org.
692 Southeastern Naturalist Vol. 7, No. 4
impacts of cattle grazing on stream health (Muenz et al. 2006). Specifically,
we examined (1) stomach contents of larval salamanders in streams with
and without cattle access, and (2) prey selection relative to prey available
in the environment.
The Southern Two-lined Salamander: Ecological background
Many plethodontid salamanders, including E. cirrigera, have aquatic
larvae that require instream habitat for development and survival (Petranka
1998). Southern Two-lined Salamanders occupy a wide array of stream
habitats throughout their geographic range, from southern West Virginia to
eastern Illinois and south into northern Florida and eastern Louisiana. Adult
and juvenile Southern Two-lined Salamanders inhabit stream margins, but
the larvae are totally aquatic (Duellman and Wood 1954) and typically occur
in the benthos of slow-moving pools (Petranka 1998). In general, larvae
avoid silty, highly embedded areas of streams and tend to occupy those areas
with the greatest amount of available suitable substrate (Smith and Grossman
2003). Throughout their 2- to 3-year larval period, Southern Two-lined
Salamanders feed on the streambed using chemical, tactile, and visual cues
to locate prey, including various macroinvertebrates such as plectoperans,
dipterans, and crustaceans (Caldwell and Houtcooper 1973; Petranka 1984,
1998). Petranka (1984) described larval Southern Two-lined Salamanders as
being opportunistic generalists, feeding on the same type and size of prey
over the entire larval period. However, Zaret (1980) found that larval Southern
Two-lined Salamanders are gape limited.
Materials and Methods
All streams were located on a diversified row crop and beef cattle farm in
Early County, GA, in the Fall Line Hills physiographic district. The area is
characterized by frequently meandering streams underlain by easily eroded
sands, clays, and gravel. Streams are typically located 15–75 m below the
adjacent ridge tops, experience extensive erosion (Southwest Georgia Regional
Development Center 2005), and receive considerable amounts of
ground-water discharge (Couch et al.1996). Average monthly temperatures
in the region range from 3–15 °C in January to 21–33 °C in July (SERCC
2004). Average annual precipitation is 142 cm, with the average minimum
monthly rainfall occurring in October (7 cm) and the maximum in January
(16 cm) (SERCC 2004).
Five 100-m stream reaches were selected for physical, chemical, and
biological assessment. All were located in the Factory Creek sub-watershed,
a 2nd-order tributary of the Lower Chattahoochee River. Three stream sites
were unfenced, permitting cattle access (unbuffered), herein referred to as
UB-1, UB-2 and UB-3, and two had been fenced (buffered) for >20 years
to limit cattle access, B-1 and B-2 (M. Brownlee, property owner, Blakely,
GA, pers. comm.). Total fl oodplain width in the study area ranged from 15
2008 T.K. Muenz, S.W. Golladay, L.L. Smith, and G. Vellidis 693
to 30 m. The canopy cover in the riparian area was dominated by Magnolia
grandifl ora L. (Southern Magnolia), M. virginiana L. (Sweetbay Magnolia),
Nyssa bifl ora Walter Sarg. (Swamp Tupelo), Liquidambar styracifl ua L.
(Sweetgum), and Liriodendron tulipfera L. (Tulip Tree). All streams were
perennial, with an average width of 2.0 m, an average depth of 0.09 m, and
an average velocity of 0.01 m/s. Stream temperatures ranged from 12.1 °C
in December to 23.3 °C in August, and dissolved oxygen from 4.4 mg/L in
October to 9.2 mg/L in February.
