An Assessment of the Environmental Impacts of. Red-Eared Slider Introduction

Transcription

1 An Assessment of the Environmental Impacts of Red-Eared Slider Introduction Richard Aaron Gibbs ENVS 190; Senior Thesis California State University, Sacramento December 14, 2017

2 Table of Contents: Abstract pg. 2 Introduction.. pg. 2 Background pg. 2 Description..... pg. 3 Range.. pg. 3 Habitat pg. 3 Biology... pg. 4 Predators.. pg. 6 Area of Focus... pg. 6 Methods. pg. 7 Results... pg. 7 Impacts.. pg. 7 Management... pg. 11 Discussion pg. 14 Are Red-Eared Sliders Invasive?. pg. 14 What Do Their Impacts Entail?... pg. 15 Influence Near Sacramento... pg. 16 How Can Red-Eared Sliders be Managed?. pg. 17 Conclusion.. pg. 19 Figures... pg. 21 Literature Cited... pg. 23 1

3 Abstract The Red-Eared Slider (Trachemys Scripta Elegans) is a widely spread freshwater turtle native to the Mississippi River valley. It became popular in the food and pet trade and began getting exported around the world, where they started to impose negative impacts on native turtles outside of their native range. Red-Eared Sliders have been able to spread to so many regions due to their high tolerance of climatic differences and highly variable omnivorous diet. The goal of the research paper is to inform people of the complex environmental impacts from RES and what should be done to manage them. Getting more people to understand the implications of new species introductions and the possible impacts that come with them is paramount for effective species management. Also, establishing a reference condition and understanding of invasive species will help shape the ideals of society that can bring about policy and practices to help improve the quality of future ecosystems. Introduction Background Red-Eared Sliders (RES) are an abundant subspecies of freshwater slider turtles originating from the Mississippi River Valley of the Midwestern and Southern United States. This particular species was discovered in the early 1800s during one of Prince Maximilian of Wied-Neuwied s expeditions through North America (Somma et al., 2017). It is likely that Native Americans had been exposed to RES prior to its declared discovery. Extensive research on the species was not conducted until the mid to late 1900s, with most of the information being gathered in the last 30 years (Somma et al., 2017). Generalist feeding habits and environmental adaptability has allowed RES to move out of their 2

4 original Mississippi Valley Region into other parts of the United States. Through its popularity in the last 30 years as a prime candidate in the North American pet trade, it has been widely relocated outside of its natural range. RES can now be found across much of the United States agricultural and wild ecosystems; RES have been transported and established worldwide due to exportation in the pet trade. Description RES get their common name from the horizontal red stripe that forms along their head behind their eye. They have a lifespan of 30 years for an average adult. Female RES are typically larger than the males. Average carapace length of adult sliders is typically between 5 to 11.5 inches (Somma et al., 2017). Males will typically grow longer frontal claws as they mature and have longer tails compared to their body size. Coloration as a juvenile (Figure 1) for both male and female entails yellow and green striped skin that becomes more subtly olive and green with age. Their shell changes from brighter greens to browns with yellows (Figure 2). The range, habitat, and biology of the RES must be understood to also understand the impacts of RES displacement and invasions. Range The natural range of RES spans from parts of eastern New Mexico to western Georgia as well as along the coast of the Gulf of Mexico up to southern Ohio, Indiana, and most of Illinois, Missouri, and Kansas (Figure 3). However, RES has been spread to many parts of the US outside of its natural range and can be found in clusters throughout the eastern and western United States. RES have not been recorded in the states of Montana, North Dakota, South Dakota, Utah, and Wyoming (Somma et al., 2017). Habitat 3

