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Diet of Trachemys scripta (Red-eared Slider) and Graptemys geographica (Common Map Turtle) in an Urban Landscape



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No. 21 2019
Diet of Trachemys scripta (Red-
eared Slider) and Graptemys
geographica (Common Map Turtle)
in an Urban Landscape
Jessica D. Stephens and Travis J. Ryan
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Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
2019 No. 21:1–11
Diet of Trachemys scripta (Red-eared Slider) and Graptemys
geographica (Common Map Turtle) in an Urban Landscape
Jessica D. Stephens1,2 and Travis J. Ryan1,*
Abstract - Urban environments present many challenges for aquatic turtle species. Here,
we investigated whether the diets of Trachemys scripta (Red-eared Slider) and Graptemys
geographica (Common Map Turtle) may help explain the spatial ecology of these 2 species
in a pair of constructed aquatic habitats in Indianapolis, IN, USA. We conducted stomach
ushings on 43 turtles from 2 sites (Central Canal, n = 33; IMA Lake, n = 10). Common
Map Turtles from the Central Canal (n = 27) consumed mostly mollusks and craysh,
which comprised ~86% of the volume of stomach contents. We captured no adult Common
Map Turtles at IMA Lake, likely due to the lack of mollusks within this habitat. There was
considerable variability in the diet of Red-eared Sliders between the 2 habitats, with 98.8%
of the diet contents comprised of plant material in the Central Canal (n = 6) and only 67%
plant material in IMA Lake (n = 10). This difference in diet may have been due to the lower
abundance of vegetation found in IMA Lake compared to the Central Canal, or possibly a
diversication of diet in response to decreased interspecic competition in IMA Lake. Diet
comparison between species in the Central Canal shows almost no overlap, which may
partially explain habitat association and movement differences between the 2 species docu-
mented in a previous study. The descriptions of Red-eared Slider and Common Map Turtle
diets presented here are the rst to be described from an explicitly urban landscape. Further
understanding of the ecology of these species in urban habitats can aid city planners and
managers with the goal of maintaining species diversity in urban landscapes.
Aquatic systems are extremely sensitive to urbanization. These systems are
challenged by surface runoff (via impervious infrastructure), bank erosion, and
changes in nutrient loads, while also supplying cities with potable water (Faulkner
2004, Paul and Meyer 2001). These apparent threats to aquatic ecosystems have
prompted rigorous research in riparian systems examining microbial (Gibson et
al. 1998, Zuma 2010), algal (Patrick 1973), and invertebrate (Thorne et al. 2000,
Wright et al. 1995) responses as indicators of water quality and measures of biodi-
versity declines. Underrepresented in riparian urban ecology, however, is research
examining community interactions, population dynamics, habitat distribution, and
behavioral ecology of larger-bodied taxa (discussed in Walsh et al. 2005, but see
Mitchell et al. 2008). This gap in understanding is dismaying given that larger
animals are thought to be more susceptible to the negative effects of urbanization
because of their larger ranges (Ryan et al. 2008, 2014), smaller population sizes
(Woodroffe and Ginsberg 1998), and road fatalities (Steen and Gibbs 2004).
1Department of Biological Sciences and Center for Urban Ecology, Butler University, 4600
Sunset Avenue, Indianapolis, IN 46208, USA. 2Atlanta Botanical Garden, Atlanta, GA
30309, USA. *Corresponding author -
Manuscript Editor: Iriana Zuria
Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
In recent years, ecological investigations of freshwater turtle responses to ur-
banization have provided new insight. These studies have documented skewed
sex ratios resulting from road mortality (Gibbs and Steen 2005), changes in nest
distribution (Marchand and Litvaitis 2004a), and non-random spatial distribution
along aquatic gradients with varying degrees of urbanization (Harden et al. 2009,
Marchand and Litvaitis 2004b). Similar patterns have been detected in turtles within
human-made habitats located in Indianapolis, IN, USA. Ryan et al. (2008) noted
non-random habitat association and hibernacula selection across the Central Canal
within Indianapolis for both Trachemys scripta elegans Wied-Neuwied (Red-eared
Sliders) and Graptemys geographica Le Sueur (Common Map Turtles). In addition,
there were differences in spatial ecology between the 2 species, with females of
these species exhibiting similar distances for daily movements, although the female
Common Map Turtles had signicantly larger home ranges. Furthermore, Conner et
al. (2005) noted a difference in the relative abundance of these species in the Central
Canal and a human-made lake located ~165 m away, with Common Map Turtles the
most abundant species in the canal and Red-eared Sliders the most abundant species
in the lake.
