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April 2001

Identifying Wildlife Holes

There's a fascinating world of fur and claws underfoot. Here's how to tell who's down there.

My wife and I labored up the brutally steep trail to Hidden Lake as a young couple hightailed it downhill, breathing every bit as hard as we were.

“If you’re going to the top,” the young fellow gasped and pointed toward the mountain, “you’d better be careful. They’re everywhere!”

Everywhere? They? I scanned the ridgeline for thunderstorms, ever a

threat in Washington’s North Cascades National Park. Or perhaps “they” meant pollen-crazed killer bees in this time of sweet-smelling wildflowers.

Not even close.

“Wolverines!” the hiker announced with a shudder. “We must have seen a dozen up there. And their holes are all over the place!”

This boy had read one too many Jack London stories. How else to explain his misidentification of tunnel-loving, pacifistic yellow-bellied marmots for a passel of bloodthirsty cat-bears? And while I had to snicker at his poor grasp of mammalogy, I certainly understood his confusion over zoological aperture ecology, aka what-critter-you-reckon-made-that-hole?

After all, holes in the ground are among the most common animal signs a backpacker is likely to see, yet most hikers pass them by with little consideration. “People are overwhelmed by all the big stuff in a landscape,” says Pinau Merlin, an Arizona-based naturalist and author of A Field Guide to Desert Holes. “When they do notice an animal hole, they have no way of knowing what made it or why. Holes are a big mystery.”

They don’t have to be. Like animal tracking, identifying dens and burrows is a great way for backpackers to get to know the wild neighborhood. Besides, it’s good to know if that burrow next to the tent is an innocent mole hole or the abyss of a venomous spider.

Down The Hatch

Animals burrow beneath the earth for one reason: security. “Whether they seek a retreat from heat, cold, or predators,” explains Susan Morse, founder of the Vermont-based tracking organization Keeping Track, “animals want to worm their way into a tight place out of the elements-one that’s small enough to prevent a bigger animal from getting in.”

Burrows are often much smaller than you’d expect. A marmot den, for instance, will be just big enough for that marmot, so a larger coyote can’t run in after him. A 1,000-pound grizzly bear might excavate tons of dirt when it digs its winter den, but the entrance to the den will be just large enough to accommodate the bear. That’s why the classic cartoon image of a big bear snoring away the winter in a huge cave “is all Walt Disney,” Morse says.

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