Invasive Red-eared Slider Research Articles

Population Demographics of Native Red-Bellied Cooters and Invasive Red-Eared Sliders in a Virginia Lake

Population Demographics of Native Red-Bellied Cooters and Invasive Red-Eared Sliders in a Virginia Lake

Trained quantity discrimination in invasive red-eared slider and a comparison with the native stripe-necked turtle

Little is known about the behavioral and cognitive traits that best predict invasion success. Evidence is mounting that cognitive performance correlates with survival and fecundity, two pivotal factors for the successful establishment of invasive populations. We assessed the quantity discrimination ability of the globally invasive red-eared slider (Trachemys scripta elegans). We further compared it to that of the native stripe-necked turtle (Mauremys sinensis), which has been previously evaluated for its superior quantity discrimination ability. Specifically, our experimental designs aimed to quantify the learning ability as numerosity pairs increased in difficulty (termed fixed numerosity tests), and the immediate response when turtles were presented with varied challenges concurrently in the same tests (termed mixed numerosity tests). Our findings reaffirm the remarkable ability of freshwater turtles to discern numerical differences as close as 9 vs 10 (ratio = 0.9), which was comparable to the stripe-necked turtle’s performance. However, the red-eared slider exhibited a moderate decrease in performance in high ratio tests, indicating a potentially enhanced cognitive capacity to adapt to novel challenges. Our experimental design is repeatable and is adaptable to a range of freshwater turtles. These findings emphasize the potential importance of cognitive research to the underlying mechanisms of successful species invasions.

A misconstrued alien: the freshwater turtle Emydura macquarii in the Greater Sydney region

ABSTRACT Many freshwater turtle species have spread beyond their natural distributions through human agency, but introduced populations can be difficult to differentiate from natural ones. The occurrence of an Australian freshwater turtle, Emydura macquarii, in the Greater Sydney region, Australia’s most populous urban and peri-urban area, has alternatively been assumed to be natural or deduced to be due to anthropogenic introduction. I apply multiple lines of evidence to show that the occurrence of E. macquarii in the Sydney region is not natural and that the species has proliferated and spread there much more than the notoriously invasive red-eared slider turtle, Trachemys scripta elegans. The E. macquarii population of the Sydney region is highly diverse morphologically, with individuals variously resembling E. macquarii from Queensland, the north coast of New South Wales, and the Murray–Darling Basin. Better understanding is needed of the population genetics of E. macquarii in the Sydney region, the interactions among the region’s native and introduced turtles, and the impacts of E. macquarii on biota other than turtles.

Bacterial communities of the threatened Western Pond Turtle may be impacted by land use.

As semi-aquatic species that use both terrestrial and aquatic habitats, freshwater turtles and their microbial communities are especially sensitive to the impacts of habitat disturbance. In this study, we use 16S rRNA amplicon sequencing to characterize the shell and cloacal bacterial communities of turtles in the San Francisco Bay Area. We captured western pond turtles (Actinemys/Emys marmorata) across eight sites located in urban and rural environments, along with invasive red-eared sliders (Trachemys scripta elegans). We assessed differences in western pond turtle bacterial communities diversity/composition between shell and cloacal samples and evaluated how alpha/beta diversity metrics were influenced by habitat quality. We found phylum-level bacterial taxonomic turnover in the bacterial communities of western pond turtles relative to the host tissue substrate samples. Our findings indicate that location identity elicits a high degree of lower-level (i.e. species/genus) bacterial taxonomic turnover. Further, we found that samples originating from good quality habitat had poorer shell bacterial communities but more diverse cloacal ones. The shell bacterial communities of red-eared sliders overlapped with those western pond turtles suggesting the existence of microbial dispersal between these two species. Our results add to our current understanding of turtle symbiont microbial ecology by establishing patterns of bacterial symbiont variation in an urban to rural gradient.