Although these differences in movement and relative abundance may be at-
tributed to a variety of factors, chief among them may be contrasting feeding
preferences between the 2 species (Conner et al. 2005, Ryan et al. 2008). In par-
ticular, the Central Canal supports a more robust population of several aquatic snail
species and aquatic vegetation than the lake habitat, potentially inuencing turtle
assemblages (Conner et al. 2005, Ryan et al. 2008). Previous studies of chelonian
diets have suggested that food preference can impact species’ habitat selection (Hart
1983, Plummer and Farrar 1981) and can inuence how species respond to habitat
alteration (Lindeman 2013, Richards-Dimitrie et al. 2013). Given habitat variability
in prey items, our aim in this study was to describe the diets of Red-eared Sliders
and Common Map Turtles in Indianapolis, IN, across these 2 human-made aquatic
habitats in the context of the hypothesis presented in Conner et al. (2005) and Ryan
et al. (2008), that food availability may be a contributing factor inuencing differ-
ences in habitat association, movement, and turtle assemblages.
Study area
We conducted our fieldwork at 2 sites in the northwest corner of Marion
County (Fig. 1), which is home to Indiana’s largest city, Indianapolis, and is in the
top 2% of most populated counties in the US (human-population density = 857
inhabitants/km2; US Census 2018). The Central Canal is a human-made water-
way created in the 1830s, originating at the White River and extending 11.2 km
before it enters a water-treatment facility. The Central Canal provides the city of
Indianapolis with ~60% of its annual water use, and therefore, efforts are made to
control water level, flow rate, vegetation, and debris. The banks of the canal vary
considerably, with turf grass, riprap, native plantings, and forest edge as the most
common groundcovers. The canal is no more than 25 m wide and 2 m deep and is
Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
bordered by a habitat matrix composed of commercial, residential, and recreation-
al areas (Ryan et al. 2008, 2014).
The Virginia B. Fairbanks Art and Nature Park, owned by the Indianapolis
Museum of Art (IMA), is adjacent to the Central Canal. It comprises 40.5 ha of
woodlands, lake, and mown lawn ~30 m from the White River on the northern edge
and 165 m from the Central Canal on the southern edge. The park was an agricul-
tural eld in the 1920s and was later converted into a gravel pit used to excavate
material for the construction of an interstate in the 1960s. The resulting borrow
pit was then converted into IMA Lake, which is roughly 14.7 ha in size with a
maximum depth of more than 15 m. Narrow strips of wooded areas surround the
lake along most of its shoreline. There has been recent effort to inventory taxa and
promote reestablishment and restoration of native species (Dolan et al. 2011).
Turtle capture and diet assessment
Although there are 6 species of turtles in the Central Canal and IMA Lake (Con-
ner et al. 2005), we conducted diet assessments on 2 of the largest and most com-
mon species, the Common Map Turtle and the Red-eared Slider. We captured turtles
used for this study between July and August 2004 with aquatic hoop traps (76.1-
cm–diameter hoops, 30 cm x 30 cm coated nylon mesh with a funnel at one end
and a closed bag at the other) baited with sardines as part of a co-occurring study of
population and community ecology in both the canal and lake habitats; see Conner
et al. (2005) for additional details regarding trapping. The turtle assemblages within
Figure 1. Urban-land use in northwest corner of Marion County, Indianapolis, IN, USA.
Turtles were collected along the Central Canal and Indianapolis Museum of Art (IMA) Lake.
Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
these habitats are described in further detail in earlier papers (Conner et al. 2005;
Peterman and Ryan 2009; Ryan et al. 2008, 2014). We opened sardine cans <1 cm to
ensure that turtles would not ingest the bait and skew analyses of stomach contents.
We checked traps daily, refreshed bait every few days, and relocated traps weekly.
Although the sampling period represented only a portion of the active period of
Red-eared Sliders and Common Map Turtles, previous diet studies have relied on a
similar temporal range (e.g., Demuth and Buhlmann 1997), and the diet of female
Common Map Turtles seems to vary little across a wider range of the active period
(Richards-Dimitrie et al. 2013).
