ANSC 3180 Lecture 10: Energy Hibernation and Torpor
2 May 2018
School
Department
Course
Professor
An animal's energy supply comes only from food (used to deposit body fat)
•
Some animals switch to another less desirable food source
○
Some use body fat stores
○
Some go to where food is available --> migration
○
Some reduce energy requirements by reducing body temperature -->
seasonal hibernation or daily torpor
○
When food is scarce/absent:
•
Energy (without access to energy required)
Short-nosed echidna/spiny anteater: min temp = 4C (384h)
○
Monotremes:
•
Western pymgy possum: min temp = 4.7C (264h)
○
Little pygmy possum: min temp = 5.9C (144h)
○
Eastern pygmy possum: min temp = 1.3C (552h -23 days)
○
Feathertail glider: min temp = 2.1C (192h)
○
Mountain pygmy possum: min temp = 1.8C (480h)
○
Marsupials:
•
European hedgehog: min temp = 5.4C (231h)
○
Eulipotyphia:
•
Big brown bat: min temp = 5C (600h)
○
Little brown bat in Ontario: min temp = 1.3C (750C)
○
*some bats in temperate zones migrate
○
Chiroptera (bats):
•
Many undergo torpor/dormancy instead of a deep hibernation
○
American Black Bear/ Grizzly: min temp = 32.3C
○
Eurasian badger: min temp =28.4C (1080h)
○
Carnivora:
•
Yellow bellied marmot: min temp = 7.5C (430h)
○
Fat/Edible Dormouse: min temp=1C (792h; 33days)
○
…
○
*see diagram
□
Spend a very large amount of time in hibernation (~2/3)
!
Male is first to aroose out of hibernation
!
Found in White Mountain, CA at 3800m
!
This is an extreme example of hibernation
!
Plants they feed on must be in phase with their cycles --> growth
and flowering -seed production/dispersal
!
Golden-mantled ground squirrel:
○
Rodentia:
•
Common poorwill: min temp=6C (96h; 4 days)
*first bird known to hibernate
○
Aves:
•
Hibernators:
Mammals, birds
!
Maintain a relatively constant core body temperature despite wide
fluctuations in environmental temperature
!
Body temperature is determined by heat from body metabolism
(endothermic)
!
Homeotherms:
○
Reptiles, amphibians, fish, invertebrates
!
Body temperature is determined by external heat sources
(ectothermic)
!
Poikilotherms:
○
Reducing energy requirements by reducing body temperature
•
Mammals: 30-39C
○
Birds: 38-42C
○
These core body temperatures are not always maintained
(hibernation/torpor)
○
*see core body temperatures of mammals and birds:
•
Body Temperature:
Passing the winter in a torpid or resting state
○
An animal or plant spending winter in a dormant state
○
Common usage:
•
Hibernation (& aestivation)
○
Torpor
○
Hypothermia
○
Scientific usage:
•
Hibernation:
<24 h (daily) -short-term torpor
○
>4days (seasonal) -prolonged
○
Duration of low temperature episode
•
Few degrees above freezing (<6C)
○
Few degrees below normal body temperature (>15C)
○
Minimum core body temperatures
•
Yes -homeotherms
○
No -poikilotherms --> hypothermia
○
Animal's ability to rewarm using only endogenous heat
•
Distinguishing hibernation, torpor & hypothermia:
Duration Min. Body Temp Body Weight
Hibernation (seasonal/prolonged) >4days <6C 5g -4kg
'Winter sleep' -bears, badgers >28C 13-80kg
Torpor (daily and short-term) <24h >15C 2g -9kg
Protected against lethal freezing depends on choosing a protected area
before ambient temperature drops too low
○
Ex. Manitoba toad burrows into soft soil as temperatures decrease in late
fall and becomes hypothermic BUT detects frost and digs deeper as winter
progresses, then reverses the process as temperatures increase in the spring
○
Hypothermia -in poikilotherms (reptiles, amphibians, fish, invertebrates)
•
Body temperature drops -thermoregulatory control (new lower set-point)
○
Reduced metabolic activity
○
Reduced heart rate
○
Reduced respiration rate
○
Animal can rewarm using only endogenous heat (arousal)
○
Decreasing body temperature in hibernation (<6C) and torpor (>15C)
•
Energy savings (relative to remaining active): ~88% in hibernation and ~
66% in torpor
○
Animal enters hibernation in a curled position of sleep (except bats)
○
Animals usually hibernate alone (except hazel dormouse; usually 2+
hibernate in the same nest)
○
Animals seek safe, sheltered area/nest (with insulation to buffer ambient
temperature changes), the hibenaculum -ambient temperature just above
0C
○
Common hamster adapts summer burrow to include food storage
areas
!
