Thursday, January 31, 2013

Beavers Gnaw and Dig Their Way Up My Valley

On August 23, 2007, I was so enthralled by what I saw that I wrote a poem about it:

The cut winterberry, a dozen inch wide stumps
fingering out of the moss draped roots snaking over
the black bottom of the now dry bog, pointed
the way, fifty yards through ferns, under barbed wire,
over poplar stumps rotting dark grey. The duckweed
gave way to mud, mud to bright yellow brown water,
the blood of a living beaver pond circulating
through the canals the beavers ply to reach up
and strip the bark of cut elms down to yellow wood.

Half girdled maples blush in the shallow water,
the first trees in the valley to greet autumn.
Other trees are half fallen, others touching water,
their touch then cut into logs. The lodge still

a loose pile of sticks is ready for mud to seal
the family from winter. The mud and stick dam,
verdant now, is ready to back up November rains.

In backing up the water, the beavers stop time,
denying Mullet Creek its measure. Wielding mud
and incisors, they defeat the seasons. The frogs jump
into the pond heedless of whether this paradise
is the end or the beginning.

I discovered this beaver development just below 52 acres of woodland we own 4 miles south of the St. Lawrence River. In the summer my wife and I sleep at the land every night, and we visit almost daily throughout the year. Although they were not on our land, they were about 200 yards from our little summer house. I could go out along a wooded ridge every summer evening, find a clear vantage point on the cliff west of the pond,

brave the mosquitoes and then when I learned something about the beavers for that night, I could dash back to our little house, and every trip back and forth would make a safer pathway.

During the day as I walked through the boggy pools and thick vegetation of our land, I could look for beaver gnawing.

I saw some here and there but assumed it would be 3 or 4 years before the beavers did much foraging that far up the valley.

They were all over the pond I discovered and also foraging in the pond below. I wondered if they were living in the lower pond which was why I hadn't seen a beaver. I also needed a name for the pond. That came on September 6 when I sat high on the ridge west of the lodge as it got dark.

It looked like stripped sticks had been pushed up on the lodge, but I didn't see any muddy water in the relatively shallow pond that a beaver might raise as it swam around. Then I saw a bobcat strutting down the east shore of the pond cackling, so much for stalking its prey.

Then I heard a beaver slap its tail in the canal below the dam. I heard the bobcat go down the east shore and then start coming up the west shore. I headed home, didn't see a beaver but I had a name for the pond -- Wildcat Pond. In September we didn't spend many nights at our house at our land -- got dark too early and we slept at our electrified house on Wellesley Island, where by the way I was observing a beaver family with three kits that were often out in the daylight. But we stayed late several nights and I tried but failed to see a beaver in Wildcat Pond. The fall rains hadn't come yet, and the two ponds were drying down to their basic channels which at least showed me all the work the beavers did here to make the ponds viable. The canal down to the pond below Wildcat looked well used.
Then just when I was about to conclude that the beavers were staying in the pond below Wildcat Pond which had more water, I not only began seeing freshly stripped logs in Wildcat Pond, but saw a trail through the leaves that the beavers made up into our land
where they cut some small hornbeams and evidently hauled some down to Wildcat Pond.
What I learned about these beavers very much depended on how I approached Wildcat Pond. If I walked along the ridge to the west of the pond, I saw where the beavers had cut red oak and maples high above the pond and dragged branches down to Wildcat Pond where they were making a cache outside their lodge.
But if I walked down the valley through our land, I saw signs that the beavers, who lived 150 yards and two dry flats below, were rather interested in the small trees on our land. There were a series a pools in the middle of our part of the valley. Some were simply pools of water behind an old moss covered fallen tree so venerable that live trees were rooted in the old trunk. The beaver had cut one of those trees.
The pool farthest up on our land was about a foot deep at places and hemmed in by mossy logs. One day I was surprised to see that pool muddy with small sticks stripped by a beaver.
I called the largest of the pools on our land Boundary Pool because a string of barbed wire between our land and our neighbors dangled across the water. That pool was also muddy,
But it didn't cross my mind to wait by the pools on our land and try to see the beavers. I was sure just one restless beaver was straying so far. In November 2007, I started seeing beavers on a regular basis in Wildcat Pond, especially one kit, then about 6 months old.

Soon the ponds froze and the snow got deep that winter, especially in the valleys. A few times I saw beaver tracks in the snow going up to our land, but I spent most of my time checking out what the beavers were doing outside of holes in the ice of Wildcat Pond.
And in the spring, when beavers are at their hungriest, they seemed to carefully get all the bark close to their lodge that they missed getting earlier. Back in the summer of 2007, a big birch tree the beavers had been cutting finally blew down. In April 2008, one of the beavers climbed high up in the crown of the tree before taking quite a dive into the pond below.

