There are five species of frogs that are able to enter a “frozen state” as they hibernate for the winter: the Wood Frog, Cope’s Gray Tree Frog, the Eastern Gray Tree Frog, Spring Peepers, and the Western Chorus Frog.
Even in their protected winter homes, temperatures are sure to drop below freezing. This causes the water in their outer cells to begin to freeze. Once this begins, their liver starts producing glucose, which the heart pumps through the blood to all vital organs. This glucose helps prevent the tissue from drying out and freezing completely. During this time the heart slows and eventually stops. The frog, at this point, appears dead, and may remain this way throughout the entire winter, though many go through freeze/thaw cycles. As spring approaches, and temperatures warm, the frog thaws and the heart begins beating again as organ function returns. Most frogs experience some cellular damage and must spend a period of time recovering from their winter freeze.
THE MAGIC: Scientists have yet to explain exactly how the heart is triggered to begin beating again…