5 RES is a versatile freshwater turtle in that it can occupy a variety of freshwater habitat types; however, they do tend to favor soft bed waters with plentiful basking sites and plants (Ernst et al., 1994). Freshwater habitats include lakes, marshes, ponds, rivers, reservoirs, streams, and the aquatic phase of vernal pools. RES thrive in both drought regions such as southern California as well as regions that experience harsh winters like Illinois (Gibbons, 1990). Commonly, RES have been found in roadside ditches and in a specific instance, a slider turtle population had been found in a radioactive waste basin and in the runoff of a hog farm in Georgia (Lindsay et al., 2013, Gibbons, 1990). During the spring, riparian areas will be used by RES for nesting sites; additionally using the same areas for hibernation during the winter in more northern regions (Lindsay et al., 2013). Typically, RES move back and forth from land to water to reach basking sites on land while they use the water as refuge from predators (Ernst et al., 1994). Biology RES are omnivores and feed opportunistically, meaning that they will opt for whichever food they can acquire. RES diet has been known to consist of insects, various other animals, fruits, vegetables (Ernst et al., 1994). RES will switch from being primarily carnivorous or herbivorous based on the resources available in their habitat (Lindsay et al., 2013). Juvenile slider turtles prefer a primarily carnivorous diet that turns herbivorous with age (Ernst et al., 1994). The carnivorous diet exhibited in juvenile RES leads to faster growth and higher success in survival for the turtles (Lindsay et al., 2013). Diet shift has been aligned with a habitat shift from low water foraging sites to sites in deeper water (Ernst et al., 1994). Carr (2008) has observed adult RES being particular to take a few bites of a plant before retreating to the water near their foraging site to swallow. 4

6 Body growth of RES has been closely linked to feeding habits and the more pertinent factor of temperature. RES growth periods vary from March to early November in warmer, southern regions and from May to early September in the colder, northern regions (Ernst et al., 1994). During those growth periods the ability to bask is important to growth as the turtles bask in the sun to keep warm and digest food properly. During dormant periods, RES will typically eat less or partially hibernate if it is cold enough. Feeding habits and growth are aligned with temperature; RES will hibernate for a brief period before emerging on a warm winter day and returning back to hibernating if the temperature stays low for another extended period of time (Ernst et al., 1994). RES in northern regions have been recorded as having minimal activity when the temperature falls below 50 F (Ernst et al., 1994). Hibernation can last as little as one month or as long as four to six months. During hibernation periods, RES use downed logs, burrows, or nesting sites as shelter and sometimes will be submerged in water for the duration of hibernation (Ernst et al., 1994, Gibbons, 1990). In the spring, hibernation ends and hatchlings make their way out of their nests (Ernst et al., 1994). RES in captivity have been known to live from 30 to 40 years (Ernst et al., 1994). Longevity of RES is much more variable in the wild due to predation and environmental stressors. Turtles live for at least 25 years if they can reach standing water from their nest (Gibbons, 1990). Males generally reach maturity based on body size where time plays less of role on reproductive ability putting more pressure on the males to consume and grow to sexually able size (Gibbons, 1990). Females reach maturity on the parameter of age where their size is the lesser factor and they will be sexually ready based on time passed to reach an optimal window of fertility where mating would be more likely to produce young (Gibbons, 1990). 5

7 Males are identified as mature once their front claws are elongated and their growth rate becomes slower (Ernst et al., 1994). Females reach maturity in a range of three to five years as they become large enough to be fertile even though they could start mating earlier, but would have less optimized fertility with a higher chance of losing eggs before they are laid (Ernst et al., 1994). In regards to reproduction, male and female RES are equally as likely to court one another (Ernst et al., 1994). A female RES can typically lay six clutches of eggs per year of 30 eggs each which allows for quick population expansion if RES is introduced into a new habitat (California Department of Fish and Wildlife, 2016). Predators: Though RES are not an endangered species they do have a variety of predators and environmental hazards that harm some of their populations. Predators of adult RES are medium to large animals such as alligators, bobcats, coyotes, crows, foxes, otters, and raccoons (Ernst et al., 1994). Juvenile RES are typically eaten by small to medium animals such as frogs, snakes, other turtles, various birds, and various small mammals (Ernst et al., 1994). Despite predation, these turtles still manage to flourish and have expanded well outside their natural range, primarily by humans releasing them in new areas as they were a common pet in the 1990s. Area of Focus The goal of this research is to compose an accurate assessment of the impacts of red-eared slider when they are introduced into various regions and propose management strategies for mitigation of the impacts. This paper also aims to relay information on the complex topic of invasive RES and what should be done in regards to their management. Helping people to understand the implications of invasive species introduction and the 6