Turtles collected from traps were immediately taken to the lab to be measured and
marked (see Cagle 1939), and we placed those to be used for the stomach-ushing
procedure (≥15 cm in carapace length) in a cold room (~2 °C) in order to slow di-
gestion and allow for easier manipulation (Ford and Moll 2004). Common Map
Turtles demonstrate strong sexual size dimorphism (Lindeman 2013); thus, only
females were large enough to be included in our analysis. We followed the procedure
described by Legler (1977) to ush the stomach contents of collected turtles. This
procedure has been successful in a number of studies on diets (Fields et al. 2003,
Legler and Sullivan 1979) with a very low risk of harm or death (Legler 1977, but see
Lindeman 2006). We returned all turtles to their collection sites within 48 h of cap-
ture. We collected stomach contents in a 0.5-mm–mesh sieve and preserved them in
70% ethanol. We examined stomach contents under a dissecting microscope to iden-
tify food items to the lowest taxonomic level possible. Plant material was difcult to
distinguish, except for Lemna (duckweed), therefore we used plant-anatomy catego-
ries (e.g., owers, seeds, bark) for all plant material other than duckweed.
We used frequency of occurrence (% FO) for each identication level to describe
diets, which is presented as the number of turtles that contained a given item (Bow-
en 1983). We also measured the abundance of each food item in diet by measuring
the total volume of each diet item using water displacement for all samples from
each site/species divided by total volume across those samples. We determined
diet-taxon richness for each location and turtle species. We used the vegan package
(Oksanen et al. 2010) in R v2.6.2 statistical software environment (R Development
Core Team 2008) to calculate diversity of prey taxa in each sample using the Simp-
son (D') and Shannon diversity (H') indices, which account for the number of taxa
and abundance of each species. We calculated Horn–Morisita dissimilarity indices
in the vegan package (Oksanen et al. 2010) to compare how similar the diets were
between the same species across location and different species within location. The
Horn–Morisita dissimilarity index varies between 0 and 1, with values close to 1
indicating no overlap in diet and values close to 0 indicating no difference in diet.
We chose this index over others because the Horn-Morisita dissimilarity index is
better suited to handle differences in sample sizes and diversity (Wolda 1981).
We obtained stomach contents from 43 turtles from the 2 sites (Central Canal,
n = 33; IMA Lake, n = 10). We captured a total of 6 Red-eared Sliders from the
Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
Central Canal and 10 from IMA Lake, while all the Common Map Turtles (n = 27)
were from the Central Canal. We captured only juvenile Common Map Turtles at
IMA Lake, which were not of sufcient size to conduct stomach ushings. The
average carapace length of Common Map Turtles and Red-eared Sliders was 160.8
mm and 133.4 mm, respectively.
Stomach contents displayed a wide variety of prey, comprising 7 phyla and 5
classes. We were also able to identify taxa belonging to 6 orders, 4 families, 2 gen-
era, and 1 species (Table 1). Two-thirds of Common Map Turtle samples from the
Central Canal contained snails (Gastropoda), whereas we found no snails within
the stomach contents of Red-eared Sliders in either the Central Canal or IMA Lake.
Red-eared Sliders consumed large amounts of plant material, with 100% of indi-
viduals in the Central Canal and 60% in IMA Lake consuming plants. Although
Table 1. Stomach contents of Common Map Turtles and Red-eared Sliders from the Central Canal
and IMA Lake, Indianapolis, IN. Only Common Map Turtle juveniles were captured in IMA Lake,
and therefore, were not of sufcient size to conduct stomach ushings. Sample size is indicated by n;
%FO is the percent frequency of occurrence of each respective taxon.
