GNAWING CURIOSITY – What’s That Sound?

From some quiet bay the eerie wails of loons poured across the lake. My thoughts would drift that way until the sharp snap of a jack pine knot popping in the campfire pulled them back.

At 15, I was on my first unguided northern Minnesota wilderness canoe trip with five of my buddies. There we sat one night after dinner. We'd put our makeshift log benches close to the fire so we could dry our socks, waving them on sticks, steaming, over the flames.

Then, somewhere beyond the cozy wrap of radiant heat and conversation, I heard something that just didn't fit with the rest of the scene. It was a faint, rhythmic grinding or "munching" sound. I scanned my friends' mouths and hands to see if anyone was chewing, whittling, rubbing stones together or anything that might explain the mysterious sound.

No, it was coming from the other side of the fire pit, somewhere behind my friends, close to the edge of the deep woods.

I stepped closer, with that simultaneous craning 
of neck and tilting of head that so often precede discovery.

Pushing aside my small concern about the ever-hungry and occasionally forward black bears often drawn to campsites, I got up and walked toward the pulsing noise. Sure enough, it got louder. I couldn't imagine what it could be if not some kind of abrasion. A beaver on the night shift? A deer rubbing felt from its antlers?

I followed the sound to a pine tree and shone my flashlight right on the spot it seemed to be coming from. There was something there. I stepped closer, with that simultaneous craning of neck and tilting of head that so often precede discovery.

PHOTO: Steven Katovich, US Forest Service

Aha! A BB-sized hole in the bark, and all around it a golden extrusion of hardening resin. I put my ear as close to the rough bark as I could without touching the sap. Sure enough, whatever the little critter was, it was the one responsible for that prodigious munching.

When I called my friends over, they too were fascinated, but we agreed our curiosity wouldn't justify gouging and injuring the tree. So we had to wait a while to learn the identity of that little buzz saw.

When our trip was over, a camp naturalist explained that the pine engraver beetle (Ips Pini) actually does gnaw its way through the wood, like a tiny beaver, just below the bark where the adult male excavates—"engraves"—a lattice of tunnels.

        

PHOTO: Dennis Profant'

I've heard pine engravers a couple of times since, and have taken great delight in amazing my paddling companions, who'd either not heard the sound before or never taken the time to investigate. (Or could it be that they had, indeed, been curious, but were just afraid of bears!)