2018-02-10 / Columnists

Nature Notes

Surviving the Winter Sometimes Creates Strange Bedfellows
By Patricia Martin

Well, friends, it’s winter. The temperatures have been a bit up and down. At one point, within 48 hours it went from minus-12 degrees Fahrenheit to almost 40 degrees Fahrenheit, a swing of about 50 degrees. But now it seems to have settled down to just being cold and snowy. Well, what do you expect in February in northern Michigan? With the interesting winter we’ve had, it got me to thinking about how our feathered and furry friends and others deal with the cold and storms.

Many of the insects that winter over here do so in an egg or larval stage in the ground or in some protected area, but there is one that uses a different strategy. The mourning cloak butterfly actually winters over as an adult butterfly. It survives the cold by going into rotted logs and stumps for the winter. The heat from the decomposing wood keeps the butterflies warm. This is also why on a warm, sunny day in the early spring, when snow is still all around, you may see fully developed butterflies flitting around. If you are not familiar with the mourning cloak butterfly, they have predominantly black/dark gray wings with a yellow band along the edge.

Some of the woodpeckers use a similar strategy. Many, like our pileated woodpecker, build their nests in snag trees, in which it is easy to drill nesting holes. The birds then line the holes with insulating materials (grasses), which also keep them warm. Many of these trees have some rotting in the wood, which creates some heat.

A number of the squirrels also use hollows in trees or stumps. Most people are used to seeing squirrel nests made of leaves in the branches of trees, but they also like to curl up together to keep warm in the trunks of trees. Our gray squirrels (gray and black) have been fairly active the early part of the winter, but should now be hunkering down in their nests to while away the cold. Red squirrels are usually out and about most of the winter.

Chipmunks, on the other hand, head underground to their dens where the snow and the soil insulate their homes (although this winter, with the frost going down more than 40 inches already, they may get a little chilly). Their underground runs can be more than 30 feet long with multiple chambers, one or more for food storage (the pantry), one for waste (the bathroom, if you would), and one or more for nesting (the bedroom). By the way, the runs have multiple entrances. We won’t see much of these guys until spring.

Our cold-blooded residents take on the temperature of their surroundings. Many frogs and salamanders burrow down into the mud, which acts as some insulation, and the fluids are such in their system that it acts as an antifreeze and they just hibernate.

Snakes often create a hibernaculum under the rotting roots of a dead tree or stump. The rot creates some heat and the snakes wind themselves around each other in a ball. Often different species of snakes may be found all rolled up together, even those who don’t normally like each other very much. Snakes, like the milk snake (of the king snake family), who will eat other snakes, will often curl up with their future dinners. Winter does create some “strange bedfellows.”

Speaking of strange bedfellows, a guest of mine recently told me of a sighting they thought unusual. Near their house there is a den of a woodchuck or groundhog. Repeatedly they’ve seen a mink going down the woodchuck hole. They think it is using part of the den as a nest.

Another example of strange bedfellows is happening on the shores of Mackinac. At least one muskrat (Ondatra zibethicus) has taken up residence in the beaver lodge right along with the juvenile beaver. Muskrats are about the size of a small house cat, weighing in at between 1.75 to 3.5 pounds. They are uniformly dark brown on the back and a bit silver-tipped on the belly. In the water, where they spend much of their time, and with their webbed feet, like their distant cousins, the beaver, there may be some difficulty telling young beaver apart from a muskrat. There are, of course, some distinct differences. The tail of the beaver is rounded, large, flat, leathery, and scaly, and it is this tail that makes the loud splatting sound when it’s slapped on the water. It scares away predators and warns others of danger. In contrast, the muskrat has a long (almost as long as its whole body), black, almost naked tail that is laterally flattened.

Both of these mammals are rodents and are considered semiaquatic, spending much of their lives in water. Although their food habits overlap somewhat, as they both eat a lot of aquatic vegetation, there are differences. Muskrats are not totally vegetarian. They will also eat mussels, turtles, frogs, and fish. Beaver, on the other hand, will primarily eat bark and buds of trees, although aquatic plants are also ingested. Another big difference is their building ability. Beaver, with their large head, jaws, and sharp teeth, can cut down trees and build very impressive structures, whether it’s a dam to create a pond, or a lodge to make a cozy home. Muskrats do build dens with underwater entrances, but they are no way as skilled as their much larger cousins.

It has been known for a long time that muskrat sometimes move in with beaver, particularly during the winter. It has always been thought that they were just “freeloaders” or opportunists. Recent studies have shown that these two species of rodents often live together in harmony. Muskrats have been seen helping to maintain and repair the lodge, making repairs and placing new material. They have also been seen carrying grasses for young beaver to eat. It is not all peace and light, though. If the lodge gets too full, it’s the muskrat that gets kicked out.

Have a good winter; spring will come.

Trish Martin is a year-around resident of Mackinac Island, has earned a master’s degree in botany from Central Michigan University, and owns Bogan Lane Inn.

Return to top

Click here for digital edition
2018-02-10 digital edition