Central Canal IMA Lake
Common Map Red-eared Red-eared
Turtle (n = 27) Slider (n = 6) Slider (n = 10)
Prey taxon n %FO n %FO n %FO
Total plant material 8 30 6 100 6 60
Duckweed 4 15 3 50 0 0
Flowers 0 0 2 33 0 0
Seeds 0 0 0 0 3 30
Bark 0 0 0 0 1 10
Gastropoda (snails) 18 67 0 0 0 0
Cambaridae (craysh) 8 30 2 33 0 0
Total Anisoptera 0 0 2 33 0 0
Larvae 0 0 1 17 0 0
Adult dragonies 2 7 1 17 1 10
Zygoptera nymphs 1 4 0 0 0 0
Nematoda 2 7 1 17 7 70
Arachnida (spiders) 2 7 0 0 0 0
Annelid (Hirudinea) 1 4 0 0 0 0
Hemiptera (Corixidae) 1 4 0 0 0 0
Diptera (Culicidae larvae) 5 19 0 0 0 0
Ephemeroptera (Baetidae) 3 11 0 0 0 0
Coleoptera (Popillia japonica) 2 7 0 0 5 50
Osteichthyes 0 0 0 0 1 10
Styrofoam 0 0 1 17 0 0
Unidentiable 4 15 0 0 1 10
Unidentiable animal 2 7 0 0 2 20
Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
some Common Map Turtle samples contained vegetable matter, it may have been
coincidental by-catch, as it was exclusively duckweed, a small, surface-oating
plant. The samples from Red-eared Sliders contained not only duckweed (in canal
samples), but also structures from other plant species.
Common Map Turtles consumed 92% of the total taxonomic groups (not in-
cluding unidentiable and styrofoam categories) identied in this study, giving a
species richness value of 11 (Table 1). The species richness of Red-eared Sliders
across both the IMA Lake and Central Canal was 6 (50% of the total taxonomic
groups identied). More specically, prey taxon richness values for Red-eared Slid-
ers at IMA Lake and Central Canal were 4 and 5, respectively. It should be noted
that species richness can be inuenced by sample size, and therefore the difference
in taxon richness may be explained in part by the higher capture-frequency of
Common Map Turtles. The Shannon index value was accordingly higher for Com-
mon Map Turtles (H' = 0.721) than for Red-eared Sliders (H' = 0.088) in the same
habitat. However, H' = 1.83 for Red-eared Sliders found in IMA Lake, indicating
a much higher dietary diversity than in the Central Canal. The results were similar
using the Simpson index values of 0.331, 0.029, 0.511 for Common Map Turtles,
Central Canal Red-eared Sliders, and IMA Lake Red-eared Sliders, respectively.
Most of stomach-content volume consisted of plant material (99%) for Red-
eared Sliders in the Central Canal (Fig. 2). Plant material made up < 1% of the total
stomach contents in Common Map Turtles within the same habitat. Additionally,
Figure 2. Percent abundance of total stomach contents of the most abundant taxa listed in
the diet of Common Map Turtles (Gg) and Red-eared Sliders (Ts) from the Central Canal
and IMA Lake, Indianapolis, IN, USA. “Other” includes all taxa, other than those listed
here, from Table 1.
Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
the Common Map Turtle diet was primarily composed of snails (Gastropoda; 81%),
with Red-eared Sliders showing no consumption of this prey in either habitat. The
Horn–Morisita index value was 0.989 between Common Map Turtles and Red-
eared Sliders in the Central Canal. This nding indicates very little dietary overlap
between the 2 species. Comparisons of Red-eared Sliders between the 2 habitat
types show similar preferences, as the Horn–Morisita index value was 0.085.
We were unable to capture Common Map Turtles at IMA Lake that were of suf-
cient size (carapace length >15 cm) to conduct stomach ushing (see also Conner
et al. 2005), therefore we could not make diet comparisons between the 2 habitats
for this species. However, the stomach contents of Common Map Turtles from
Central Canal indicate a predominately molluscivore diet, which is consistent with
other diet studies for this species (Gordon and MacColluch 1980; Lindeman 2006,
2013; Richards-Dimitrie et al. 2013; Vogt 1981; White and Moll 1992). The lack
of adult Common Map Turtles at IMA Lake may be attributed to the relatively low
abundance of snails in this habitat (T.J. Ryan, pers. observ.). The Central Canal
supports a robust population of several aquatic snail species; IMA Lake lacks these
populations (Conner et al. 2005; T.J. Ryan, pers. observ.). The absence of snails
may be a result of the characteristics of this type of human-made aquatic habitat.
Freshwater snails typically prefer lake bottoms covered with leaf litter and other
plant detritus (Dillon 2000, Spyra 2010). IMA Lake, however, is a converted gravel
pit with a deep, rock basin and steep-banked slopes. Our results, together with the
lack of adult Common Map Turtles at IMA Lake (Conner et al. 2005), indicate that
the difference in abundance of Common Map Turtles between the 2 habitats may
be attributed to preferred food availability.