But after the thaw I saw more small trees cut on our land and I saw that the lower shore of the large lower pool was being shaped by the beavers into a dam.
That seemed to be a logical progression, though I thought there were still plenty of trees to cut around Wildcat Pond and that Wildcat Pond dam could be built up to flood water back into the valley. For about 30 yards only a narrow canal connected our Boundary Pool with the neighbor's Wildcat Pond. Then I noticed that the beavers fashioned a dam about 40 yards behind Boundary Pool dam. I called it Log Pool dam because they used some old chainsaw cut pine logs in the dam.
And it looked like they had rearranged some brush forming a dam of sorts even farther up the valley. I decided it was a bit of spring exuberance, beaver instincts warmed by the sun. I lurk on a scholarly discussion list called H-Animal and that spring to provide some chatter for a London show on artists using animals, the curator opined that animals did not make art. At that time I was entranced by the beavers' behavior at Wildcat Pond. As each one came out of the lodge, they swam over and sniffed a small mud bar crisscrossed with cut logs stripped of their bark.
I thought the beavers might be leaving messages, inspiring other beavers... why not call it art? So I kept trying to get a video of the beavers making and receiving log messages, but once again the beavers seemed to be scarce in Wildcat Pond. I heard them and then saw them in the pond below which was getting deeper flooding back to Wildcat Pond dam.
But I was also seeing new activity up in Boundary Pool, a nibbled stick at the Last Pool, as I was beginning to call it. But I wasn't sure a beaver had been up the trail through the ferns between Boundary Pool and the log dam.
Then I got down to Boundary Pool and saw a beaver lodge!
A week later I got a video a beaver working on the lodge.

Let me fast forward with the memory of that muddy channel below Wildcat Pond dam fresh in mind. Here is how that trail through the shaded ferns between Boundary Pool and log dam looked 14 months later.
By that time, I discovered why the beavers were so eager to get to the end of the Last Pool. The winterberry and hornbeams were not the only attractions. There were 6 tall aspens there and by May 2009, the beavers were well on their way to cutting the first one down.
Although it took them a long time to get those aspens down, in retrospect, I think their obsession with those aspens drove the beavers up the valley. It didn't dawn on me at the time because their obsession with other trees more plentiful lower down the valley was more easily requited. Back in Wildcat Pond I noticed they had a taste for hemlock, which I had not noticed observing other beavers gnawing. They stripped all the bark off small hemlocks, without cutting them down, and gnawed the roots of larger hemlocks.
The east shore of Boundary Pool, which became Boundary Pond when the beavers built up the dam, had a dense stand of hemlocks of all sizes. The beavers girdled almost all of them and cut down a few.
That girdling makes a pretty picture, but in two years all the hemlocks were dead.

The beavers cut down the elms, ash trees, birches, red oaks, and maples they used for food. It took time to gnaw off all the limbs, eat many of the leaves and gnaw the bark off the trunks and branches they couldn't haul away. They seemed to have a brief obsession with cutting small white oaks high on the ridges on either side of the ponds, but there were not that many up there. And then there were the hornbeams, always a small tree and we had a few hundred of them in the valley, probably sprouting up 20 years or so ago when a previous own cut down some large pines in the valley for lumber.

Back in 2006, before there were any signs of beavers being there I took a photo in the early spring of what called a "valley bog." Birches always attract a camera, but around them and all in the background, the smaller, thinner, and plainer hornbeam were everywhere.
In the fall, I watched the beavers bring hornbeam after hornbeam down to the lodge in Boundary Pond, building up that lodge and caching food for the winter.

Let me hasten add that I didn't weep for the hornbeams. So many of them were in the way of seeing the beavers and I assumed they'd grow right back. I was more puzzled by the beavers' insistence on piling more and more on and around the lodge, and, of course, there was no shortage of logs on the dam.
That was a photo taken in July 2009. Here is how the dam looked a year later.
It took my about two years to figure out that this dam presented problems for the beavers, and another year for it to dawn on my how they solved it. When beavers moved into an area that has been forest bottom for a long time, they dig through more humus and roots than they do soil. These beavers dredged up what they could from the bottom. They had to deepen channels to the lodge and the pushed up what they dredged on the dam.
But it was much easier for water to seep through that material than it would have been to seep through packed mud soon to be baked by the sun. The beavers had to compress that humus and that's why they kept piling logs on top of the dam and not just below the dam as I usually see beavers do. They were less worried about the dam washing away than they were about it not being dense enough.

