Which frog can survive being frozen solid during winter?

The wood frog is the frog that can survive being frozen solid during winter. As temperatures fall, it allows ice to form in much of its body while protecting its cells with natural cryoprotectants.

Its liver converts stored glycogen into large quantities of glucose, which helps prevent lethal cellular dehydration and damage. Urea also accumulates in its tissues and contributes to freeze protection. During deep freezing, the frog may have no detectable heartbeat, breathing, circulation, muscle movement, or brain activity.

The wording “frozen solid” is a useful shorthand, although typically about 65–70% of the frog’s total body water freezes rather than every molecule of its body. Northern populations can remain frozen for months and revive when spring temperatures rise. Alaskan wood frogs are especially cold-tolerant, with some surviving temperatures far below 0°C.

The wood frog is not the only freeze-tolerant frog: Europe’s moor frog and Japan’s Japanese tree frog also withstand freezing. However, the wood frog is the standard answer in general-audience biology quizzes and is the best choice among the listed options.