Macroinvertebrate and larval salamander collection
Invertebrates and salamander larvae were collected bimonthly from February
2002 to February 2003 with a 500-μm mesh Hess sampler (Wildco®,
Buffalo, NY). Collections were made between 09:00 hrs and 16:00 hrs
(EST). Three randomly selected transects were established within each 100-
m reach. At each transect, two composite Hess samples were taken in representative
habitat types within the stream channel. Samples were rinsed into
plastic bags, preserved in the field with 70% ethanol, and stained with rose
bengal dye. In the laboratory, samples were rinsed through a 1-mm and 500-
μm sieve. Salamander specimens were identified (Petranka 1998), and their
snout–vent length (SVL) measured in mm. Invertebrates from salamander
gastrointestinal (GI) tracts as well as Hess-sampler collections were counted
and identified to the lowest taxonomic level possible, usually order or family,
but in some cases to genus (Berner and Pescador 1988; Epler 1996, 2001;
Needham et al. 2000; Pescador et al. 1995; Stewart and Stark 1993; Thorp
and Covich 2001; Wiggins 1996). Larval Chironomidae (Diptera) captured
in the Hess sampler in February and August 2002 were mounted on slides
and identified to genus (Epler 2001). Samples with >500 individuals were
subsampled; three 5-ml subsamples (Hax and Golladay 1993) were taken
from each original sample. Larval chironomids within salamander GI tracts
were processed in a similar manner, and identified to genus when possible.
Chemical and physical measurements
Grab samples (500 mL) were collected biweekly from each stream to
determine nutrient concentrations and bacterial and sediment levels (see
Muenz et al. 2006). Physical characterizations of each stream included descriptions
of general land use, stream origin and type, and measurements of
stream bankfull width and depth. Stream fl ow velocity, depth, temperature,
and dissolved oxygen concentrations were also measured at each site (see
Muenz et al. 2006). Stream substrate composition (sand, gravel, roots, etc.)
was estimated visually across each cross-stream transect using the lineintersect
method (Davis 2000).
A Kruskal-Wallis Test (P < 0.05) (SAS Institute, Inc. 2002) was used
to compare physical, vegetative, and water-quality parameters, and macroinvertebrate
metrics among sites (see Muenz et al.  for further
694 Southeastern Naturalist Vol. 7, No. 4
description of analytical procedures). Salamander abundance by site was
also compared using a Kruskal-Wallis Test (P < 0.05).
We used Strauss’ (1979) linear index of feeding electivity to evaluate
prey selection. Strauss’ index was selected because it addresses potential
biases based on dissimilar sample sizes of gut contents and habitat, and is
considered to be a more statistically reliable index with a less complex variance
structure (Strauss 1979). The linear index is calculated as follows:
L = ri – pi,
where ri is the relative abundance of each prey item (i) in the gut, and pi is the
relative abundance of each prey item in the habitat. This index gives a value
ranging from -1 to +1, with values near zero indicating neutral selection or
opportunistic feeding, positive values indicating selectivity for a prey item
(relative to its availability in the habitat), and negative values indicating
avoidance. For this study, relative patterns were reported based on whether
scores were positive or negative. Only those taxa represented in both the
salamander stomach contents and the Hess collections (environment) were
used. Due to the mesh size of the Hess sampler and invertebrate sieving
methods, smaller crustacean taxa (e.g., Cladocera, Copepoda, and Ostracoda)
were not retained in the habitat samples and thus were not available for
electivity calculations. Therefore, we focused on larval chironomids.
Forty Southern Two-lined Salamander larvae were recovered from the
210 Hess collections, their SVL values ranging from 7 to 35 mm (median =
14.5 mm). Larvae were collected during every sampling date and at all study
sites except UB-2, with >90% of larvae collected from the two buffered sites
B-1 (n = 18) and B-2 (n = 20). The total number of captures was significantly
higher at buffered sites than unbuffered sites (P < 0.0001).
Physical and chemical parameters
Differences in physical and chemical measurements between buffered
and unbuffered sites were apparent in this study. As detailed in Muenz et
al. (2006), variability occurred among sites and treatments, but overall,
buffered sites showed lower and more stable concentrations of nutrients,
sediment, dissolved oxygen, and bacterial levels (Table 1). Riparian habitat
also appeared more stable at buffered streams, showing greater percentages
of vegetative cover and leaf-litter cover (Table 1). Instream habitat also appeared
to be more favorable at buffered sites, with higher percentages of leaf
debris, wood/roots, and benthic organic matter (ash-free dry mass [AFDM])
(Muenz et al. 2006).
