Frogs and toads, snakes, chipmunks and mice
What do mosquitoes and spiders do under the ice?
And what about grasses, and mushrooms and trees
What do they do when the temperatures freeze?
— Lucy Cutler, 2009
The woods are quiet in the winter. No rustling leaves, no insect calls and few birds singing, just a sparkling silence and hidden life. Perhaps this is a good time to explore some of that hidden life.
Inside, Outside, Underside. The snow blanket isn’t just a coating; it has dimension. At least one local animal makes use of all aspects of the snow cover. The meadow mouse (Microtus pennsylvanicus) runs around on top of the snow, tunnels through the snow and caches up to three quarts of seeds in logs under the snow.
Mosses stay green all winter and are busy photosynthesizing right through the snow cover. Why aren’t they covered by the dead leaves that are all over everything else? Because the leaves stay on the flat ground or stick in cracks and crevices, while the tiny, pointy tips of the mosses hold them up so the slightest breeze blows them off. Not only do they stay green and photosynthesize, they also produce a substance (arachidonic acid, for the technically inclined) that helps them, and any animals that eat them, to protect their cell membranes against freezing.
In addition to insulating the soil, dead leaves feed all sorts of bacteria and fungi. Below the dry, brittle leaves that were fun to scuff in the fall are moldy, decaying ones. They’re involved in a fascinating process whereby the cellulose and other parts of the leaves are slowly being turned into soil by fungi and bacteria, some of the few living creatures that can digest cellulose (cattle need special bacteria in their rumens to do the job). The digesting slows but does not stop in the winter and goes on under as well as above the soil.
Mixed with the leaves or tucked under loose bits of bark are overwintering insects. Some of these are wooly bear caterpillars (these fuzzy brown and orange creatures can survive to –90ºF!), mourning cloak butterflies ready to emerge and fly on the earliest warm days and cecropia moth cocoons in which the larvae are busy metamorphosing into lovely moths.
Roots are able to absorb and store water all winter to be ready for their rapid growth in spring. Helping them do this are underground mycelia. That’s the part of mushrooms that we usually don’t see, and a very important part it is. Not only do mycelia nourish the mushrooms we do see, they also help trees grow by sharing, from tree to tree, water, nutrients and, in the growing season, information, like “a bug just nibbled my leaf.”
We’re not likely to see the tunnel entrances to chipmunk burrows, since they’re concealed by leaves and have no telltale mound of excavated dirt, that having been carried away during the digging. Inside the burrows are food, a bathroom and a bed that is not only mattressed with soft leaves and seed down but also perched atop a food supply so the sleepy chipmunk can snack without bestirring itself when it arouses from its light winter sleep (they don’t actually hibernate, just doze and snack). At the beginning of the winter the bed plus hoard is near the top of the nest cavity; by spring near the bottom, as the stored seeds have been nibbled away.
Diana Thottungal is a naturalist at the Eloise Butler Wildflower Garden. Text and mouse trail, mycelia and wooly bear photos copyright © 2010 Diana Thottungal. Chipmunk photo by Tammy Mercer. Moss Photo from Friends photo library. Diana Thottungal and Tammy Mercer are employees of the Minneapolis Park and Recreation Board.
Note: This article was published in the Fringed Gentian™, Winter 2009-2010, Vol. 58, #1.