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KnoWanUKnow2 t1_j5uutzb wrote

Reply to comment by IsaacQqch 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

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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