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Sight of a predator induces a corticosterone stress response and generates fear in an amphibian.

Narayan EJ, Cockrem JF, Hero JM - PLoS ONE (2013)

Bottom Line: Urinary corticosterone metabolite concentrations increased in male ground frogs exposed to the sight of a toad for 1, 3 or 6 h, whereas corticosterone did not change in frogs exposed to another male ground frog, a ball, or when no stimulus was present in the test compartment.The results provide novel evidence that the sight of a predator can induce a corticosterone response and lead to increased fearfulness in amphibians.In addition, they show that endemic frogs can recognise an introduced predator as a threat.

View Article: PubMed Central - PubMed

Affiliation: Environmental Futures Centre, School of Environment, Griffith University, Gold Coast Campus, Southport, Australia. e.narayan@ga.griffith.edu.au

ABSTRACT
Amphibians, like other animals, generate corticosterone or cortisol glucocorticoid responses to stimuli perceived to be threatening. It is generally assumed that the corticosterone response of animals to capture and handling reflects the corticosterone response to stimuli such as the sight of a predator that are thought to be natural stressors. Fijian ground frogs (Platymantisvitiana) are preyed upon by the introduced cane toads (Rhinellamarina), and we used ground frogs to test the hypothesis that the sight of a predator will induce a corticosterone stress response in an amphibian. Urinary corticosterone metabolite concentrations increased in male ground frogs exposed to the sight of a toad for 1, 3 or 6 h, whereas corticosterone did not change in frogs exposed to another male ground frog, a ball, or when no stimulus was present in the test compartment. The frogs exposed to a toad initially moved towards the stimulus then moved away, whereas frogs exposed to another frog moved towards the test frog and remained closer to the frog than at the start of the test. Tonic immobility (TI) was measured as an index of fearfulness immediately after the test exposure of the frogs to a stimulus. The duration of TI was longer in frogs exposed to a toad than to another frog or to a ball. The results provide novel evidence that the sight of a predator can induce a corticosterone response and lead to increased fearfulness in amphibians. In addition, they show that endemic frogs can recognise an introduced predator as a threat.

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Histogram showing mean durations of tonic immobility (seconds) of male Fijian ground frogs after exposure to a cane toad, a ball, another frog or no stimulus.Sample sizes at each time point were n = 7.
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pone-0073564-g004: Histogram showing mean durations of tonic immobility (seconds) of male Fijian ground frogs after exposure to a cane toad, a ball, another frog or no stimulus.Sample sizes at each time point were n = 7.

Mentions: The mean duration of tonic immobility (TI) of the male ground frogs differed significantly between stimuli (F3,72 = 56.09, p < 0.0001, Figure 4) and time (F3,72 = 11.78, p < 0.0001, Figure 4). There was no significant interaction between treatment and time (F3,72 = 1.97, p = 0.080, Figure 4). The frogs that were subjected to a toad had the longest durations of TI at 1, 3 and 6 h (Figure 4). The highest mean TI duration (75.0 + 13.2 seconds) was recorded at 3 h for the frog group that was subjected to the sight of a toad. There was no significant difference between time in mean TI durations for frogs that saw a frog or ball (Figure 4; p > 0.05 for all time comparisons). There was a significant difference between the times in mean TI durations of the control frogs and frogs that had perceived the cane toad (Figure 4; p < 0.05 for all time comparisons). The mean TI durations of the frogs that saw another frog were significantly shorter than those of frogs that saw a toad, and significantly longer than the mean TI durations of frogs that saw a ball 1, 3 or 6 h (Figure 4; p < 0.05).


Sight of a predator induces a corticosterone stress response and generates fear in an amphibian.

Narayan EJ, Cockrem JF, Hero JM - PLoS ONE (2013)

Histogram showing mean durations of tonic immobility (seconds) of male Fijian ground frogs after exposure to a cane toad, a ball, another frog or no stimulus.Sample sizes at each time point were n = 7.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3757005&req=5

pone-0073564-g004: Histogram showing mean durations of tonic immobility (seconds) of male Fijian ground frogs after exposure to a cane toad, a ball, another frog or no stimulus.Sample sizes at each time point were n = 7.
Mentions: The mean duration of tonic immobility (TI) of the male ground frogs differed significantly between stimuli (F3,72 = 56.09, p < 0.0001, Figure 4) and time (F3,72 = 11.78, p < 0.0001, Figure 4). There was no significant interaction between treatment and time (F3,72 = 1.97, p = 0.080, Figure 4). The frogs that were subjected to a toad had the longest durations of TI at 1, 3 and 6 h (Figure 4). The highest mean TI duration (75.0 + 13.2 seconds) was recorded at 3 h for the frog group that was subjected to the sight of a toad. There was no significant difference between time in mean TI durations for frogs that saw a frog or ball (Figure 4; p > 0.05 for all time comparisons). There was a significant difference between the times in mean TI durations of the control frogs and frogs that had perceived the cane toad (Figure 4; p < 0.05 for all time comparisons). The mean TI durations of the frogs that saw another frog were significantly shorter than those of frogs that saw a toad, and significantly longer than the mean TI durations of frogs that saw a ball 1, 3 or 6 h (Figure 4; p < 0.05).

Bottom Line: Urinary corticosterone metabolite concentrations increased in male ground frogs exposed to the sight of a toad for 1, 3 or 6 h, whereas corticosterone did not change in frogs exposed to another male ground frog, a ball, or when no stimulus was present in the test compartment.The results provide novel evidence that the sight of a predator can induce a corticosterone response and lead to increased fearfulness in amphibians.In addition, they show that endemic frogs can recognise an introduced predator as a threat.

View Article: PubMed Central - PubMed

Affiliation: Environmental Futures Centre, School of Environment, Griffith University, Gold Coast Campus, Southport, Australia. e.narayan@ga.griffith.edu.au

ABSTRACT
Amphibians, like other animals, generate corticosterone or cortisol glucocorticoid responses to stimuli perceived to be threatening. It is generally assumed that the corticosterone response of animals to capture and handling reflects the corticosterone response to stimuli such as the sight of a predator that are thought to be natural stressors. Fijian ground frogs (Platymantisvitiana) are preyed upon by the introduced cane toads (Rhinellamarina), and we used ground frogs to test the hypothesis that the sight of a predator will induce a corticosterone stress response in an amphibian. Urinary corticosterone metabolite concentrations increased in male ground frogs exposed to the sight of a toad for 1, 3 or 6 h, whereas corticosterone did not change in frogs exposed to another male ground frog, a ball, or when no stimulus was present in the test compartment. The frogs exposed to a toad initially moved towards the stimulus then moved away, whereas frogs exposed to another frog moved towards the test frog and remained closer to the frog than at the start of the test. Tonic immobility (TI) was measured as an index of fearfulness immediately after the test exposure of the frogs to a stimulus. The duration of TI was longer in frogs exposed to a toad than to another frog or to a ball. The results provide novel evidence that the sight of a predator can induce a corticosterone response and lead to increased fearfulness in amphibians. In addition, they show that endemic frogs can recognise an introduced predator as a threat.

Show MeSH
Related in: MedlinePlus