This April 24, 2018 photo provided by Clara do Amaral shows a wood frog in Ohio. In a report released on Tuesday, May 1, 2018, scientists have found that wood frogs, which don’t urinate in the winter, recycle urea _ the main waste in urine _ into useful nitrogen which keeps the small animals alive as they hibernate and freeze, inside and out. It doesn’t warm them up, but protects cells and tissues, even as the amphibian’s heart, brain and bloodstream stop. (Clara do Amaral, Mount St. Joseph University via AP)

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