The appearance of the mounds signals the beginning of winter for me because I often see them during my first skate around the beaver ponds usually in December. In 2003 as I skated around two large ponds I took photos of 11 mounds. I blush to say I have never made a study of these mounds either from the aesthetic or scientific angle. I like the texture of the one below.
This next one seems strategically placed since it must be the nexus of many channels through the grasses
In the deeper part of the ponds, the muskrats often incorporate old stumps or shrubs into their mound
Perhaps I’d get a better sense of how the muskrats use the mounds by analyzing how they are grouped together. There are three along the shore in the photo below.
But I find it hard to be scientific on skates, and then mounting snow, which will also force me to leave the skates at home, defeats any attempt to figure out how the muskrats use their mounds. However, at the end of the winter of 2010-2011, that pond lost most of its water and on March 23 I saw how one mound along the shore related to the pond and got some idea of how the muskrat used it.
Pressed down by snow, and dug into by minks and coyotes, muskrat mounds don't look too famous in March. You might say minks wire them with their trails.
Judging from the tracks coming in and out of that muskrat mound, a mink made a home of it.
I can’t easily see what the muskrats are doing under the ice. Before snow covers the ponds I can try to track them by the bubbles they leave under the ice. There are clear bubbles, white bubbles, lines of bubbles, bubbles of bubbles
Go figure indeed. The muskrats also continue to live in beaver lodges and burrows into the banks of the pond. I skated over one muskrat swimming under the ice. It scooted back into a burrow.
In December there are usually enough warm days and nights to open large patches of pond water and the muskrats sit on the ice and dive down and bring up greens to eat. Then the cold freezes the pond again and I can walk around and see the grassy leftovers.
But I know I should know a lot more about what the muskrats are doing. The sight of all the mounds in December always reminds me of how I have neglected keeping track of the muskrats in the pond. Muskrats and their works are easy to neglect in the fall. The beavers in the same pond are doing some magnificent lumbering, completely stripping bark off the trunks of trees they cut down
And otters in the fall can be rather diverting.
I generally don’t pay close attention to muskrats in the fall. So much to say, that I have never seen muskrats build a mound, but I think I would have noticed if it took them a long time, more than a day.
But the cold winters here which last at least three months have a way of framing animal life and death in stark relief. In the first week of March 2006, I was hiking on snow covered White Swamp tracking otters. I had some dumb luck. A half mile from where I was walking, I saw a family of otters leaping in the air outside a snow covered mound.
The otters disappeared, and I don’t think I scared them. Of course I walked up to check the mound and saw their slides, and prints and scats
And I saw a dead muskrat.
Since minks use the same holes, and coyotes dig into the mounds, I can’t be sure the otters killed the muskrat. The wound on the muskrat, who was no bigger than my glove, was quite small and otters have big teeth.
But this is a grim topic. I check every mound I see that's been dug into and usually see no signs of a muskrat being killed. Of course, when a mink kills a muskrat it usually drags it back to its den.
Mink tracks generally give the impression of an animal dancing through the snow
but sometimes the tracks look quite labored
and there is a line, almost a trough on one side of the trail. That's made by the dead muskrat the mink is dragging. On the January day I took that photo, I followed the trail to a hole into the mink's den and there was a drop of blood outside the hole.
Coyotes are not very subtle when they dig into a mound and its hard to imagine a live muskrat being caught.
Minks seem to be a bigger threat to muskrats. They can make a surgical hole into a mound.
There are advantages to stalking something bigger than you.
But “surgical hole” is not the right phrase. The mink, even in midwinter, is too happy go lucky to ever be compared to a surgeon. In February 2006 I gave an aspiring nature photographer a tour of the ponds during a thaw. I hoped to show him otter slides at least and a beaver in the sun. Then a mink and a muskrat diverted us. The mink led us to the muskrat who was curled up on a small beaver dam grooming itself in the warm sun.
The mink looked to have all the advantages: the element of surprise, the high ground, and it had been active outside much of the winter while the muskrat eked out a living in small dark mounds. It looked bad for the muskrat.
But water is elastic and muskrats are complete masters of water.
The mink was going down, the muskrat forward. To make a long story short, the muskrat escaped under the ice. But muskrats are tough. It surfaced in the open water and the mink, that had gotten back up on the dam, attacked again and the muskrat got away again. The mink didn’t leave this time but sat up on the ice, but the muskrat didn’t surface. The mink scampered around the nearby beaver lodge, likely the muskrat’s den, then gave up and went on its merry way. Then I thought the muskrat was coming back, but instead a beaver surfaced behind the dam and found something to nibble.
Then the muskrat surfaced and made a quick dive, seemingly more afraid of the beaver than the mink. (Beavers seem to welcome muskrats in their lodges but out in the pond seem to prefer that the much smaller muskrats keep out of their way.)
During that February thaw I got the impression that muskrats might come out from inside their mounds and walk around on the snow. I saw muskrat tracks going from the open water in a pond to a mound.
I was not sure what the muskrat did outside the mound. Make some repairs?
But let me hasten to add, I've never seen them make repairs. Once I was tracking otters in a large swamp and I saw where coyotes had completely destroyed a muskrat mound. Then not far away I saw a large muskrat out in the snow, not in a panic, but seemingly getting a bite to eat.
Usually the muskrat tracks I see in the winter go back and forth, which suggests foraging. But once I found tracks going from a large pond, up a road about a quarter mile and into a small pond.
Muskrats can survive the winter in a shallow ditch and while they can live in deep bodies of water, like the St. Lawrence River where I often see them diving off ice sheets looking for greens or clams or small invertebrates to eat, they thrive in marshes.
Scientific studies muskrats in that ideal marsh environment suggest that a strong family structure helps muskrats survive. Minks usually kill the muskrats that are fending for themselves. I suspect that familial vigilance protects the muskrats when they winter under the ice. Minks might be at a disadvantage when there is plenty of water under the ice, but often water drains away so minks can run under the ice. A mink is more agile on land than a muskrat.
But muskrats are high strung animals and from what I've seen winter doesn't slow them down.
The day before, January 3, I had checked on that lodge and saw three beavers up on the ice nibbling sticks. On the 4th, after the muskrats dived back into the lodge, a beaver surfaced and had a meal.
Still by the end of winter the muskrats I see on the edges of the retreating ice seem to have their mind on solely on eating. Even honking geese defending nests sites don't disturb them.
As for the muskrats mounds, few survive the winter.
The big ones ribbed with live saplings and built around a old beaver lodge have a better chance
Some mounds that coyotes dug into seem to be cradled to rest by clumps of neighboring grass
As for the muskrats, they go where the grass is greener, first diving into the holes in the ice at the deep center of the pond
then they muddy the shallows as the ice retreats revealing green life
Looking at that photo one might think life becomes easy for muskrats again. But muskrats move in the spring which means claiming territory. In the warming sun, I forget about muskrat mounds and scan the rocks and logs along the shore for their pellet-like black poop.
They are not, as that photo might suggest, between a rock and a soft place. Muskrats have a very intense spring -- a subject for another post.