Transcript Carlson - York College of Pennsylvania

Invasive Species
http://www.torontozoo.com/adoptapond/turtletally.asp?t=form
Red-Eared Slider
(Trachemys scripta elegans)
Native Species
INVADING TURTLES: Basking activities of Invasive Sliders
(Trachemys scripta) in Lake Marburg, PA.
Kevin Carlson – Department of Biology, York College
Yellow-Bellied Slider
(Trachemys scripta)
METHODS
INTRODUCTION
Painted Turtle
(Chrysemys picta)
Red-Bellied Turtle
(Pseudemys rubriventris)
DISCUSSION
Photo taken from Victoria Kentner’s senior thesis poster
∙ Lake Marburg is located near Hanover in York
County, PA and contains a number of aquatic turtle
species. The species that are native to the lake are the
painted turtle (Chrysemys picta) and the red-bellied
turtle (Pseudemys rubriventris). The invasive sliders
are the red-eared slider (Trachemys scripta elegans)
and the yellow-bellied slider (Trachemys scripta).
The three observational sites that turtles were
studied at are circled: Dubs Cove, Chapel Cove and
Sailboat Cove.
Figure 3. Turtles emerging from hibernation in April. Data shown are
average values for the day ± SEM. A two-way ANOVA with a
Bonferroni Posttest shows a significant difference between painted
turtles and the remaining species on the 6th and 15th.*
Up close shot of turtle basking platforms at Chapel
Cove.
∙ The introduction of invasive species affects
both the structure and the functioning of ecosystems
by altering processes such as energy flows through an
ecosystem by displacing native species from their
ecological niches (Herbold and Moyle 1986).
*
∙ Basking is common in aquatic turtles and is
generally accepted to be a thermoregulatory behavior
(Peterman and Ryan 2009). The active season is
typically limited by environmental temperatures;
basking can elongate the active season.
∙ Being able to emerge from hibernation earlier
(spring: April) and abstain from hibernation later (fall:
October) would give the sliders a competitive
advantage. A longer active season for the sliders
would allow the species to feed more and allow for
the possibility to double-clutch in a single season.
Sample Site-Chapel Cove
Sampling Schedule:
Response to both low and high temperatures:
April – emerge from hibernation
July – response to high temperatures / estivate?
October (mid-September to mid-November) - hibernation
I conducted an observational experiment to determine
whether or not the sliders within Marburg Lake are, as
an invasive species, outcompeting the native turtle
species based on their temperature tolerances and
basking behaviors.
Kestral Pocket Weather
Tracker 4000
Leupold Spotting Scope
http://www.spotters4less.com/
∙ The time spent basking and basking-location
selection are thus expected to obey optimality rules
(Cadi and Joly 2003). Optimality is the idea that the
organism will use specified internal or external
variables to maximize its biological fitness. In this
experiment the main basking optimality principles
would be: 1) The depth of water to maintain safe
escape response; 2) The greatest amount of sunlight
the location receives throughout the day.
Sample Site-Dubs Cove
∙ Larger turtles came out earlier in
the spring – due to their smaller
surface area per body – they had
more potential to hold more heat.
∙ In the summer, larger turtles were
found more likely to estivate or
bask in the water (floating on
vegetation) to avoid overheating.
Turtle Basking Platform
∙ In the fall, observed many fewer
turtles. This may be due to the
water levels being significantly
lower, limiting available basking
locations. This was the opposite of
our expected results.
http://www.aceselectronics.co.uk/product.php?xProd=104
Sampling:
Observation of basking platforms (Leupold Spotting Scope)
Recorded number of:
http://www.lakenormanwildlife.org/basking_platform_project.htm
Red-eared sliders
Future Experiment(s)
Yellow-bellied sliders
Red-bellied turtles
Figure 5. Turtles hibernating in Fall. Data shown are average values
for the day ± SEM. A two-way ANOVA with a Bonferroni Posttest
shows a significant difference between painted turtles and the
remaining species on the 2nd day (September 18th).
Painted turtles
Unknown turtles
Environmental characteristics:
(Kestral Pocket Weather Tracker 4000)
Temperature, Wind speed, Wind chill, Humidity, % Cloud cover, Wet bulb
RESULTS
Cadi, A. A., & Joly, P. P. (2003). Competition for basking places between the endangered European
pond turtle (Emys orbicularisgalloitalica) and the introduced red-eared slider (Trachemys
scripta elegans). Canadian Journal of Zoology, 81(8), 1392-1398. Retrieved from EBSCOhost.
Average Temperature
Temperature (C)
HYPOTHESIS
Ho: There will be no difference in
temperature tolerance between the four
species.
2009
2010
Herbold, B., and Moyle, B.P. 1986. Introduced species and vacant niches. Am. Nat. 128: 751–760.
Peterman, W. E., & Ryan, T. J. (2009). Basking Behavior of Emydid Turtles (Chysemys picta,
Graptemys geographica, and Trachemys scripta) in an Urban Landscape. Northeastern
Naturalist, 16(4), 629-636. Retrieved from EBSCOhost.
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Figure 1. Average temperature recorded
while observing the turtles basking.
Data shown are average values for the
month ± SEM. A one-way ANOVA with a
Tukey Posttest shows no difference
between sampling times.
In my experiment, it was observed that there was a lack of
available basking locations for the turtles due to a
significant drop in the lakes’ water level. It would be worth
investigating the effects and impacts that less basking area
has on all turtles and if it would be beneficial to the turtles’
basking habits to have basking platforms located in the
deeper sections of the lake when water levels drop.
Works Cited
30
H1: Sliders have a wider temperature
tolerance, giving them a complete
advantage over the native species
Figure 4. Average number of turtles observed basking. Data shown
are average values for the month ± SEM. A two-way ANOVA with a
Bonferroni Posttest shows a significant difference both between
species and over the course of the year.
∙A significant difference was
observed between species in
response to temperature. However,
the difference was in the tolerance
of painted turtles (more basking at
higher temperatures and less at
lower temperatures) not in the
tolerance of invasive sliders.
Figure 2. Average temperature recorded by the
National Weather Service for the months of May
through October in 2009 and 2010. Data shown
are average values for the month.
Figure 6. Average basking area available for turtles in spring and fall.
Data shown are average values for the season ± SEM. A two-way
ANOVA with a Bonferroni Posttest shows no difference between
sampling times.
Acknowledgments
I would like to thank Dr. Nolan for her outstanding guidance
and continuous support throughout the entire experiment
as my mentor, this would have never gotten done without
her. Also I would like to thank Dr. Thompson for being a
positive instructor to help my poster and written lab come
together. Finally, I would like to thank the Marburg Lake
(Codorus Creek) staff for their trust and allowing me to
perform my experiment at their park.