The Dietary Composition of Chrysemys picta picta (Eastern Painted Turtles) with Special Reference to the
Seeds of Aquatic Macrophytes
Donald J. Padgett, Jeffrey J. Carboni, and Daniel J. Schepis
Northeastern Naturalist, Volume 17, Issue 2 (2010): 305–312
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2010 NORTHEASTERN NATURALIST 17(2):305–312
The Dietary Composition of Chrysemys picta picta
(Eastern Painted Turtles) with Special Reference to the
Seeds of Aquatic Macrophytes
Donald J. Padgett1,*, Jeffrey J. Carboni1, and Daniel J. Schepis1
Abstract - Animals facilitate macrophyte seed dispersal in various ways despite specializations
of macrophytes for water dispersal. Previous diet analyses of freshwater
aquatic turtles revealed that several North American turtle species consume a variety
and abundance of seeds among other plant material and animal prey. We quantified
the dietary habits of Chrysemys picta picta (Eastern Painted Turtle) in a Massachusetts
lake to examine if these animals included hydrophyte seeds in their diet
and evaluate their capacity as passive seed-dispersal agents. Fifty-four turtles were
trapped and housed to collect feces. Examination of feces revealed a diverse diet with
comparatively high frequencies of animal, plant, and algal matter. Eight hundred
fifty-seven seeds of at least nine plant species were egested (among 87% of turtles),
with all but five (99%) seeds visibly intact. Seeds of Nuphar (473) and Decodon
(305) were most abundant in the feces. Life-history characteristics of both C. p. picta
and Nuphar suggest an effective endozoochorous seed dispersal association.
Introduction
Animal-facilitated seed transport (zoochory) is a key mechanism in plant
population establishment, regeneration, and gene flow. Dispersal in aquatic
vascular plants is common, but aquatic plant seed dispersal by animals is not
fully understood (Cook 1987, Sculthorpe 1967). Many aquatic macrophytes
are known to be specialized for water dispersal, and studies have shown that
a variety of seed-ingesting animals, including waterfowl (Clausen et al. 2002,
Figuerola et al. 2005, Santamaria et al. 2002) and fishes (Agami and Waisel
1988, Pollux et al. 2006), not only facilitate the dispersal of seeds within and
between water bodies, but can enhance seed germination capability.
Waterbirds and fishes have long been considered likely candidates to play
a role in zoochory in aquatic plants (Charalambidou and Santamaria 2002,
Cook 1987, Holt Mueller and van der Valk 2002, Schenck 1886). However,
freshwater turtles could be an underappreciated, yet effective, vector for
freshwater hydrophytes in gut-mediated seed dispersal (endozoochory).
Several North American turtle species consume seeds amid a multitude of
other plant and animal prey. For example, large quantities of intact Nymphaea
odorata Aiton (American Waterlily) seeds have been found in Chelydra
serpentina (L.) (Common Snapping Turtle), Chrysemys picta (Schneider)
(Painted Turtle), and Trachemys scripta (Schoepff) (Yellow-bellied Slider)
(Lagler 1943, Parmenter 1980). The diet of Sternotherus odoratus (Latreille
in Sonnini and Latreille) (Musk Turtle) exhibits a moderate frequency and
1Department of Biological Sciences, Bridgewater State College, Bridgewater, MA
02325. *Corresponding author - dpadgett@bridgew.edu.
306 Northeastern Naturalist Vol. 17, No. 2
abundance of aquatic plant seeds, including seeds of American Waterlily,
Nuphar advena (Aiton) Aiton f. (Yellow Pond-lily), Ludwigia (primrosewillow),
Bidens (beggarticks), and others (Ford and Moll 2004, Lagler
1943). Acorns of a wetland Quercus (oak) species were the most abundant
food by weight and volume of Macroclemys temmincki (Troost in Harlan)
(Alligator Snapping Turtles) (Sloan et al. 1996). Despite seeds of various
hydrophytes being listed as food items of turtles, the focus of these dietary
studies centered on life-history aspects of the animal as opposed to the potential
dispersal implications for plants.
Painted Turtles (Family Emydidae) are common aquatic turtles, inhabiting
slow-moving shallow waters of freshwater lakes, ponds, creeks, rivers,
and wetlands over most of North America (Ernst et al. 1994). They are opportunistic
omnivores that eat a wide variety of animals and plants as they
forage among vegetation. Dietary studies of Painted Turtles indicate substantial
geographic variation in degree of carnivory or herbivory, which may
be related, at least in part, to certain life-history traits (e.g., growth rates,
body size, and fecundity), seasonal food availability, and/or habitat type
(Cooley et al. 2003, Knight and Gibbons 1968, Lindeman 1996, MacCulloch
and Secoy 1983, Raney and Lachner 1942, Rowe and Bowen 2005, Rowe
and Parsons 2000).
