Tracking science: Biologist’s findings show forest diversity, health influenced by wolves

2009-10-25T09:00:00Z Tracking science: Biologist’s findings show forest diversity, health influenced by wolvesWritten and photographed by MICHAEL JAMISON of the Missoulian

POLEBRIDGE - A clinging mist quieted the morning meadow, the icy hem of its robes brushing silent against autumn's crackling knee-high grass.

In the darkest shadows, the cold crunch of snow remained, criss-crossed with wolf tracks, bear tracks, elk and deer tracks. Scat and bone and hair and hide. These were the morning news reports written in muddied prints, each with a thin film of ice.

Cristina Eisenberg scanned the headlines, then waded into the meadow to read the particulars.

"It's all here," the researcher said. "You just have to know the language."

To the west, ranging grasslands rose gently to an aspen knoll, the trees all tall white ghosts trembling in the dull gloom of fog. A low row of leafy 10-footers skirted the meadow, backed by a towering canopy now a week or more past fall's golden height.

There were small young trees, and tall old trees, but no middle-aged aspens and that, combined with the frozen tracks, told Eisenberg something very important about this place.

Until about 1920, wolves patrolled these meadows, which have long been an important wintering ground for elk. Then humans hunted the predators into extinction here, and for 60 years or more the elk grazed in peace. By the mid-1980s, however, wolves were recolonizing the landscape, straying south from Canada to reclaim this western fringe of Glacier National Park.

The 100-year-old aspens grew up with wolves. So did the 20-year-olds. There are no middle-agers, Eisenberg said, because without wolves to run the elk, all the young aspen sprouts were browsed to death.

"It is," she said, "clear and profound. The wolves leave an indelible mark on the entire ecosystem."

Eisenberg's work shows that before wolves were killed out, about one in every six aspen trees grew to reach the canopy. When wolves were absent, perhaps one in 300 made it.

Aspen ecosystems are considered some of the finest and richest songbird habitat on the continent, second only to river-bottom riparian zones. Remove the wolf, and you remove the songbirds. Remove the songbirds, and the bugs move in. Everything changes, top to bottom, right down to the dirt.

Eisenberg calls it a "trophic cascade," and it forms the core of her scientific research. Her insights could very well change the way biologists manage predators, and likewise could change the way society counts an endangered species as "recovered."

In Glacier Park, Eisenberg is making a strong case for cascades, proving that the presence, or absence, of wolves sends dramatic ripples throughout the food web.

This is a special place, still home to most of the predator and prey relationships that existed back when 250,000 or more wolves ranged across the Lower 48.

"This," she said, "is how it was."

She's working in the North Fork Flathead River drainage.

She's also working near St. Mary's, where there are no resident wolves; and she's working up in Waterton Lakes National Park, too, where there are some, but not many.

Each study site is about the same size, and each has a similarly large elk population, native to an aspen-based winter range, and each has the same general density of cougars and bears.

Tree-core samples from each study area make clear the impact of canis lupus on aspen - without wolves, elk will stand around eating until they've browsed young aspens to the ground.

"Being hammered over and over by an elk really stresses a tree," she said. "Pruning is healthy, but this is like pruning your roses way back every week or two. The trees become shrubs, essentially, little bonsai aspens."

Some had thought drought or disease or insect infestation was killing young aspens, but fences to keep out the elk helped show heavy browsing was a primary culprit.

Likewise, birders have offered many reasons for avian species' decline, but Eisenberg's songbird counts have shown that while there are only a half-dozen species in the old aspen groves where wolves are absent, the younger stands driven by the keystone predator are home to four or five times as many.

Remove the wolves, she said, and you lose the birds.

Remove the wolves, she said, and the coyotes fill the niche. The coyotes eat the ground squirrels, and so the meadows don't get "plowed," and soil productivity declines.

Remove the wolves, she said, and the deer eat the river-bottom willows, and the bull trout lose both their shade and their food, as insects no longer fall from overhanging brush.

Remove the wolves, she said, "and everything changes."