8 associated adverse impacts that come with it is paramount. Having a reference and understanding of invasive species will help shape the ideals of society that can bring about policy and practices to help improve the quality of future ecosystems. Methods I conducted a literature research synthesis to compile the results of previous studies on invasive RES and their impacts. A literature review of government documents, library reference material, and scientific journals was conducted. Results Impacts This section is organized starting with international issues, then national, and finally the more local occurrences of RES. RES have been classified by the International Union for Conservation of Nature s (IUCN) Invasive Species Specialist Group as one of the worst invasive species globally (Kikillus et al., 2010, Van Dijk et al., 2011). The IUCN s list of endangered species currently ranks RES as a least concern species which is the lowest amount of endangerment on their scale (Van Dijk et al., 2011). Areas outside of the United States that have established wild populations of RES include: Australia, France, Guam, Italy, Japan, Spain, and various other places (Kikillus et al., 2010). Kikillus et al. (2010) studied suitable habitats that RES would thrive in, comparing the data to the suitable habitats in New Zealand. Kikillus et al. (2010) found that New Zealand was climatically better than 16% of the sites analyzed for their suitability model. However, they had not seen any RES breeding outside of captivity in New Zealand but now know that their region has the potential to harbor a wild population of RES well (Kikillus et al., 2010). If the turtles escaped captivity they could easily invade native habitats in New Zealand. Half of the 7

9 Australian continent is at risk to RES population expansion. Queensland, Australia has developed RES eradication programs (O Keeffe, 2009). Multiple groups of wild RES were found and observed to be breeding by using a detection dog to find RES eggs (O Keeffe, 2009). Turtles taken are used for research on other methods of detecting the species throughout the region. Queensland is encouraging its citizens to bring in as many RES as they can under eradication program areas (O Keeffe, 2009). Large scale programs have more difficulty in confirming the eradication of an invasive species (García-díaz et al., 2017). Many eradication campaigns have been taken up against RES worldwide to fight negative impacts that they bring when out of their natural range. García-díaz et al. (2017) modeled the type of effort it would take to eradicate a population of RES in using data from multitudes of trapping campaigns across the Iberian Peninsula and southern France. Either one of the two types of basket traps would require hundreds of traps used multiple times to get a higher probability of eradication (Ibid.). The data showed that basket traps were found to be more effective than net traps (Ibid.). However, tools are not currently available for confirmation and appropriate declaration of eradication for alien reptiles such as RES (Ibid.). Studies to develop proper tools for verifying eradication are important to mitigating impacts of invasive species so they are not left to re-establish. In Slovenia, just east of northern Italy, Standfuss et al. (2016) examined the reproductive success of slider turtles (Trachemys scripta) at three sites of varying climate within Slovenia. Most of the turtles caught were morphologically correspondent to RES (Standfuss et al., 2016). The objective of this study was to provide information on if RES might become invasive in Slovenia and Standfuss et al. (2016) at least found that the 8

