It’s not hard to notice the turn of the season as the snow line slowly creeps down the mountains. Nature has noticed too, and every living thing has prepared to stick-it-out or move out.
Honking over head heralds the passing of geese and other waterfowl as they make their way south to warmer locations where there will be more food available over the winter months. Most migratory birds that spend their summers here have long since flown the coop. But not all birds classified as “migratory” relocate for the winter. Some stay here year round and peck out a living. These can include geese, ducks, kingfishers, eagles, robins and herons. Some stay because there is enough food and they can withstand the cold, others stay because they cannot make the journey south for one reason or another.
Our resident birds have put on a more robust feather jacket, and many have switched their diets from predominantly insects to energy packed seeds and grains. Only about 35 per cent of the bird species observed in the Columbia Valley stay here year round.
Many furry critters migrate too. Ungulates typically migrate to lower elevations where there is less snow and better access to food throughout the winter. In fact, many mammals do this. However, some prefer to put on extra thick coats and a good layer of fat and live off a larder that they spent a great deal of effort stuffing full over the summer, like the beaver.
But why go to all the bother when you could just sleep off the winter cold? This is the tactic many plants and animals employ. Reptiles, turtles and amphibians typically find a burrow or bury themselves, reduce their metabolism to almost nil, and allow their body temperature to drop to below freezing. These creatures, like many insects, have natural “antifreeze” in their blood that prevents cell damage while they hibernate. Mammals that hibernate are not so fortunate. They still must keep their body temperatures above freezing, which means they burn a lot more energy while they sleep. Small mammals allow their body temperatures to drop to four degrees Celsius to reduce energy consumption, but in order to prevent brain damage they have to warm their bodies up every few days. Because they just can’t put that much fat on their tiny bodies, this means they have to wake up to eat and then pass waste. This is why you see ground squirrels, mice, marmots and pikas busily collecting and storing food all summer.
Larger mammals don’t have to lower their temperature as much as they can pack on more fat. Bears only lower their body temperature by about 10 degrees Celsius and can doze for 100 days without food, water or passing waste. On some cold, gloomy days I wish I could just sleep off winter too!