Our objective was to examine the dietary composition of a population of
adult Chrysemys picta picta (Schneider) (Eastern Painted Turtles), a common
and ordinarily abundant turtle of the northeastern United States. Our
principle focus was to determine the extent to which Painted Turtles include
aquatic plant seeds as dietary items and evaluate their capacity as passive
seed dispersal agents. The findings would represent the easternmost diet
report for the species and provide baseline data for this eastern subspecies.
Methods
Our study site was Carver Pond in Bridgewater, Plymouth County, MA.
This 14-ha (35-acre) lake has an extensive floating-leaf community dominated
by American Waterlily and Nuphar variegata Durand (Bull-head Pond-lily).
A diverse submersed community included various Potamogeton spp. (pondweeds),
Utricularia spp. (bladderworts), and Ceratophyllum demersum L.
(Hornwort). The shallow lake edge is dominated by a dense zone of Decodon
verticillatus (L.) Elliott (Water-willow), and includes Cephalanthus occidentalis
L. (Common Buttonbush) and Clethra alnifolia L. (Sweet Pepperbush).
We collected Painted Turtles between 25 June and 10 July 2008. We
captured 28 male and 24 female adults (i.e., straight-line carapace length
>110 mm) using hoop nets or occasionally hand nets. No individuals were
recaptured. Turtles were transported in buckets to the laboratory and housed
individually in 10-gal. aquaria for a 5-day period. Fecal samples were collected
daily and pooled by individual. Feces were preserved in 70% ethanol
and later examined under a dissecting microscope for animal, plant, and algal
remains. Prey items were identified to lowest possible taxon and grouped by
2010 D.J. Padgett, J.J. Carboni, and D.J. Schepis 307
animal, plant (seed), plant (non-seed), and alga categories. Mean numbers of
prey items within animal and plant (seed) categories were compared among
prey taxon and between sexes of turtles by two-factor ANOVA, followed by
Tukey’s HSD post-hoc test. The effects of sex within diet categories were determined,
as diet variations have been reported to vary by gender in aquatic
turtles (e.g., Ford and Moll 2004). Analyses were run separately for animal
prey and plant (seed) prey. Food item abundance comparisons between prey
categories and within algal and plant (non-seed) categories were not tested
due to the inability to effectively resolve single individuals in these groups.
Results
All but one turtle (98%) had identifiable animal remains in their feces,
with a variety of animal matter overall (Table 1). The most frequent animal
Table 1. Dietary composition of Chrysemys picta picta (Eastern Painted Turtles; n = 52) in
Carver Pond, Bridgewater, MA based on fecal samples. See Table 2 for seed composition. A
two-factor ANOVA (followed by Tukey’s HSD post-hoc test) of animal items revealed insects to
be most abundant and indicated a sex-by-animal item effect with female feces exhibiting more
insects than that of males. SD = standard deviation.
Category/taxon Frequency (%) Mean (± SD)
Animal material 98.0 41.3 (39.7)
Insecta 92.3 16.7 (17.7)
Diptera 82.7 9.6 (12.8)
Odonata 59.6 1.5 (2.8)
Hemiptera 53.8 2.6 (8.5)
Trichoptera 50.0 2.0 (3.1)
Coleoptera 42.3 0.6 (0.8)
Ephemeroptera 17.3 0.2 (0.4)
Hymenoptera 5.8 0.1 (0.3)
Homoptera 3.8 0.1 (0.3)
Megaloptera 1.9 0.0 (0.1)
Plecoptera 1.9 0.0 (0.1)
Crustacea 30.8 0.3 (0.5)
Decopoda 25.0 0.3 (0.4)
Isopoda 3.8 0.0 (0.2)
Conchostraca 1.9 0.0 (0.1)
Cladocera 1.9 0.0 (0.1)
Mollusca 48.1 2.1 (3.7)
Gastropoda 46.2 2.1 (3.5)
Pelecypoda 7.7 0.1 (0.3)
Arachnida 50.0 1.5 (2.0)
Cnidaria 1.9 0.0 (0.1)
Platyhelminthes 1.9 0.0 (0.1)
Nematoda 40.4 1.5 (3.8)
Anura 3.8 0.0 (0.2)
Plant material (non-seed) 100.0 -
Wolffia (water-meal) 100.0 -
Lemna (duckweed) 100.0 -
Ceratophyllum demersum (Hornwort) 96.2 -
Unidentified 21.2 -
Algae (filamentous) 100.0 -
308 Northeastern Naturalist Vol. 17, No. 2
prey were dipteran larvae (mostly Ceratopogonid midges) and odonate larvae
(mostly Libellulid dragonflies), egested by 83% and 60% of the turtles,
respectively. Other animal prey included adult water bugs (Hemiptera), caddisfly larvae (Trichoptera), and snails (mostly Planobidae). Among animal
prey, insects (mean = 16.7, st. dev. = 17.7, per turtle) were statistically more
abundant than all other animal items and did show a sex-by-animal item effect
(F = 3.83, df = 7, P < 0.001), with female feces exhibiting more insects
than that of males. Filamentous algae (unidentified) and vegetative plant
material were found in all turtles (Table 1). Non-food items evident in the
feces included pebbles, styrofoam, fishing line, and glass.
