Differences in Predation Responses of Native and Invasive Freshwater Turtles

Victoria Kentner Department of Biological Sciences, York College of Pennsylvania

Cost of Staying in Shell-Decreased time for foragingand mating -Risk of over heating

Native Species:Red-Bellied Turtle

Invasive Species:Red-Eared Slider

Introduction•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).

Marburg Turtles

Ho: There will be no difference in the escape responses by speciesHo: There will be no difference in the escape response by location with varying boating traffic

•Threatened in Pa•25-30cm

• 10-15cm

•13-28cm

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

Methods Results

Discussion•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).

ConclusionAlthough 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.

Painted Turtle

Works CitedIUCN. 2000. Guidelines for the Prevention of Biodiversity Loss Caused by Alien Invasive Species. Species Survival Commission, IUCN, Gland, SwitzerlandMartin, Jose; Lopez, Pilar; Polo-Cavia,Maria. 2008. Interspecific Differences in Responses to Predation Risk may Confer Competitive Advantages to Invasive Freshwater Turtle Species. Ethology 114:115-123

AcknowledgmentsI 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.

Basking Abundance of Each SpeciesRed Bellied Red Eared Painted Baby P.

12 5 69 13

Table 1. The abundance of each species found basking during the experiment.

•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.

•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.

ObjectivesDetermine 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.

Predator Response by Species

Red-B

ellie

d

Red-E

ared

Painte

d

Painte

d (bab

y)0

5

10

15

20

25

30

Figure 1. The mean ( 1 S.E.) distance between thekayak and the platform when turtle entered water.One-way ANOVA indicates no signifcant differencebetween species (p=0.1186).

Turtle Species

Dis

tan

ce f

rom

Pla

tfo

rm (

m)

Temperature

Air

Surface

Wat

er

Bottom

Wat

er0

10

20

30

40

Figure 3. Mean ( 1 S.E.) temperature recordedof the air, water at the surface and water atdepth, at the platform. Letter signify differencebetween temperatures from one-way ANOVA(p<0.0001).

ab b

Tem

per

atu

re (

C)

Predator Response by Location

Dubs Cove

Chapel

Cove

Sailb

oat L

aunch

Black

Rock

0

5

10

15

20

25

Figure 2. Mean ( 1 S.E.)of the distance betweenpainted turtles and predator when turtle left theplatform at four sites. Dubs Cove is an area ofprohibited boating, Chapel Cove and SailboatLanch have low boating and Black Rock has highboating traffic. Means that are significantlydifferent are represented by asterisk from One-wayANOVA (p=0.0333).

*

Dis

tan

ce f

rom

Pla

tfo

rm (

m)