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IsaacQqch t1_j5urdez wrote

Reply to comment by KnoWanUKnow2 in Where do bears go when they hibernate? Cartoons convinced me they all lived in caves, but I'm not so sure. by Forge_craft4000

Wait, polar bear hibernate ???? The température don't change why hibernating ?

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MrWrock t1_j5usklc wrote

Temperature definitely changes but food source changes probably have more of an effect. Black bears on BC's Vancouver Island don't hibernate due to tear round food sources.

In fact, no bears truly hibernate. They wake up, stir around, stretch, and go out for food when the weather is nice. What they do is called torpor

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CFL_lightbulb t1_j5vgth7 wrote

This is neat, and I never knew this. Thanks for the facts!

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very_busy_newt t1_j5wle0d wrote

What is the difference between torpor and hibernation?

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djublonskopf t1_j6mlod3 wrote

True hibernation is a long-term period of dormancy...weeks, or even months of continuous metabolic slowdown. Going into and out of it takes hours. Very few animals actually hibernate—certain snakes, bees, and bats, as a few examples. They generally stay "asleep" for the entire period, perhaps waking up only rarely to relieve themselves.

Torpor, instead, is much more short-lived, and generally involuntary...when it's cold their metabolism slows down and they conk out, if it warms up they get up and stretch and move around, maybe go find a snack. A lot of "hibernating" animals really just experience torpor during cold nights for a season, but are still somewhat active most days.

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MadcapHaskap t1_j5utcg9 wrote

The Arctic is sunny all summer, and dark all winter. The temperature changes a ton, as do hunting conditions.

In Grise Fiord, for instance, the average high in July is 7⁰C, the average high in February is -27⁰C

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KnoWanUKnow2 t1_j5uutzb wrote

Only the pregnant female polar bears dens. Technically they don't hibernate, as their body temp does not fall and her heart rate does not drop. But she will stay in the den from around October until around May, not eating and not leaving, while she gives birth to her cubs and feeds them for the first few months.

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Limos42 t1_j5x82oi wrote

I can understand not eating, but what about drinking?

How do they not dehydrate just from breathing?

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KnoWanUKnow2 t1_j5ya81i wrote

She doesn't pee. Apparently her kidneys shut down and other processes are used to remove toxins from the blood without wasting water.

She doesn't sweat.

The only water she loses is from respiration. This quickly forms ice on the surface of her den, which solidifies and creates a physical barrier that hinders further moisture from leaving.

She's using her fat reserves, she'll emerge having lost 30% of her weight. Part of the biological process of breaking down fat into energy releases water. For instance, the equation for breaking down triglycerides is:

C^(55)H^(104)O^(6) + 78 O^(2) --> 55 CO^(2) + 52 H^(2)O + energy

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cookerg t1_j5uy8zl wrote

It definitely changes. Google "tundra" for arctic summer and winter landscape scenes.

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Alittlebitmorbid t1_j5vd26u wrote

"Planet Earth" has shown a mother polar bear hibernating. She gave birth in her den, nourishing the little ones until they are big enough to follow and withstand the cold. She does not leave until then and is really famished. And you see her rolling around in the snow to clean herself.

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