Since the beavers spent so much time, about two years, to create a rather spectacular dam that held back enough water to make the pond about 5 feet deep around the lodge,
I was lulled into thinking the the beavers would be loath to abandon such a set up, with which I had become quite comfortable. Here are kits bugging one of their parents in July 2008:

And two kits wrestling over food in 2010:

As far as I was concerned this could go on forever. But while the dam presented a challenge to the beavers, making a lodge in the valley, and finding other dens was easy. Throughout the valley bogs, as I called them, were mossy mounds created as the stumps of old trees rotted. I assume that years ago a fierce wind blew down several trees. The holes left by the upturned stumps became pools, and the stumps became mossy mounds. Here is a photo I took in April of 2008 of stripped sticks next to mossy mounds in Boundary Pool.
Before the beavers built up the dam and built a lodge, they fashioned what I call wallows below the dam. I've often seen other beavers do this, and the first time I saw it, I thought it was done by young beavers imitating their parents who were building a serious dam. Now I think they make wallows to slow down the flow of water which will make it easier to work on the dam behind the wallow and the channel below and at the same time provide a comfortable place to lurk if not hide. Anyway I took a photo of the wallows below the Boundary Pool dam in late May 2008 just before they built the lodge. You can make out a mound of moss behind the dam just getting topped with green vegetation. That's where the beavers starting piling on sticks to make their lodge.
Once it was covered with sticks, they could dig into the mossy mound for a chamber to sleep in. There were mounds like that throughout the valley. The photo below shows what the area that would become the Last Pool looked like in September 2006.
Not that I had the least suspicion that they'd build a lodge there soon. As the photo below shows, when they gnawed those aspens at the end of the Last Pool, they did not have the comfort of water lapping their finned back feet.
Meanwhile the beavers did what they do so well, as they built up the Boundary Pond dam, they dredged a channel at least 2 feet deep directly up toward the aspens. Here's the channel in September 2009. It is muddy from the beavers' constant dredging.
Earlier in the post, I alluded to tentative dams above Boundary Pond. As water from Boundary Pond dam backed up, the beavers broke through the small log dam. As for their tentative dam at what became the Last Pool. Instead of piling logs on top of thick roots to make a dam, they dug under the roots to connect the upper pool with all the water below.
Of course, I set myself the task of getting images of the beavers working in the channel and in the Last Pond. It was less than 50 yards from my summer home, but the beavers almost always swam under water in the channel, and if they had to surface they swam as fast as they could.
They were also shy in the pond. To see them, I had to sit so far away that it was difficult to see through all the small trees between them and me. During the winter of 2009-10, they proved to me how well they dredged the channel, and how much confidence they had in it, by swimming some 75 yards from their lodge behind Boundary Pond dam all the way up under the ice to a hole in the Last Pond ice where they came out and cut some hornbeams.
In the spring of 2010 I began seeing beavers in the Last Pool,
But it was still easier to commune with the beavers down in Boundary Pond.
That large pond hosted wood ducks, spring peepers, leopard frogs, painted and snapping turtles. And after three years of watching beavers in the valley often confined to narrow channels, it was a pleasure seeing them swim leisurely throughout what was now a large pond and where they hunched up and ate the duckweed, frog bit, pond weed, and even the jewel weed growing along the shore and on the dam.
My valley had been perfected by the beavers, and I trusted they understood its perfection. Yes, they were still dredging up the valley, the easier to bring aspen branches down I thought. The second aspen that they cut down fell into the Last Pool.
And at the same time they found large aspen to cut high up on the ridge east of Boundary Pond lodge. The beavers must have a sense of all directions, not just the one direction up and, I hoped never, out of my valley.
I accepted them even as their obsession with girdling hemlocks continued and they started girdling some large white oaks, beeches and sugar maples.
Back around the lodge in the early evenings I often saw the beavers and the two kits born that year.
One evening I saw the two kits have a shoving match.