Female-biased Sex Ratios and Control Effects Observed in Two Local Populations of Red-eared Slider Turtles (Trachemys scripta elegans) in Western Japan

High abundance of invasive red-eared slider (RES) turtles (Trachemys scripta elegans) in Japan has been a serious issue in freshwater ecosystems. Information on reproductive parameters, such as sex ratios, of RES turtles is needed to effectively control the invasive species. We conducted a long-term field study on RES turtles at two study sites: the Taisho River (a shallow river) and Teradaike Pond (an irrigation reservoir that was irregularly drained to maintain the embankment and water quality) in western Japan. Using trapping and muddling methods, we captured RES turtles and checked for sex, carapace length, and body weight. We also examined whether the population of RES turtles could be reduced by continuously removing the turtles captured at each study site. The sex ratio (male/both sexes) of RES turtles that could be sexed by external morphology (presumably adult turtles) was 0.27 at the Taisho River and 0.26 at Teradaike Pond. At both sites, these sex ratios were almost the same as those of RES turtles that could be sexed only by necropsy after euthanasia (presumably juvenile turtles). These sex ratios were markedly biased toward females and consistent between the adult and the juvenile turtles, thus suggesting that more females had been produced than males. At the Taisho River, a total of 1,366 RES turtles were captured and eliminated over more than ten years. Nevertheless, the annual catch did not tend to decrease and only an effect of preventing population growth was observed. At Teradaike Pond, a total of 1,831 RES turtles were captured over nine years. Nearly half of them were caught for the initial two years, during which the pond was drained. Thereafter, the annual catch of RES turtles clearly decreased. These results suggest that it is difficult to control RES turtles established in rivers but that it is feasible to effectively control RES turtles in enclosed small water bodies, such as irrigation reservoirs, by intensively capturing and eliminating the turtles during the drainage period.

Coexistence of Native and Invasive Freshwater Turtles: The Llobregat Delta (NE Iberian Peninsula) as a Case Study

The global degradation of wetlands is increasing their susceptibility to invasions, which is greatly determined by a niche overlap between native and invasive species. We analyze its role in regulating the coexistence of the native Mediterranean stripe-necked terrapin Mauremys leprosa and the invasive Red-eared Slider Trachemys scripta elegans in a coastal wetland. We analyzed both water chemistry and landscape attributes, using variance-partitioning analysis to isolate the variance explained by each set of variables. Then, the influence of environmental variables on species co-occurrence patterns was assessed by using latent variable models (LVM), which account for correlation between species that may be attributable to biotic interactions or missing environmental covariates. The species showed a very low niche overlap, with clear differences in their response to environmental and landscape filters. The distribution of T. s. elegans was largely explained by landscape variables, preferring uniform landscapes within the daily movement buffer, whereas at larger scales, it was associated with a high diversity of habitats of small and uniform relative sizes. A high percentage of the distribution of M. leprosa was unexplained by the measured variables and may be related to the competitive exclusion processes with T. s. elegans. The species was positively related with large patches with high perimeter values or ecotone area at medium spatial scales, and it was benefited from a marked heterogeneity in the patches’ size at larger scale. According to latent variable models, both species had wide eutrophication and salinity tolerance ranges, but they showed different environmental preferences. T. s. elegans was related to eutrophic freshwater environments, whereas M. leprosa was related to more saline and less eutrophic waters. Our results suggest that M. leprosa modifies its habitat use in order to avoid interaction with the T. s. elegans. Thus, management actions aimed at removing the invasive species from the territory and promoting habitat heterogeneity might be needed to protect M. leprosa and avoid local extinctions.

A Captive Study of Interactions between the Invasive Red-eared Slider, Trachemys scripta elegans (Wied 1838), and Native Indian Turtles

A Captive Study of Interactions between the Invasive Red-eared Slider, Trachemys scripta elegans (Wied 1838), and Native Indian Turtles

The invasive red-eared slider turtle is more successful than the native Chinese three-keeled pond turtle: evidence from the gut microbiota.

