Wisconsin’s resident wildlife has to be able to handle some pretty extreme climate fluctuations, from more than 90 degrees in the summer to well below zero in the winter. For me personally, I like the cold; it is a lot easier to put on warmer layers than it is to cool down in the heat of summer.
For wildlife, it seems there are stresses and dangers in the heat and bitter cold, and survival depends on adapting to those extremes. Our own ruffed grouse is a great example of wildlife species adapting to cold winter weather. The ruffed grouse is a gallinaceous bird, which is a group of heavy-bodied birds that generally walk and feed on the ground—like chickens and turkeys.
The grouse has some excellent adaptations to help them function in the cold and snowy Northwoods winters. They have a short, stout, downturned beak that gives them the ability to snip the buds off of tree branches. Because some of these tree buds have bitter toxic compounds, the bird’s digestive system is specially modified to break those compounds down. They also have special pouches between their large and small intestines to allow them to store bulky fiberous material until they are able to digest it. This means that they are able to eat woody material, like deer in a way, and extract the nutrients they need to survive in wintertime when there are no other foods (green plants, seeds or insects) available.
Another cool wintertime survival adaptation ruffed grouse have is a snow roosting behavior. Snow roosting is basically flying into a soft snowbank. They then dig a little tunnel, a couple feet long, and make a small chamber where they will spend the night. If you have never made a winter snow survival shelter, you might be surprised to learn how warm they can be. Snow is a very good insulator; temperatures inside a snow shelter can be 30 to 50 degrees warmer than outside in the wind and elements.
Whenever we have a poor snow winter, I hear concerns from sportsmen that the lack of quality roosting snow could hurt the grouse population. The research I have read seems to indicate that, while snow roosting is favored by grouse in northern climates whenever possible, the populations do not drop notably in years when snow conditions are poor. What is a good quality snow year for a grouse? I think this year would be an excellent example—they need at least eight inches or so of soft, fluffy snow. They fly into the snow head first travelling at a pretty good speed, and they can get injured if the snow is too heavy.
If a grouse roosts in a tree, they are exposed to the cold, wind and precipitation. They are also vulnerable to predatory birds. Snow roosting eliminates all of that; however, snow roosting has its trade-offs, the way I see it. They are now on the ground level, and their scent may be detected by industrious predators like foxes or coyotes. They cannot see danger coming, either. In a winter like this one, the choice is easy to see; who could resist a chance to sleep in warmer conditions?
Another interesting winter adaptation is the seasonal development of pectinations. Special rows of bristles grow from the sides of their toes in the winter, helping them to walk on top of the snow with their strong, stout legs. Imagine growing your own custom snowshoes on your feet every winter.
Ruffed grouse are a great emblem of life in the woods of northern Wisconsin. They are rugged and adaptable. They have found a way to not only survive, but thrive during our most difficult time of year.
Jeremy Holtz is a wildlife biologist with the Wisconsin DNR and writes a weekly column in the Star Journal. To contact him, call 715-365-8999.