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| The Wolf Settles In At Yellowstone |
| Reintroduced top predator is influencing everything from bears to beetles |
| Article by Hank Fischer |
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Springtime in Yellowstone National Park's Lamar Valley. Dawn was spreading over the melting landscape of brown and white, and I was hoping the low morning clouds would part so I might glimpse a family of wolves, the Druid Peak pack. The previous day the pack had killed a bull elk, and researchers thought the wolves might return to feed. |
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Large snowflakes were falling, and I could see only a few hundred yards to the ribbon of gray and black cottonwoods that defines the Lamar River. The treeline on the far side of the valley where the wolves had made their kill - more than half a mile away - was obscured by wispy clouds and snow. The squall passed quickly. Through a spotting scope, a crimson splotch in the snow with a ragged antler thrusting skyward came sharply into focus. |
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No wolves were near, but a pulse of excitement raced through me as I spotted a large grizzly lying belly down on the carcass, front and rear paws stretched out on each side as far as they would go. It looked like a giant bearskin rug spread-eagled over the elk. We all know that in the human world, possession is nine tenths of the law. In the grizzly's world, possession is the law. Even from a distance, every aspect of the bear's posture and demeanor communicated one message: This is mine and you'd better stay away. Ravens, usually fearless, sat respectfully in the trees, biding their time. |
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This bear, which appeared to weigh around 400 pounds, probably had been out of its den only a few days. Male bears and females without cubs usually start to emerge from hibernation around mid-March. I watched the bear for several hours. Occasionally it got up and ripped off chunks of flesh, but most of the time it lay prostrate on the elk. Finally, about mid- afternoon, with the carcass largely devoured, the griz charged up a snowy hillside and disappeared. The wolves never appeared. |
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The next day: Dawn patrol again in the Lamar Valley, searching once more for the Druid Peak wolves. I was with park researchers, and they had picked up a strong signal from a radio-collared member of the Druid pack near where the Lamar River and Soda Butte Creek join. The juncture of these two streams marks the approximate epicenter of the Druids' territory. It lies about a mile east of where, the day before, the grizzly had seized the Druids' kill. |
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Through his binoculars, someone caught a brief glimpse of the wolves in an aspen grove, but a small rise thwarted a good view. Our small group of wolf-watchers and researchers quickly scrambled uphill in search of a better vantage point. We post-holed through knee-deep snow for nearly a quarter of a mile until we found a bluff that overlooked the valley. There we set up our spotting scopes. It was like peering right into the wolves' dining room. |
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The Druids had killed another bull elk, and a spiderweb of tracks, like the spokes of a wheel, led to a reddish-yellow spot in the snow. Eight wolves crouched around the carcass, all feeding actively as ravens wheeled about and a golden eagle sat on a nearby stump. Five of the wolves were black, three gray. One of the latter, gangly and very large, was so light it was almost white. The blood on its face was visible from three quarters of a mile away. |
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We watched the wolves feeding together for more than half an hour. Then an all-black adult with silver haunches and a white patch on its chest - the alpha (highest-ranking) male - tore off a huge chunk of meat and bone and retreated to the base of a lodgepole pine to chew on his dinner by himself. One by one, the other pack members followed suit, except for a black pup that for about 15 minutes made it his mission to prevent the ravens from feeding. |
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Finally, all the wolves were at least 15 yards from the carcass and 15 or more ravens waddled in to consume their fill. I watched through the spotting scope as the eagle bounced off its perch and began walking through the snow to the carcass, its huge brown and white wings partly unfolded. But the snow was soft, and the ten-pound bird's legs sank deep into the snow as it approached the dead elk. |
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Watching intently, I murmured to no one in particular, "That eagle could be in trouble if a wolf came after it." No sooner had the words left my mouth than one of the wolves leaped up and bounded through the snow toward the eagle. The eagle took a hop to get airborne but only settled deeper into the mushy snow. The wolf charged forward in big bounds, gobbling up distance with its long legs. The eagle took a second hop but still couldn't get aloft. Then, as the wolf hit deeper snow and slowed, the eagle took one more hop and finally lifted off. The wolf snapped at the eagle's tail as the giant raptor flew away. |
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It is now three years since wolves were restored to Yellowstone. The 31 brought from Canada in 1995 and 1996 have expanded into nine packs and more than 80 individuals. While much has been learned about Yellowstone's wolves in the three years, the essential scientific question remains: Has this bitterly contested reintroduction fundamentally influenced the entire Yellowstone ecosystem, or have wolves slipped into the world's most famous park with insignificant impact? |