And then something happened. I am not sure whether it was beaver logic or beaver emotion. Logically beavers move. They had lost interest in Wildcat Pond below, and I could see that pond was on the way to becoming a meadow.
They had begun cutting trees in the valley above the Last Pool, even on the path down to our summer house. Another big aspen fell into the Last Pool.
They started making a lodge in the Last Pool.
I refused to accept this logical progression. I didn't call it a lodge. I called it a "pile." Yet there were emotional reasons to leave the Boundary Pond lodge. One morning in late August, I saw one of the kits floating out in the pond beside the lodge. It was dead. In late September I began seeing the surviving kit in the Last Pool.
The beavers stopped dragging aspen branches down to Boundary Pond. They began amassing a cache for the winter in the Last Pool.
This story was about to end, though I was slow the sense it. During the winter the beavers came out of holes in the ice just outside their lodge and went off to cut trees and drag branches back to the hole.
But they never swam under the ice back down to Boundary Pond, which worried me because I knew that dam needed attention. Not that the beavers would repair the dam in the winter, but at least, I thought, they should be aware of what state it was in. Indeed, much of the runoff from the thaw went right through the dam and the Last Pool in early April looked rather bleak.
Boundary Pond had more water. Maybe they tried to move back there. On April 6, I found the other kit ripped apart along the shore of Boundary Pond.
It's true what they say about the cache of logs and branches the beavers amass in the fall. It can keep them fed during the winter. But the cache can be even more important in the spring to fatten the beavers up so they can find another pond in May. I saw it happen once in a pond that I thought still was viable for beavers, and it happened with the beavers in the Last Pool. I'm still waiting for beavers to move back and prove I'm right, that in their rush up the valley the beavers did not eat themselves out of food. But the memory of what the valley was, and its lushness was twice what the early spring photo below shows, gnawed on me. Many trees had been cut, most still standing in the pond where dead. Three years in standing water will do that to even the largest tree.
At least, I thought, I still had a pond to enjoy along with muskrats, ducks, frogs and turtles. But the pond did not fill up quickly, and while it was still low, something dug through the bottom of the dam to ease its way down to Wildcat Pond. I suspect a snapping turtle. I didn't think of repairing the dam myself. Let the leaking water attract another beaver, and debris must have clogged the hole because the pond didn't drain away that quickly. How inviting the Last Pool lodge might look to other beavers. It was still flanked with aspens still bearing some bark and the summer vegetation is now free to grow higher with those aspens trees cut down, and there were still plenty of trees along the shore. But I'm afraid beavers judge viability not by how things look at their best. The Last Pool did not serve them well enough in the winter. I have seen beavers move back into old lodges but Boundary Pond lodge wouldn't serve either. Yes, I wondered if a bobcat killed the kits. I had seen a bobcat stalking beavers in another part of our land, three valleys over. I found one beaver there dead. But I don't think that entered the beavers' calculations. Beaver parents often try to get away from their clinging kits. In the summer of 2010, the adult beavers fashioned a one-beaver stick hut on the shore.
Just when the lodge in the Last Pool was being built, I often saw one or both of the adult beavers simply sleeping on the east shore of the lower part of Boundary Pond, in the middle of the day, right along the path I saw the bobcat take back in 2007.
After another winter's freezing and thawing there were enough holes in the dam to spell the end of the pond during a dry summer. I was fascinated with what was revealed. The Last Pool was soggy under the dense growth of grasses, but there was no pool anymore.
The beavers had cut the channel down to Boundary Pond deep enough to hold a little water. While several of the tall trees flooded for two years in Boundary Pond died, most of the tall sugar maples and a white oak the beavers only half girdled along the Last Pool channel are still flourishing and still shading parts of the valley.
But the shade means there will be no beaver meadow here and I will have many stumps of small trees to contemplate for a while.
Since this area was only flooded for a few months, the stumps might sprout out with new shoots. On the whole, the beavers are leaving the Last Pool area more dry. Beavers generally create wetlands with their dams but in this case they drained a patch of wetland far above their dam with the deep channel they dug. Boundary Pond resolved itself into a lazy channel 3 to 10 feet wide.
From a distance Boundary Pond looked like a lush meadow.
The only small trees growing back quickly were the winterberry. There were no signs of life from the stumps of the many small trees the beavers cut and which had been flooded for at least two years.
But when the water still held back by the breached dam evaporated in mid-July, I saw that the bottom there looked quite a bit like it did before the beavers built the dam.
But just behind that, the lodge fashioned with logs piled on top of a lush mossy mound of a an old rotting stump was now a sprawling mass of logs. I took the photo below in 2011 when the pond held a little water. That water reminds me that the beavers had to negotiate that wooden bottom of the pond.
Maybe that's why they abandoned that lodge. So while I regret the beavers leaving, they left me much to think about. The story of this valley is not over. I'll try to patch the hole in the dam, but my experience is that beavers do that much better than I can.

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