Energy for Hibernation

Question 1

what happens when food items are scarce or absent?

Answer 1

switch to a less desirable food source

utilize body fat stores

move to where food is more plentiful (migration)

decrease body temperature (Tb) to decrease energy requirements

• seasonal hibernation
• daily torpor

Question 2

extended dormancy

Answer 2

larger mammals undergo an extended dormancy (winter sleep) rather than true hibernation or torpor
- American black bear tb of ~31 for up to 225 days

• brown bear: Tb of ~32 up to 200 days
• Eurasian badger Tb of 28 for 45 days

Question 3

Comparing duration of Tb reduction

Answer 3

< 24 hrs: torpor (short-term, daily episode)

> 4 days: hibernation (long term, seasonal episode)

> 45 days: extended dormancy

Question 4

Comparing minimum Tb maintained

Answer 4

<6: torpor (moderately above freezing)

> 15: hibernation (moderately below normal Tb)

> 28: extended dormancy (barely below normal Tb)

Question 5

Comparing average body weight and hibernation strategy

Answer 5

<9kg: torpor
< 4kg: hibernation
> 10 kg: extended dormancy

Question 6

Reducing Energy Requirement during hibernation and torpor

Answer 6

1. decrease Tb
   a. thermoregulatory control is not abandoned
   b. a new, lower Tb set-point is established
   c. rewarming achieved using only endogenous heat
2. decrease metabolic activity
   a. minimum metabolic rate is established
   b. on average ~15% of BMR (including arousal periods)
3. decrease metabolic heat
   a. HR may drop by more than 85%
   b. in some cases, beats may be missed entirely
4. decrease respiratory rate
   a. RR will drop comparably to HR
   b. periods of apnea may occur

Question 7

Energy saving relative to remains active

Answer 7

hibernation ~90%

torpor ~65%

animals hibernate in a curled position to reduce SA and water loss

animals usually hibernate alone

animals will seek a safe sheltered area- hibenaculum

Question 8

Arousal periods

Answer 8

NO animal will remain dormant through an entire hibernation

hibernators will experience periodic, spontaneous arousals

occurs using only endogenous heat

increased Tb, HR, RR ( O2 consumption)

stage 1- non shivering - brown fat
stage 2- shivering

Question 9

Why wake up?

Answer 9

to eat…

1. food storers
   - store food in hibernaculum
   - will eat during arousal periods
2. fat storers
   - deposit fat prior to hibernation so won’t eat when awake

to drink… depends on water conservation

to urinate… need to remove toxins from eh body