The Alaskan wood frog is an amazing creature whose winter adaptations have amazed even scientists. This frog freezes completely during the cold season, its heart stops, breathing stops, and blood circulation stops. In other words, it goes into a living but temporarily "dead" state.
Up to 65% of its body water turns into ice, and then the frog looks like an iceberg. However, even in this state, its cells are not damaged. This is because its liver secretes a special type of sugar (glucose), which prevents the harmful effects of the ice that has accumulated inside the cells. This process is called cryoprotection, which protects the cells from cold damage. In winter, when the temperature drops below freezing, 60-70% of the water in the frog's body turns to ice. As a result, the frog completely freezes and goes into a kind of stasis. During this time, its heartbeat, breathing, blood circulation all stop, and even brain activity stops completely. From the outside, it looks like a frozen stone, as if there is no living being.
This is a remarkable phenomenon, because the frog somehow survives in this freezing winter. Its liver secretes glucose and urea, which act as natural antifreeze. These substances prevent the water in the cells from freezing, so that ice does not form inside the cells and the cells are not damaged. The ice only accumulates on the outside of the body and around the organs, but the cells inside are protected.
When spring comes and temperatures begin to rise, this wood frog slowly thaws and surprisingly comes back to life, its heart beats again, breathing starts, and it starts moving normally. As temperatures rise in the spring, the ice that has accumulated on the body begins to melt. Within 8 to 12 hours, the frog's heart starts beating again, blood circulation and breathing also return. Within 24 hours, the frog can move normally again, as if nothing had happened. It is truly an incredible winter adaptation.
Reference:
[1] "The Alaskan wood frog: A winter survival miracle," Science Daily. [Online]. Available: https://www.sciencedaily.com/releases/2014/07/140722164359.htm [Accessed: Oct. 5, 2025].
