Download the effect of prior exposure to chemical cues on the antipredator

THE EFFECT OF PRIOR EXPOSURE TO CHEMICAL CUES ON THE ANTIPREDATOR BEHAVIOR
OF HYLA CINEREA TADPOLES
NIKKI ROMBOUGH, CHRISTOPHER BRENNAN,
and MEGAN E. GIBBONS
Abstract
•Prior exposure to chemical cues had no effect on the survival
of tadpoles.
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Results of Behavioral Experiment
•Tadpoles with prior exposure to chemical cues showed less
activity than naïve tadpoles.
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25
Altig et al.
Figure 2. Hyla cinerea tadpole
Methods
Collection and Experiment Preparation
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Conclusions
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Experienced
Treatment
Naïve
Control
Figure 4. Average time that tadpoles spent moving
•Although tadpoles from this site do not coexist with fish predators,
they have maintained their ability to respond to predator cues
•Prior exposure was necessary to elicit antipredator behavior
•Reduction in activity and avoidance of visual predators (e.g., fish)
may reduce the likelihood of predation
•However, the results of our survival experiment suggest that
antipredator behavior of tadpoles may have lost some effectiveness
over evolutionary time
•Bluegill in a screen cage added to chamber and behaviors observed
for 15 min
•Some species of tadpoles significantly reduced activity when exposed to
fish chemical cues (Laurila, 2000; Stauffer and Semlitsch, 1993)
Naïve
Control
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•Tadpole acclimated for 10 min in experimental chamber
•Many larval amphibians have the ability to detect and respond to chemical
cues from predators (Gallie et al., 2001; Laurila, 2000)
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Figure 7. Average number of surviving tadpoles
Behavioral Experiment
•When in the presence of fish predators, limiting movement may be
advantageous (Wellborn et al, 1996)
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0
•Survival experiment: tadpoles immersed for 2 hr in either water with
predator cues (experienced) or dechlorinated water (naïve)
•Active prey may be more conspicuous to predators (Lawler, 1989)
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Experienced
Treatment
•Behavioral experiment: tadpoles immersed for 15 min in either
water with predator cues (experienced) or dechlorinated water
(naïve)
Background
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t=-2.326, df=48, p=0.024
•The night before each test, bluegill isolated and fed 5 tadpoles
Figure 1. Study organism (Hyla cinerea)
t=0.394, df=18, p=0.699
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1
10
•Tadpoles of Hyla cinerea collected at Red Lake at Ruffner Mountain
in Birmingham, AL
Number of Surviving Tadpoles
7
Time (sec)
For aquatic amphibians, the expression of antipredator behaviors
may be essential for survival. In most cases, chemical cues from
predators are important triggers for those behaviors. We conducted a
study to determine if tadpoles of green tree frogs (Hyla cinerea) from
ponds without fish predators would exhibit antipredator behavior, and
if prior exposure to chemical cues from the predator (bluegill,
Lepomis macrochirus) was necessary to elicit such behavior. We
also conducted a survival experiment to determine if tadpoles with
prior exposure to predator cues had a higher chance of survival when
exposed to a predator for 24 hrs. During the behavioral trials,
tadpoles with prior exposure to chemical cues were less active and
spent less time near the predator than those without prior exposure.
There was no significant difference between survival of tadpoles with
and without prior exposure to chemical cues of predators. Our results
suggest that prior exposure to predator cues may trigger antipredator
behavior in tadpoles, even from populations that do not coexist with
fish predators.
Results of Survival Experiment
•Activity level and time in proximity to the predator recorded
•N=25 tadpoles for each group
Survival Experiment
•After experiment preparation, 10 tadpoles (either experienced or
naïve) added to survival chamber and allowed to acclimate
Figure 5. Predator bluegill (Lepomis macrochirus)
•Bluegill added to chamber
•Tadpoles previously exposed to chemical cues spent
significantly less time within 10 cm of the predator.
•24 hrs later, number of survivors recorded
•N=10 trials for each group
600
•Prior exposure may be necessary to elicit antipredator behavior (Murray
et al., 2004)
(s e c )
500
Purpose
T im e
To determine if there is a difference between antipredator behavior of
green tree frog (Hyla cinerea) tadpoles with and without prior exposure to
chemical cues from bluegill (Lepomis macrochirus).
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t=-2.141, df=48, p=0.037
Figure 8. Chris and Nikki collecting at Red Lake
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Literature Cited
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Hypotheses
•Tadpoles with prior exposure to chemical cues from predators will be less
active and spend less time in close proximity to the predator
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•Tadpoles with prior exposure to chemical cues from predators will have a
higher rate of survival when exposed to the predator for 24 hrs
0
T r e a tm e n t
Experienced
Figure 3. Collection site: Red Lake
C o n tr o l
Naïve
Figure 6. Average time that tadpoles spent in close
proximity to the predator
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