We all take different approaches to staying warm during the winter season. Some of us dig out that heavy coat and head outdoors to explore, while others plan the day’s activities by how many coffee shops we can stop in along the way. Others of us limit our time outside or just plainly refuse to spend any time outdoors whatsoever.
Yes, I do enjoy eggnog in front of a warm fire but I also enjoy spending time outside during the winter. I especially relish the brisk air blowing in my face; the lack of crowds on my favorite hiking trails; and the expansive views through the leafless trees. As a young kid I remember watching the ice form over the pond behind my house and I always wondered what happened to the turtles and other wildlife that had basked in the sun all summer long. Sure, I knew that turtles buried in the mud in the bottom of the pond, but it was several years later before I learned how they survived all winter down there in the cold.
As it turns out the cold is not a problem for turtles. When the temperature drops, they, like other cold-blooded animals, tend to slow down and go into a state of dormancy. In this inactive state their metabolism slows down, they eat little to no food and they require little oxygen ⎯ but this is exactly where the problem comes in. The problem they face is finding a way to breath despite being engulfed in mud, deep under water. Turtles normally use their lungs to breath air but during their ‘winter’s nap’ they acquire oxygen in a most unusual way. They absorb it from the surrounding mud and water through their cloaca (a.k.a. their bum). The skin of the cloaca includes a vast network of blood vessels that functions similarly to a fish’s gills. Turtles are not the only animals spending winter in the pond’s muddy bottom, bullfrogs (Rana catesbeiana), like turtles, also absorb oxygen through their skin.
Though beavers (Castor canadensis) do not bury in the mud, they do spend most of the winter underwater. They stay warm and even dry while under the water by resting in their submerged lodge. These lodges can be relatively warm even on the coldest of days. One lodge was recorded to have an internal temperature of 60 degrees F. when the outside temperature was 2 degrees F. Beavers are also resourceful in that when they do leave the lodge and go for a swim they breathe from the air bubbles that collect underneath the ice. Even more amazing is how beavers lower the level of pond in order to create a layer of air between the bottom of the ice and the top of the water. With the precision of an engineer, beavers modify the height of the dam in order to allow a select amount of water to flow over thus creating the pocket of air under the ice. The beavers are then no longer “trapped” under the ice without air to breathe.
Using gills, fish have no problem acquiring oxygen from the water and thus are not in the same danger of being trapped. That is, until the pond completely freezes over. When this happens, the layer of ice over the pond seals off oxygen from entering the water below. As the fish swim around they begin to use up the limited amount of oxygen. In areas where the winters are long, as in upstate New York, some fish may have to survive under ice for 4 to 5 months with ever-depleting oxygen reserves. If only we could hold our breath that long!
These are just a few examples of the many amazing ways animals endure and sometimes even flourish amid winter’s cold and ice. So, why not don your scarf and gloves and head outdoors to discover your own winter wonders. Happy Exploring!