What do Alaskan wood frogs do with their urine while they are hibernating for 8 months?

In Alaska, wood frogs go eight months without peeing. And scientists have now figured out how they do it, or more accurately, how they survive without doing it.

Recycling urea – the main waste in urine – into useful nitrogen keeps the small frogs alive as they hibernate and freeze, inside and out. It doesn’t warm them up. Instead, urea protects cells and tissues, even as the critter’s heart, brain and bloodstream stop.

The frogs can do it because special microbes in their guts recycle the urea, according to a new study in Tuesday’s journal Proceedings of the Royal Society B.

Some call the frog pee a type of antifreeze, but study co-author Jon Costanzo, a zoologist at Miami University in Ohio, bristles at that term.

“Their eyes are white. Their skin is frosty. They’re like little rocks. They’re frozen,” Costanzo said.