Tuesday, July 13, 2010

A BUSY RED SQUIRREL

On July 5, I spent some time watching a Red Squirrel (Tamiasciurus hudsonicus) processing Sitka Spruce (Picea sitchensis) cones at Manning Provincial Park, British Columbia. These small squirrels (around 250 g) are frenetically active and noisy, and watching them is much like watching birds go about their activities.

Two things impressed me about this behavior, persistence and proficiency. The forest floor, in a big grove of spruces, was literally covered with cones. Obviously it was a great cone year, not always the case in any given stand of conifers, and the squirrels were taking advantage of it. This particular squirrel would take only a few seconds to locate a cone on the ground, grab it in its mouth, and carry it up to one of its favored perches on a big fallen spruce trunk.

Fortunately, this was at eye level for me, right out in the open and allowing for continued photography. I don’t know why, but he (it was an obvious male) kept coming back to the exact spot to open the cones. And he did it again and again and again. That was the persistence part. But there is every reason for them to be persistent. When food is abundant, go for it.

Proficiency was also obvious. Each cone was held only for a few minutes, while the squirrel bit off each cone scale and swallowed the seed beneath it. I couldn’t determine whether the seeds were chewed or merely swallowed, as the process was so rapid. Sitka spruce seeds are relatively small (3 mm) conifer seeds, so perhaps they could be swallowed without chewing. However, they also have a “wing” that facilitates their dispersal by wind, so that must presumably be discarded.

In any case, each cone was reduced to its central axis in just a few minutes of manipulating it, the scales falling like confetti in front of the squirrel. It was then dropped, and invariably the squirrel gave its territorial chattering call for a few seconds. then it would hop off the log and pick up another cone and start again.

This squirrel processed cone after cone as I watched. Although Tamiasciurus squirrels are well known to store many of the seeds they harvest to feed on them over the winter, I saw no indication of any caching behavior. Red Squirrels cache bushels of green spruce cones in a single protected spot throughout the summer, and these cones become important when the ground is made inaccessible by deep snow.

When cached by certain verterbrates, some seeds that are stored are lost or forgotten, and they have the potential to sprout into new plants. In some cases (gray squirrels with oaks, nutcrackers with pines), the animal may be as important in the dispersal and reproduction of the plant as the plant is in the diet of the animal. This is not the case with Red Squirrels, which, because they store cones before they open, function entirely as seed predators and not as seed dispersers.

Closer to the coast of the Pacific Northwest, including all of Puget Sound country, it is the Douglas Squirrel (T. douglasii) that typically feeds on Sitka Spruce seeds. It is just as persistent and proficient.

Dennis Paulson

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