Groundhog digs separate winter burrow
!
Fossorial hibernators either adapt the summer burrow, or dig a separate
winter burrow
○
~5% BMR at a body temp of ~5C
!
~15% BMR (including arousal periods)
!
Basal metabolic rate drops, min metabolic rate = 3.2 x BW1.03 (kcals/day)
○
Ground squirrels, marmots, groundhogs: 3-10 beats/min
!
Compared to active groundhog: 80 beats/min
!
Heat rate drops, possible missed beats
○
Hedgehog -apnea periods up to 150 mins
!
Garden dormouse -apnea up to 112 mins
!
Golden-mantled ground squirrel -apnea up to 55 mins
!
Respiration rate frops, and there may be periods of apnea (groundhog -~1
breath every 6 mins)
○
Animal can re-warm using only endogenous heat
○
Periodic or spontaneous arousals
○
No hibernators rain in deep torpor throughout hibernation period
○
2-10 days -syrian hamsters
□
10-15 days -ground squirrels, dormice, hedgehogs
□
30+ days -small bats
□
Periods between arousals:
!
Periods of arousal more frequent at start and end of hibernation
!
Bats and ground squirrels -93-99% total hibernation time spent not in
arousal but 84-90% of total energy usage is associated with arousals
○
Eastern chipmunk, common hamster
!
Some hibernators store food in nest/burrow before hibernation (food
storers eat during arousal)
○
Groundhogs, ground squirrels
!
Bats (25% weight loss in hibernation)
!
Other hibernators put on fat before entering hibernation (fat storers)
○
Length of periods between arousal not necessarily different between 'food
storers' and 'fat storers'
○
Energy is expended during arousal
!
Energy used in single arousal (by dormouse) is equivalent to 10 days
of hibernation
!
If hibernation is to save energy, arousals contribute to energy use
!
Why arouse?
○
Many hibernators can survive whole winter without eating or
drinking
!
Arctic ground squirrel -blood sugar replenished from glycogen in
liver
!
Arousal to eat?
○
Some hibernators may urinate during arousal (remove toxins?)
!
Arousal to urinate?
○
Increased core body temp, increased heart rate, increased respiration
rate, increased oxygen consumption
!
1st non-shivering thermogenesis -oxidation of brown adipose tissue
stored around shoulders
!
2nd visible shivering (violent in anterior part of body) -main heat
source in many rodents, hedgehogs, bats
!
Arousal involves:
○
Anterior part of body warms faster than posterior due to differential
blood flow
!
Syrian hamster -up to 20C difference between head and posterior
!
Increased body temperature during arousal:
○
Big brown bat -25 mins
!
Golden-mantled ground squirrel -75+ mins
!
Arousal time:
○
Incapable of co-ordinated movement while hibernating -must undergo
complex arousal first
○
Arctic ground squirrel: early October -late April (one of the longest)
!
Golden-mantled ground squirrel (high elevations): early Sept -late
April
!
Total length of hibernation:
○
Hibernation/seasonal torpor
•
Energy saving (relative to remaining active) ~66% (hibernation= ~88%)
○
BMR drops; min. metabolic rate = 15.2 x BW0.99 (kcal/day)
○
Animal does not necessarily enter torpor in curled up position of sleep
○
Animal may be capable of uncoordinated locomotion and may eat/drink in
torpor
○
Energy saving: 18-31%
○
Many bats from temperate areas will go into torpor while roosting during
the day
○
Mouse lemurs (smallest primates) go into torpor during the day during
winter (nocturnally active)
○
Deer mice go into torpor diurnally in winter, several animals may huddle
together in winter nest
○
Ruby-throated -overnight heart and breathing rates decrease by
90%; body temp drops to 20C
!
Broad-tailed -body temp of females and eggs may drop to 6.5C
overnight
!
Black-capped chickadee -body temp may drop to 30C on cold nights
!
