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Differences in Predation Responses of Native and Invasive Freshwater Turtles Victoria Kentner Department of Biological Sciences, York College of Pennsylvania Predator Response by Species 10 0 •Although there was no difference in predation responses, the red-eared sliders entered the water more quickly than native turtles, which does not support the results of Martin et al. (2007) (Fig. 1). •In addition, the red-bellied turtle has the largest adult size of the Marburg species, which may give it an advantage of having fewer predators. Also, it was observed sitting on top of and pushing other smaller turtles off of the platforms to maximize basking. • Exposure to aquatic predators and interruptions in basking caused by entering the water is especially costly to a growing baby painted turtle, which may explain their tendency to remain on the platform. • Predation responses did differ by location, particularly at Black Rock where the frequent boating disturbances may have a negative impact on turtle basking (Figure 2). •The cooler water temperatures demonstrate the energetic costs to these poikilotherms as they leave air for water (Figure 3). 10 5 B la ck R au nc h Sa ilb oa tL ha pe l C 40 a b 30 b 20 Conclusion Although invasive species often have a negative impact on native species, the red-eared sliders response to predation does not give it an advantage over the native Marburg species. In addition, boating traffic may be a perceived predation risk causing turtles in areas of high boating traffic to incur unnecessary costs of escape. Works Cited 10 at er 0 W ot to m Ho: There will be no difference in the escape responses by species Ho: There will be no difference in the escape response by location with varying boating traffic Temperature B Determine if the invasive red-eared slider will incur fewer energetic costs than native Marburg species and if differences in boating traffic will affect the turtles response to predation. Figure 2. Mean ( 1 S.E.)of the distance between painted turtles and predator when turtle left the platform at four sites. Dubs Cove is an area of prohibited boating, Chapel Cove and Sailboat Lanch have low boating and Black Rock has high boating traffic. Means that are significantly different are represented by asterisk from One-way ANOVA (p=0.0333). at er Objectives oc k 0 W •13-28cm ) 15 Su rf ac e Continue until platform is reached Record location, boating traffic, 02, water temperature at surface and bottom, and air temperature (b ab y * 20 ir Invasive Species: Red-Eared Slider d 25 ub s • 10-15cm Move forward 3m then stay stationary for 1 minute Record distance between turtle and kayaker when turtle leaves platform Pa in te ed -E ar Predator Response by Location C ov e Gear: binoculars, temperature and DO meter Turtle Species Figure 1. The mean ( 1 S.E.) distance between the kayak and the platform when turtle entered water. One-way ANOVA indicates no signifcant difference between species (p=0.1186). C ov e Gear: 100m tape measure attached to kayak and shore Observer Pa in te ed d l ie ed -B el Kayaker (Predator) d Discussion R Identify turtles approximately 40m away from platform at 4 locations Painted Turtle 5 A •At Lake Marburg in Codorus, Pa, the red-bellied turtle Pseudemys rubriventris, the painted turtle Chrysemys picta and the red-eared slider often bask on offshore platforms built by the park. •Because of the offshore location there are no predator disturbances for the basking turtles besides boating traffic. 15 D •A study in Spain found that the red-eared slider Trachemys scripta elegans may invade the Spanish terrapin Mauremys leprsoa habitat (Martin et al. 2007) by having a larger adult size and staying in its shell and thereby incurring fewer costs. Native Species: Red-Bellied Turtle •Threatened in Pa •25-30cm Basking Abundance of Each Species Red Bellied Red Eared Painted Baby P. 12 5 69 13 20 Temperature (C) Cost of Entering the Water -Energy lost escaping and climbing back on platform -Lower body temperature -Decreased efficiency of digestion and metabolism -Exposure to aquatic predators (small turtles) -Alerts predator previously unaware of turtle 25 Marburg Turtles Distance from Platform (m) Cost of Staying in Shell -Decreased time for foraging and mating -Risk of over heating Table 1. The abundance of each species found basking during the experiment. 30 Distance from Platform (m) •Invasive species often have a negative impact on the native biodiversity when they are placed in an unnatural habitat (IUCN 2000). •Although invasive species are widely studied, little is known about the species specific differences in predation responses. •Turtles have two predator avoidance strategies each with different costs (Martin et al. 2007). R Introduction Results Methods Figure 3. Mean ( 1 S.E.) temperature recorded of the air, water at the surface and water at depth, at the platform. Letter signify difference between temperatures from one-way ANOVA (p<0.0001). IUCN. 2000. Guidelines for the Prevention of Biodiversity Loss Caused by Alien Invasive Species. Species Survival Commission, IUCN, Gland, Switzerland Martin, Jose; Lopez, Pilar; Polo-Cavia,Maria. 2008. Interspecific Differences in Responses to Predation Risk may Confer Competitive Advantages to Invasive Freshwater Turtle Species. Ethology 114:115123 Acknowledgments I would like to thank Dr. Nolan for all her wonderful ideas and kayak skills, the Codorus State Park staff for being so helpful and flexible and Dr. Kleiner for his guidance.