MethodsTurtle Visual SurveysWe conducted visual surveys at four ponds in Green-Wood Cemetery and four ponds in Prospect Park. Surveys were performed for 15 minutes and turtles were identified using binoculars while walking around the pond. We recorded the species and approximate size of all turtles.Basking SpaceBasking space was defined as rocks, logs, and pond bank at an angle of approximately 45° or less, wide enough to climb on (approximately 0.3 m), and clear of tall vegetation or rocks that could impede access. Basking space was measured using a one meter PVC pipe. Each meter of pond bank in which more than half of the PVC pipe was considered basking space was counted. Rocks and logs were also measured using the PVC pipe. The basking space (m) was divided by the pond area (m²). Pond areas were measured using Google Maps.Duckweed CoverageEach pond was rated on a 0-10 scale for amount of duckweed covering the surface, with 0 meaning 0% of the surface was covered and 10 meaning 100% of the surface was covered.Water QualityDissolved oxygen tests were conducted on samples from each pond site using a LaMotte dissolved oxygen test kit. Multiple trials were carried out at each site and the results were averaged.

Introduction Results

Acknowledgements

References

DiscussionRed-Eared Sliders vs. Eastern Painted TurtlesWe found significantly more Red-Eared Sliders than Eastern Painted Turtles at our pond sites, as seen in Figure 1. The invasive populations were most likely established through pet drop-offs and continue to be increased by pet drop-offs. Our team suggests greater efforts to educate the public about the detrimental effects of invasive species through programs or signs as a preventative measure.Basking SpaceFigure 2 shows a direct relationship between Red-Eared Slider abundance and basking space, supporting our hypothesis. The Pearson correlation coefficient (r) indicates a moderate correlation.Dissolved OxygenFigure 3 shows a direct relationship between Red-Eared Slider abundance and dissolved oxygen, supporting our hypothesis. The r-value shows a moderate correlation. In future studies, we would perform more dissolved oxygen trials at regulated times of day. Duckweed CoverageFigure 4 shows an inverse relationship between Red-Eared Slider abundance and the amount of duckweed covering the pond, which does not support our hypothesis. The r-value shows a moderate negative correlation. We concluded that other factors, such as basking space, played a larger role in determining turtle abundance.Additional NotesBecause of the very low number of Eastern Painted Turtle sightings at all pond sites, there is little correlation between Eastern Painted Turtle abundance and the pond variables shown in Figures 2-4. In Figures 2-4, the pond site Vale of Cashmere was excluded as an outlier because of its extremely small size and high surrounding wall.

This research was funded by the National Science Foundation as a part of Project TRUE, a partnership between the Wildlife Conservation Society and Fordham University. We would like to thank Green-Wood Cemetery and the Prospect Park Alliance for giving us access to their ponds. We would also like to give a special thank you to our amazing site leaders Sarah Davis and Carol Henger for their guidance.

¹ Somma, L.A., Foster, A., Fuller, P. 2017. Trachemys scripta elegans. U.S. Geological Survey: Nonindigenous Aquatic Species Database.² Invasive Species Specialist Group. 2009. Species profile: Trachemys scripta elegans. Global Invasive Species Database.³ Cadi, A., Joly, P. 2003. Competition for basking places between the endangered European pond turtle (Emys orbicularis galloitalica) and the introduced red-eared slider (Trachemys scripta elegans). Canadian Journal of Zoology 81: 1392-1398.⁴ Polo-Cavia, N., Lopez, P., Martin, J. 2012. Feeding status and basking requirements of freshwater turtles in an invasion context. Physiology and Behavior 105: 1208-1213.⁵ Burger, R., Gehrmann, W., Ferguson, G. 2007. Evaluation of UVB reduction by materials commonly used in reptile husbandry. Zoo Biology 26: 417-423.⁶ Tennessee Wildlife Resources Agency. 2017. Eastern Painted Turtle. Tennessee’s Watchable Wildlife.⁷ Texas A&M University, 2017. Dissolved Oxygen. Department of Wildlife and Fisheries Science⁸ https://www.pinterest.com/pin/368310075746817946/?lp=true⁹ https://www.pinterest.com/pin/523684262890751313/?lp=true

Research QuestionQuestion: How is turtle abundance related to differing pond variables?Hypothesis 1: There will be a greater abundance of Red-Eared Sliders than Eastern Painted Turtles at the pond sites.Hypothesis 2: Turtle abundance will be positively correlated with available basking space, dissolved oxygen level, and duckweed coverage.

Red-Eared Slider vs. Eastern Painted Turtle Abundance in Brooklyn Ponds

Nancy Rutishauser, Eleaka McDonald, Anthony Saravo, Ivy Trocco, Sarah Davis, Carol Henger

Figure 1: Bars represent the total number of turtles and are separated by species. The values used for turtle abundance show the largest number of individuals of each species seen during a single survey for each pond. Ponds are listed in order of increasing basking space.

Figure 2: Trend lines show a direct relationship between turtle abundance and basking space.Red-Eared Slider: r = 0.392Eastern Painted Turtle: r = 0.201

Figure 3: Trend lines show a direct relationship between Red-Eared Slider abundance and dissolved oxygen and an inverse relationship between Eastern Painted Turtle abundance and dissolved oxygen.Red-Eared Slider: r = 0.490Eastern Painted Turtle: r = -0.516

Figure 4: Trend lines show an inverse relationship between turtle abundance and duckweed coverage.Red-Eared Slider: r = -0.453Eastern Painted Turtle: r = -0.187

Red-Eared Slider (Trachemys scripta elegans)⁸ Eastern Painted Turtle (Chrysemys picta)⁹

Red-Eared Sliders, a turtle species native to the Mississippi River Valley, are among the top 100 invasive species in the world.¹ They have been distributed widely as pets, but are often released by individuals unprepared to care for full-sized adults that can live for 40 years or more in captivity.² Red-Eared Sliders and Eastern Painted Turtles, a native New York species, are present in Prospect Park and Green-Wood Cemetery ponds. Red-Eared Sliders have several traits that may allow them to outcompete the native Eastern Painted Turtles, including larger adult size, higher fecundity, and younger age at which maturity is reached.³ These traits could help Red-Eared Sliders outcompete native turtles for resources, such as basking space. Pond turtles are poikilotherms; their body temperatures vary with the environment. They bask to maintain a high enough body temperature for metabolic activity and normal growth and reproduction rates.⁴ UVB rays from the sun are also necessary for turtles to properly maintain vitamin D3 levels, which aid in calcium processing.⁵ Pond turtles may also compete over duckweed, a potential food source.⁶ Additionally, dissolved oxygen is a good indicator of pond health and impacts the amount of turtles and fish (another turtle food source) that the pond can support.⁷

Turtle Survey