Friday, September 13, 2013

July 2013: Beaver Observations Practical and Philosophical

I think we have the terminology all wrong: dams, ponds, lodges, canals, channels are all wrong. I was on a better track about 10 years ago when I put up one of my first web pages on beavers. I called the pond the bed and the dam the beavers’ pillow, or something like that.

You see my trouble is that the one beaver family still operating on my end of the island, that I’ve probably watched now for about 14 years did not build its way up a creek. It specialized in surviving at the top of small watersheds or cul-de-sacs, if you will, in larger water sheds. It created all those things I now say we mislabel, but always in a soft and subtle way. I have seen beavers build straight deep canals and channels, but these beavers fashioned (let’s axe that word “build”) ways to survive without drying out the valley.

When humans build dams, lakes, canals, channels and houses, they almost always wind up drying more land than they flood, and that’s not what beavers are after. This struck me on July 6 as I sat up on the rocks forming the north shore the East Trail Pond and I watched a beaver drag a cut maple branch from the southwest shore of the pond to the new lodge close to the north shore. Two still photos begin to the show what I am talking about.

In the first, the beaver is facing me.

In the second photo, showing the beaver seconds later, it is moving to my left.

Here’s a larger view of where it was swimming.

Should we bend the definition of a pond to include what that photo shows? A beaver pond is a depth of water behind a beaver dam made to afford beavers protection and ease their transportation of branches to their lodge by allowing them to take it in a straight line from any point along any shore of the pond to their lodge. I have seen many beaver ponds like that. But this is different. There are no straight lines.

There are no curves either. Most of the grand dams, beaver or human, have a bit of a curve in them. These beavers fashioned something else, a subtle saw tooth arrangement that looks to be designed to keep the  vegetation from overtaking the water.

And the so-called lodge which is supposed to be either a bank lodge on the shore or a true castle of a lodge safely surrounded by water is not to be found in this not-be-called-a-pond.

As far as I could see the beaver carried the branch into the “lodge” by swimming under the grassy patch just to the right of the “lodge.“ Here’s the video.

As you can see, I lost sight of the beaver which generally doesn’t happen  when a beaver is dragging a branch across a pond.

So where am I seeing these beavers? A maze? They are rodents after all. A labyrinth? Just call it a wetland and leave it at that?

Beavers want more than wet land as I soon saw that day. A beaver was up on its lawn.

Ten years ago the area of the pond the beavers live in now was the shallow upper end of a much larger pond. Here is a photo of the lower end of the pond taken on May 27, 2003.

Here is a photo of the upper end of the pond taken in April 12, 2003.

The beavers in the pond now are not offspring of the family that fashioned that huge pond. They left in 2005 without paying much attention to the upper end of the pond which was serviceable only in the spring when the beavers ate the green vegetation growing in those shallows in May. The family there now moved into the valley in 2010. Here’s how the center of the area they eventually fashioned looked on June 14, 2010, when I first heard these beavers gnawing there.

Needless to say through flooding and foraging things have changed. The “lawn” where the beaver was foraging in 2013 was made possible by the beavers cutting down most of the trees along the south shore. Of course, for humans lawns are a perfection of nature. The beavers are simply making the best of the changes resulting from their tree cutting. 

On this granite island, survival is enough of a challenge for beavers. They have no sense of perfection. To anyone who has not paid much attention to beavers that sounds obvious. It’s a hard lesson for those of us who have enjoyed watching beavers thriving in large ponds behind seemingly perfect dams. Here’s what the old East Trail Pond dam looked like in 2000 after beavers had been “perfecting” it for 15 years.

It's riddled with holes today through rotten logs after being neglected by beavers for several years.

The tenacity of the beavers now in the valley surprising me. I keep expecting that over a decade of trying to survive in narrow valleys and marginal pools that they will soon give up. But I am pretty sure there are two kits, at least, being nurtured in one of the lodges. I definitely heard them whining when I sat by the pond on July 22.

Over the years I’ve seldom heard the whines of this family’s kits but this year the lodge is right below where I sit. I also saw a beaver on the dam.

I got the impression that the beaver, probably a yearling, was tasked with feeding the kits. It cut a cattail from the swath of them below the dam and brought it back to the lodge.