Many hummingbirds go into torpor during part of day when they aren't
feeding
○
Daily/short-term Torpor
•
Energy: Hibernation and Torpor
Monday,*February*27,*2017
1:05*PM
An animal's energy supply comes only from food (used to deposit body fat)
•
Some animals switch to another less desirable food source
○
Some use body fat stores
○
Some go to where food is available --> migration
○
Some reduce energy requirements by reducing body temperature -->
seasonal hibernation or daily torpor
○
When food is scarce/absent:
•
Energy (without access to energy required)
Short-nosed echidna/spiny anteater: min temp = 4C (384h)
○
Monotremes:
•
Western pymgy possum: min temp = 4.7C (264h)
○
Little pygmy possum: min temp = 5.9C (144h)
○
Eastern pygmy possum: min temp = 1.3C (552h -23 days)
○
Feathertail glider: min temp = 2.1C (192h)
○
Mountain pygmy possum: min temp = 1.8C (480h)
○
Marsupials:
•
European hedgehog: min temp = 5.4C (231h)
○
Eulipotyphia:
•
Big brown bat: min temp = 5C (600h)
○
Little brown bat in Ontario: min temp = 1.3C (750C)
○
*some bats in temperate zones migrate
○
Chiroptera (bats):
•
Many undergo torpor/dormancy instead of a deep hibernation
○
American Black Bear/ Grizzly: min temp = 32.3C
○
Eurasian badger: min temp =28.4C (1080h)
○
Carnivora:
•
Yellow bellied marmot: min temp = 7.5C (430h)
○
Fat/Edible Dormouse: min temp=1C (792h; 33days)
○
…
○
*see diagram
□
Spend a very large amount of time in hibernation (~2/3)
!
Male is first to aroose out of hibernation
!
Found in White Mountain, CA at 3800m
!
This is an extreme example of hibernation
!
Plants they feed on must be in phase with their cycles --> growth
and flowering -seed production/dispersal
!
Golden-mantled ground squirrel:
○
Rodentia:
•
Common poorwill: min temp=6C (96h; 4 days)
*first bird known to hibernate
○
Aves:
•
Hibernators:
Mammals, birds
!
Maintain a relatively constant core body temperature despite wide
fluctuations in environmental temperature
!
Body temperature is determined by heat from body metabolism
(endothermic)
!
Homeotherms:
○
Reptiles, amphibians, fish, invertebrates
!
Body temperature is determined by external heat sources
(ectothermic)
!
Poikilotherms:
○
Reducing energy requirements by reducing body temperature
•
Mammals: 30-39C
○
Birds: 38-42C
○
These core body temperatures are not always maintained
(hibernation/torpor)
○
*see core body temperatures of mammals and birds:
•
Body Temperature:
Passing the winter in a torpid or resting state
○
An animal or plant spending winter in a dormant state
○
Common usage:
•
Hibernation (& aestivation)
○
Torpor
○
Hypothermia
○
Scientific usage:
•
Hibernation:
<24 h (daily) -short-term torpor
○
>4days (seasonal) -prolonged
○
Duration of low temperature episode
•
Few degrees above freezing (<6C)
○
Few degrees below normal body temperature (>15C)
○
Minimum core body temperatures
•
Yes -homeotherms
○
No -poikilotherms --> hypothermia
○
Animal's ability to rewarm using only endogenous heat
•
Distinguishing hibernation, torpor & hypothermia:
Duration Min. Body Temp Body Weight
Hibernation (seasonal/prolonged) >4days <6C 5g -4kg
'Winter sleep' -bears, badgers >28C 13-80kg
Torpor (daily and short-term) <24h >15C 2g -9kg
Protected against lethal freezing depends on choosing a protected area
before ambient temperature drops too low
○
Ex. Manitoba toad burrows into soft soil as temperatures decrease in late
fall and becomes hypothermic BUT detects frost and digs deeper as winter
progresses, then reverses the process as temperatures increase in the spring
○
Hypothermia -in poikilotherms (reptiles, amphibians, fish, invertebrates)
•
Body temperature drops -thermoregulatory control (new lower set-point)
○
Reduced metabolic activity
○
Reduced heart rate
○
Reduced respiration rate
○
Animal can rewarm using only endogenous heat (arousal)
○
Decreasing body temperature in hibernation (<6C) and torpor (>15C)
•
Energy savings (relative to remaining active): ~88% in hibernation and ~
66% in torpor
○
Animal enters hibernation in a curled position of sleep (except bats)
○
Animals usually hibernate alone (except hazel dormouse; usually 2+
hibernate in the same nest)
○
Animals seek safe, sheltered area/nest (with insulation to buffer ambient
temperature changes), the hibenaculum -ambient temperature just above
0C
○
Common hamster adapts summer burrow to include food storage
areas
!
Groundhog digs separate winter burrow
!
Fossorial hibernators either adapt the summer burrow, or dig a separate
winter burrow
○
~5% BMR at a body temp of ~5C
!
~15% BMR (including arousal periods)
!
Basal metabolic rate drops, min metabolic rate = 3.2 x BW1.03 (kcals/day)
○
Ground squirrels, marmots, groundhogs: 3-10 beats/min
!