10 current population is growing at a threatening rate. An earlier experiment by Cadi and Joli (2004) used experimental ponds to show the invasive potential Standfuss et al. (2016) observed. In France, Cadi and Joli (2004) tested the impacts RES would have when introduced to European pond turtles (Emys orbicularis, EPT) using four controlled ponds. Control groups consisting entirely of EPT were observed to have more stable body conditions and higher survival rates. Experimental heterogenous groups experienced domination by RES and higher mortality in EPT (Cadi and Joli, 2004). Cadi and Joli (2004) noted that their experiment validated multiple European countries halting the importation of RES from North America, demonstrating that RES are very much a risk to native turtles of the regions RES are introduced to. A comparative study in Pennsylvania tested competition between RES and redbellied turtles (Pseudemys rubriventris, RBT), which are native to the east coast of the United States (Pearson et al. 2015). In controlled feeding, RES negatively impacted RBT growth rates and out-competed RBT in limited resource conditions (Ibid.). Pearson et al. (2015) also found that in either controlled or limited food resources with RES only housing, competition was less than if it was mixed housing containing both RES and RBT. RES was more competitive with its own species rather than when it was in the same space as RBT. RBT were observed to have faster growth rates if there was no limitation on food resources in a mixed housing scenario (Ibid.). Plentiful resources seemed to help RBT thrive in the presence of RES. Prolonging the experiment was predicted to decrease the survivorship of RBT (Ibid.). 9

11 Western pond turtle (Emys marmorata, WPT) is native to the western coast of North America ranging from Washington down to Baja California (Spinks at al., 2003). WPT populations were out-competed by non-native turtle species in the University of California (UC) Davis waterway as RES produced more offspring (Spinks et al., 2003). During their study, Spinks et al. (2003) released 31 hatchling WPT that were headstarted (or raised in captivity) into the Putah Creek arboretum waterway. Headstarted WPT were better able to reach maturity in the conditions of the waterway however, RES still outcompeted the western pond turtles even after RES were removed from the waterway (Spinks et al., 2003). Otherwise, Spinks et al. (2003) notes that the decline of WPT by non-native turtles, mainly RES, would most likely be caused by people releasing RES that were bought as pets. The release of these turtles into Putah Creek adversely impacts the native WPT populations but people either are releasing more RES into the waterway or RES are breeding much faster than they are being removed. A later study by Thomson et al. (2010) took a broad look at the relationship between RES and WPT in the Sacramento River basin. High density sites for RES are adjacent to areas of higher human populations, which again points to continued pet releases contributing to RES population growth (Thomson et al., 2010). Also, Spinks et al. (2003) found viable RES eggs at the UC Davis Arboretum. Thomson et al. (2010) captured and observed multiple RES hatchlings in the arboretum waterway. RES is reproducing near different parts of the Sacramento River basin and presents the risk of being a major competitor with WPT (Thomson et al., 2010). Costa (2013) examined the factors influencing competition between RES and WPT along the UC Davis waterway. RES are less vulnerable to predators than many native 10

12 turtles. A key factor negatively impacting native turtles is competition for basking sites which can affect turtle growth and survival (Ibid.). Due to RES being less inclined to flee, they may occupy basking sites and keep WPT from basking which results in declined health and increased mortality for the native turtles (Ibid.). WPT did flee further than RES overall and reaffirmed the lack of terrestrial predator sensitivity in RES (Ibid.). Turtle escape decisions were found to be based on multiple factors including time of day, visibility, temperature, and possibly basking behavior; WPT were more susceptible to these factors (Ibid.). Management Burbink et al. (1998) looked into the potential uses or drawbacks that come from dispersal corridors which link core habitats and allow species, disease, and possibly fires to spread. In southern Illinois, Burbink et al. (1998) used the Cache River to study the effect of dispersal corridors along the river. RES were among the 13 species that were observed across all four sites along the river (Ibid.). Species richness of amphibians and reptiles was not substantially different depending on the size of the riparian corridor of each site, but species abundance increased in narrow corridors (Ibid). Width of the corridor is not as important when designing a successful corridor when success relies more on what the corridor is composed of (Ibid). Burbink et al. (1998) suggests that the diversity of the habitat must be specifically designed for a target species considering ecology and natural history for proper conservation practices. Bodie (2001) compiled information on a suite of information on ten management practices in relation to freshwater turtles. Removal of woody debris impacts freshwater turtles that rely on the debris for use in basking (Ibid.). When floodplains are drained, it 11

