20 NEEPAWA BANNER & PRESS MARCH 12, 2021
Moments in Riding Mountain: Small winter miracles By Ken Kingdon Submitted
I don’t need to tell you that this past February had some nasty cold temperatures. We happened to be in self-isolation in Onanole when the temperature dipped down to -45ºC. These cold snaps make one appreciate the day to day miracles of modern life, such as central heating. I might also add the winter miracle that occurred when someone decided to add a shot of Bailey’s to hot chocolate. However, while being tucked up warm and cozy in our house, I got to thinking about the chickadees feeding at the bird feeder. There is something miraculous about small bodied animals surviving the coldest of the cold. Small animals keeping warm As many of you recognise, the smaller a body is, the harder it is to keep warm. This is a function of physics, in which the surface area of an object increases at a lower rate as its mass increases. Huh? I’m no physicist, so let’s just say that small people tend to complain about the cold more than big people. This difference is even greater when you think of very small animals, which need to work even harder to keep warm. In previous articles, I have talked about strategies used by chickadees, including
sleeping with a bunch of their friends jammed into a small cavity in a tree, and going into torpor, or suspended animation, during the night. Their feathers act as great insulation and they have almost no flesh in their legs and feet, which means that they don’t have to keep them very warm. They also feed on high energy foods such as insects, berries and seeds. I have also been thinking about mice, voles and shrews. Again, these are all small bodied animals and staying warm in the winter is always a challenge. These species tend to avoid the coldest temperatures by staying under the snow, which provides some insulation. This sub-nivean world stays at about -4ºC, which, while cool, provides enough warmth and protection over winter. There are some challenges though for these rodents and shrews. First of all, not all areas of the prairies get snow before it turns cold. Thus a snowfree November or December likely leads to pretty high mortality rates among small bodied mammals. And even if we get snow, we can get some crazy weather, such as winter rainfalls, which can result in an ice layer building up on the snow. This can create an interesting situation where the exchange of air in the snow
layer is really reduced and carbon dioxide begins to build up under the snow. Imagine dealing with four months of mouse farts, shrew body odor and morning breath from voles, and you get the idea. Small mammals have to occasionally head for the surface just to get some fresh air.
animals are cold-blooded and very tiny. How can they possibly survive the winter? Add to this the fact that most of these invertebrates are simply finding shelter under bark, or in crevices and holes in a tree. I can’t imagine that a tree offers much insulation value when it has been -30ºC for a week.
Insects in winter And then there are the other small things that persist through the winter. One of the most obvious species are the snow fleas that show up on mild days in the winter. As soon as temperatures get above 0ºC, these insects magically appear along ski tracks or snowshoe trails. Where do they come from? In the cold weather, they spend their time in the leaf litter under the snow. As the temperature rises, they make their way to the surface. I’m not entirely sure what they are up to, whether they are eating or mating, but regardless, they do it in abundance. Another common invertebrate you can spot are spiders. There are few weirder sights on a winter’s day than seeing a spider slowly walking along the surface of the snow. Likely, having been blown from their winter hiding spot under bark, they don’t move very fast or far, but the optimist in me hopes that they survive their winter walks. Unlike birds and mammals, though, these
Internal freezing For most organisms, the enemy is not the cold, per se, but rather it’s the ice that forms inside their bodies. When cellular water freezes, it creates sharp ice crystals which puncture the cell wall. This leads to the death of the cell and, when bad enough, the death of the individual. For overwintering insects and spiders, they get around this issue by producing a protein which binds to any ice crystals. This prevents the ice from damaging the cells. It’s a neat trick that cold-blooded organisms have developed, but one which science is interested in researching for such applications as de-icing airplane wings. I’ll add one final winter miracle. By March, the sun is shining, the snow melting and spring begins to make her presence known. Thank goodness for small miracles indeed. Ken Kingdon lives and works in Prince Albert National Park. 210326G0