I learned something about gray squirrels recently, and my teacher was none other than a gray squirrel!
About a year or so ago, I watched a gray squirrel (Sciurus carolinensis) cross the frozen Mill Pond by scurrying across the ice. This was a narrow bay of the pond, near its western beginning point at the gatehouse near the dam. Nevertheless, it was a wide stretch for a squirrel to be out in the open, perhaps a hundred feet from the mixed forest on the south bank to the pine grove on the north bank. Sure, gray squirrels in the suburbs will cross similar treeless distances from house to house or across a road, but it was surprising to see a squirrel in a nearly natural environment daring to venture so far out into the open.
A gray squirrel (Sciurus carolinensis) scampers across the frozen western bay of the Mill Pond. Click the picture to see a video.
It was also surprising to see that the squirrel's territory in winter encompassed both shores of the pond. What would happen when the ice melted? The squirrel would be stranded on whichever side of the pond he happened to be, and there he would stay until the pond froze over the next winter. For a creature that only lives a couple of years, that could easily be a life sentence. (I assumed that their home ranges were not large enough that they could travel all the way around the western end of the pond via the road that passes between the gatehouse and the spillway into the pond. This would be a distance of nearly 400 feet from where I saw the squirrel crossing.)
The very next day, I happened to see a squirrel that I recognized on the north side of the pond. This squirrel had a distinctive stumpy tail (but that's another story). I had seen him once before on the south side of the pond, and now there he was on the north side. Clearly, many squirrels cross the pond in winter.
Video of a gray squirrel (Sciurus carolinensis) with a stump tail making his way along the north shore of the Mill Pond. Click the picture to see a video.
Just a couple of months ago, in October of 2008, I got an education in squirrel behavior.
I was sitting on my favorite rock beside the Mill Pond when a strange sight caught my eye. A squirrel was crawling along the high-tension electric wires some eighty feet above the pond.
It was Stumpy!
A gray squirrel (Sciurus carolinensis) with a stumpy tail crosses the Mill Pond via high-tension wire.
He was using the wires to cross from the south shore to the north shore of the unfrozen pond. He was having a hard time keeping his balance, since he didn't have a useful tail, but he was able to crawl slowly along the wire. I supposed a squirrel with a normal tail would simply bound along the wire and cross the pond in no time.
Now, there's nothing remarkable about squirrels using utility wires as pathways. Suburban gray squirrels do it all the time. But that's different. The electric and phone wires in the suburbs pass right among the branches of the trees. A squirrel can easily jump from a tree to a wire or a utility pole. From the viewpoint of a squirrel, utility poles and wires are just another kind of trees and branches, a highway from here to there.
But this squirrel on the high-tension wire was no suburban "tree rat." This was a truly wild animal, living very much as his ancestors had for millions of years. And this wire he was climbing on was not just a long, thin branch among many intertwining branches, but a separate thing, utterly devoid of covering foliage, which could be reached only by crossing many feet of treeless right-of-way and climbing a bare wooden tower, half again as tall as any tree in the area. These towers are set back rather far from the edges of the pond, so that the circuit from one shore to the other, a straight-line distance of about 100 feet, would require about 80 feet of walking on the ground up the hill, climbing up a 50-foot tower, crossing nearly 300 horizontal feet of wire, nearly 80 feet above the pond, then climbing down a 60-foot tower on the north side of the pond, and coming down the hill on the other side along more than 100 feet of open ground.
This was quite the eye-opener for me.
- A squirrel does not expand its home range in winter. Its home range can encompass both sides of the pond all year long. The winter ice simply provides a convenient short-cut across the pond.
- A squirrel's home range is much larger than I would have guessed. If these squirrels are willing to take a 600-foot circuit above the pond, there's no reason to doubt that they would just as readily take an 800-foot circuit around the end of the pond if they wanted to.
- Some intrepid and inventive squirrel must have been the first to discover that these towers and wires could be used to get across the pond. How did this happen? Did a squirrel actually think about this? Could the squirrel imagine the entire route and see the connection between the two sides of the pond? That's astonishing!
- If these squirrels have home ranges that are so much larger than I had thought, then perhaps they are not so isolated from man-made environments as I had thought. It's not so very far from the south shore of the Mill Pond to the city's public works garage and parking lot. Maybe these squirrels are as familiar with snow plows and garbage trucks as the ones that live in my back yard. I just didn't think that they would travel so far, but now I've seen that they do indeed travel distances of many hundreds of feet.
Stumpy, you've taught me something.