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Copy Right Bear Trust International 2011For Education Use Only
Two Adaptive Strategies Bears Have Evolved
Adaptive Strategies: Hibernation
Torpor Hibernation
Short-term hibernation
?X Heart rate
Metabolic rate
Body temperature
Breathing rate
Hibernation
Heart rate
Metabolic rate
Body temperature
Breathing rate
Heart rate
Breathing rate
Metabolic rate
Hibernation
Heart rate
Metabolic rate
Body temperature
Breathing rate
A LOT !Near Freezing
A LITTLE Only about 10 degrees F
Body temperature
Heart rate
Breathing rate
Metabolic rate
Must wake up every week
For 12-20 hours
Bears don’t do this
Raise body temp
Eat stored food
Pass waste
Go back to deep sleep
Can go for 100 dayswithout eating, drinkingor passing waste
Enter dormancy fastHard to awaken
Enter dormancy slowlyEasy to awaken
Torpor Hibernation
Short-term hibernation
?
Winter LethargyWinter SleepDenning Period
It is a Period of Amazing Physiology!
Can go for months without drinking, eating, urinating, defecating, or exercising
Fat Tissues
Water Calories
Muscle and Organ Tissues
Protein
Urea
Nitrogen
We can learn a lot from bears
Bears do not get dehydrated
Implications for people with chronic kidney failure
It is a Period of Amazing Physiology!
Denning bears have very high cholesterol levels
Dissolves cholesterol gall stones, eliminating need for surgery
It is a Period of Amazing Physiology!
Bile juice
Do not develop cholesterol gall stones
Humans
We can learn a lot from bears
Bears: no muscle or bone atrophy
Space travel
It is a Period of Amazing Physiology!
We can learn a lot from bears
Do all bear species use this adaptive strategy?
M. Riley/ADFG
K. Burguess/NJDFG
Asiatic Black Bear ?
Yes
Denning period is similar to that of American Black Bear
Enter den Nov-Dec
Pregnant females givebirth around Jan
Emerge from den between March-AprilSouthern Asia, Northeast China, Japan and Far Eastern Russia
Polar Bear ?
Only pregnant females enter a den, give birth Nov/Dec, and emerge whencubs can trek
• state of “walking hibernation”
Do not overwinter in dens like brown bears and black bears
Most remain active year-round
Have ability to reduce theirmetabolic rate when food is scarce
• polar bears come ashore after ice melts in Hudson Bay each summer
• maintain normal body temps
• reduce metabolic rate
• recycle proteins
Spectacled Bear Giant Panda Bear
Sun Bear Sloth Bear
These bears appear to remain active year-round
Although………pregnant females build birthing dens or nests
Live in areas wherefood sources areavailable year-round
Adaptive Strategy:
?Reproduction
Delayed Implantation
….fertilized egg divides a few times…
…development STOPS!
…several weeks before female enters maternity den…
….fertilized egg attaches to uterine wall….
….cubs!
Only happen if female has stored sufficient fat/protein
If not, then embryo is reabsorbed back into female’s body
Why is this reproductive strategy advantageous?
Adaptive Strategy: Reproduction
Female bear mates…
…fertilized egg floats free in the uterus for several months…
….continues for about 8 weeks…
….development RESTARTS