13 essentially takes away the preferred shallow water habitat of a freshwater turtle (Ibid.). Habitat fragmentation from the formation of reservoirs also puts stress on turtles as it can decrease the size of their habitat and increase competition in reduced territories. Competitive exclusion may result in removal of a species from the system (Ibid.). Bodie (2001) asserted that passive management could help in reducing impacts of bad management practices. Encouraging management that focuses on promoting successful turtle reproduction and a diverse group of species in the habitat would increase species survival (Ibid.). Habitat fragmentation is an important species management issue. However, there is a need for research on dispersal of aquatic turtles across fragmented landscapes (Rizkalla and Swihart, 2006). The Wabash River basin of north-central Indiana served to test whether aquatic turtles were non-randomly distributed across different wetlands of a region (Ibid.). RES was found to be negatively affected by habitat fragmentation compared to native turtles, which were less affected by the interspersed agricultural land (Ibid.). RES are more limited in Indiana and were found to prefer smaller, highly connected wetlands and showed particularly restricted occupancy patterns in the wetlands (Ibid.). Rizkalla and Swihart (2006) also note that there was no evidence to suggest competitive exclusion in their study. In Texas, a state where RES are native, Brown et al. (2011a) examine the rate at which RES escape from capture by hoop nets. Larger openings in the nets allow for greater chances of escape but hoop nets have a reputation for being lower quality traps for capturing turtles (Brown et al., 2011a). However, female RES moved more when in the traps, and females escape while males hold onto the net near the opening of the trap and do 12

14 not escape (Brown et al., 2011a). RES also had a lower escape rate than other turtles of the state in similar tests (Brown et al., 2011a). Another study by Brown et al. (2011b) examined the effects of harvesting RES and Texas spiny softshells (Apalone spinifera) under harvest regulations at the time. Brown et al. (2011b) estimated that 2.2% of the water bodies in Texas were protected from harvesting by harvest regulations and RES was lightly present in the protected areas observed. The assumption that protected areas have sustainable populations of turtles is dangerous for the sustainability of the turtles in the region since overharvesting can easily occur in unprotected areas (Brown et al. 2011b). If overharvesting does occur in unprotected areas, there is difficulty in expanding the populations back to their sustainable numbers due to the lack of regulation. Factors of harvesting practices, the amount of turtles eliminated by roadway traffic, and water level fluctuations all come into account but Brown et al. (2011b) suggests that management and regulation of turtle harvesting change to a system similar to how waterfowl are used as a wildlife resource, or at least be revised to better protect waters the turtles are present in. Lindsay et al. (2013) demonstrated the impacts and changes RES contributes to an ecosystem through an experimental pond study in Bastrop, Texas. Specifically, Lindsey et al. (2013) examined how RES affects sediment accumulation, water chemistry, decomposition of leaf litter, and the ability for turtles to transfer bacteria from terrestrial systems into the experimental ponds. Leaf litter decomposition was found to not be significantly affected by the presence of RES in the experimental ponds but had still increased (Lindsay et al., 2013). RES influenced water chemistry and sediment accumulation, enhancing both (Lindsay et al. 2013). When turtles were present, ph of the 13

