Muskrat Species Dossier

by Carl Strang

Last week’s literature review of muskrat population dynamics inspired this week’s choice of species dossier to share. These dossiers are limited to what I know about an animal from my own experience. I created them in the mid-1980s, writing an introductory paragraph of what I could say I had observed to that point. Subsequent dated entries expanded on that base.

Muskrat

Muskrats are aquatic rodents, but more closely related to meadow mice than to beavers.

This rodent lives in marshes, ponds, lakes, and streams. I have seen it in Illinois, Indiana and western Alaska. The den may be a tunnel in a bank (streams, lakes) or a cattail-mound nest (marsh). Muskrats cut runways in aquatic vegetation. They eat both plant and animal foods. One ate dead fish preferentially while recovering from injuries at the Willowbrook Wildlife Center hospital. At the Culver (Indiana) Fish Hatchery in late winter 1986, muskrats left the ponds and crawled up to the service roadway where they picked out leaves of English plantain to eat, selecting that species from a typical assortment of weedy herbs. Muskrats leave scent posts of feces on floating objects, sometimes creating a raft of cut water plants for this purpose. Their tracks are fairly distinctive. Front footprints are much smaller than hind; deep ones show a small 5th toe. Toes are relatively parallel on both front and hind feet. A tail drag mark often shows.

Muskrat tracks, the larger hind foot to left, front foot to right.

8JL73 (from field notes). In western Alaska, a muskrat observed taking Carex aquatilis into its bank nest.

2SE86. At Willowbrook (Glen Ellyn, IL), a muskrat ate a fallen (still yellow-green) mulberry leaf, and leaves + stem + flowers of Polygonum cespitosum longisetum on the bank, then cut several stems of the latter and returned downstream with them. Half an hour later, 2 muskrats, one smaller and grayer, one larger and browner with greater variation and demarcation of coloring, grazed in the same area at the ford of Glen Crest Creek. After at least 10-15 minutes of grazing, each went downstream with a mouthful of grasses. Despite this apparent episode of household establishment, this was the last I saw of these animals.

Front foot of dead muskrat. The large toenails are important digging tools.

26DE86. Muskrat 70 yards from shore in Lake Maxinkuckee at the Culver town park, diving in a small area where canvasbacks fed a month earlier. Under water 10-15 seconds, on surface 20 seconds to 2 minutes, tail lifting and turning actively. Head too low for me to see what the animal was doing, but probably feeding.

8MR87. Fresh muskrat tracks at Waterfall Glen, heading downstream in an empty streambed (Willowbrook received lots of calls last week about muskrats well away from water). The gait pattern resembles a woodchuck’s: like a diagonal walk, with front feet just behind and inside same-side hind print, and showing a definite straddle. About 3.5″ between sets of prints.

Bones of a muskrat revealed by a controlled burn. This muskrat died far from water, presumably while dispersing.

26AP87. McKee Marsh. A muskrat saw me, dove, brought its head up within a small cattail clump a few feet away to check me out. Just the top part of head was revealed, buried partly in cattails. Another was working on a mound nest at mid-morning, noisily pulling or breaking cattails near it, and repeatedly walking up to the house top with cattails in its mouth.

10MY87. McKee Marsh. One seen scratching itself while floating.

23DE87. Muskrats feeding on small branches of a large willow that fell into Glen Crest Creek within the past couple of days.

30OC89. One or more muskrats have devastated the tops of the volunteer cattails which established themselves in the Willowbrook marsh during the summer. The muskrats appeared about a month ago. Almost all leaves were cut at water surface level.

Leaves cut by muskrat.

14DE89. Willowbrook. Tracks show that a muskrat emerged from an island bank den in the marsh pond, and foraged briefly on land. It broke through the top of its burrow to do so, and resealed the breach with mud, which has frozen.

19DE89. Willowbrook. The muskrat has additional breakout spots on the island, separated by 15-20 feet.

3JA90. Willowbrook. Tracks in snow show that a muskrat went up and down Glen Crest Creek on the ice, following the same route each direction. Dragged its tail in one direction, but not the other. Diagonal walk, both, throughout. Direct register when not dragging its tail.

Muskrat scats, dry type.

 

Muskrat scats, wet type.

5JA90. Willowbrook. On the night before last (a relatively warm, rainy night), a muskrat burst out of the pond bank, walked along edge of the pond, then headed toward the stream. Later, it came back. Tail dragged more in the gallop gait, not so much in diagonal walk of return. It followed same route back. From that emergence spot (on main bank near island), there were other out and back paths up onto land. Tracks did go into the stream and back.

22JA90. Willowbrook. A muskrat was up on the shore of the pond at mid-day (last week’s thaw made all pond edges ice-free). It ran into the water at my approach. I could see it through the ice, swimming rapidly with skulling kicks of its hind feet (both feet kicked simultaneously, ~2-3 feet and 1 second between kicks).

Muskrat venturing onto land, Fullersburg Woods.

28MR97. 11:30pm. Muskrat at Thornewilde/Edgebrook subdivision entrance (Butterfield Road, Warrenville, IL), on road, 100 yards from nearest stream.

(I see I have been negligent in copying notes from my later observations at Willowbrook, Fullersburg and Mayslake. For instance, in more recent years I have observed muskrats diving for clams on several occasions in Salt Creek at Fullersburg, and learned to recognize the piles of empty clam shells they leave on the shores of ponds and rivers. I have seen how they manage entrances to bank dens, excavating them deeper as water levels drop. They seem to prefer mound nests, building them in the parking lot marsh at Mayslake when there was ample cattail building material but using bank nests in years when this was not the case. One winter at Willowbrook, tracks revealed how one came onto land in winter, was trapped in a culvert for a while when a coyote chased it there, and eventually made its way back to its den. I also have found where coyotes have killed muskrats. For at least 2-3 years I had a frustrating battle with muskrats at Willowbrook, building exclosures to keep them out of patches of wild rice I was trying to protect. They were persistent, revealing the ability both to tunnel beneath the fence and to climb over a vertical 3-foot barrier of chicken wire.).

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2 Comments

  1. jomegat said,

    January 6, 2012 at 5:26 pm

    Last winter I saw a pair of muskrats swimming under the ice. I followed them for a good 30 yards. I have also seen tremendous piles of mussel shells on the shore there, but for some reason, never connected the two (I assumed it was the work of raccoons). I will look for tracks next time (though my dog often frustrates such attempts).

    I have looked for their entrance tunnels in the vicinity, but either they don’t have them, or I lack the necessary skill to locate them. I suspect it’s the latter.

    • natureinquiries said,

      January 9, 2012 at 7:06 am

      Hi, JT,
      Around here muskrat tunnels come close to the surface in soils that usually are sufficiently soft that animals or people may collapse them in places. Otherwise their presence may be revealed by the runway cut through vegetation or worn in the bottom by the rodent coming and going. When the approach is in deeper water to a more supportive bank, the location is determined mainly by happening to see the animal entering or leaving the den.
      Regards,
      Carl


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