Thursday, December 12, 2013

Beavers react to the first snow fall

Ice doesn’t keep beavers from getting to the food they stored for the winter. On December 3 I saw a trail of air bubbles under the ice between the burrow where at least some of the beavers were living and their pile of branches in the pond.

Not that beavers accept the inevitability of iced over ponds. I could see bubbles under that patch of clear ice because the beavers had tried to keep the water open since it started getting cold enough to freeze the ponds in mid-November. On the 26th I saw three of them, adult, yearling and kit, swimming in open water there, and munching twigs on the surrounding ice.

In October and November they did most of their foraging along the south shore near that bank lodge and cache pile. They had cut down some large maples and were well on their way to bringing down a red oak just a few yards from the pond.

We had had a light snow the day before, and a bit of sleet as I sat looking down on them from the ridge. I noticed drag marks in the snow below and behind me.

When it was too dark to watch the beavers, I followed that trail higher up the ridge,

and saw that a beaver had nipped a small sapling and dragged it down to the hole in the ice.

When I first saw the beavers on the 26th, two beavers were collecting sticks to sink in the pond.

Then they got a whiff of me and spent several minutes sniffing the air

before they decided it was OK to at least fish sticks up from underwater and have nibble as they sat on the ice.

Fair enough to say the beavers were busy but when I watch them up on the ice, their complete lack of panic despite the cold relaxes me, though when I start shivering, I hurry home.

I think it takes the first deep snowfall to concentrate the beaver's mind on the reality of the coming winter. We had 6 inches on November 27 and then the temperature stayed well below freezing until the 2nd. On the 3rd, I headed to the East Trail expecting that the beavers would have been out that morning.

I head north to get to the East Trail Pond so I come down to the south shore. The patch along the south shore where I saw the beavers swimming on the 26th was iced over, but since there was clear ice there, I knew that the patch was open as the snow fell. Judging from the tracks around it, the beavers had been active during the snowfall, but they didn't venture far, not even to the red oak they had been cutting which was a few yards from the pond.

I could also see that on the 26th they were careful to swim under the ice to fetch sticks from their cache because I was around. I saw plenty of tracks on the ice showing beavers going back and forth on the ice from the cache to the open water.

since the freeze they had not been out there again.

As wet snow melts, it weakens the pond ice making it easier for beavers to make holes in the ice and get back out to the trees around the pond. So ironically keeping the water in that patch open kept snow from accumulating on it thus making the ice harder to break after the storm. The ice also weakens where the inlet creek swelling with melt water flows into the pond. Water flows into the East Trail just behind the north end of the dam. I saw two patches of open water behind the dam and as I walked around the pond, I kept looking at them expecting a beaver to surface.

Walking around the pond, I was able to look down at the beavers’ lodge. Air bubbles were there too in a patch of ice not covered by snow. There were also tracks in the snow showing one beaver's walk around the lodge.

While I embrace the snow as a blank slate on which the animals will reveal to me their everyday wanderings, I know that the first snow can be as exciting to them as me. Not since last winter has that beaver had a chance to walk around its lodge, and for a good number of animals that was the first snowfall of their life.

Not far from the lodge, a large pine tree that the beavers had cut blew down along the north shore not far from their lodge.

Since there was snow on the downed trunk, it was probably blown down before or during the snow storm. Beaver tracks from the lodge went to and from the tree. A circle of brown ice suggests the beavers kept water open there as long as they could. I bet the beavers in the burrow along the south shore moved back to the lodge.

It seems the reaction of the beavers to the snow as it fell was to stay close to the pond. I read a different story at the holes in the ice behind the dam. There I saw the distinctive woody color of freshly nibbled sticks.

Some of the tracks from the hole slushed through the melting ice, but others led up the ridge northeast of the pond

past fresh work, which included several smaller trees cut down and branches and trunks segmented and dragged down to the hole behind the dam.

The beavers’ prints went higher up the ridge.

And two small tree were cut down on the plateau of the ridge, both the perfect size for dragging down the 50 yard slope to the pond.

I cut dead trees up on ridges on my own land and sometimes sled them down in the snow. I suppose beavers appreciate the slicker surface and they must, as I do, appreciate the snow for weighing down and covering over small bushes that can make it difficult to drag things in the woods. 

I got the impression that the beavers had shifted into another gear, going farther away to gather wood for the winter. Of course, the ease of tracking in the snow makes it easy to overestimate the extent of activity. But on the 26th a beaver went up the south ridge and cut a sapling and dragged it back. Coming to the pond, I could see that beavers had not been up there again. Today, I saw evidence of several trees cut and dragged away from a ridge just as far from the pond if not quite so high.

Since I've kept journals of doings around the beaver ponds for 20 years, I can extend this discussion of the reaction of beavers to a first snowfall. Sounds easy, almost a scientific paper in the making, but there are too many variables. In December 2010, our snows came an inch one day, an inch another day, and finally three more inches convinced me that the beavers who had just moved into the East Trail Pond would have taken advantage of the snow to break the ice on the pond and do some foraging. But they didn't. I do have photos to show what the East Trail Pond dam looked like then.

A lot more vegetation behind the dam then. Here's how it looks in 2013.

In 2010 the beavers did cut large trees around the pond, but perhaps there was enough foraging and dredging to do in the pond, under the ice, so the beavers didn't bolt out from the pond and up ridges for food.