Benthic macroinvertebrate community
A total of 7560 individual organisms were identified, representing
30 genera. Collections were dominated by Diptera (87%), of which 88%
were chironomids, and Coleoptera (8%), of which 73% were in the family
2008 T.K. Muenz, S.W. Golladay, L.L. Smith, and G. Vellidis 695
Table 1. Average mean values for selected physicochemical measurements from all study sites,
2002–2003 (Kruskal-Wallis test with respective P-value; see Muenz et al. 2006).
Parameter Unbuffered Buffered P value
Wood/roots, % 5.7 22 <0.0001
Leaves, % 17.7 16 0.0436
Exposed streambed, % 6.3 1 <0.0001
Canopy opening (over stream), % 13.3 7 <0.0001
AFDM, kg m-2 † 0.23 0.22 <0.0001
Apparent color, PtCo 70.3 28.5 <0.0001
Suspended solids, mg L-1 4.1 0.8 <0.0001
pH†† 5.2 5 N/A
Alkalinity†† 7.7 4.3 N/A
F. coliform, col 100mL-1 410.3 196.5 N/A
NO3-N, mg L-1 0.54 0.57 <0.0001
PO4-P, mg L-1 0.02 0.01 <0.0001
NH4-N, mg L-1 0.05 0.02 <0.0001
† AFDM = ash-free dry mass.
†† Denotes measurements taken once during the entire study.
Elmidae. Average densities for chironomids, as well as for all taxa combined,
were highest in August and December 2002 and lowest in February
2002 (Table 2, Fig 1). Within the Chironomidae, 70% were in the subfamily
Chironominae, 27% in Tanypodinae, and 3% in Orthocladiinae. Larval
Tanypodinae were present at all streams and did not differ in abundance
between sites. The most common chironomid genera were: Ablabesmyia,
Polypedilum, Saetheria, Thienemannimyia, Zavrelimyia, and members of
the tribe Tanytarsini. A detailed explanation of macroinvertebrate variation
between sites is provided by Muenz et al. (2006). Overall, buffered sites contained
more unique taxa (Muenz et al. 2006), many of which are sensitive to
disturbance (Lenat 1993). Buffered sites also harbored higher percentages of
certain invertebrate groups that can be valuable indicators of water quality,
including percentages of Crustacea, Amphipoda, and Decapoda, as well as
more sensitive taxa, e.g., elmid beetles and Ephemeroptera, Plecoptera, and
Salamander diet composition
Of the 40 salamander stomachs examined, 34 contained macroinvertebrates,
from which we identified 293 prey items (Table 3). The relative
number of dietary items varied among sample dates, with highest numbers
in late summer/fall (August and October 2002) and lowest numbers in the
summer (June 2002) and winter (December 2002 and February 2002/2003)
(Fig. 1). Dipterans composed 60% of the stomach contents, of which 98%
were chironomids—Chironominae (58.3%), Orthocladiinae (2.4%), and
Tanypodinae (39.3%) (Table 3). Although chironomids from GI samples
were difficult to identify to genus, possibly due to damage incurred during
digestion, we identified the following genera: Ablabesmyia, Microspectra,
Polypedilum, Thienemannimyia, and Zavrelimyia. Crustaceans accounted
for 38% of total stomach contents and included the orders Cladocera (28%),
696 Southeastern Naturalist Vol. 7, No. 4
Table 2. Benthic macroinvertebrates collected by a Hess sampler at 5 stream sites in Early County, GA. Expressed as an average density (average individuals/m2;
rounded to the nearest whole number) with percentage of total organisms in parenthesis.