Common Map Turtles in the Central Canal preyed on a high diversity of prey
items besides mollusks, especially compared to Red-eared Sliders in that habitat.
Specically, ~30% of Common Map Turtles captured consumed decapods (i.e.,
craysh), though they made up only 5.5% of total prey volume. This nding is not
unusual, as Common Map Turtles, while mollusk specialists, have also been known
to feed on craysh (Ernst and Lovich 2009, Lagler 1943, Penn 1950). Excluding
unidentiable material, all other items combined made up the remaining 2% of total
prey contents, most of which may have been consumed incidentally. The continued
presence of Common Map Turtles within the urban landscape appears to be largely
dependent on the fact that the biota of the Central Canal, despite its anthropogenic
origins, approximates that of more natural habitats, like the nearby White River,
which is also inhabited by Common Map Turtles (T.J. Ryan, pers. observ.).
Despite the wide breadth of food items available in the Central Canal, it is
interesting to note that Red-eared Sliders were specializing on vegetation. Vegeta-
tion accounted for 98.8% volume and occurred in all individuals sampled. In more
natural settings, Red-eared Sliders tend to be opportunistic omnivores, consuming
vegetation and soft-bodied insects (Ernst and Lovich 2009, Minton 2001, Parmenter
and Avery 1980). However, changes in diet are well documented for this species,
Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
whereby juvenile Red-eared Sliders tend to have a more carnivorous diet with a
shift towards herbivory coming with maturation (Clark and Gibbons 1969, Hart
1983, Marchand and Litvaitis 2004b). To prevent possible harm to small turtles, we
did not conduct stomach-ushing procedures on juveniles, which may have biased
our analyses relative to Red-eared Sliders. Another possible interpretation for the
high abundance and volume of vegetation in the Central Canal Red-eared Sliders’
diet may be the overall plant abundance in the Central Canal. Previous research
in the Central Canal found that this turtle species non-randomly associates with
areas lined by woodlots (Ryan et al. 2008), where vegetation is more prevalent.
In addition, Parmenter and Avery (1990) hypothesized that Red-eared Sliders may
consume vegetation in areas with greater plant abundance due to the ease of forag-
ing compared to available animal matter; our ndings were consistent with their
hypothesis. In the lake habitat, Red-eared Sliders appeared to be generalists, with
vegetation only making up 67% of food content volume. While this result may be
due in part to there being less aquatic vegetation in IMA Lake compared with the
Central Canal (T.J. Ryan, pers. observ.), Red-eared Sliders at IMA Lake may be
experiencing a release from competition for food with the other species, which are
typically more abundant in the Central Canal.
The populations of Red-eared Sliders and Common Map Turtles located in the
Central Canal show a high degree of resource partitioning with almost no overlap in
prey. This difference in diet may help explain the differences in movement patterns
between these 2 species in the Central Canal. We found that Red-eared Slider and
Common Map Turtle females moved the same distance on a daily basis, but female
Common Map Turtles tended to have larger ranges than female Red-eared Sliders
(Ryan et al. 2008). While these 2 species move amongst basking sites throughout
the day (Peterman and Ryan 2009), the basking-related movements did not ad-
equately account for the movement difference between species. The difference in
range size may be attributed to a preference for snails by Common Map Turtle,
necessitating active foraging over a larger area as local prey availability becomes
scarce (Pluto and Bellis 1988, Vogt, 1981).
Studies of diet differences have aided in elucidating life history (Ford and
Moll 2004) and habitat selection (Hart 1983, Plummer and Farrar 1981) for many
populations of turtles in natural settings. This study is, to our knowledge, the rst
to describe the diets of Red-eared Sliders and Common Map Turtles in explicitly
urban habitats. Our results suggest that within an urban landscape, diet may help
shape turtle assemblages and it may account for differences in home ranges and
habitat selection for these species, although other factors are likely important as
well (e.g., water depth and buffer-zone width; see Elston et al. 2016). We found no
signicant deviation from patterns reported in previous diet studies conducted in
more natural habitats, which underscores the fact that urban planners should con-
sider all facets of species’ ecology—including the needs of both dietary specialists
and generalists—when creating or altering urban aquatic habitats to promote and
sustain diversity.
Urban Naturalist
J.D. Stephens and T. J. Ryan
2019 No. 21
We thank the Indianapolis Water Company and the Indianapolis Museum of Art for al-
lowing us to trap on their properties. We are also grateful to Sean Sterrett and 2 anonymous
reviewers for helpful comments and suggestions that greatly improved this manuscript.