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Scientists disagree over which animals most influence natural systems - the species at the top of the food chain or those at the bottom. The Roman natural historian Pliny the Elder once wrote, "Nature is to be found in her entirety nowhere more than in her smallest creatures." To appreciate his wisdom, one need only split open a decaying log and observe the complexity of activities within. Or look at Yellowstone. While the park's elk and bison inspire never-ending debate and controversy, few people realize that in some years grasshoppers comprise three times the biomass (total weight) of these big grazing animals and eat twice as much forage. |
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But some scientists believe major impacts on the natural world originate at the top rather than the bottom. Duke University professor John Terborgh calls large predators "the big things that run the world." He believes big carnivores have a disproportionate impact on the structure and function of natural systems and that the impacts of these species ripple through the entire ecosystem. To the extent that Yellowstone serves as a testing ground for these alternate hypotheses, the early reaction of most Yellowstone scientists is unequivocal: Yellowstone's wolves are having an extensive influence on the ecosystem, affecting everything from grizzly bears to beetles. The most obvious though not necessarily most important impact is that the wolves kill other animals. |
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So far, the Yellowstone predation story is a simple one. Wolves are killing elk - lots of them. According to researchers, 98 percent of the wolves' diet last year and early this year was elk. In other locations such a restricted wolf diet would be noteworthy, but given the fact that Yellowstone has one of the highest elk densities in North America, it's not so surprising. |
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Some people worried about the possible cruelty of uprooting wolves from their native habitat in Canada and translocating them in Yellowstone. From a wolf's perspective, however, it must have been like being dropped into a cafeteria. On the average, each wolf pack kills an elk about every three days. This varies greatly, however, with the size of the pack and whether the wolves are killing young animals or adults. For instance, last March the Rose Creek pack (then numbering a dozen) killed 19 elk, nearly all calves. During the record snow winter of 1996-97, researchers observed that wolves did not completely consume many of their kills. Other animals were doubtless grateful. |
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After elk, Yellowstone's mule deer (usually present only in the summer) rate a distant second in the wolf diet. So few other animals were killed by wolves in the first three years that researchers could almost count them on both hands: about a dozen moose, three bison, two pronghorn antelope and a single mountain goat. No bighorn sheep kills were recorded. Researchers know wolves also killed beavers, ground squirrels and voles for food. |
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Wolves kill some animals not for food but because they view them as competitors. Biologists have seen wolves kill at least half a dozen coyotes and several badgers. Once, they watched wolves attack a pair of river otters caught far from water (both otters escaped). Bob Crabtree, director of a long-term Yellow-stone coyote study, believes that wolves have reduced the coyote population by as much as half. Yellowstone wolves have killed at least four of their own kind. |
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It is too soon to assess a forecast by scientists that wolves will reduce the Yellowstone elk population by five to 20 percent. So far, winter has been the fiercest predator. Elk numbered more than 20,000 when wolves were reintroduced in 1995. Only 10,000, however, survived the extremely harsh winter of 1996-97. Researchers say wolves last year killed 300 to 350 elk, not counting calves killed in June and July. Wolves aren't the park's top elk predator. Human hunters on the park's periphery normally kill about 2,000 elk in the same herd yearly. Grizzlies, coyotes and mountain lions also prey on elk, especially their calves. |
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Wolf expert L. David Mech doesn't expect wolves to reduce the park's elk population significantly unless the packs compact their territories. "To have a really major impact on elk," says Mech, "there will have to be a lot more wolves in the park." In normal situations, he explains, wolves defend large territories against other wolves. A typical northwestern Montana wolf territory might be 20 miles long by 20 miles wide. But Mech believes wolves may "stack" their territories more tightly on top of each other to take advantage of the dense elk population. |
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The potential impact on elk arouses more conjecture than any other Yellowstone wolf topic. But John Varley, Yellowstone's chief scientist, maintains that wolf impacts extend much farther. "You have to stand back and look at the subtleties of the entire system," he says. "The single biggest change wolves have brought to Yellowstone is the ability to place red meat on the ground throughout the entire year. There's no other way to put it - wolves are feeding large numbers of other species." |