Taxon Feb 2002 April 2002 June 2002 Aug 2002 Oct 2002 Dec 2002 Feb 2003
Crangonyx sp. 3 (2.2) 8 (2.4) 6 (1.6) -- 1 (0.3) 2 (0.4) --
Microcylloepus 1 (0.7) 10 (3.0) 5 (1.3) 1 (0.1) 2 (0.7) 1 (0.2) 1 (0.3)
Stenelmis (adult) -- 1 (0.2) -- -- 1 (0.3) -- 1 (0.4)
Stenelmis (larvae) 7 (4.6) 51 (15.0) 49 (13.0) 29 (3.9) 27 (8.4) 47 (8.6) 18 (5.7)
Decapoda 3 (2.2) -- -- -- 1 (0.3) 5 (0.9) 1 (0.4)
Ceratopogonidae 6 (4.1) 32 (9.4) 6 (1.5) 11 (1.4) 18 (2.6) 18 (3.3) 19 (2.9)
Chironomidae (other) 63 (41.2) 173 (51.1) 262 (69.4) 656 (89.0) 244 (75.7) 332 (60.9) 208 (65.7)
Tanypodinae 52 (34.0) 40 (11.6) 23 (6.1) 15 (2.0) 21 (6.5) 49 (9.0) 43 (13.7)
Simulium sp. 2 (1.3) -- 1 (0.3) 4 (0.5) -- 1 (0.2) 1 (0.3)
Hexatoma sp. 1 (0.7) 1 (0.3) 5 (1.2) -- -- -- --
Pseudolimnophila sp. 5 (3.3) 1 (0.3) 1 (0.3) -- -- 9 (1.7) 3 (1.0)
Tipula sp. 3 (1.7) 1 (0.3) -- -- -- -- 1 (0.3)
Baetidae -- -- 1 (0.3) 1 (0.1) 1 (0.3) 16 (3.0) --
Stenonema sp. -- 1 (0.3) 2 (0.5) 1 (0.1) 2 (0.7) 18 (3.3) 8 (2.5)
2008 T.K. Muenz, S.W. Golladay, L.L. Smith, and G. Vellidis 697
Table 2, continued.
Taxon Feb 2002 April 2002 June 2002 Aug 2002 Oct 2002 Dec 2002 Feb 2003
Rhagovelia sp. -- 2 (0.5) 1 (0.3) 4 (0.5) 3 (1.0) -- --
Hydracarina -- -- 1 (0.3) 1 (0.1) -- 16 (2.9) 1 (0.3)
Calopteryx sp. 1 (0.7) -- 1 (0.3) -- -- -- 1 (0.3)
Progomphus sp. -- -- 1 (0.4) -- 1 (0.3) 6 (1.1) --
Plecoptera 2 (1.5) 6 (1.7) -- -- -- -- 1 (0.3)
Diplectrona sp. 1 (0.7) -- 1 (0.3) -- -- -- 5 (1.5)
Hydropsyche sp. -- -- 1 (0.3) -- -- -- 1 (0.3)
Lepidostoma sp. 1 (0.7) 1 (0.3) -- -- -- -- 2 (0.5)
Ceraclea sp. -- -- 1 (0.3) -- -- -- --
Psilotreta sp. -- -- 4 (1.1) 1 (0.1) -- -- --
Average no. individuals 153 338 378 738 322 545 316
698 Southeastern Naturalist Vol. 7, No. 4
Copepoda (6%), and Ostracoda (4%). Rare taxa (<2% of individuals) included
Collembola, Coleoptera (Elmidae), and Hydracarina (Table 3).
Strauss’s linear index showed a wide range of individual and temporal
variability in salamander electivity for different taxa (Fig. 2).
Selection for chironomid larvae was generally positive through time, except
Figure 1. Aquatic invertebrate
number of individuals
for all taxa combined
and for the family
Chironomidae within (A)
tracts and (B) benthic
Hess collections from
February 2002 to February
2008 T.K. Muenz, S.W. Golladay, L.L. Smith, and G. Vellidis 699
Table 3. Composition of invertebrate taxa within the diet of larval Eurycea cirrigera (Southern Two-lined Salamanders) collected in Early County, GA. The
values are expressed as an average of the total number (and percent) of dietary items for each stomach per date. N = the number of stomachs examined.
