Figure 2
Satellite image of the Cahaba River site, at Sprott, Alabama, where we had 9 trap sites upstream of Alabama Highway 155 and 7 trap sites downstream; our camp was under the bridge.
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The present ethnobotanical investigation reports 21 species of Gesneriaceae used by the indigenous tribal communities namely Adi, Galo, Nyishi, Tagin, Tangsa and Lisu of Arunachal Pradesh. Rhynchotechum parviflorum, Rhynchotechum ellipticum and Boeica fulva were found abundant and widely used as both food and medicinal purposes. However, Rhynchotec...
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... To evaluate dietary overlap between sexes, we calculated Morisita's modified index of niche overlap (Ck) by employing the frequency (f) of food items in adult females and males (Krebs 1989); the Ck values can vary from 0 (no resources are shared) to 1 (the food resources are used in the same proportion; McCoy et al. 2020). ...
The Central American river turtle (Dermatemys mawii) is one of the of the most critically endangered turtle species worldwide, as a result of habitat loss and heavy hunting for consumption. Research on D. mawii becomes more challenging as wild populations are disappearing, while basic ecological data are still required to inform conservation efforts. In this study, our aim was to analyze the diet of D. mawii based on sex, and compare the information provided by stomach flushing and fecal samples. We examined both types of samples from individuals captured in 2017 and 2018 in a lentic system in the Lacantun River Basin, Chiapas, Mexico. We identified 3 broad categories (aquatic macrophytes, riparian resources and invertebrates) and 12 different food items, of which four are new reports of vascular plants for the diet of this turtle. The principal items consumed by D. mawii were Pistia stratiotes (a free-floating macrophyte) and Ludwigia sp. (a riparian plant). A low index of relative importance (≤ 0.5) for invertebrates suggests that they may be ingested accidentally when feeding on plants. We did not detect significant sex differences in the relative contribution of food items between the two sampling methods; additionally, we found a large dietary overlap (Cλ ≥ 0.89) between sexes that indicates a similar use of resources in this lentic system. We found all 3 broad food categories in stomach flushing samples and only one (riparian resources) in fecal samples; however, we did not find significant differences in the number of food items. The use of both postingestion sampling methods provided a more comprehensive view of the diet of this herbivorous freshwater turtle.
... In contrast, the only dietary studies of G. oculifera are those of Kofron (1991, based on 29 museum specimens from various sites in the Pearl drainage) and McCoy et al. (2020, based on 47 stomachflushed specimens from 1 site on the middle Pearl River), neither of which included a breakdown of dietary data based on body sizes or sex of the specimens from which samples were taken. In addition, whereas sponges were the most important prey in the studies of G. flavimaculata and G. nigrinoda, no sponges were reported in the diet of G. oculifera by Kofron (1991) or McCoy et al. (2020). ...
... Our prediction that a strongly spongivorous diet would characterize G. oculifera, based on the diets of the other 2 sawback species (Lahanas 1982;Lindeman 2016;Selman and Lindeman 2018), was borne out in the present study, in contrast to the dietary results reported for the species by Kofron (1991) and McCoy et al. (2020). McCoy et al. (2020) likewise did not report sponges to be part of the diet of either of the other 2 sawback species. ...
... Our prediction that a strongly spongivorous diet would characterize G. oculifera, based on the diets of the other 2 sawback species (Lahanas 1982;Lindeman 2016;Selman and Lindeman 2018), was borne out in the present study, in contrast to the dietary results reported for the species by Kofron (1991) and McCoy et al. (2020). McCoy et al. (2020) likewise did not report sponges to be part of the diet of either of the other 2 sawback species. Fragmented, partially digested freshwater sponges may be easily overlooked in dietary samples, which likely accounts for the fact that previous workers have not reported consumption of sponges for G. oculifera. ...
The map turtles and sawbacks (Graptemys) sort by female head width into narrow-headed (microcephalic) females of 5 species that eat few mollusks, moderately broad-headed (mesocephalic) females of 4 species that eat moderately high amounts of mollusks, and broad-headed (megacephalic) females of 5 species that eat mollusks almost exclusively. The microcephalic species include a clade of 3 sawbacks, Graptemys nigrinoda, Graptemys flavimaculata, and Graptemys oculifera. The first 2 are sponge specialists, but 2 previous dietary studies of G. oculifera did not report sponges; both also lacked comparisons between the sexes. Both of the other sawbacks also feed on brackish-water mussels near the coast, but this phenomenon has not been examined for G. oculifera. Increased body sizes occur in coastal populations of both other sawbacks as well. We examined G. oculifera diets using fecal samples and found that contrary to the earlier results, they also fed primarily on sponges, as well as insects. Females also consumed algae, Asian clams, and, in a coastal population, mussels. In low-gradient river reaches near the coast, G. oculifera achieved large body sizes compared to populations inhabiting sandbar-dominated inland reaches; they were also large at the confluences of the Pearl River and a tributary creek with the Ross Barnett Reservoir. The fact that G. oculifera at the 2 confluences with a large inland reservoir showed the same trend in body size as they did at the coastal sites suggests that the primary reason for large body size may be thermal stability and/or slowing current that promotes biological production, rather than consumption of brackish-water mussels in coastal populations, as the mussels were absent near the reservoir. In addition, high predation by alligators may also occur at the reservoir confluence and coastal sites and select for large body sizes. Overall, the 3 allopatric sawbacks show a pattern of vicariant divergence as ecological analogues, consistent with findings for other allopatric sets of related species.
