Transcript Kentner - York College of Pennsylvania

Differences in Predation Responses of Native and Invasive
Freshwater Turtles
Victoria Kentner
Department of Biological Sciences, York College of Pennsylvania
Predator Response by Species
15
10
•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).
d
10
5
R
Sa
B
la
ck
La
un
ch
ilb
oa
t
ha
pe
l
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).
Temperature
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
B
ot
to
m
W
W
at
at
er
er
0
ce
Record location,
boating traffic, 02,
water temperature at
surface and bottom,
and air temperature
C
Record distance
between turtle and
kayaker when turtle
leaves platform
oc
k
0
Su
rf
a
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
in
te
15
ir
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.
d
Pa
*
20
C
Move forward 3m
then stay stationary
for 1 minute
Continue until
platform is reached
Objectives
Pa
-E
ed
25
C
ov
e
Gear: binoculars,
temperature and DO meter
Predator Response by Location
ov
e
Gear: 100m tape measure
attached to kayak and
shore
Observer
Invasive Species:
Red-Eared Slider
•13-28cm
in
te
ar
ed
lie
el
-B
ed
Kayaker (Predator)
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).
ub
s
• 10-15cm
(b
ab
y)
0
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.
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
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.
25
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
Table 1. The abundance of each species found
basking during the experiment.
30
Marburg Turtles
Distance from Platform (m)
Cost of Staying in Shell
-Decreased time for foraging
and mating
-Risk of over heating
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.