Wilderness Underfoot: The muskrat

StoryImage( ‘/Images/Story//Auto-img-114003847614734.jpg’, ”, ‘The muskrat is named for musk glands near the base of its tail; these glands become active during breeding season – Ondatra zibethicus belongs to the family of “murid rodents,” which includes the deer mouse, the house mouse, the black rat, the lemming, and the vole. A muskrat is actually a large vole. Most members of the muridae family are land lubbers, but muskrats are specialized for life in water. They’re agile swimmers, with webbed hind feet, sleek fur, and an uncanny ability to paddle backward and forward.’);
StoryImage( ‘/Images/Story//Auto-img-114003848514734.jpg’, ”, ”);

This water-loving mammal is built for cold weather survival

Within any mile-long stretch of wet ditches or well-vegetated river banks, as many as 60 of these animals might be holed up in dens, waiting for the dark of night before they come out to look for food or fight over mates and territory.

Muskrats are the most wide-ranging mammals in North America. They can be found from the Gulf of Mexico all the way up to the bitterly cold Arctic Ocean. They don’t hibernate. Weighing only 2 pounds as adults, these rugged little animals have adapted to prevent heat loss in cold weather. Their pelts are multi-layered, with fuzzy underfur trapping air for insulation, and oily guard hair to resist water penetration.

Before diving into frigid winter waters, a muskrat will prepare by increasing its body temperature by about 3 degrees Fahrenheit. Its dives generally last less than a minute but, if necessary, it can hold its breath for several minutes.

On cold days, muskrats huddle together to warm themselves. This is quite an accomplishment for these feisty creatures, which at other times of the year are prone to nastiness and irritability toward one another. They do their huddling in comfortable winter lodges, where otherwise hostile and non-related groups come together in peace. Muskrat lodges are constructed like beaver dens; mounds of plant debris and mud are built over the waterline, with entrances underwater. Reeds and cattails are common building materials, but any wetland plant may be used.

Some muskrats avoid constructing lodges, instead favoring holes dug into the banks of ponds, creeks or rivers.

Winter survival depends on having an adequate food supply. The muskrat diet consists of plants found near marshes and rivers—cattails, bulrush, waterlilies, lotus and wild rice. If cultivated fields are nearby, muskrats gladly take excursions to collect food from those as well. Occasionally, they’ll eat crayfish, clams, fish and turtles, but their diet is mostly vegetarian. In the cold of winter, their primary food is the root and young shoot of the cattail.

From the Feb. 15-21, 2006, issue

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