We followed Butler University ACUC Protocol 132 and our study was conducted under
an Indiana DNR permit (scientic collector’s license number 2599). This manuscript is a
contribution of the Center for Urban Ecology at Butler University.
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... Several dietary studies assessed the stomach and/or intestine content of Slider populations, both from the native range (Pierce, 1992;Dreslik, 1999;Stephens and Ryan, 2019) and from the non-native range (Prevot-Julliard et al., 2007;Outerbridge, 2008;Lee and Park, 2010;Pérez-Santigosa et al., 2011;Wang et al., 2013;Works and Olson, 2018). These identify both native and non-native populations as omnivorous, with different life stages having different diets; for example, smaller Sliders are more carnivorous, whereas adults are more herbivorous. ...
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Pond Sliders, Trachemys scripta, are among the widest-spread animal species outside their native range, and habitat suitability modelling has demonstrated that the current range of this species can expand even further. This species is also widely reported in Europe with successful reproduction being reported mainly from southern locations, though increasingly from more northern populations, e.g., Germany. Nonnative Trachemys scripta impact native species and ecosystems, e.g., they can displace native turtle species and are known to harbour pathogens and parasites. Surprisingly little attention has been given to their impact on freshwater ecosystems, and additionally, dietary studies are few in number and do not implement a methodology that allows identification of all prey taxa. Here, we report how a live duckling (Anas platyrhynchos) was predated on by a large adult Trachemys scripta. The event, where the turtle grabbed the duckling from the water surface and submerged underwater, only took several seconds. Although vertebrate prey has been identified in stomach/intestine samples of Trachemys scripta, the general explanation has been this species’ scavenging behaviour. Our report provides an alternative explanation, namely predation of live prey that has not been frequently observed due to the speed of such events. Therefore, from a biological invasion perspective, the effect of non-native Trachemys scripta populations on native vertebrate fauna may be underestimated. We argue that to better understand the occurrence, frequency and diversity of prey in future dietary studies of Trachemys scripta (and other taxa), genetic techniques should be applied.
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The Rio Grande cooter (Pseudemys gorzugi) is an imperiled freshwater turtle native to the southwestern United States and northeastern Mexico. Previous studies investigating P. gorzugi diet have focused on the population occupying the Black River drainage in southeastern New Mexico, while Texas populations have remained unexamined. During the summer and fall of 2020, we studied the dietary habits of P. gorzugi and the syntopic red-eared slider (Trachemys scripta elegans) at San Felipe Creek, Texas, USA using fecal content and stable isotope analyses. We also compared the isotopic niches of these 2 co-occurring turtle species. Filamentous algae were, volumetrically, the most important food item for male, female, and juvenile P. gorzugi. Stable isotope mixing models indicated that lotic and lentic filamentous algae had the greatest proportional contribution to P. gorzugi and T. s. elegans diets, respectively. Stable isotope dietary mixing models also indicate T. s. elegans had a more carnivorous diet, composed mostly of red-rimmed melania (Melanoides tuberculata) and red swamp crayfish (Procambarus clarkii). Carnivory in this species was further supported by enriched δ15N values and higher trophic position estimates. Pseudemys gorzugi and T. s. elegans had δ13C and δ15N signatures that significantly differed, and the 2 species showed little overlap in isotopic niche space, suggesting a low likelihood of intense resource competition. Our results demonstrate that the diet of P. gorzugi, and the isotopic niche overlap between P. gorzugi and T. s. elegans at San Felipe Creek differ from that in the Black River drainage of New Mexico. The information provided here contributes toward a more complete understanding of P. gorzugi ecology, is useful for identifying suitable habitat worthy of conservation, and can help guide the development of feeding regimes for captive assurance colonies.