BackgroundThe mutualistic symbiosis between the gut microbial communities (microbiota) and their host animals has attracted much attention. Many factors potentially affect the gut microbiota, which also varies among host animals. The native Chinese three-keeled pond turtle (Chinemys reevesii) and the invasive red-eared slider turtle (Trachemys scripta elegans) are two common farm-raised species in China, with the latter generally considered a more successful species. However, supporting evidence from the gut microbiota has yet to be collected.MethodsWe collected feces samples from these two turtle species raised in a farm under identical conditions, and analyzed the composition and relative abundance of the gut microbes using bacterial 16S rRNA sequencing on the Roach/454 platform.ResultsThe gut microbiota was mainly composed of Bacteroidetes and Firmicutes at the phylum level, and Porphyromonadaceae, Bacteroidaceae and Lachnospiraceae at the family level in both species. The relative abundance of the microbes and gene functions in the gut microbiota differed between the two species, whereas alpha or beta diversity did not. Microbes of the families Bacteroidaceae, Clostridiaceae and Lachnospiraceae were comparatively more abundant in C. reevesii, whereas those of the families Porphyromonadaceae and Fusobacteriaceae were comparatively more abundant in T. s. elegans. In both species the gut microbiota had functional roles in enhancing metabolism, genetic information processing and environmental information processing according to the Kyoto Encyclopedia of Genes and Genomes database. The potential to gain mass is greater in T. s. elegans than in C. reevesii, as revealed by the fact that the Firmicutes/Bacteroidetes ratio was lower in the former species. The percentage of human disease-related functional genes was lower in T. s. elegans than in C. reevesii, presumably suggesting an enhanced potential to colonize new habitats in the former species.

Newly discovered vital population of the European pond turtle Emys orbicularis in Prilipe oxbow lakes (SE Slovenia)

In this study we examined the population of the European pond turtle (Emys orbicularis) in the Prilipe oxbow lakes along the Sava River. The species’ sex and age structure were estimated as well its population size. In the area of approximately 5.9 ha of water surface, 3 individuals were found in 2008 and 70 in 2019, when a more detailed survey was conducted. The population size was estimated at 125 individuals. According to the age structure and confirmed reproduction, the population is recognized as viable. The main threats to the survival of European pond turtles in this area are potential direct interventions into habitat as well as indirect changes such as alterations in flood regime or in groundwater level. Additionally it is threatened by the invasive red-eared slider (Trachemys scripta elegans), the reproduction of which was also confirmed during our survey. Although the studied area meets all conditions for the establishment of the Natura 2000 site, it was not included in this network in 2003 due to lack of knowledge as far as this species was concerned.

Environmental DNA detection and quantification of invasive red-eared sliders, Trachemy scripta elegans, in ponds and the influence of water quality.

Environmental DNA (eDNA) is a powerful tool for monitoring the distribution of aquatic macro-organisms. However, environmental factors, including the water temperature and water quality, can affect the inhibition and/or degradation of eDNA, which complicates accurate estimations of eDNA concentrations and the detection of the presence/absence of species in natural habitats. Further very few eDNA studies have been conducted for reptiles, especially with respect to estimating their biomass and/or abundances. Here we examined the relationship between the visually-observed number of red-eared sliders (Trachemys scripta elegans) and eDNA concentrations across 100 ponds. Additionally, we evaluated the effect of water quality on red-eared slider eDNA concentration in these ponds. We found that there was a significant positive correlation between the observed number of red-eared sliders and the eDNA concentration in the ponds. On comparing various water quality indicators, including dissolved nitrogen, dissolved phosphorous, organic matter, and chlorophyll a (Chl. a), we found that only Chl. a had a negative correlation with the red-eared slider eDNA concentration, while we did not find any inhibition in the quantitative PCR. We conclude that concentrations of eDNA can potentially be used for estimating the abundance of the red-eared slider. Additionally, Chl. a might indirectly influence the degradation of eDNA through the microorganisms bonded to the phytoplankton in the ponds, as microbial activity is thought to decrease eDNA persistence.

