Naturespeak A naturalist's view of the world

January 17, 2008

Muskrat Burps

Filed under: Uncategorized — wykes @ 9:25 pm

In this, the third and final (for now) installment of the muskrat trilogy, I would like to call your attention to the subject of bubbles – muskrat bubbles to be precise. I’ve been keeping an eye on a group of local ‘rats and have recorded their antics for several years now. Even when their world is locked in the frigid grip of winter, I still stop by to check up on things every now and then. These active rodents still keep up a hectic schedule under the ice. Their movements can be harder to track under these circumstances, but in some ways this task is actually made easier. In order to explain this, I’ll need to call up some trapper wisdom.

  Muskrat trappers have to do most of their work in the dead of winter – which means working the marsh when it is sealed in ice and snow. The most essential piece of knowledge is to determine whether muskrats are active in any given area. Fresh cuttings from cat-tail roots, floating mounds of vegetation (sometimes called feeding “bogs”), and piles of fresh muskrat doo deposited as scent posts are all open water signs of muskrat. All these signs are covered once the ice sets in. It was veteran trapper Dave Venier that showed me how to inventory the whereabouts of winter muskrats.  “You look for the open water in front of the lodges,” he says. “The ‘rats keep moving around and they keep the water from freezing up. This shows where they are going into and outta their lodges.” Dave also pointed out the plentiful bubble trails, evident under the patches of clear ice, which mark the muskrat subway routes.

  Once glance at this view of one of “my” muskrat lodges certainly proves this out.  The recent cover of ice captured this bubble trail leading to and from the main entrance of this particular lodge. Earlier in the winter, I was able to record an even clearer bubble effect at the same lodge (see here) and after a healthy fall of snow an open water spot still remained (see here).  

  Even though the evidence of activity was sufficient to notify me of their presence, I was delighted with the opportunity to follow the course of an individual ‘rat one day as it left the lodge and took the standard route to a feeding area. The creature was reduced to a golden brown blob when viewed through the frosty ice pane, and was easily tracked as it plowed through the bubbles like an amoeba pushing through glassy sand grains.  It shifted about amorphously under the ice at a spot located some 50 feet away– its tail pressing up against the glassy ceiling as it dug though the bottom mud for cat-tail rhizomes. Once the prize was secured, the ‘rat returned to the lodge along the same bubble highway. It never once broke surface – even in the open water next to the entrance.

  This foraging ‘rat stayed submerged for one minute while so engaged in his under-ice pursuit. For an animal that can stay under (on a single breath) for as long as 15 minutes during the warm season this kind of thing is the norm. During a hard freeze, however, a winter muskrat is sometimes forced to rely solely upon the stale air within the lodge. This supply of trapped air is saturated with near fatal Carbon Dioxide levels. On top of this, the muskrats rest and eat in complete darkness when in the tight confines of the shelter. Only the pale reflected light from the entry tunnel softens the blackness and only momentary gulps of fresh air relieve the staleness.

  Muskrats are able to cope with, and even thrive, in these conditions.  Dave, the trapper notes that animals forced to endure ice conditions for a long time start to exhibit what he calls “kidney spots.” These are marks that become evident on the hide once it is processed.  There probably is a physiological reason for this, but I’ve not taken that investigative route yet.

  I pointed out the ice bubble trails to a friend of mind and joked that they were “muskrat burps” ejected as the critters exited the lodge. Dennis, an inquisitive sort of fellow, gazed back at me with a pondering look and calmly asked if I wasn’t sure that they came out of the other end, “you know like bubbles in the bath tub!”  “Dennis, “I said, “I guess you’ll just have to walk out there and smell one of those bubbles as it melts out of the ice. Let me know if it smells like cat-tail root.”


  1. nowadays, it is sometimes to get fresh air in big cities and even in suburbs.*:~

    Comment by Samuel Johnson — June 21, 2010 @ 12:35 pm

  2. i love the smell of fresh air in the morning. it is so rejuvenation…”

    Comment by Brody James — July 20, 2010 @ 2:03 pm

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