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.
If the frogs were human, they would be called dead, Costanzo said. But once the temperatures warm, they come back to life.
Wood frogs live all over America and in the Arctic Circle. Some Alaskan wood frogs get as cold as zero degrees (minus 18 degrees Celsius), he said.
Other animals don’t urinate when they hibernate, but mammals don’t do the big freeze quite like wood frogs, which wake up in still-cold February to mate, he said.