Red-eared Sliders Trachemys scripta elegans in southern Sydney, including new incursions

The invasive Red-eared Slider Trachemys scripta elegans has spread extensively, forming naturalised populations on all continents except Antarctica. Ranked among the 100 worst invasive species, there are biosecurity concerns that native turtles become outcompeted and displaced, as well as other speculative impacts. The actual ecological impacts in Australia have not been properly studied, however impacts shown in other countries are concerning. Incursions have presented in New South Wales, Queensland, Victoria, Western Australia and the Australian Capital Territory. A number of sightings have been reported from southern Sydney, including six sites where more than one slider has persisted. The incursions at Yeramba Lagoon in the Georges River National Park and the Centennial Parklands have been the most documented, whereas incursions in the Lime Kiln Bay Wetland, Rockdale Wetlands Corridor and Audley in the Royal National Park appear to have occurred recently. To date, breeding in southern Sydney has only been confirmed at Yeramba Lagoon. A range of removal techniques have been successfully applied to eradicate isolated incursions in Brisbane and Melbourne. However, these options are difficult to implement in southern Sydney sites where incursions occur in high visitation public lands.

Distribution of invasive Red-eared Sliders, Trachemys scripta (Testudines: Emydidae) in the wetlands of Gujarat State, India

Distribution of invasive Red-eared Sliders, Trachemys scripta (Testudines: Emydidae) in the wetlands of Gujarat State, India

Relative Abundance of Invasive Red–Eared Sliders (Trachemys Scripta Elegans) and Native Western Pond Turtles (Emys Marmorata) at Clear Lake, Lake County, California

Abstract During 2010–2018 we studied the relative abundance of invasive red-eared sliders (Trachemys scripta elegans) and native western pond turtles (Emys marmorata) at Clear Lake and its associat...

HEALTH ASSESSMENT OF FREE-RANGING CHELONIANS IN AN URBAN SECTION OF THE BRONX RIVER, NEW YORK, USA.

The Bronx River in Bronx, New York, US spans an area of significant human development and has been subject to historic and ongoing industrial contamination. We evaluated the health of freeranging native common snapping turtles ( Chelydra serpentina) and nonnative invasive red-eared sliders ( Trachemys scripta) in a segment of the Bronx River between May and July 2012. In 18 snapping turtles and nine sliders, complete physical examinations were performed, ectoparasites collected, and blood was analyzed for contaminants (mercury, thallium, cadmium, arsenic, lead, selenium, oxychlordane, alpha-chlordane, dieldrin, DDD, DDE, polychlorinated biphenyls). Complete blood counts and the presence of hemoparasites were determined in 16 snapping turtles and nine sliders. Swabs of the choana and cloaca were screened for ranavirus, adenovirus, herpesvirus, and Mycoplasma spp. by PCR in 39 snapping turtles and 28 sliders. Both turtle species exhibited bioaccumulation of various environmental contaminants, particularly organochlorines and polychlorinated biphenyls. Molecular screening revealed a unique herpesvirus in each species. A Mycoplasma sp. previously isolated from emydid turtles was detected in red-eared sliders while a unique Mycoplasma sp. was identified in common snapping turtles. Ranaviruses and adenoviruses were not detected. Our study established a baseline health assessment to which future data can be compared. Moreover, it served to expand the knowledge and patterns of health markers, environmental contaminants, and microorganisms of freeranging chelonians.