Feb 2002 April 2002 June 2002 Aug 2002 Oct 2002 Dec 2002 Feb 2003
Taxon n = 5 n = 11 n = 2 n = 2 n = 5 n = 1 n = 8
Elmidae larvae 0.2 (5.9) -- -- -- -- -- --
Microcylloepus sp. -- -- 0.5 (12.5) -- -- -- --
Unknown larvae -- -- 0.5 (12.5) -- -- -- --
Collembola 0.2 (5.9) -- -- -- -- -- --
Chydoridae -- 7.4 (70.6) -- -- -- -- --
Copepoda -- 0.9 (8.7) -- -- -- -- --
Calanoida -- 0.3 (2.6) -- 0.5 (3.6) -- -- --
Cyclopoida -- 0.1 (0.9) -- -- -- -- --
Ostracoda -- 0.4 (3.5) -- -- 1 (5.3) -- 0.5 (13.8)
Ceratopogonidae -- 0.1(0.9) -- -- -- -- 2.4(65.4)
Chironomidae (unknown) -- 0.5 (4.3) -- 4.0 (28.6) 11.8 (63.8) -- 0.6 (17.2)
Chironominae 0.4 (11.8) 0.5 (4.3) 0.5 (12.5) 9.0 (64.3) 3.2 (17.0) -- --
Tanypodinae 1.6 (47.1) 0.4 (3.5) 2.5 (62.5) 0.5 (3.6) 2.8 (14.9) 1 (100.0) --
Empididae 0.2 (5.9) -- -- -- -- -- --
Tipulidae 0.2 (5.9) -- -- -- -- -- --
Unknown pupae 0.2 (5.9) -- -- -- -- 0.2 (1.1) --
Hydracarina -- -- -- -- -- 0.2 (1.1) --
Unidentified 0.4 (11.8) 0.1 (0.9) -- -- -- -- --
Average no. of individuals 3.4 10.4 4.0 14.0 18.8 1.0 3.6
700 Southeastern Naturalist Vol. 7, No. 4
Figure 2. Linear electivity (Strauss
1979) for chironomid, tanypodine,
and non-tanypodine midges collected
from GI tracts of larval Eurycea cirrigera
(Southern Two-lined Salamander)
in Early County, GA. Electivity
index values (L0) are for all dates
combined, and ranges of index values
(reported as minimum and maximum
values) are from all dates and individual
salamander larvae in the study.
2008 T.K. Muenz, S.W. Golladay, L.L. Smith, and G. Vellidis 701
in February 2002 (no selection) and April 2002 (slight avoidance). Overall,
indices suggest no selection for chironomids (L0 = -0.043); however, selection
for larval Tanypodinae was consistently positive through time, suggesting
slight selection (L0 = 0.228) for members of this subfamily, whereas selection
for non-tanypodine chironomids was consistently negative, suggesting slight
avoidance (L0 = -0.349) of these taxa (Fig. 2).
Eurycea spp. are considered to be opportunistic predators, feeding on
whatever prey are available (Petranka 1984, Zaret 1980). However, our
linear electivity indices suggested that Southern Two-lined Salamander larvae
showed slight selection for tanypodine chironomids in the streams we
surveyed. This finding, coupled with the observation that chironomid larvae
composed over half of Southern Two-lined Salamander stomach contents,
suggests some preference or selection for this group.
Numerous macroinvertebrate taxa collected in benthic samples were not
found in salamander GI tracts; however, the dominant group, dipterans and
more specifically, chironomids, occurred with similar frequency in both GI
tracts and benthic collections. We found small benthic invertebrates, e.g.,
chironomid larvae, ostracods, copepods, and dipteran pupae to be the most
frequently consumed prey, which corresponds with dietary reports for Eurycea
species in the northern US (Burton 1976, Caldwell and Houtcooper
1973, Petranka 1984). However, Plecoptera (stonefly) nymphs, which were
also common to these studies, were not ingested. Burton (1976) noted a
seasonal shift in diet for Eurycea bislineata (Green) (Two-lined Salamander),
with chironomids being an important prey source during warm weather
and copepods being a common food source during cooler weather. However,
we found chironomids to be a major prey source year round, composing
at least 50% of individuals per sampling date, except in April, when
chydorid crustaceans were the main prey type. Burton (1976) also found
chydorids to be an important food item for E. bislineata, composing 61%
of the total number of prey during October. In our study, there appeared to
be low selection for tanypodine chironomids in April, even though abundances
or availability of this taxon was high. In addition, strong negative
selection for non-tanypodine midges overall was apparent (Fig. 2), perhaps
reflecting the shift of selection to chydorids. Although chydorids were too
small to be collected by the Hess sampler, their high abundance in GI tracts
suggests that Southern Two-lined Salamanders may at times feed selectively
on chydorids, and that prey consumption may reflect seasonal influences
of macroinvertebrate distribution and abundance.
