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The wake of a swimming muskrat breaks the perfect reflection on a freezing lake. Photo by Emily Stone.

November was giving a big gray sigh of frustration as the sky tried to decide if it would rain or snow, and the lakes hemmed and hawed about the proper schedule for freeze up. There was beauty in its hesitation, though. The shimmering sheet of ice reflected the pale gray sky on its gossamer, crystalline fibers. The pale edge of the ice contrasted with the silky blackness of open water, which mirrored the lacy skeletons of shoreline trees.

Although eager to get home before dark, the scene pulled me to a stop. In any season—but especially the shoulder ones—moments of a certain beauty are ephemeral and must be appreciated promptly or not at all.
As I was pondering that, the glassy surface of the open water--where I had been admiring the faithfully reflected trees--was cut open by a V-shaped furrow. What was marring this delicate surface? I tracked the V as it sliced from right to left and neared the pale white edge of the ice sheet. Through my camera’s zoom, I could see a furry brown head and small hump of a back.

To my surprise, instead of diving down under the ice and disappearing, it climbed up onto the precarious, perforated margin, fully revealing its plump, brown body. Well, this was just a pit stop apparently, because it spun right around and slipped back into the water, its dark, rope-like tail following closely. Well, that answers that question.

Although beavers and muskrats are both furry, brown, aquatic rodents, their tails offer instant differentiation even when a size comparison is difficult. Beavers, of course, have those flat, paddle-like tails, while muskrats’ tails are long, skinny, and slightly taller than wide.
Muskrats are active year-round, even in the frozen north. While that thought sends a shiver down my spine (I may do a polar plunge, but I’m not going to swim laps under the ice!), muskrats are as well-adapted to their particular lifestyle as anything in nature. Plus, while we endure -40-degree wind chills, their watery world stays above 32 degrees. 

A warm coat is their first line of defense against the cold, and to be warm, it must also be dry. Dense underfur traps air and keeps moisture away from their skin while also adding buoyancy. Of course, their soft, warm pelts are also a liability, since humans want a piece of that cozy warmth. The early 1900s were the height of fur trapping for muskrats, but it’s a tradition that continues today.

In fact, my first, rather memorable encounter with a muskrat was to watch my older brother peel the skin off one as it hung from our basement rafters. He sold the furs for a little money, but I think that his true motivation was an excuse to tramp around outdoors. He’s passing on his skills, now, to my middle nephew. Derek is trapping muskrats out of the landscaped pond in a neighboring suburban development. In exchange, the association will let him bike over and go fishing whenever he wants. When you’re 13, that’s a pretty good deal.

I’ve often puzzled over the continued demand for muskrat fur, even though at $3 per pelt, the demand doesn’t seem very high. At some point, a warm jacket made of anything would be welcome—and they are so soft—but a musky-old-rat stole just doesn’t have the same cachet as mink. To get around this, old-time furriers had the pelts specially trimmed and dyed, after which this rodent’s fur was sold as “Hudson seal.” It was so popular that muskrats were introduced as a fur resource into Japan, Scandinavia, and Russia, and then spread throughout northern Europe and Asia.

Warm fur isn’t enough to keep muskrats going all winter long, though. As with any animal that stays active through the cold months, the ability to find food to fuel their metabolism is crucial. Unlike beavers, muskrats don’t store food. Instead, they continue to forage for vegetation under the ice. When the water is shallow or the ice is especially thick, muskrats may even dig channels in the mud to help them get around.

Food, in their case, is mostly the leaves, stems, and roots of aquatic plants like cattails, rushes, sedges, water lilies, and arrowheads. Bacteria in muskrats’ guts ferment this high-fiber diet and make more nutrients available. While a partnership with bacteria isn’t unique in itself, the fact that muskrats can vary their diet to include significant amounts of meat in the form of frogs, fish, turtles, and crayfish without killing off their fiber-digesting bacteria is unique. It’s no wonder that these omnivores are such opportunists—they need to eat 25-30% of their weight in food every day!

Even with the consumption of that much food, getting enough nitrogen is a challenge once the most nutritious plants die back and animals go into hiding. Muskrats deal with this shortage by reducing the amount of nitrogen they excrete and increasing the surface area in their gut available for absorption.

The surface area of ice on the lakes expands for winter, too, and in fact, most have already frozen up since that calm, gray day. Like the sleek muskrat slipping out of sight, that one moment of beauty is gone. Such endless moments of beauty drift around us every day, and we can choose to appreciate them promptly or not at all. Which will you do?

 
Special Note: Emily’s book, Natural Connections: Exploring Northwoods Nature through Science and Your Senses is here! Order your copy at http://cablemuseum.org/natural-connections-book/. Listen to the podcast at www.cablemusum.org!

For 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI! Our new exhibit: “Better Together--Celebrating a Natural Community” is now open!