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Table 2.

Hypotheses from the vertebrate literature explaining lowered ventilation rate and heart rate after sudden stimuli

HypothesisReference
(1) Decreased heart rate, decreased ventilation rate and behavioural freezing reduce movement and noise from the animal. This helps it hide from predators. Jacobsen, 1979; Barham et al., 1985  
(2) Ventilation rate and heart rate slow because metabolic rate drops. Lowered metabolic rates allow diving and burrowing air-breathing vertebrates to remain hidden underwater or in a hypoxic den for longer. Smith and Woodruff, 1980; Smith et al., 1981  
(3) In preparation for flight, blood is redistributed from vegetative to locomotory muscles. This causes a reflexive drop in heart rate. Laming and Savage, 1980; Laming and Austin, 1981  
(4) Heart rate drops to reduce blood pressure. This protects delicate tissues and capillaries during the subsequent increase in blood pressure at the onset of locomotion. Ide and Hoffmann, 2002; Cooke et al., 2003  
HypothesisReference
(1) Decreased heart rate, decreased ventilation rate and behavioural freezing reduce movement and noise from the animal. This helps it hide from predators. Jacobsen, 1979; Barham et al., 1985  
(2) Ventilation rate and heart rate slow because metabolic rate drops. Lowered metabolic rates allow diving and burrowing air-breathing vertebrates to remain hidden underwater or in a hypoxic den for longer. Smith and Woodruff, 1980; Smith et al., 1981  
(3) In preparation for flight, blood is redistributed from vegetative to locomotory muscles. This causes a reflexive drop in heart rate. Laming and Savage, 1980; Laming and Austin, 1981  
(4) Heart rate drops to reduce blood pressure. This protects delicate tissues and capillaries during the subsequent increase in blood pressure at the onset of locomotion. Ide and Hoffmann, 2002; Cooke et al., 2003  
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