15 water was higher with a mean of 7.19 compared to the mean ph of 6.77 in ponds without turtles (Lindsay et al. 2013). Sediment accumulation was increased in the ponds including turtles, contributing to the breakdown of leaf litter and variability of invertebrates present. Lindsay et al. (2013) explains that the increased disturbance of the sediment can likely cause different nutrient levels of ammonium, nitrogen, and phosphorus to be present. As far as bacterial transfers, Lindsay et al. (2013) suggested that turtles are not the most potent vector for introducing bacteria such as Salmonellae and, while it is certainly possible, bacteria would more likely be washed into the water from terrestrial systems by substantial rainfall. Discussion A synthesis of research data resulted in four key questions to assess both the threat RES can pose to non-native ecosystems and how that threat can be mitigated. The following section is organized as follows: 1.) Are red eared sliders invasive; 2.) What do their impacts entail; 3.) What is their influence to the Sacramento region; and 4.) How can they be managed? Focus of the third question is in relation to RES influence on WPT. Are Red-Eared Sliders Invasive? The short answer is that RES are invasive in the sense that they are not native in many of the regions they are found in. Otherwise, RES are an average pond turtle. Typically, an invasive species will impact an ecosystem by decreasing biodiversity and upsetting the balance of an ecosystem s health as a result. The behaviors that these turtles exhibit become invasive given proper circumstances as seen in studies by Cadi and Joli (2004), Thompson et al. (2010), and Costa (2014), Pearson et al. (2015), Standfuss et al. (2016). 14

16 Many studies (Spinks et al., 2003, Thompson et al., 2010, Pearson et al., 2015) of RES attribute the spread of this species across the world to food and pet trade. Whether the turtles are being released by people who are saving them from being food or by pet owners who no longer wish to care for their pets, RES will colonize and disperse in an environment they were not already present in. In the cases of RES being introduced into experimental populations of native turtles, RES were shown to be generally more competitive and would take enough resources that both turtle populations could not coexist in long-term time scale (Caid and Joli, 2004, Pearson et al., 2015). Combine RES competitive advantages with environmental plasticity (such as the variable diet and adaptation to diverse habitat) and RES become a problem for native turtles. RES are not an invasive species on their own. When people disperse them internationally through the pet and food trade, their behavior can bring about the impacts of an invasive species. What Do Their Impacts Entail? If RES are introduced into an area with a more docile turtle species, RES will have a specific advantage due to its resistance to predators (Costa, 2014, Pearson et al., 2015). Regarding negative impacts to an ecosystem, RES out-competes other turtle species and replaces them in the turtle niche of the system. Lindsay et al. (2013) studied multiple factors of concern for RES being introduced to ponds in their experiment in Texas. Again, some factors important to a pond ecosystem include: sediment accumulation, water chemistry, leaf litter decomposition, and turtles as a possible carrier of bacteria between systems (Lindsay et al., 2013). Overall, RES improved the condition of the ponds by disturbing sediment and escalating the cycle of nutrients, showing that they are an inherently useful species within their native range (Lindsay et al., 15

17 2013). Also, they were shown to be a minimal conduit for transferring bacteria such as toxic salmonella from land systems into pond systems (Lindsay et al., 2013). However, the California Department of Fish and Wildlife (2016) determined that RES were a major source of salmonella infections in 1975 from hatcheries that sold the turtles and eggs. These turtles are still very capable of spreading bacteria and disease, but it must be understood that they are not the strongest source unless they are being spread on a mass scale by unsanitary hatcheries. Pet RES are generally safer to handle in regard to the chance of contracting a bacterial infection or disease when given clean and well sized habitats. In the wild, cleanliness and size of the habitat are still important but there are more environmental buffers (Predators, insects, plants, etc.) that can make it difficult for bacteria and diseases to spread. The negative impacts come from when RES out-competes turtles that are native to a specific ecosystem. In that case, reduced ecosystem productivity may result and the ecosystem would lose more of its native populations of plants and other animals from being unbalanced. RES are mainly a danger to other freshwater pond turtles. Also, RES are a popular prey for many species of animals and can seamlessly be integrated into a new ecosystem outside of its native range if a turtle species goes extinct and the niche needs filling (Ernst et al., 1994). RES are beneficial when the niche of turtle in an ecosystem needs to be filled. Influence Near Sacramento? A series of studies on the relationship between RES and WPT near and in the Sacramento region, examined the threat RES can be to WPT (Spinks et al., 2003, Thompson et al., 2010, and Costa, 2014). RES were shown to be encroaching on WPT populations 16

