Dormancy

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Dormancy
2
Different types of controlled hypothermia
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Facultative torpor
Willmer et al. 2005 Fig. 15.33
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Different types of controlled hypothermia
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Hibernation stats

• Minimal Tb values as low as -3oC in arctic ground
  squirrel

Barnes BM. Freeze avoidance in a mammal body
temperatures below 0 degree C in an Arctic
hibernator. Science 244 15931595, 1989.
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Hibernation stats

• heart rate reduced from 200-300 beats/min to 3-5
  beats/min
• 30 min or longer between breaths
• metabolic rate around 5 of normal BMR
• 1 of RMR at low Ta
• Energy expenditure reduced by 85
• enables survival for 5-7 months on body fat

7
Different types of controlled hypothermia
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Scaling issues

• Smaller animals have higher metabolic rate/ body
  mass

MR/ BM
0.6 0.72 0.25 0.12 0.09
Physiological and Biochemical Zoology
76(2)165179. 2003.
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Scaling issues

• Smaller animals have higher metabolic rate/ body
  mass
• Smaller animals lose heat more quickly (larger
  surface area/body mass)

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How is it done?

• Preparation
• Preference for polyunsaturated fatty acids in diet

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How is it done?

• Typical pattern for golden-mantled ground
  squirrel
• from Physiological Reviews 83 11531181. 2003

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Metabolicinhibition

• Bears
• Metabolic rate reduced to 25 of non-hibernating
• Expect reduction to 65 based on Q10 effects

Hibernation in Black Bears Independence of
Metabolic Suppression from Body Temperature Tøien
et al. 2011 Science 331 906-909.
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Reduced metabolism

• Bears
• Heart rate is reduced from
• 55 bpm to 9

Hibernation in Black Bears Independence of
Metabolic Suppression from Body Temperature Tøien
et al. 2011 Science 331 906-909.