Compared to active groundhog: 80 beats/min
!
Heat rate drops, possible missed beats
○
Hedgehog -apnea periods up to 150 mins
!
Garden dormouse -apnea up to 112 mins
!
Golden-mantled ground squirrel -apnea up to 55 mins
!
Respiration rate frops, and there may be periods of apnea (groundhog -~1
breath every 6 mins)
○
Animal can re-warm using only endogenous heat
○
Periodic or spontaneous arousals
○
No hibernators rain in deep torpor throughout hibernation period
○
2-10 days -syrian hamsters
□
10-15 days -ground squirrels, dormice, hedgehogs
□
30+ days -small bats
□
Periods between arousals:
!
Periods of arousal more frequent at start and end of hibernation
!
Bats and ground squirrels -93-99% total hibernation time spent not in
arousal but 84-90% of total energy usage is associated with arousals
○
Eastern chipmunk, common hamster
!
Some hibernators store food in nest/burrow before hibernation (food
storers eat during arousal)
○
Groundhogs, ground squirrels
!
Bats (25% weight loss in hibernation)
!
Other hibernators put on fat before entering hibernation (fat storers)
○
Length of periods between arousal not necessarily different between 'food
storers' and 'fat storers'
○
Energy is expended during arousal
!
Energy used in single arousal (by dormouse) is equivalent to 10 days
of hibernation
!
If hibernation is to save energy, arousals contribute to energy use
!
Why arouse?
○
Many hibernators can survive whole winter without eating or
drinking
!
Arctic ground squirrel -blood sugar replenished from glycogen in
liver
!
Arousal to eat?
○
Some hibernators may urinate during arousal (remove toxins?)
!
Arousal to urinate?
○
Increased core body temp, increased heart rate, increased respiration
rate, increased oxygen consumption
!
1st non-shivering thermogenesis -oxidation of brown adipose tissue
stored around shoulders
!
2nd visible shivering (violent in anterior part of body) -main heat
source in many rodents, hedgehogs, bats
!
Arousal involves:
○
Anterior part of body warms faster than posterior due to differential
blood flow
!
Syrian hamster -up to 20C difference between head and posterior
!
Increased body temperature during arousal:
○
Big brown bat -25 mins
!
Golden-mantled ground squirrel -75+ mins
!
Arousal time:
○
Incapable of co-ordinated movement while hibernating -must undergo
complex arousal first
○
Arctic ground squirrel: early October -late April (one of the longest)
!
Golden-mantled ground squirrel (high elevations): early Sept -late
April
!
Total length of hibernation:
○
Hibernation/seasonal torpor
•
Energy saving (relative to remaining active) ~66% (hibernation= ~88%)
○
BMR drops; min. metabolic rate = 15.2 x BW0.99 (kcal/day)
○
Animal does not necessarily enter torpor in curled up position of sleep
○
Animal may be capable of uncoordinated locomotion and may eat/drink in
torpor
○
Energy saving: 18-31%
○
Many bats from temperate areas will go into torpor while roosting during
the day
○
Mouse lemurs (smallest primates) go into torpor during the day during
winter (nocturnally active)
○
Deer mice go into torpor diurnally in winter, several animals may huddle
together in winter nest
○
Ruby-throated -overnight heart and breathing rates decrease by
90%; body temp drops to 20C
!
Broad-tailed -body temp of females and eggs may drop to 6.5C
overnight
!
Black-capped chickadee -body temp may drop to 30C on cold nights
!
Many hummingbirds go into torpor during part of day when they aren't
feeding
○
Daily/short-term Torpor
•
Energy: Hibernation and Torpor
Monday,*February*27,*2017 1:05*PM
Document Summary
An animal"s energy supply comes only from food (used to deposit body fat) Some animals switch to another less desirable food source. Some go to where food is available --> migration. Some reduce energy requirements by reducing body temperature --> seasonal hibernation or daily torpor. Short-nosed echidna/spiny anteater: min temp = 4c (384h) Western pymgy possum: min temp = 4. 7c (264h) Little pygmy possum: min temp = 5. 9c (144h) Eastern pygmy possum: min temp = 1. 3c (552h - 23 days) Mountain pygmy possum: min temp = 1. 8c (480h) Big brown bat: min temp = 5c (600h) Little brown bat in ontario: min temp = 1. 3c (750c) Many undergo torpor/dormancy instead of a deep hibernation. American black bear/ grizzly: min temp = 32. 3c. Yellow bellied marmot: min temp = 7. 5c (430h) Spend a very large amount of time in hibernation (~2/3) Male is first to aroose out of hibernation.
