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Wandering with eyes, ears, senses open

Posted: Friday, November 19, 2010

Someone once asked me if I go out on hikes and walks looking for something in particular. Many times, I just go wandering with my eyes and ears open, and maybe nothing special is observed, or maybe I get lucky. Sometimes, however, I do have a particular objective, and chance to observe something that is not related to my initial objective at all.

Courtesy Of Bob Armstrong
Courtesy Of Bob Armstrong

On a recent November stroll near the glacier, I was engaged in a survey of active beaver lodges. Beavers often build caches of branches near their lodges in fall. They pile up branches in a heap that often sticks up above the surface of the water and winter ice. This is the winter food supply; they can just cut off a chunk and carry it to the lodge for lunch. Beavers seldom come out on top of the ice; they are very vulnerable to predators when they cannot dive into deep water. According to the books, adult beavers eat less of the winter cache than young beavers do. The young ones are still growing and need lots of food, but adults can live mostly on body fat that is stored mainly in the tail.

The presence of a cache is a good sign that a beaver family is in residence. However, some lakes with lots of beaver sign don't have a cache in front of the lodge. I see fresh cuttings and a dam in good repair, but no cache. So the beavers are there, for sure. Then I have to wonder if there's no cache because there are no young, growing beavers in that lodge; I would love to know!

As I was cruising around, I got a lucky break. As I plodded along, a great flurry of wings beat through the brush. Startled, I spun around, and there was a goshawk in immature, brown and white striped plumage just rising up into a young cottonwood.

Then I looked at the spot it had come from, and there was the limp body of a young snowshoe hare, still intact. The hawk must have just nabbed it. I quickly went on down the trail, so the hawk could eat in peace. Foot traffic on the trail was scant, so I hoped the predator would remain undisturbed.

About an hour later, I was homeward bound on the same trail, and again the goshawk flushed up into a tree. At the site where I originally saw it, there was only a scattering of fur. The hawk had moved its prey about fifteen feet through the brush. Now all that remained were the guts and hind legs. No doubt the hawk would have eaten more if it hadn't been disturbed a second time.

I looked around for the hare's head, and found only the lower jaws, separated and picked clean, and a small assemblage of tiny bone fragments. So I couldn't add the skull to my collection. But this made me think about the fact that heads provide good nutrition for predators, not only in the musculature but also in the fat around all the nerve cells in the brain and behind the eyes.

Just a couple of minutes later and down the trail a short distance, I saw the hawk flying rapidly off into some spruces. Below its line of flight was a raven in a tree, with a large gobbet of fresh red meat and bone in its bill. The raven had quite a time, organizing its scavenged goodies into a tractable package. Then it, too, flew away.

The deceased hare had acquired part of its winter coat of white fur, so it was a patchwork of brown and white. White fur against a background of dead, brown leaves is very conspicuous, which may have increased the risks for this young hare.

Molting into winter colors in hares (and weasels and ptarmigan) is not keyed to the presence of snow on the ground - although that is when it would be useful as camouflage. The fall molt into winter white is probably triggered by shortening day length, which does not always accord with the presence of snow. So there are times when hares are just the wrong color for safety.

• Mary F. Willson is a retired professor of ecology.



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