Answer: Wood Frogs

Animal adaptation is a marvelous thing, and within the animal kingdom, you’ll find incredible examples of animals that survive extremely cold temperatures. Among them, there is the arctic ground squirrel which hibernates in the tundra at below freezing temperatures and the Greenland shark that survives just fine in ocean temperatures so low the water would freeze if it didn’t have such a high salinity.

But among all the hardy animals out there, none is quite so hardcore as the very hardy little wood frog, native to North America and found all throughout the continental United States and even up into Alaska—a particularly unpleasant place for a frog. Considered one of the most cold tolerant species on the planet, the wood frog survives Alaskan winters by hibernating.

Cold weather hibernation is hardly a feat unheard of, but what happens during this animal’s hibernation is. The wood frog undergoes a complex process in which it pushes significant amounts of water out of its cells and organs into the spaces between the cells and into its body cavity, then large amounts of glucose enters the dewatered cells, creating a syrupy solution that functions as an anti-freeze. Despite that effort, however, nearly 70 percent of the water in the frog’s body turns to ice and it effectively freezes as solid as the ground it has burrowed into—even the frog’s eyes freeze solid.

Despite this, come spring the frog thaws out just fine and begins moving around and mating again when the temperatures are barely above freezing.