18 throughout the Sacramento River basin which presents an issue for conservation, as WPT is a declining freshwater turtle that is native to California (Costa, 2014). WPT are better suited to exist within native ecosystems in California. WPT are state sensitive species highly vulnerable to extinction due to prolonged drought, fragmentation of habitat, and increased predation. For the sake of conservation, RES negatively impact the ability to conserve and restore native pond ecosystems in California. WPT also serve as an important research specimen in regard to freshwater turtles native to mediterranean climate; second to research on cascade effects that lead to extinction events (Rathbun et al. 2002). Also, the reason the RES are in California is because people brought them to the region through the pet trade and released them into waterways, which allowed populations of RES to establish. The California Department of Fish and Wildlife (2016) has recognized RES as an invasive threat and support removal of RES from native California habitats. How Can Red-Eared Sliders Be Managed? The question of accountability and responsibility are important when establishing a management system for freshwater turtles whether they are invasive or not. Burbink et al. (1998) examined the importance of established corridors of dispersal which had shown that the size of a successful corridor can vary somewhat but the presence of a corridor strengthens ecosystems. When species are allowed more space and resources to flourish, they generally will. Well established corridors can allow species to move through regions while resources replenish putting less stress on the ecosystem all together. RES populations are stronger in areas with less habitat fragmentation (Rizkalla and Swihart, 2006). While fragmenting an ecosystem to attempt to remove a species is an option, it is a very ill-advised option that should not be used except for controlled experimental 17

19 purposes. California is already fragmented due to extensive urban and agricultural partitions, but further fragmentation would still be detrimental. A substantially better and ecologically friendlier option for getting rid of an invasive species is the specific removal of the species from the invaded habitat. Trapping or capturing and removing RES from invaded territories is the recommended option for RES removal. Basket nets tend to work better but will still require extensive effort and time to capture most of a RES population (García-díaz et al., 2017). As well, hoop nets seem to have a higher escape rate as far as traps are concerned (Brown et al., 2011a). Citizens of California can help in catching and removing RES so long as they have a valid sport-fishing license (California Department of Fish and Wildlife, 2016). Those with valid licenses can take as many RES per person that they want but must either keep it in captivity until it dies, give it to a local reptile shelter or euthanize it according to the American Veterinary Medical Association Guidelines for Euthanasia of Animals (California Department of Fish and Wildlife, 2016). RES eradication programs have been established in nations outside of the United States for the purpose of invasive species risk management (O Keeffe, 2009, García-díaz et al., 2017). Since RES are present in so many regions around the world eradication programs, while sounding brutish, are somewhat necessary to conserve native species and habitats of invaded regions. Native turtle management should focus on protecting the species from human caused hazards such as: removal of woody debris for basking sites from habitats, habitat fragmentation from typically agriculture or urban development, and floodplain draining which complete changes the habitat (Bodie, 2001). Brown et al. (2011b) recommended protection of RES within their native range become more robust. Constructing 18

20 management platforms that offer more protections to RES in their native region will be a benefit to the ecosystems that they persist in. Recent management is too relaxed in the sense that RES only occur in a few regions, at least in Texas, where they are removed from their habitat at an unsustainable rate (Brown et al., 2011b). Increasing turtle protection and management for RES would be beneficial for both the turtle populations and ecosystem integrity. As well, more education on the effort that goes into raising and caring for RES as pets is needed to inspire people to take better care of their RES or at least know where to take the turtles if they cannot be properly cared for. Better enforced restrictions for the RES pet trade would further reduce the release of RES into the wild. Conclusion Red-Eared Sliders have been spreading across the world for the at least fifty to sixty years if not longer. Being able to gather research about this species in its native habitat and as an invader is invaluable to future freshwater turtle studies. While RES is a risk to many turtle species outside of the Mississippi River Valley, it is important to the balance of ecosystem health in its native range. Information that can be gathered on RES is currently limited by the amount of studies focused on the turtle. More studies will only help in the management of RES. This report sought to assess the impacts of RES introduction and at least was able to compile information from the past few decades indicating what kind of threat RES can pose. Additionally, review and suggestion of management practices were recommended focusing on both better protections for RES within its native range and recommending nonnative RES removal more efficient. RES are more of a threat to other turtles and their native habitat than they are to humans. RES management would conserve and restore habitats 19