A few minutes later a beaver swam out of the lodge and back to the dam. It also found a cattail to haul back to the lodge. And as it swam back, another beaver swam out of the lodge heading toward the dam.

The beavers swam right past each other. A month ago when I saw the two yearlings get near to each other there was usually a little byplay. Not today.

I’ve always known this family to be tightly disciplined, but that is a subject for another post.

The photos give the impression of the beavers swimming in open water and that is indeed the case for the half of their haul behind the dam. To get to the lodge they have to negotiate a channel through and under the grass. Then they surfaced in a small clearing beside the lodge.

The deliveries of the cattails seemed to quiet the whining and the beaver that had just gone to the dam seemed to be off duty. It fed itself on the greens growing on the dam and slowly moved toward the south shore.

Of course, I wanted the kits to swim out from the lodge, but instead a huge black turtle that I mistook for a snapping turtle climbed up on a patch of mud and grass close to the beaver lodge. Then it turned its head toward me and I saw that it was a Blanding’s turtle.

I finally heard something swim out of the lodge, but I think it was an adult beaver or a yearling, definitely not a kit, as it surfaced below the nearby north shore, climbed up the slope, bit a branch and brought it back down to the pond.

It swam in a channel that would take it right below the turtle, but when the beaver got close to the turtle it dived and when it swam by underwater the turtle didn’t’ seem to notice.

Shortly after that, I heard another dive into the water from inside the lodge. I could see the wake made by the underwater swimmer and saw it emerge by the north slope again. A large adult beaver shook the water off its coat of fur and climbed up the slope.

It nosed the huge maple trunk that I have seen beavers take many bites out of, but it was after a log and started gnawing on the trunk of a smaller tree the beavers cut a few weeks ago that had fallen behind the maple.

It took several minutes to cut a hefty but portable log and the beaver dragged that down to the water,

When the turtle saw that log heading its way, it dived into the water well before it got close.

As it began to get dark, I waited for the kits to appear, but they didn’t and I heard no more whining.

There was nothing atypical about the beaver behavior I saw on the 22nd, but I get a different vibe from these beavers that is hard to explain. In large beaver ponds, I’ve seen beavers in the same family get quite out of touch with each other. Humans with families often think of their home as a dimension of their loneliness, relaxing with people you love, especially if they are in the other room. Beavers spend half their life packed with their family in a dark lodge. When they leave the lodge, they can go off and be alone. There is one beaver family to a pond and any unfamiliar beaver entering the pond is a very rare event. The family now in the truncated East Trail Pond hardly separates when they go out into the pond. There are grasses to hide in, but once the wind dies down, I can hear the slightest splash from any part of the pond.

I don’t think this is an idle observation. I think there are two strategies beavers have followed which has allowed their survival. There is the expansive damming of watersheds, moving up and down valleys, and then out when food is not so easy to fine, and then there are beaver families who play a smaller game. In that strategy abandoning a valley is not an option. The family I’ve been watching specializes is living in portions of ponds abandon by other families or a small ponds of which my first impression was that no beaver could possibly survive there.

I probably won’t live long enough to see it, let alone prove it, but I think the persistent families who develop skills to survive low water and droughts assure that when environmental conditions get tough for beavers, some beavers will survive. To be sure, all beavers probably have that skill but some are better at it, like the well disciplined beavers I've been watching.

That brings me back to the engineering terms applied to beavers which I feel don't fit what I am saying. It strikes me that the beavers I am watching base their life on trenches that are shaped so that they do not drain an area but instead retain water in drought conditions. "Trenches to nowhere" is not the happiest phrase, so I'll keep pondering this.

Walking where the beavers on our land had a pond, I noticed a depressed circle of ground formed by large moss covered roots.

Actually before the beavers built their dam (these were the engineering sort of beaver,) the mossy logs formed a vernal pool. Then the beavers built a deep canal through the valley leaving the mossy circles high and dry.

The beavers who built that canal were up and out of a valley in 6 years that is as large as the area the beavers in the East Trail Pond have been living in for the last 14 years.

I'll have to wait until the truncated East Trail Pond dries out to be sure, but I think the beavers there, who are persistent dredgers, have taken advantage of these circles of roots to assure themselves of a depth of water.What word describes that unheroic but effective way of fashioning a world?

It is indeed fun to have such deep thoughts while sitting by a beaver pond, but I would have preferred seeing the kits.

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