Walking through the lowlands of southwest Washington, I have spotted plenty of signs of beavers at work. But I never came upon anything quite like this tree that I hiked by in late April.

From a distance, it seemed this hardwood was so precariously perched that a modest shove might knock it over. Then I got close, and gave it a push. It didn't budge. The trunk still had a strong inner core of wood that had yet to be chewed through by the beaver's teeth.

I wondered what was the beaver was up to. Why not just saw it all the way through, and be done with the job?

I called Greg Hood, a senior research scientist for the Skagit River System Cooperative.

Hood said the beavers take down these trees in pursuit of food that includes the live cambium tissue underneath the bark, and the leaves and upper branches. Beavers also may drag away limbs to help build their dams.

Hood says he once saw a cottonwood some three feet in diameter that had been gnawed on by a beaver, creating a notch big enough for the animal to actually sit in as he went about his job.

This can be dangerous work. If the beavers cut too far through the trunk, and the trees begin to fall, they may get squashed.

Sometimes, Hood says, the beavers may make a partial cut, then back off. Eventually, the winds will topple the tree and complete their task.

So maybe that was the plan with this tree. Here's a close-up of the beaver's bite-work.

I was impressed by the beaver's tree smarts, and wondered what I would find when I returned to visit the site several weeks later.

I found the tree splayed down on the ground, having fallen away from the river in the direction of the beaver's deep cut.

I wondered whether the beaver had chewed away some more during my absence, or had simply let the wind finish the job. I looked close at the splintered stump, but couldn't say for sure.