That matters because the places with greatest biodiversity are the places most resilient, most able to adapt to, say, changing climate. That also matters because birds eat bugs and beetles, which are killing entire Western forests. And it matters, she said, because courts have been consistently confounded as to how to determine an endangered species "recovered."

Wolf populations aren't recovered with 12 breeding pairs, or 15, or 20, Eisenberg said. They're recovered when there are enough wolves and other top-end predators to maximize biodiversity.

That's what the 8-year-old alpha female is doing here, the leader of the Dutch Pack, ranging through her prime. She's making the meadow more lively, not less.

She's part of what Eisenberg calls "the ecology of fear."

The North Fork, Eisenberg said, is "full of wolves," and has been for 20 years now. It's also full of elk - as many as 14 elk per square kilometer in this meadow, where the wolf den site is located. Elk scat litters the ground not 20 yards from the den.

Clearly, the wolves aren't eating all the elk. But aside from the tracks and the scat and the bones and the antlers, there are no elk to be seen.

"They've totally changed their behavior," Eisenberg said. "For 60 years we've become used to complacent elk. These elk aren't complacent. They're on high alert."

From a browse standpoint, that means elk eat a bit and move on, eat a bit and move on, never standing in one place long enough to eat a tree down to its roots. And from a human standpoint, it means hunters see far fewer elk even as state wildlife officials insist Montana has more deer and elk than it's had for years.

Eisenberg has made a study of how elk act in the presence and absence of wolves - at St. Mary, where elk graze unmolested, they spend only 5 or 6 percent of their time head up, on alert, "vigilant." But in the North Fork, they spend nearly a third of their time on high alert, "watchful and always skittish."

"Wolves certainly eat elk," she said, "but they don't eat them all. This meadow's pretty clear proof of that. But what wolves really do is make elk hyper-vigilant. These are wily elk, now."

Hunters, of course, prefer elk that aren't quite so wily, but trophic cascades work both ways in wildlife management. Remove the wolves, and elk are easier to find. But then coyote populations explode, eating their way through the local game-bird population. Enhance one hunting opportunity, and you affect another.

When Eisenberg tracks the brushy thickets at St. Mary, where game generally hunkers down for thermal cover, she finds dozens of piles of elk poop. But in North Fork thickets, she finds perhaps two. The elk here live in the open, where they can see and smell, where nothing can sneak up.

"They are," she said, "very different animals in terms of behavior, and that's driven by fear."

For years, Eisenberg has picked these places apart, laying hundreds of kilometers of "transects" across the landscape. Dead-reckoning with a compass, she cuts straight lines through meadow, marsh and deadfall, each a kilometer long, across forest and grassland, noting everything she encounters in a two-meter-wide swath.

Then, she moves over 50 meters and does it again. And again - "tedious work."

She adds in historic and archival data dating back a century, stirs in radio-collar data from both predator and prey.

Her findings: Wolves increase biodiversity; wolves affect elk behavior more than elk populations; and aspen growth in elk winter range is directly related to wolves.

"It's pretty rock-solid," Eisenberg said. "The information coming out is unbelievably clear."

Her next project will take these methods out of protected parks and put them to work on multiple-use national forest lands. With help from the National Science Foundation, she'll explore wildlands in Washington state, where wolves are only now returning.

The predators are, perhaps, something like forest fire - highly controversial, once maligned as a controllable evil, later understood to be one of the keys to overall forest health.

As Eisenberg crunches through the autumn meadow, and the unseen sun labors to burn away the murky drear, it's not hard to know who's here. The wolves appear first on the telemetry equipment, a steady ping registering from the northeast, punctuating a steady stream of radio static.

And then an elk bugles, and as fog swirls eddies around Eisenberg's boots a single howl, a low and steady note, swells to fill the basin. Another joins, pitched higher, then more, many more, wolfsong vaporous as the morning air, wraithlike, overlain by the yips of young pups.

Even the crows are silenced.

After a long minute it stops, suddenly as it started, and the world is, for a moment, absolutely quiet, and close, and full of ancient energy, right down to your fingertips.

"Let's get to work," Eisenberg whispers.

The hunt, it seems, is on once again.

Reporter Michael Jamison can be reached at (406) 862-0324 or

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