21 that they have either been a detriment to or that they can enhance. There is a known population of RES interacting with WPT in the American River Parkway of Sacramento on the south side of Cal Expo that could benefit by using the resources provided by this report. The site under the supervision of Dr. Michelle Stevens is currently in need of management practices to apply to its non-native RES population that is intruding on native WPT. RES will require more understanding of their biological processes in future reports but Ernst et al. (1994) has a magnificent base of information in that regard. This report might serve to raise more questions about RES and the processes that it exhibits and affects. As more studies are performed to better understand RES, better management and educational resources can be formed to help reduce the impacts that RES impose when introduced to new areas. 20

22 Figures Figure 1: Juvenile Red-Eared Slider ( Figure 2: Image of an adult Red-Eared Slider partially submerged (Somma et al., 2017). 21

23 Figure 3: Range and distribution of the Red-Eared Slider (Trachemys Scripta Elegans) in the United States. The yellow/orange color represents the native range of this turtle while the red/brown color represents areas that Red-Eared Slider has been spread to (Somma et al., 2017). 22

24 Literature Cited Bodie, J.R., Stream and Riparian Management for Freshwater Turtles, Journal of Environmental Management, v.62(4), p Brown, D., DeVolld, B., and Forstner, M. 2011a. Escapes From Hoop Nets by Red-Eared Sliders (Trachemys scripta), The Southwestern Naturalist, v.56(1), p Brown, D., Farallo, V., Dixon, J., Baccus, J., Simpson, T., and Forstner, M., 2011b, Freshwater Turtle Conservation in Texas: Harvest Effects and Efficacy of the Current Management Regime, Journal of Wildlife Management, v.75(3), p Burbrink, F.T., Philips, C.A., and Heske, E.J., 1998, A Riparian Zone in Southern Illinois as a Potential Dispersal Corridor for Reptiles and Amphibians, Biological Conservation, v.86(2): Cadi, A., and Joly, P., 2004, Impact of the introduction of the red-eared slider (Trachemys scripta elegans) on survival rates of the European pond turtle (Emys orbicularis), Biodiversity & Conservation, v.13(13), p California Department of Fish and Wildlife, 2016, California s Invaders: Red-Eared Slider, Carr, J., 2008, Terrestrial Foraging by Two Species of Semiaquatic Turtles (Testudines: Emydidae), Southeastern Naturalist, v.7(4), p Costa, Z., 2014, Responses to Predators Differ Between Native and Invasive Freshwater Turtles: Environmental Context and its Implications for Competition, Ethology, v.120(7), p Ernst, C.H., Lovich, J.E., and Barbour, R.W., 1994, Turtles of the United States and Canada. Smithsonian Institute Press, Washington D.C. García-díaz, P., Ramsey, D.S.L., Woolnough, A.P., Franch, M., Llorente, G.A., Montori, A., Buenetxea, X., Larrinaga, A.R., Lasceve, M., Alvarez, A., Traverso, J.M., Valdeon, A., Crespo, A., Rada, V., Ayllon, E., Sancho, V., Lacomba, J.I., Bataller, J.V., Lizana, M., 2017, Challenges in confirming eradication success of invasive red-eared sliders, Biological Invasions, v.19(9), p Gibbons, J.W., 1990, Life History and Ecology of the Slider Turtle, Smithsonian Institution, Washington, D.C. Kikillus, K.H., Hare, K.M., and Hartley, S., 2010, Minimizing False-negatives When Predicting the Potential Distribution of an Invasive Species: a Bioclimatic Envelope for the Redeared Slider at Global and Regional Scales, Animal Conservation, v.13, p

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