By Donna Barski
Early last spring, I gently lifted a small frog that was trapped in a mat of thick icy-slush covering my pond. I suspect this frog unwittingly leaped into the pond during the previous night and began to slosh through the cold mush until his leg muscles stopped moving. There it remained, in the numbing cold, until I came along.
I’m not sure why I felt I needed to “rescue” this seemingly helpless amphibian. After all, he was a wood frog. Becoming a living frogsicle during winter was completely natural for him. Dying from hypothermia is simply not in his DNA.
Amazingly, wood frogs freeze nearly solid each winter. As the temperature in autumn starts to drop, their thin-skinned bodies prepare for the deep freeze. Stored urine mixes with liver glycogen, a sugar, and this natural anti-freeze solution protects their essential internal organs. Eyes solidify, looking like pearls. Skin and muscles freeze to brittle. And, incredibly, the heart and lungs stop functioning. Now, the amphibians are ready to survive winter in a state of suspended animation, unthawing and freezing with changing temperature conditions during the season. This cold adaptation allows wood frogs (New York’s state amphibian) to survive even as far north as Alaska.
Distribution range (source: Wikipedia):
Then, with spring’s dependable warm-up, wood frogs, hidden under only a blanket of leaves, a thin layer of soil or beneath logs in the woods, defrost in just a couple of days, their hearts begin to beat again and they begin to breathe.
So, this wood frog in my hand had only to wait until the pond’s icy-mix melted and his body warmed again in the noon-day sun in order to resume swimming to his destination, a shallow breeding pond.
These amphibians, along with spring peepers, are the first frog species to breed. The males arrive just after ice melts off their ancestral vernal pools. Together they sing a chorus that is sure to make you think you are hearing a flock of quacking ducks. Of course, the females don’t make this mistake and can hear the males' irresistible cacophony up to a half-mile away.
Their mating frenzy lasts a week or two. Once all the eggs have been deposited and fertilized, the adults return to their adjacent woodland habitat, disbursing to hunt for insects, spiders, slugs, and snails.
In a few weeks the tadpoles will have transformed into miniature versions of the adults, crawling out of the water and into the forest, where they will grow to adulthood and prepare to freeze for the winter, just as wood frogs have done for thousands of years.
Warmed by my hand, the wood frog in my palm began to stir, so I carried him to the edge of the breeding pond where I slowly lowered his body into open water. Soon he was floating about and quacking along with the other males. Perhaps, I thought, I’ll see him again next year.
Note: Wood frogs are elusive in their forest habitat. The best time to locate and observe them is in late winter or early spring when they are gathered in wetlands, and the males are quacking. If you are able to quietly access their breeding pools after sunset, during a warm spring rain, you might witness a show called The Big Night when great numbers of spotted salamanders join them in a “water ballet,” where they mate and leave their eggs in jelly-like masses.
Donna Barski is a retired teacher who lives in Arcade, New York and has an Environmental Studies degree and a life-long interest in nature. Read her previous post on the Land Conservancy's blog.
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