Friday, December 21, 2012


Even as I parked my car at the trailhead, my eyes were alert for tracks in the slushy snow. Although the parking lot itself was almost snow-free, little plops of slush marked where a dog and their person had walked through the snow, compacting it underneath, and pushing snow out to the sides of their soles. The denser snow of their tracks melted more slowly, and left a curious pattern of raised tracks on the damp pavement. Such small actions can make the difference between solid or liquid water at this time of year.

After examining the tracks, I walked up the leaf-strewn and snow-lined path toward the North Country Trail. I had never been to this section, just north of Lake Owen, but it is beautiful! Soon I noticed curious tracks in the deeper snow on the side of the trail. A five-pointed crown of toes topped an oblong footpad. The impressions of the hind feet were almost as big as my hand. In one spot, I could see the faint trough from the otter’s belly slide.

Farther along, a skinnier trough, only an inch or so wide, crossed the trail between a fallen log and the base of a big white pine. Tiny voles and shrews make these channels in the snow, often burrowing beneath the snow when it is deep enough. This time, their furry little backs may be have been exposed to the watchful eyes of a raptor. But luckily for the little mammal, there were no signs of blood.

At the base of another tree, a dead maple, lay the scattered chips from a frenzied woodworker. Smaller holes, just over an inch in diameter, accented a long vertical groove where the pileated woodpecker chiseled into the center of the tree. While you may blame the bird for the damage, it was only feeding on the carpenter ants that have already colonized the tree. Since the ants eat interior wood that is already dead and retired from transporting water and nutrients, a tree can survive for a long time while being hollowed out by ants and their predators.

Around another corner, I found a tree with a completely different injury – a huge white pine was twisted and splintered across the path. Here was an entirely different tracking medium. Many insects inscribed their stories in the woody scroll.

Most striking at first were the 8mm diameter exit holes of adult sawyer beetles. On a warm July day, an odd-looking creature emerged from the perfectly round hole. Aptly nicknamed the longhorned beetle, a male’s antennae can be twice the length of his body. Those antennae contain chemical receptors finely tuned to finding recently dead or stressed trees. Although it may just smell like pine to us, the beetle smells dinner and the potential for romance.

After adult sawyer beetles mate and lay eggs on dead tree (live trees would defend themselves by covering beetles in sticky, turpentine resins), the larvae burrow into the tree to feed on the phloem and cambium layers. This inner bark of the tree is responsible for sugar transport (including maple sap!) and growth, and provides more nutrients than the hollow dead tubes of the xylem (sapwood) that carry mostly water. Shallow, wiggling furrows, ending in small, dark holes, marked the beetles’ feeding progress on this fractured white pine.

In early fall, the sawyer beetle larvae begin to excavate clear through to the center of the trunk with a scraping, sawing sound. Just like the woodpecker, they leave behind a trail of splintery frass that is not ingested. Next summer, they will exit through much larger holes, the ones I noticed first.

Nearby, on a dead balsam fir, smaller bark beetles had inscribed their life stories. Deeper horizontal burrows carved by the adults were punctuated by tiny round chambers like a string of pearls. The female would have laid an egg where there now was a round chamber. After hatching, the larvae burrowed up a bit, toward the surface, and excavated much shallower channels at right angles to their mother. When mature, they all backtracked out the entrance hole made by the father.

The light faded as I turned back toward the trailhead. Hurrying along to beat the sunset, I noticed that the trail itself was in a depression that closely resembled the belly track of the otter, the trough of the shrew, the woodpecker’s lunch counter, and the beetle’s burrows. How many feet had carved this trough, and what are their life stories?

In many small ways, we each leave our mark on the world.

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