Sure you may think Louisiana has pretty mild winters, but do not underestimate how cold our swamps get with all that cool freshwater coming from up north. Dip your toes in from the kayak and you’ll see. Now, imagine being a turtle in Louisiana or even in Minnesota under ice for a long winter. You would probably die, but turtles are much cooler than you! They are cold-blooded AND they can breath through their butt!
Humans are endotherms, so basically we are big metabolic heat furnaces that need energy to maintain homeostasis. When it’s cold, we put on a coat to trap the heat. Turtles instead hibernate underwater where the temperature is stable and never below freezing. When turtles are trapped under ice for long periods they take oxygen from the water through their butts! The pond will eventually become hypoxic or even anoxic, so some turtles like snapping and painted turtles will switch their metabolism to one that doesn’t require oxygen.
In the spring when these anaerobic turtles emerge from hibernation, their body is like one big muscle cramp and they NEED the sun to warm their bodies up and fire up their metabolism so they can eliminate the acidic byproducts that built up when they switched their metabolism underwater. Turtles in our Louisiana swamps are not trapped under ice for 100 days, but they still hibernate in the water and breath through their butts, so that’s cool.