In December 2011, we hardly had any snow so the beavers had to get ready for winter without being reminded and aided by several inches of snow. In December 2012, I was away taking care of my father-in-law.

But I've followed the fortunes of the beaver family now in the East Trail Pond for many years. In December 2007 they were facing their first winter in what I call Shangri-la Pond which is just about 30 yards up stream and, like the East Trail Pond, shaped by converging ridges. Indeed, a beaver foraging on the ridge northeast of the East Trail Pond walked along a precipice that looked down on the valley the beavers worked 6 years earlier.

Curious that it wasn't dragging a branch back to the pond. Perhaps it was one of the two beavers in the family that likely were there in Shangri-la in a rather eventful winter.

From up where the beaver walked, Leslie and I naturally looked down where the beavers lived in 2007.

Back then Shangri-la Pond wasn't much of the pond. In May the beavers had moved to it from a small pond about 200 yards to the west. They faced the winter of 2007-8 basically living in several channels snaking back from their dam.

The 6, maybe 7, beavers living there were quite busy in the fall both collecting food for the winter and dredging channels deeper so they could swim under the ice that might form within 6 weeks.

So on December 3, 2007, after our first sizable snowfall, we headed to Shangri-la Pond expecting to see beaver activity. On the 1st and 2nd the temperature didn't get over 15 degrees, but during the snow storm there was a period of sleet and rain, and the temperature got up to 30 before dropping back down to 22. So the beavers had a chance to break ice just at the time of night they were used to getting out. The pond was growing to the west and north and the beavers had made much more progress foraging and dredging to the west, so I was worried when I saw no broken ice there.

Then I saw an opening in the ice between the lodge and the cache pile.

There were even a few sticks floating there. And I could see tracks in the snow heading to the cache, but no more open ice over there. Nor had they gotten out at the dam. We walked around the pond, and I noticed that they hadn't come out since the snowfall to continue cutting the maple which seemed to be their current project in the northeast corner of the pond.

We found a hole in the ice at the end of their canal heading north, the farthest extent of their dredging. Outside the hole, over the hole, was a mini-cache of branches.

Just as this beaver family would do after the first snowfall in December 2013, they seemed eager to forage in a new direction and went farther in that direction than they ever had before cutting down new trees and dragging branches back to the hole.

One beaver veered slightly up the ridge across the valley from the ridge that would excite their interest in December 2013.

Thanks to the snow, I could see how they walked around one small ironwood as they cut it.

Meanwhile all the bigger trees they had been working had no trails in the snow to them.

It was easier to see in 2007 that beavers are prompted by the first snowfall, to forage farther from the pond and cut smaller trees and get as many branches as possible back to the pond for winter storage.

Back to that beaver in 2013, walking unencumbered where it could have easily looked down at what might have been its home from 2007 to 2009. Could a beaver remember those days six years ago?

I can recount the specific events of 2007 only because I kept a journal with photos. Other than a general idea of the beavers' foraging, the only image stamped in my memory is of the beaver who died there when a tree the beavers cut fell on it in late December.

The other beavers' reaction, from what I could see, was not akin to my stunned contemplation of the sad event. They kept cutting the branches and trunk of the tree that killed their mate or parent. But that doesn't mean they don't remember.

Yes, the line from Villon's poem, Mais ou sont les neiges d'antan - Where are the snows of yesteryear, crossed my mind. And raises the question: are the beavers reactions to the first snow instinctual or informed by memory... if beavers have a memory.

Anyone who spends a season observing the foraging patterns of beavers around a pond must get the impression that beavers are forgetful because not only are half cut trees never cut again but logs cut and ready for hauling are left untouched for years. 

I thought that was a significant observation when I first made it. Then we bought  some woodland property and I began cutting and hauling dead trees for firewood. I've been doing that for 15 years and I found myself stumbling upon logs I cut up and had ready to go that were still in woods where I left them 10 years before.

Memory in the woods operates a bit differently than it does in other realms, at least for beavers and me. But that's a subject for another post.

In the spring of 2009 the Shangri-la Pond dam was washed away twice during thunderstorms and the beavers moved back to one of their old ponds, what I call Meander Pond. During the winter of 2010 I got a demonstration of beaver memory.

The beavers cut down a large red oak but it got hung up in other trees.

Wind and gravity can often work cut trees down to the ground so I kept checking on it. Thanks to frequent snowfalls that winter, I saw that a beaver also kept checking on it. I could see tracks coming out of a hole in the frozen pond walking toward the hung up tree and then walking back to the hole. I saw that on January 20 and then again on February 12.

That it went so far to check might indicate how poor a beaver's eyesight is and surely the weak point of my suggesting that a beaver looked down from a ridge to see its old stamping grounds is that their eyes probably aren't good enough for that. But wind and gravity had brought that hanging oak lower. I found myself walking closer to it, too, because from a distance with snowfalls freshly covering the ground, I couldn't be sure until I got closer.

I have 20 years of notes and photographs to ponder for answers, but how is this for a tentative theory: The beaver's senses form memories or patterns of foraging become memories and that snowfalls, especially the first snow fall, jars such memories which inform the beavers' trails through the snow which always seem to be to the purpose at hand, survival,... save for that lap around the lodge.

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