Seeds of nine aquatic plant taxa were identified in feces, with an overall
seed egestion frequency of over 86% (Table 2). The most frequently egested
seeds were those of Water-willow (75%) followed by Yellow Pond-lily
(29%). The abundance of both Yellow Pond-lily seeds (mean = 9.1 per turtle)
and Water-willow seeds (mean = 5.6 per turtle) was statistically higher (P <
0.05) than other seed items. There was no significant sex-by-seed item interaction
(F = 0.8, df = 8, P = 0.6), indicating neither the abundance of any
particular seed nor the total number of seeds egested is dependent on the sex
of the turtle. Yellow Pond-lily represented the highest quantity of seeds from
a single turtle, with 156 in a female, followed by Water-willow with 48 seeds
in a female. Seeds were passed intact and only few (2 of Yellow Pond-lily, 3
of Water-willow) of the 857 seeds appeared damaged.
Discussion
Our findings on Eastern Painted Turtles corroborate the assertion that this
species is omnivorous (Ernst et al. 1994). In Eastern Painted Turtles, both
animal and plant material are ingested at similarly high frequencies, with a
variety in either prey group. The dietary composition of the eastern subspecies
differs from the animal matter bias in other Painted Turtle subspecies
Table 2. Seeds recovered from feces of Chrysemys picta picta (Eastern Painted Turtles; n =
52) from Carver Pond, Bridgewater, MA, their frequency of occurrence, and abundance per
turtle. Means were compared among seed species and between turtle sex by two-factor ANOVA
followed by Tukey’s HSD post-hoc test (* signifies a significant difference at P < 0.05). SD =
standard deviation. No effect of sex was determined.
Plant taxon Number Freq. (%) Mean (±SD)
Nuphar variegata Durand (Yellow Pond-lily) 473 28.8 9.1 (25.8)*
Decodon verticillatus (L.) Elliott (Water-willow) 305 75.0 5.9 (8.6)*
Bidens (beggartick) 19 26.9 0.4 (0.7)
Potamogeton (pondweed) 16 11.5 0.3 (1.1)
Grass (Poaceae) 12 17.3 0.2 (0.6)
Najas flexilis (Willd.) Rostk. & Schmidt (Common Naiad) 10 9.6 0.2 (0.6)
Nymphaea odorata Aiton (American Waterlily) 4 5.8 0.1 (0.3)
Carex (Sedge) 5 5.8 0.1 (0.4)
Other 13 19.2 0.3 (0.6)
Total 857 85.2 16.5 (27.8)
2010 D.J. Padgett, J.J. Carboni, and D.J. Schepis 309
(Knight and Gibbons 1968, Lindeman 1996, MacCulloch and Secoy 1983,
Rowe and Bowen 2005). However, it should be noted that these investigations
relied on stomach contents and not feces. Most remarkable was the
large number, and high frequency of occurrence, of intact hydrophyte seeds
found in this study.
Studies have demonstrated that terrestrial and aquatic turtle species can
be effective agents of seed dispersal (Braun and Brooks 1987, Calvino-
Cancela et al. 2007, Liu et al. 2004, Moll and Jansen 1995, Varela and
Bucher 2002, Woodbury and Hardy 1948). Aquatic turtles that have largely
indiscriminate diets and inadvertently ingest seeds could be probable seed
dispersal agents. In consideration of our seed egestion data (Table 2), several
life-history traits of Painted Turtles indicate an effective endozoochorous
involvement with hydrophytes. For example, Painted Turtles are usually
locally abundant (e.g., up to 941 individuals per hectare; MacCulloch and
Secoy 1983), and are often the most abundant turtle in a suitable water body
(Ernst et al.1994). Their feeding activities, which involve gulping small
prey, are confined to the aquatic environment. They have home ranges of up
to 2.7 ha within which they forage, and aquatic travel distances can average
68 m per day. Notably, these turtles do make overland movements to
establish nearby aquatic activity centers (Rowe 2003), and some populations
have exhibited interpond movement distances of up to 3.3 km (Bowne 2008,
Bowne and White 2004). While there are no seed retention data published
for Painted Turtles, experimental gut transit times for 2- x 2-mm particulate
markers averaged >2 days in this species (Guard 1980).
