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Below The Surface

Tuesday, November 2, 2010

Frogsicles and Other Frigid Amphibians

As accumulations of snow and frosted windows become more frequent, we think about enjoying or enduring another Vermont winter, or perhaps moving south. In the animal world, as winter approaches, animals endure, leave, or if they can do neither, they hibernate. Amphibians are ectotherms, animals that get a good deal of their body heat from their environment. Lacking appendages that facilitate adequate migrations, they hibernate. They hibernate when the energy demand to stay active and procure food exceeds the available energy in their environment. Shorter days, dropping temperatures and the reduced availability of food, induce hibernation.

In the Lake Champlain basin, not all of our native amphibians hibernate. Eastern Newts, in the adult aquatic life stage, and mudpuppies are active throughout the winter. If you can find a window into the ice of a partially frozen pond, you may be provided a glimpse of the absurd activity of the diminutive Eastern newt in the dead of winter.

Salamanders, like the Spotted Salmander, utilize other animals’ burrows, which is why they are known as ‘mole’ salamanders, to hibernate below the frost line. It’s risky business: your hibernation site could be in someone else’s dining room and you become the meal.

Our more aquatic frog species hibernate by migrating to the bottom of their chilly aquatic environment. Their metabolism slows down due to the cold temperatures. They absorb the little oxygen they need and release carbon dioxide through their skin. They are awake yet sluggish. Unlike hibernating turtles that may dig down into the mud at the bottom of ponds, these frogs stay on the surface of the mud and may actually move around. They do not feed; they live off the stored energy reserves in their bodies. If they go into hibernation without enough reserves or if their pond completely freezes, they perish.

Other frogs, our more terrestrial species like the American toad, the wood frog, the spring peeper and the grey tree frog, hibernate on land . The American toad, an accomplished digger, will dig in enough to hibernate below the frost line. Those that are not good diggers, the wood frog, the peeper and the grey tree frog, hibernate in the leaf litter or under logs and rocks. These animals benefit from a good thick blanket of snow that insulates them from some of the extreme winter temperatures we experience in Vermont. But, if there is little snow and temperatures drop below freezing, the wood frog, the peeper and the grey tree frog can actually spend winter frozen like a popsicle. While ice forms in their body cavity, they develop high levels of sugar and sugar alcohols in vital organs, which acts like antifreeze and prevents damage to those organs. Click here for an incredible video which actually shows a wood frog thawing out.

These are adaptations that have developed for the many amphibians trying to make a living in an area seemingly more suited to those animals with fur or wings. These adaptations are no less impressive than those that allow our native mammalian and avian species to cope with our extreme winter conditions but perhaps less appreciated, after all, it all takes place in the ground, under the snow and ice, and out of sight is often out of mind.

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