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Setiadi AE, Rahayu HM. 2021. Reptiles in the Pontianak and Kubu Raya Residental Area, West Kalimantan, Indonesia. Biodiversitas 22: 2763-2770. The increase in population is directly proportional to housing needs. Expansion of residential areas can threaten the diversity of reptiles in West Kalimantan. This study aims to inventory and identify the diversity of reptiles in residential areas in Pontianak and Kubu Raya, West Kalimantan province, Indonesia. This research gives a better understanding of reptilian urban species to support monitoring and evaluation of biodiversity in West Kalimantan. This research uses the descriptive exploratory method. Four study areas were selected based on a proportion of impervious surfaces. Data collection used the VES (Visual Encounter Survey). Identification refers to Reptile field guides and identification books. The data were analyzed descriptively qualitatively, the level reptile diversity was analyzed using the Shannon Diversity Index, and the similarities of reptiles between the residential area in Pontianak and Kubu Raya were assessed using the Jaccard similarity coefficient. The results showed, from 50 individual reptiles found in Pontianak and Kubu Raya, there were 13 reptile species from the order Squamata and the order Testudines. The Shannon-Wiener Diversity Index of 2.26 and Jaccard similarity coefficient 0.384, indicating that the level of diversity of reptile species in the two study areas is classified as moderate.
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The world's population is concentrated in urban areas. This change in demography has brought landscape transformations that have a number of documented effects on stream ecosystems. The most consistent and pervasive effect is an increase in impervious surface cover within urban catchments, which alters the hydrology and geomorphology of streams. This results in predictable changes in stream habitat. In addition to imperviousness, runoff from urbanized surfaces as well as municipal and industrial discharges result in increased loading of nutrients, metals, pesticides, and other contaminants to streams. These changes result in consistent declines in the richness of algal, invertebrate, and fish communities in urban streams. Although understudied in urban streams, ecosystem processes are also affected by urbanization. Urban streams represent opportunities for ecologists interested in studying disturbance and contributing to more effective landscape management.
Throughout the past several years there has been an increasing concern to reduce the pollutants within urban stormwater discharges, particularly combined sewer overflows (CSOs). The majority of the research on CSOs has focused on physical, chemical, and some biological components. This preliminary study investigated the occurrence of two pathogenic protozoa, Cryptosporidium and Giardia, in an urban stream during dry weather compared to their occurrence in a combined sewer overflow (CSO) end-of-pipe discharge to determine the loading potential and the potential human health impacts. Cryptosporidium oocysts and Giardia cysts were commonly observed in the urban stream during dry weather conditions, with concentrations of 5-105 oocysts/100L and 13-6,579 cysts/100L respectively. The CSO end-of-pipe samples during wet weather conditions discharged Cryptosporidium and Giardia at high levels, 250-40,000 oocysts/100L and 9,000-283,000 cysts/100L respectively. This preliminary study suggests that CSOs may significantly contribute to the load of Cryptosporidium and Giardia in ambient waters and source waters utilized for recreational use and potable water. However, further investigation will be needed to determine and characterize the full effect of this apparent loading source.
Although urbanization has contributed to wildlife population declines, urban ditches may present some of the last remaining refugia in expanding cities where turtles have persisted. To determine effective and easy-to-implement conservation measures, it is crucial to better understand the ecology of these urban turtle populations. Here, we assessed the influence of six easy-to-understand ditch characteristics on turtle abundance and richness using generalized linear mixed models. We based our study on capture and habitat data collected from May to August of 2011 and 2012, in seven ditches of Jonesboro, Craighead County, Arkansas, USA. Over these two years, we captured 452 turtles of six different species. Abundance and species richness were higher in ditches that were wider, longer, deeper, and had a wider buffer zone than ditches without these characteristics. No other variables (e.g., substrate type) were associated with variation in abundance or richness. Our results highlight the importance of habitat size for the persistence of turtle populations. Although other factors (e.g., water quality, food abundance) might be more ecologically relevant to urban turtles, ditch dimensions, being easy to manipulate, should be strongly considered when building or modifying a ditch system to minimize impact on turtle populations.
The diet of red-eared turtle shifted gradually from insect to plant material with increasing plastron length, and paralleled a habitat shift from feeding sites in shallow to deep water. Basking perches used by small turtles were narrower, more steeply sloped, and located in shallower water than those used by large turtles.-from Author
Sternotherus odoratus is an omnivorous turtle inhabiting shallow littoral zones of lakes and swamps in the eastern United States. Previous studies have quantified the diet of this turtle, but few have addressed seasonal and sexual differences. Stomach and fecal samples were collected from June through October 1998. Although males and females consumed similar taxa, there were monthly dietary differences likely, in part, because of sexual differences in peak activity and reproductive conditions. Patterns of consumption suggest that Stinkpots are omnivorous but show some dietary preferences.