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