As the first heavy frost of the season begins to seal up the ground, my thoughts go to the fate of a woodland songster I heard a few weeks ago, a young male whose mating hormones had him singing plaintively for a companion.
It happened when the weather was damp, the days a bit longer than right now, and the daytime temperatures were still consistently in the double digits ... on the plus side. A strongly presented, very definite, "PEEP! PEEP! PEEP!" came from the shrubby area beside our little marsh.
A spring peeper was terribly mixed up with his seasons, yet bang-on for his interpretation of spring-like atmospheric conditions. Frogs are usually associated with spring, but this guy was an autumn soprano, a tad mixed up in the seasons, yet giving it his best shot.
Today, as I walk by the thin wrap of ice that covers the still water, the fate of the late season songster stirs my curiosity. Usually, by this time of year, things like frogs are lumped with other items that are out of sight and therefore out of mind. But what of this one? Is it buried in mud or is it tucked under leaves?
A bit of research revealed some amazing information about our slimy non-migrating amphibious friends. At least 'non-migrating' in the bird sense, as by the time a wee green frog were to hop from here to the shores of Lake Erie, swim across, and continue hopping southwards to, I don't know, Tennessee, it would arrive just in time to turn around and retrace its hops all the way back.
That journey in itself would be overly exhausting, never mind the predators along the way. No, frogs are smarter than that. They stay home.
Seems that our froggy friends can be divided into two styles of survivalist camps: those that go underwater; and those that take to the woodlands. Each has its challenges and rewards but, depending on its species, it will be genetically programmed to do one or the other.
The water survivalists include bull frogs, green frogs, mink frogs and leopard frogs. Like all their cousins, they spend the autumn fattening up, dining on as many bugs, worms and other delicacies as can be found. And then, just before bedtime, they stop eating and empty their bladder and bowels (very smart these frogs ... smarter than me some nights).
The old tale is that the frogs then dive to the bottom of the pond, burrow deep in the mud and hibernate there all winter. Wrong-o! Apparently the frog needs to have some of its skin exposed to the water to obtain oxygen. While they may indeed snuggle into the mud, their back must still be exposed.
And herein lies a flaw in the plan. If their back is exposed, that means they aren't hiding very well. And if they aren't well hidden, they are therefore available to predators.
Otters and mink are active all winter, diving under the ice is search of food, and certainly appreciate a fresh meal of frogs legs (and all that is attached to them). I have found many dead frogs taken mid-winter by screech owls who hunt shallow streambanks.
Perhaps noting this weakness in the water plan, the woodland amphibious hibernators feel much superior. The wood frog (pictured), tree frog, and spring peeper have their own, and very unique, manner to get through winter. Even better than old Mister Toad, who just digs a hole straight down until it's below the frost line. Boring. This frog trio uses high-tech chemical shifts of bodily functions to beat the wintertime blues.
As soon as the first serious freezing sensation hits their skin, a hormonal response is sent to the liver, where naturally occurring glycogen is broken down into a type of sugar, called glucose. For the next several hours this glucose is then pumped into the blood stream and into all parts and organs of the frog.
This process is similar to a diabetic person, but here's the difference: normal levels of glucose (sugar) in frogs are about 1 milligram per millilitre of blood. (A pre-diabetic person has about 4 to 6 milligrams.) But the now sugar-laced frog has a reading of 45 milligrams!
The water within the frog's body that is between the cells and within the body cavity, freezes. But not the organs. Over half of the frog's body can be frozen solid, yet critical functions continue to take place. As there is so much glucose sugar within the cells, the temperature at which it freezes is much lower than sugarless water, so the frog can survive with just a thin covering layer of leaves and a bit of snow above it.
The tiny bit of energy that is required to maintain life is obtained from the sugar itself via a fermentation process. Kind of like having a battery backup system, trickle charging the body until next spring.
Imagine, frogs in suspended animation. Perhaps people will someday be able to do that. But not me, as I still have to get up in the middle of the night.