These Frogs Prepare for Winter – By Freezing Themselves

Hibernating, growing a thicker coat, and migrating are all different ways that animals have come up with to endure the coldest months of the year. Yet, one animal is doing it differently. The wood frog freezes itself completely during the wintertime.

Kenneth Storey is a professor of biochemistry at Carleton University in Ottawa, Canada, whose research specifically focuses on extreme environmental stressors. He explained to National Geographic, “The reason you freeze is to extend your range farther north or higher in elevation, like the top of a mountain. You can get a better niche in the world if you can freeze.” This concept is called freeze tolerance. It is a way for the frogs to deal with and survive the winter. When the frogs are going about their business, and then ice comes in, the process begins where the ice will go through the frogs’ veins and arteries. Then, the ice will continue to move through the frog’s body, eventually freezing the brain and the heart. There is no need to fret. This is just nature taking its course, with significant changes in the frog’s biochemistry helping it to do so.

The microRNA molecules will reorganize the cells to keep them from damage, and the frog’s liver will produce glucose in large quantities to assist. They spend their winter in a state of cryosleep until, eventually, the temperatures start rising again. Storey said, “the sun will shine, mud will form, they’ll warm up, and then they’ll thaw.” Not all wood frogs freeze alike, either. “Wood frogs in Alaska will freeze down to negative 5 degrees Fahrenheit. Others in North Carolina cool to 8.6 degrees,” according to National Geographic. They are also not the only animal to freeze during the wintertime. This captivating survival method has been seen in the southern brown tree frog, the spring peeper frog, cricket frogs, and many insects. 

While we humans may bundle up and drink hot cocoa to combat the cold weather, wood frogs transform themselves to be frozen rock solid. Frogs continue to be a fascinating species, and so does planet Earth. Stay tuned for more breaking discoveries.