The natural history of the Painted Turtle seems to complement the pondlily
seeds in their diet. The abundance of Yellow Pond-lily seeds (55% of all
seeds expelled) in Painted Turtle feces indicates that pond-lilies, in general,
may be well suited for turtle-mediated dispersal. Seeds of this genus have
been mentioned in other dietary studies of North American aquatic turtles.
For example, Actinemys marmorata (Baird and Girard) (Western Pond
Turtles) were observed to feed “extensively” on fruits of Nuphar polysepala
Engelmann (Western Pond-lily; Evenden 1948), Musk turtles had Common
Pond-lily seeds as a major component of their gut contents (Lagler 1943),
and pond-lily seeds were found at moderate frequencies within Chrysemys
picta marginata Agassiz (Midland Painted Turtles; Raney and Lachner 1942,
Rowe and Parsons 2000). Pond-lily species are floating-leaved, highly clonal
hydrophytes thought to be dispersed primarily by water (Padgett 2007). Their
abundant, leathery, berry-like fruits (0.5–5 cm in diameter) ripen at the water
surface and dehisce irregularly to release numerous, floating, mucilaginous,
seed-bearing units known to travel on the water surface for days before the
seeds sink (Hart and Cox 1995, Smits et al. 1989). Numerous floating seed
masses could be enticing to foraging Painted Turtles (an animal that often cooccurs
with pond-lily, evidently does not discriminate seed prey by gender,
and colonizes areas of dense, floating-leaved vegetation), and pond-lily’s
hard seeds are more likely to pass through an animal intact (Pollux et al. 2006,
310 Northeastern Naturalist Vol. 17, No. 2
Santamaria et al. 2002). Moreover, as a truly aquatic species, seeds of Yellow
Pond-lily (which must remain wet to retain viability; Padgett 2007) are likely
to be deposited into a suitable environment by aquatic turtles. In our study,
99% of Yellow Pond-lily seeds egested by Eastern Painted Turtles were visibly
unharmed, an observation consistent with that of other researchers (e.g.,
Raney and Lachner 1942). In two other emydid turtles, the effects of digestion
on the capacity of seeds to germinate—paramount to seed dispersal success—
have been shown not to influence (Moll and Jansen 1995) or only marginally
influence (by 9% on average; Calvino-Cancela et al. 2007) germination levels.
Any germination effect of Painted Turtle digestion on pond-lily seeds has
yet to be ascertained. Germination analyses of seeds were not possible in our
study due to the alcohol preservation of feces prior to seed detection.
Little is known about seed dispersal in Water-willow. Like pond-lily species,
Water-willow is a highly clonal plant and primarily specialized for water
dispersal (Graham 2007). Its small (0.6 cm in diameter) fruits are dry and held
above the water surface. When the capsules dehisce, the small (ca. 1 mm)
seeds drop onto the water surface where they float (Graham 2007). The seeds
are known to be eaten by waterfowl (Tiffney 1981).
In a review of seed dispersal by animals, Schupp (1993) concluded that
there are both quantity and quality components to consider when evaluating
disperser effectiveness. As defined by Schupp (1993), Eastern Painted Turtles
would have high potential to be “effective” dispersers for hydrophytes like
pond-lilies. In terms of the quantity of dispersal, Painted Turtles are usually
abundant, capable of handling a high number of seeds, and have a high probability
of dispersing a handled seed. In regard to quality of seed dispersal, these
turtles provide a high quality of treatment, as seeds are egested intact (with
the assumption that such seeds are viable), and a high quality of deposition, as
seeds are likely deposited in water.
Acknowledgments
We are grateful to the Office of Undergraduate Research at Bridgewater State College
(BSC); K. Curry for technical support; C. Bloch for statistical analyses; H. Moore,
C. Edge, and two anonymous reviewers for critical review of the manuscript; and the
Massachusetts Division of Fisheries and Wildlife for a scientific collection permit. This
research was funded largely by The Adrian Tinsley Program at BSC.
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