Sunday, January 27, 2013

A frozen pond, and one mystery solved

With our recent cold snap, the beaver's pond is frozen over.
The frozen beaver pond.

The top of the food cache visible above the ice.

The mystery wood pile.

I think I have solved the question: "What is that pile of wood near the bank of the stream?" It appears to be a cover of the ventilation hole of the beaver's bank den.

Beavers don't always build a lodge in the middle of their pond. 

A bank den.
They also build bank  dens, or underground homes they enter from under the water. These dens are caves under the ground next to the stream. The nest chamber has to be above water level so it cannot get air from its entrance.  To supply fresh air, they have a ventilation hole; sometimes hidden in tree roots, sometimes not. The illustration to the right shows the layout. If there is not enough soil to support a chamber, or if the soil collapses,  beavers sometimes make a lodge over the top of the chamber. I believe that is what we have at Cromwell Valley Park.

With our recent cold snap, the beaver's pond is frozen over. I looked at the slides, or trails where the beaver comes and goes from the stream to the land. I saw no tracks. The beaver must be staying under the ice, just has he planned to do. He's built himself a pond to hide in, put up a nice food supply and built himself a nice den. Aside from the fact that he cannot watch the Australian Open tennis tournament, I'm just a tad jealous. 

Can you spot the camera?
I placed the camera today, overlooking the dam. And the dam is definitely larger than it was last week.

More next week. 

Wednesday, January 23, 2013

Some observations, and a little success

My son and I went out last Monday, to get the pictures off the camera. The camera had been looking at the dam all week. When we got home, we discovered, much to our chagrin, that there were problems with the formatting of the memory card. Drats, and double drats.

We did notice a couple interesting things, however. The dam is higher than it was, and bigger. We compared the picture we took that day with an earlier one. The difference is subtle, but the dam is thicker and stronger. It also seems to be three or four inches higher. You'll notice the water flooding the meadow on the left of the picture.

We also noticed that the pile of sticks we thought might be a food pile is something different, entirely. But what is it? That we do not know. Look at this picture, though, and you'll see that the beaver is somehow packing it with leaves and mud. Is it some sort of den? If so, there is no visible entrance, and it seems awfully small for a beaver lodge. Any guesses?

I would love to put the camera somewhere that it can see this feature. I cannot find a secure place to do that.

As we looked around, we saw several places where the beaver appears to leave the water and head inland. One had a stump overlooking it. That is where we chose to set up this week. The camera is very low, and overlooking the trail from Minebank Run, on the west side.

So, here is our little success. We did capture an animal in the camera. A beautiful red fox.

They are beautiful animals, aren't they. And if you note the information strip on the bottom of the picture, it got pretty cold last night, didn't it?

On that note, I will stop with one more picture. I took it this afternoon. You'll see that the beaver pond, if I can call it that, is partially iced over. Our friend has a nice supply of food under the ice, and a nice den, and is snug and happy withal.

More later.


Monday, January 14, 2013

More observations

This week my son and I went out on Sunday afternoon and Monday afternoon to see what was to be seen. We made some interesting observations.

Is this a food cache? or something else?
First observation. Is it a food cache, or something else? Last week and again this week we noticed a pile of small branches on the east side of Minebank Run, between the dam and underwater food cache, near a slide where the beaver enters and exits the pond. Is it a pile of food left by the beaver? It doesn't look to me like a random thing. You might also notice dark, wet leaves on the side of the pile closest to the stream.
We put the critter cam in a place where we might observe the beaver eating, or tinkering with this pile. No luck. The plot cam setting revealed no activity. This, while frustrating, is probably pretty good evidence that the beaver is very nocturnal. The plot cam takes a picture every 30 seconds from about 20 minutes before sunrise for the next two hours. It does the same in the evening, ending about 20 minutes after sunset. the fact that the beaver did not appear in any plot cam pictures suggests that it is hiding away from people as the sun rises. There are a lot of people to hide from in Cromwell Valley Park. I understand that beavers are more or less strictly nocturnal in response to the number of people in the area.

Several eaten sticks are visible in this picture. 
Second observation. The dam has been built up since our last visit. Not a lot, but some. What struck us is that several of the new sticks on the dam have had the bark eaten off by the beaver. The bark on the bottom layers of the dam appear to be uneaten. I can only guess, but presumably building the dam is a priority for the beaver, so it limits eating until the dam is reasonably secure? Then it can strengthen the dam at leisure? This sounds reasonable to me anyway. I certainly welcome your suggestions.

Is this the start of a new dam?
Third observation. About 120 feet downstream of the dam my son noticed these pieces of wood lying across the stream. You'll note that some have been cut down by the beaver. Is this just chance, or the beginning of another dam? We'll keep an eye peeled and let you know what develops.

Fourth observation.  Some more trees are down, and farther away from the dam. We observed some trees cut down by the beaver as far as 600 feet from the dam. Like last week, the trees cut on the west bank were considerably larger than those on the east bank. The trees serve two purposes, food and dam material. The food comes from the cambium, the layer of growing, nutrient rich material under the bark. The wood itself is not eaten.  

Tree cambium is the layer under the bark that grows new bark and wood. It is rich in nutrients and is the part of a tree that beavers eat. It is primarily winter food for the beavers. they store a cache of twigs and branches under water. Beavers also eat various grasses when they are available. 

And, have you noticed that we have no pictures of the beaver from the trail camera? That is one elusive critter, isn't it? (And no Rebecca, there are no pictures of Sasquatch this week.)

This week the camera is set up overlooking the dam. It's set to take pictures in trail camera mode, around sunrise and sunset, as well as to respond to its motion sensor. More next week.....

Sunday, January 6, 2013

A small disappointment

So, after a week I went back to check on the camera.

The tree is gone!
I was excited to note that the tree I hoped to capture images of the beaver eating was cut down, and taken away. I made a quick check of the camera and it had several files on it. Oh boy, I'm gonna see video of the beaver cutting down the tree and carrying it away!

The tree is in this photo
Not so fast, buddy. You've got things to learn.  It turns out that I did have several videos of the area. These included some deer browsing and a woman walking her dog. From them I learned that the beaver cut down and removed the tree between 9:41 pm on the 3rd and 5:07 pm on the 5th. (BTW--do you have an alibi for those dates? Better get one, 
or a good lawyer.)

The tree is completely goneI would be delighted to show you those videos right here and now, but for some reason, cannot upload them in blogger. But you can see one of them here.

But in between those images there were no others. No beaver chomping, carrying, dragging, just nothing. I don't really know how I failed, but I suspect one of two problems. Either the beaver is too small to trigger the motion detector on the camera, or the motion detector was set too high, looking above the target.

"Press on Regardless" as the Royal Air Force says.

So, I scouted around and made two observations. The first is the number of trees that the beaver has cut down. I counted 25 on the west side of Minebank Run and 64 on the east. Interestingly, those on the west side were much larger, some even five or six inches diameter. Those on the east side were primarily 1.5 inches or so in diameter.
new target tree

On the east side I did notice this tree, newly cut down by the beaver. I decided to press on. So I set up the camera looking at this tree. This week I have it set to take pictures at set intervals around dawn and dusk--called a plot cam. Let's hope we get some pictures of this creature.

The next post will discuss more those 90 or so trees the beaver has cut down. Is this animal destructive, or constructive?.....