The frogs can cope with freezing temperatures by producing "cryoprotectants," substances that prevent ice crystals from forming inside their cells.
Cryoprotectants, like the antifreeze you put into your car radiator, prevent ice from forming by reducing the freezing point of water.
"Cryoprotectants act by lowering the body's freezing point, preventing water freezing at temperatures well below 0C," explains Denlinger. When a cryoprotectant chemical dissolves in water, it forms strong bonds with water molecules. Water molecules bonded to the cryoprotectant can no longer bond with other water molecules to form ice, meaning that the water can be cooled to subzero temperatures without freezing.