... To address this concern, a better understanding of habitat and food requirements of turtles is needed. Traditionally, much of the current understanding of their diet has come from dissections and stomach flushing (Chessman, 1984(Chessman, , 1986Luiselli et al., 2011;McCoy et al., 2020), but these methods have a range of potential biases (Armstrong & Booth, 2005;Nielsen et al., 2018). Stomach flushing is invasive and removes stomach contents from the animal, which are often unidentifiable anyway (Chessman, 1983). ...
Australian freshwater turtles are declining, reflecting global turtle trends. Understanding variation in turtle diets and habitat requirements can guide protection and restoration of ecosystems. Diet and niche overlap were investigated in three co‐existing species of turtle—the broad‐shelled turtle Chelodina expansa , the eastern long‐necked turtle C. longicollis and the Macquarie turtle Emydura macquarii , in three rivers in the Murray–Darling Basin, Australia, in relation to environmental variables.
Dietary variation in relation to water quality (salinity) and macrophyte cover was investigated using stable isotope analyses (δ ¹⁵ N and δ ¹³ C) of turtle tissues (plasma, red blood cell, whole blood and nail) representing food assimilation over different antecedent periods. These stable isotope results were consistent with current dietary understanding based on stomach flushing, indicating that isotope analyses are a non‐invasive method for obtaining dietary information.
There were temporal dietary differences, with strong shifts between spring and summer sampling periods, particularly in the blood plasma. Intraspecific variation in diets reflected in δ ¹⁵ N and δ ¹³ C related to body size. There was evidence of high dietary overlap among the three species, potentially creating competition, particularly when they co‐occur or resources might be limited.
Continued degradation of turtle habitats and water quality affects turtle diet and reduces habitat availability, forcing the three species of turtle to co‐exist in diminishing refugia, increasing interspecific competition for food. Protecting and restoring freshwater ecosystems, including maintaining freshwater refugia, is essential to conserve already declining populations of the three Australian freshwater turtle species.
... Limited resources could affect dietary preferences and the magnitude of intra-and interspecific competition among individuals inhabiting the area (Chen and Lue, 2009;Aresco, 2010). Generalists tend to have a moderate niche overlap with other species, while specialists can either have large or small niche overlap with other species, depending on the preferred food source (McCoy et al., 2020). However, dietary habits and resource partitioning of a species may differ among communities (McCoy et al., 2020). ...
... Generalists tend to have a moderate niche overlap with other species, while specialists can either have large or small niche overlap with other species, depending on the preferred food source (McCoy et al., 2020). However, dietary habits and resource partitioning of a species may differ among communities (McCoy et al., 2020). ...
Aquatic turtles represent important biotic components of freshwater ecosystems. The Pecos River watershed is inhabited by six freshwater turtle species, including the widespread Trachemys scripta (Red-eared Slider) and a species of conservation concern, Pseudemys gorzugi (Rio Grande Cooter). Here, we assessed isotopic niche widths of Rio Grande Cooter and niche overlap where it co-occurs with Red-eared Slider in the Pecos River tributaries, New Mexico, USA. We used carbon (d 13 C) and nitrogen (d 15 N) stable isotope analyses of two different tissue types: blood and claw. Our results showed niche partitioning among different populations of P. gorzugi and among sex classes within a population. At the sites where both species occur, we documented niche overlap, especially for d 15 N values. Stable isotopes showed similar ellipse area overlap (SEA B) of T. scripta and P. gorzugi among populations (~20% 2), but little to no overlap of standard ellipse areas for small sample sizes (SEA C). The distribution of prey items in the diets of P. gorzugi and T. scripta revealed the differences in resource selection. We observed that differences in the diets of P. gorzugi among populations correspond to local resource availability, suggesting opportunistic foraging behavior of P. gorzugi. Our study aids in understanding the ecology and natural history of P. gorzugi, one of the least studied freshwater turtles in the USA. Moreover, our study provides insights to interspecific relations of T. scripta in their native range.
