Some frogs freeze, but don’t die: Here’s why 

Suppose you land in an area that is icy cold with freezing temperatures. You do not have a snow coat or any warm gloves and boots to cover you. In all probability, you will freeze to death after a few days of coping. But not a frog. Yes, frogs will freeze but will not die. Curious to know why? You would argue, they don't have thick skin and fur like a bear nor can't they take off to the skies to fly south. Yet, some frogs, such as the wood frog, survive the icy winter of Alaska. That is because they are not warm-blooded like us. Instead, they are cold-blooded. After the freezing temperatures turn them into a block of ice, a chain of events occurs to protect them from dying. Let us find out what happens to their bodies in cold.  

How frogs freeze to survive the cold 
While the wood frog is just one variety of frogs known to survive ice winters in North America, Cope’s gray tree frog, the eastern grey tree frog, spring peepers and the western chorus frog are a few others.  

But what is it in their bodies that we do not have? To figure that out, let’s first understand what leads to frostbite in us humans. When the water in our blood turns to ice, that hyper concentrates the fluid around the cells and tissues. This, in turn, draws water out of the cells. Eventually, when the cells get fully dehydrated, humans die. 

In frogs, it is not the same. Frogs are “cold-blooded”. When temperatures dip below 0 degree Celsius, the water in between their body cells freeze solid but the water inside individual cells does not freeze. So cells still function, only that they can't communicate with each other.  

After a few minutes of ice starting to form on its skin, a wood frog’s liver begins converting sugars, stored as glycogen, into glucose. This glucose does the trick; it flows through the bloodstream to every tissue where it helps keep cells from getting completely dehydrated and shrinking and keeping sufficient water inside cells to keep them alive.  

However, its heart and other organs slow down and eventually stop functioning and the frog appears to be dead. It can survive in this state all winter, undergoing cycles of freezing and thawing. But the good thing is as the weather gets warmer, the frog melts. The blood starts flowing, its heart starts beating, and it begins to breathe again. The glucose gets converted back to glycogen. And the frog happily hops away to the nearest pond or lake. 

What is special about their bodies?  
Research is still on about what protects these frogs. While the proteins may bind to the inside and outside of the cells to keep them from shrinking too much, it seems, urea, a waste that frogs get rid of in their urine, also helps them to survive all this while.  

But how long can they last like this? Though it sounds crazy these little creatures can survive temperatures as low as a negative 17 to 18 degrees Celsius for straight seven months. Wow!