Rozmieszczenie stanowisk inwazyjnego żółwia czerwonolicego (Trachemys scripta elegans) (Wied, 1838) w województwie zachodniopomorskim (północno-zachodnia Polska)

Rozmieszczenie stanowisk inwazyjnego żółwia czerwonolicego (Trachemys scripta elegans) (Wied, 1838) w województwie zachodniopomorskim (północno-zachodnia Polska)

Challenges in confirming eradication success of invasive red-eared sliders

Confirming eradication success can be notoriously difficult and costly, especially when the species is still present but remains undetected, due to very low population densities and imperfect detection methods. There has been a lack of research on appropriate guidelines and estimation procedures for declaring eradication success for programs aimed at eradicating alien reptiles. Here we develop quantitative rules for confirmation monitoring in eradication campaigns of the red-eared slider turtle (Trachemys scripta elegans). We used a database of slider trapping data from control and eradication campaigns conducted in localities across the Iberian Peninsula and southern France to construct models for inferring appropriate trapping efforts for confirming slider turtle eradication. Basking traps were slightly more efficient than net traps in capturing sliders, although trapping was an inefficient monitoring method given the low capture probabilities estimated. The results of our spatially-explicit eradication scenarios revealed the importance of habitat configuration in declaring eradication success. Declaration of eradication success is contingent on the thresholds set to minimise false positives (i.e., falsely declaring eradication successful), but in any scenario large trapping efforts were required to confirm eradication. Given the low estimated capture probabilities, alternative methods such as eDNA and visual surveys should be considered for monitoring sliders. We suggest that if the costs associated with the impact of alien sliders can be adequately estimated, then eradication can be confirmed by rules minimising both false positive and negative error rates. Otherwise, rules minimising false positive errors would be more appropriate.

Distribution and Status of the Alien Invasive Red-eared Slider (Trachemys scripta elegans) in Jeju Island, South Korea

Distribution and Status of the Alien Invasive Red-eared Slider (Trachemys scripta elegans) in Jeju Island, South Korea

Unusual population attributes of invasive red-eared slider turtles (Trachemys scripta elegans) in Japan: do they have a performance advantage?

Unusual population attributes of invasive red-eared slider turtles (Trachemys scripta elegans) in Japan: do they have a performance advantage?

The high resolution melting analysis (HRM) as a molecular tool for monitoring parasites of the wildlife.

In an interconnected world, the international pet trade on wild animals is becoming increasingly important. As a consequence, non-native parasite species are introduced, which affect the health of wildlife and contribute to the loss of biodiversity. Because the investigation of parasite diversity within vulnerable host species implies the molecular identification of large samples of parasite eggs, the sequencing of DNA barcodes is time-consuming and costly. Thereby, the objectives of our study were to apply the high resolution melting (HRM) approach for species determination from pools of parasite eggs. Molecular assays were validated on flatworm parasites (polystomes) infecting the Mediterranean pond turtle Mauremys leprosa and the invasive red-eared slider Trachemys scripta elegans in French natural environments. HRM analysis results indicated that double or multiple parasitic infections could be detected from wild animal populations. They also showed that the cycle of parasite eggs production was not regular over time and may depend on several factors, among which the ecological niche and the target species. Thereby, monitoring parasites from wild endangered animals implies periodic parasitological surveys to avoid false negative diagnostics, based solely on eggs production.

Effect of an alien turtle predator on movement activity of European brown frog tadpoles

An increasing amount of attention has been devoted to studying the impact of non-native plant and animal species on native species. In this paper, we examined the antipredator response of naïve European brown frog (Rana temporaria Linnaeus, 1758) tadpoles to water-borne chemical cues from invasive red-eared slider turtles (Trachemys scripta elegans Wied, 1838) in the presence and the absence of conspecific tadpoles. The level of swimming activity was expressed as the length of the tadpoles’ trajectory. The tadpoles showed a decrease in swimming activity when predator stimuli were present, which was highly significant when the tadpoles were measured individually and did not have contact (visual and chemical) with other tadpoles. In the absence of chemical cues of slider turtles, the presence of other tadpoles had no effect on the level of swimming activity. Moreover, for the first time in tadpoles, we found that the decrease in swimming activity was also accompanied by changes in swimming trajectory, with tadpoles exposed to predator cues swimming in more zigzagged trajectories. Our experiment shows that invasive slider turtles, as a novel predator, have a measurable influence on the swimming behaviour of European brown frog tadpoles. Consequences of the reduced swimming activity of tadpoles, like its impact on growth, are discussed.