I often drive past marshes with muskrat lodges during my winter routine. I cannot help but wonder how they are faring.
Those lodges provide good cover and insulation from the winter cold. The lodge has a small living chamber above the waterline with one or two opening to the water below. Muskrats feed on the roots of cattails, bulrushes, and other aquatic vegetation. And they remain active and feed regularly under the cover of ice during the winter months.
Muskrats can keep their body temperature near normal even when in the water for a half-hour or so. So how do they do it? Grooming, grooming, and more grooming! Muskrats groom a lot! And all that grooming distributes water repellant substances throughout their pelt which not only makes the pelt water repellent, but also functions to trap the air within, thus providing good insulation. To stay well-groomed, they will conduct a thorough grooming before entering the water (think well-oiled), and again afterwards. The grooming activity also generates some body heat.
Muskrats somehow elevate their body temperature by about 1? before entering the water during the winter. That does not occur during the summer months. Although the mechanism has not been identified, it may be related to muskrats appearing to hyperventilate before entering the water during winter. Behavioral changes as well as physiological mechanisms allow muskrats to stay quite active during the winter months.
Observers occasionally have noticed air bubbles (or “bubble trails”) under the ice in muskrat travel routes. Those air bubbles are formed by the exhalations of the muskrats as they swim in the water below. Muskrats have also been observed stopping at these air bubbles, sticking their noses into them, and apparently inhaling from them. Researchers have now documented it, and estimate it allows the muskrats to roughly double their time spent in the water.
If, however, the muskrats somehow get froze out of their lodges and shallow water environment by extremely cold winters, they are in for a tough time. Even though they can still probably get enough food to make it, predators, such as mink, are the big mortality factors.
So, as you travel about and see those lonely looking muskrat lodges in the wetlands, give some consideration to all that is going on behind the scenes…or should I say below?
~Chuck Lura