... These findings are similar to previous dietary studies of megacephalic Graptemys species (Sanderson 1974;Shealy 1976;Lindeman 2016;Sterrett et al. 2020) and further support the hypothesis that dependence on mollusks is enhanced by larger jaws and bulkier jaw musculature (Lindeman 2000a). McCoy et al. (2020) reported substantially higher molluscivory in G. gibbonsi (82% of total prey volume across samples) than in G. pearlensis (24%), but they did not include details on the types of mollusks consumed or a breakdown of diet by sex and size class, making comparison to our results difficult. They also reported high consumption by G. pearlensis of fish (44%), a taxon absent from our samples and generally found to be low to absent in the diets of Graptemys spp. ...
Patterns of interspecific differences in the diets of nonavian reptiles may be complicated by intraspecific dietary diversity that is related to variation in body size and trophic morphology. Graptemys pearlensis and Graptemys gibbonsi are sister map turtle species endemic to adjacent Gulf Coastal river drainages and both are candidates for federal listing. Little has been reported about the diet of either species. We examined fecal samples collected from turtles captured throughout their respective ranges in the Pearl and Pascagoula river drainages. Females of both species primarily consumed invasive Asian clams (Corbicula spp.), with adult females being nearly exclusively molluscivorous while juvenile females also consumed softer-bodied prey items. Adult males and unsexed juveniles primarily consumed insects; males in particular specialized on trichopteran larvae and also ate more mollusks than did unsexed juveniles. In comparisons to each species' sympatric congeneric sawback species, the two focal species' avoidance of sponges caused large interspecific differences. Due to their greater consumption of insect prey than mollusks, unsexed juvenile G. pearlensis and unsexed juvenile and adult male G. gibbonsi were slightly more similar in diet to their respective sympatric congeneric sawbacks than to conspecific large juvenile females and adult females. Scoring of similarity in diet was greatly influenced by strongly predominant prey items found within each class of each species. Future studies of interspecific dietary differences in sympatric species should include consideration of intraspecific variation in diet as it relates to body size and sexual dimorphism.
... Many recent studies have focused on the diet of freshwater turtles worldwide, including studies from North America [1,2], South America [3], Europe [4,5], Asia [6], and Africa [7], but most species remain little known and there is virtually no study summarizing from a quantitative view the dietary characteristics of any turtle family. However, these kinds of reviews/meta-analyses may uncover life-history aspects that remain hidden in individual studies at the local scale, thus considerably enhancing the knowledge on the diversity of ecological strategies of freshwater turtles worldwide. ...
... More specifically, are these turtles essentially carnivorous as previously reported on the basis of general anecdotal literature [8,10]? (2) Is there any effect of species, sex, or habitat (vegetation cover) on the diet composition of the various populations? This question is relevant because many studies have showed that there are considerable dietary variations associated with these variables in freshwater turtles [11]. ...
Citation: Luiselli, L.; Demaya, G.S.; Benansio, J.S.; Petrozzi, F.; Akani, G.C.; Eniang, E.A.; Ajong, S.N.; Di Vittorio, M.; Amadi, N.; Dendi, D. A Comparative Analysis of the Diets of a Genus of Freshwater Turtles across Africa. Diversity 2021, 13, 165.
... The potential influence of sampling bias and habitat availability should be considered when interpreting the results herein presented. Additionally, studies on the trophic niche characteristics of the two species in sympatric versus allopatric conditions should be carried out, as interspecific competition and food niche partitioning often have been discovered in freshwater turtle communities from elsewhere, including West Africa [5,14,33]. Institutional Review Board Statement: Ethical review and approval were waived for this study, due to the fact that the two study species are free to catch and even to consume in Ivory Coast and do not need any capture and handling permit. In addition, no individuals were sacri-fied during the process of this study. ...
Resource partitioning, the division of limited resources by species to help avoid competition , has been observed in freshwater turtle assemblages in several natural systems but has rarely been studied in tropical African ecosystems. Here, we investigate habitat preferences of two conge-neric species in the family Pelomedusidae, Pelusios castaneus and P. cupulatta, in riverine/wetland habitats in the southern Ivory Coast (West Africa). Pelusios castaneus is a widespread species across West-central African savannahs and open forests, whereas P. cupulatta is endemic to the Upper Guinean forest region in West Africa. The two species have a similar diet composition (mainly car-nivorous) but diverge considerably in body size, P. cupulatta being much larger. We use hand-fishing nets and fishing funnel traps to record turtles in 18 distinct sites and analyze habitat preferences by species at two spatial scales. At a macro-habitat scale, P. castaneus is captured mainly in marsh-lands, whereas P. cupulatta is found in both rivers and wetlands. The two species differ significantly in their use of: (i) banks (P. castaneus being found primarily in spots with grassy banks, whereas P. cupulatta is found in spots with forested banks), and (ii) aquatic vegetation (P. cupulatta prefers spots with more abundant aquatic vegetation than P. castaneus), but both species select sites with no or moderate current. Additionally, in sites where P. cupulatta is not found, P. castaneus expands its spatial niche at multiple habitat scales, notably invading waterbodies with forested banks. Our results suggest that these two Pelomedusid turtle species potentially compete in the freshwater habitats in the southern Ivory Coast.