Chironomids are among the most widely distributed and abundant
insects in freshwater ecosystems (Armitage et al. 1995). They display a
multitude of morphological, physiological, and behavioral adaptations, as
well as sensitivities to environmental stresses and disturbances (Armitage
et al. 1995, Coffman and Ferrington 1996, Epler 2001). Under certain
702 Southeastern Naturalist Vol. 7, No. 4
conditions, such as extreme levels of dissolved oxygen, temperature, and
pH, common in agricultural systems (Schultz et al. 1995), larval chironomids
may be the only abundant macroinvertebrates available as prey in the
benthos (Muenz et al. 2006).
Factors other than abundance can play a role in prey selection, including
those relating to general life history. For example, tanypodine larvae are
epibenthic predators, crawling or swimming freely within the water column
as they feed on oligochaetes and other soft-bodied invertebrates (Mason
1998). In contrast, Chironominae are more cryptic, living on or in the
benthos in silk-lined tubes (Mason 1998). Petranka (1998) noted Southern
Two-lined Salamanders use primarily visual cues to detect prey. Our study
suggests that tanypodine larvae, being more conspicuous and mobile, are
more likely to enter a larval salamander’s visual field compared to other
chironomids. Tanypodine larvae are characterized by a rather long bulletshaped
head capsule and an elongated thorax, and fourth instar larvae of certain
species attain greater lengths than other midge subfamilies (Wiederholm
1983), perhaps making them more conspicuous.
We found that larval Southern Two-lined Salamanders were significantly
more abundant in stream sites where cattle were excluded. Although larval
salamander abundance was correlated with tanypodine abundance, these
midge larvae occurred at all stream sites, suggesting that factors in addition
to prey availability may dictate the abundance of larval E. cirrrigera. Muenz
et al. (2006) found no relationship between larval salamander and invertebrate
abundance, or between larvae and examined water-quality parameters.
However, infl uences from microhabitat requirements, and more specifically,
the amount of organic matter present within the stream, may have affected
Cattle grazing can alter stream habitat and function by increasing sedimentation
and nutrient inputs, degrading riparian and in-stream habitat, and
changing aquatic biota community composition. Such changes can decrease
overall aquatic insect diversity while increasing more disturbance-tolerant
taxa (Strand and Merritt 1999, Thomas 2002). Tanypodine chironomids as a
group exhibit a wide range of tolerance levels to the disturbances described
above; however, some species are highly sensitive (e.g., Paramerina; Lenat
1993). If Southern Two-lined Salamander larvae select prey that are sensitive
to disturbance, this salamander species may have utility as a biological
indicator of stream health. However, further knowledge of their diet (i.e.,
species-level identification of prey) and additional data on larval habitat
requirements are needed.
Lastly, studies that address life-history requirements of both predator and
prey (e.g., microhabitat) and the effects of disturbance on this interaction
are needed to determine whether agricultural land uses play a role in shaping
their distribution and abundance. If Southern Two-lined Salamanders
forage selectively on prey that are sensitive to disturbance, then conservation
of stream habitats is important. Knowledge of life-history responses to
2008 T.K. Muenz, S.W. Golladay, L.L. Smith, and G. Vellidis 703
land-use changes would help identify the utility of larval salamanders as
biological indicators of stream health.
We gratefully thank the following organizations for funding our research and
providing technical support: the Joseph W. Jones Ecological Research Center, the
University of Georgia, and the US Environmental Protection Agency. We also acknowledge
Bruce Means for his assistance with salamander identification and two
anonymous reviewers for their helpful reviews and comments. We also extend our
gratitude to the Brownlee family for permitting access to the study area.
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