Surviving the Big Freeze

SURVIVING THE BIG FREEZE
 November 15 & November 17

There was a chipmunk calling last weekend at Sandbanks Provincial Park. Just for a moment, I was camping again in the Woodlands Campground where the emphatic chip of this energetic denizen of the woods is a familiar sound in the fall of the year. But, it was cool and cloudy on this November day during a hike along the park’s Woodland Trail and it was the only chipmunk we heard in a forest that’s normally full of them.

It is getting late and chipmunks are preparing for winter; some have no doubt already entered their burrows where they will spend the winter. The chipmunk is often cited as an example of a hibernator, but how many animals truly hibernate? Not many, I dare say, and certainly not the chipmunk, if we want to get technical about it. True hibernators enter a prolonged state of torpor during the long winter months, when metabolism slows down, and there are very few mammals that do that non-stop through the entire winter Even the groundhog has been known to come out of its burrow and look around.

However, the chipmunk does go under a remarkable transformation at this time of the year during its time underground. This perky little mammal whose heart races at a brisk 350 beats per minute, drops into a whisper mode, its heart beating at a modest four beats per minute, barely enough for us to claim it is alive. The body temperature drops from 36 degrees to just three. But every two weeks or so, it wakes up to have a snack of its cached food supply, at which time it will also take advantage of the opportunity to urinate in a special chamber reserved for that occasion. During the time it is waking up, it unrolls itself, trembles a bit and proceeds to stagger around with its eyes closed, not unlike some of us when we get out of bed in the morning. Then it curls up and slumbers on for another 15 days.

Come April, though, it springs to life with renewed vigour. Friends John and Janet Foster of the Tweed area, when not filming whales in the Arctic or wolves in Algonquin, are feeding up to a half dozen chipmunks at their back door. During a barbeque at their home a couple years ago, there were no fewer than three at one time, perched on their haunches on the picnic table, not more than a few inches from my elbow. The Fosters have a container of peanuts, and when these little animals are not being hand fed, their backyard guests are not beyond helping themselves. This spring, right after the chipmunks had emerged from their winter’s sleep, one of them raced into the house the moment the back door was opened. Making a beeline for the cupboards under the lunch counter, the chipmunk went straight for the container of peanuts, stuffed his cheeks full, and scurried back outside. This one, while perhaps losing weight over the winter, certainly had not lost its keen memory.

The ability of nature’s creatures to survive the winter is an amazing study, and is one that I have incorporated into a Power Point presentation titled, “Surviving the Big Freeze.” We already know that many species of birds routinely migrate south to escape winter’s wrath, but few of us realize that migration is driven more by food requirements than it is by just temperature.

Many frog species, even turtles, burrow into the mud at the bottom of a pond. All of us learned this in public school. But what the text books failed to explain was how these creatures who depend on lungs for breathing, can hold their breath for so long. Actually, they don’t. The lungs are shut down, and since the slower metabolism doesn’t require large amounts of oxygen, they are able to pull in oxygen from the water through their skin. Some frogs that aren’t terribly water oriented to begin with, simply burrow under the leaves or a log. Their livers produce glucose which is circulated through the body like an antifreeze, protecting the vital organs. One, the wood frog, allows itself to freeze completely through, gradually thawing in the spring and continuing on its way as though nothing happened.

Insects manage in variety of ways, even among families. Praying mantids thoughtfully seal their eggs in insulated capsules. You may have stumbled upon these in fields, attached to stalks, looking much like elongated miniature Coffee Crisp chocolate bars, but without the chocolate. They pack their eggs with cryprotectants such as glycerol or sorbitol, creating a syrupy solution to prevent freezing. Some, like the black swallowtail butterfly survive in the larval state, right in the pupa. Others like the red Admiral butterfly may hunker down somewhere protected in the larval state, or it may migrate as an adult, as do Monarchs. Others winter over in the adult stage and hope for the best. The mourning cloak butterfly is perhaps our best example, and is why we tend to see them ahead of all other butterflies in the spring.

Really, we don’t need to worry much about winter survival. Thousands of years of evolution have resulted in a finely tuned system that we, as humans, can only emulate provided the hydro stays on and our fuel tanks are kept topped up. We can’t helped but stare in awe at something as small as a goldenrod gall fly and marvel at its ability to survive, in at least sufficient numbers to guarantee continuance of the species. When all adults of many insects die, leaving only eggs or larvae, it seems like a risky way of doing business, but one which obviously has proven successful.