Summer is a magical time of year, when life abounds almost everywhere you look. Plants beyond counting unfurl their green leaves to capture energy from the sun, and creatures beyond counting start munching on the plants. The astounding web of life that depends entirely on the sun’s energy for its existence (including humans, by the way) sees its connections thicken and strengthen as the sunlight intensifies and temperatures soar.
Then, the inescapable reality of our solar system causes that sunlight to slowly begin to fade. The planet changes its position relative to the sun as it follows the path of its orbit, and the Northern Hemisphere starts to shy away from the warmth and light of our very own star. The days become shorter and temperatures cool. Life begins to respond to this change and once again, it is the plants that set the tone.
Deciduous trees begin to shut down their food factories, and in so doing, some of them show visual signs of this maintenance with brilliant colors that dazzle the eye. Other plants, responding to the shortening daylight, begin to store up food for the winter, or they release thousands of embryos in stasis chambers (we call them seeds) in hope that just a few will survive the coming winter and inherit the world the coming summer.
Some species of animals gather as many of these stasis pods as possible and use them to fatten up in an effort to survive the lean times ahead. Other animals decide to avoid the lean times by moving to other parts of the planet were food remains plentiful. Still other animals are forced to come up with different solutions to the failing light and decreasing temperatures, and I find myself particularly fascinated by the solutions used by our local reptiles and amphibians. How do cold-blooded organisms survive the cold?
Well, my students and I discussed this in my biology classes recently. We were talking about the properties of water molecules and most specifically about their shape and their polarity. The two characteristics cause water to have the remarkable ability to become less dense as a solid than it is as a liquid, and this is key for the survival of many of the frogs and turtles that lend so much life to our local lakes and ponds.
Ice floats on liquid water, which means that it forms something of a thermal blanket over a pond when it starts to form on the surface. This creates a barrier to breathing atmospheric oxygen because the atmosphere is on the other side of the ice. The benefit of remaining unfrozen, however, is so dramatic that the frogs and turtles are able to survive.
At some point in the autumn (a point that is rapidly approaching), aquatic frogs and turtles will take their last breaths, dive down to the muddy bottoms of their watery homes and bury themselves. I imagine them digging down into the soft mud, getting themselves comfortable and then just relaxing. Their cold bodies require so little oxygen that they can gather enough from the water that surrounds them. All they have to do is sleep, without breathing or eating, for five to six months. Only a cold-blooded organism could do this.
What concerns me, as it might concern you, is the fact that this ever-so-delicate process might be vulnerable to change. Last week saw temperatures that seemed unusually warm. I found it especially strange that as I drove to work in the predawn darkness, I saw so many frogs hopping in the road. At one point I even saw a painted turtle attempting to cross the road, which seemed really strange in October. Is the weather “confusing” the frogs and turtles?
If the temperatures change from mid-summer to late autumn in a day or two — crashing from high temps near 90 degrees to temps that reach the mid-50s in just a matter of hours — will our cold-blooded friends find themselves cooled off and sluggish, while they are also too far from water to get back?
The answer is likely no, but we might add on the caveat, “not yet.” Life is resilient and adaptable, but there comes a point where changes become so dramatic that they cannot be dealt with. The result is a quiet fading of life. Just as the days slowly shorten in autumn, so too might the numbers and variety of living things begin to diminish almost imperceptibly. I don’t like thinking these sorts of thoughts, but seeing frogs hopping down the road after Columbus Day certainly grabs my attention.
Bill Danielson has been a professional writer and nature photographer for 21 years. He has worked for the National Park Service, the U.S. Forest Service and Massachusetts State Parks, and currently teaches high school biology and physics. Visit speakingofnature.com for more information, or go to Speaking of Nature on Facebook.