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Before wolf reintroduction, Varley explains, large quantities of meat were available only when elk and bison died following harsh winters. While such carrion is important, it's unpredictable. For instance, carrion was abundant after the winter of 1996-97 when thousands of elk died. Last spring, after a mild winter, researchers found almost none. |
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Varley points to five species besides prey animals that clearly have been affected by wolf restoration: grizzlies, coyotes, ravens, magpies and eagles (both bald and golden). These in turn have affected many other plants and animals. Biologists have been amazed at how quickly grizzlies have zeroed in on wolf kills. While meat is a terrific source of bear nutrition, most grizzlies are efficient predators only on elk calves, and only for a few weeks in early summer. But grizzlies have exceedingly keen noses. They can smell a carcass more than a mile away. |
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Park researchers following the Druid Peak and Rose Creek packs last year found that every one of the 16 elk kills made by wolves during September and October attracted a grizzly. The bears seemed to follow the wolves deliberately in order to take over the kills. In one encounter, nine wolves challenged an adult grizzly for a carcass. The bear lay down on the elk and refused to move. Checkmated, the wolves eventually gave up and left to make another kill. In clashes with wolves, grizzlies usually prevail. |
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Red meat is an incredibly rich source of nutrition and energy. Where it's not available, grizzlies rely mainly on plants, roots, berries and insects. Hibernation is an adaptive strategy that enables bears to survive through the long winter despite food scarcity. In their winter dens, bears enter a torpid state in which their metabolism drops and they live off fat reserves. In 1996, Montana researchers near Glacier National Park watched a grizzly that had discovered the trick of following wolves and mountain lions to steal their kills. This bear was so well fed he never went into a den and never hibernated. |
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Eating meat is a foraging strategy enabling animals to build up significant fat reserves. This may do more for reproductive success than any other single factor, and there is no better example than Yellowstone's wolves. Dave Mech, who has studied wolves on Michigan's Isle Royale and in Alaska, arctic Canada, Minnesota and Italy as well as at Yellowstone, calls Yellowstone's "the fattest wolves I've ever seen." When you examine one it's difficult even to feel its hip bones, he says. After a large meal, one Yellowstone male tipped the scales at 141 pounds, 20 more than the heaviest wolf ever captured by researchers in northwestern Montana. |
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Yellowstone wolf reproductive success has been spectacular, one of the highest rates documented anywhere. In a normal pack only the alpha female breeds, but last year three females in the Rose Creek pack produced pups. |
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Fat is similarly key to reproductive success in birds. The fatter a raven, for example, the higher quality its egg. The higher quality the egg, the stronger the chick. The stronger the chick, the greater its survivability. Yellowstone researchers have seen as many as 43 ravens on one kill. Moreover, ravens not only consume meat directly but may cache it in trees for a later meal. This makes small packages of protein available to many other creatures. |
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During the morning I was watching the Druid Peak wolves, several mountain bluebirds flew by. Their fluorescence reminded me of Thoreau's remark that the bluebird carries the sky on its back. I asked John Varley how these bluebirds get by during lean food times in late March and April. Varley said he once saw 30 crowded on the ribs of an elk carcass, picking fly larvae out of the rotting meat. "If you are a one-ounce bird that's just migrated from your winter habitat, your body fat may be depleted so that you need high-quality food and lots of it to get into top reproductive shape," he explained. "A rich food source like a carcass may be invaluable." |
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Yellowstone wolf researcher Douglas Smith agrees with Varley that the impacts of predation percolate through the ecosystem. "The trickle-down effect of wolves is tremendous," he says. "While we usually only look at animals like large grazing mammals or scavengers, the benefit to other creatures is quite significant." A 50 percent reduction in coyotes could lead to a significant increase in small mammals such as ground squirrels and pocket gophers, he points out. That in turn could result in an increase in hawks, owls and eagles. "Without wolves," Smith says, "we have a food chain that's heavy on elk. With wolves, we see faster cycling of nutrients because animals don't live as long. Instead of a pulse of carrion in the spring, there is a steady trickle all year long. It really enriches the entire ecosystem." |
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The consequences of all this? According to Smith, while Yellowstone is likely to retain the same panoply of species, the numbers may change. "Some rare species may become less rare, and some common species like elk may become less abundant and less dominant in the ecosystem," he predicts. Smith, who for 13 years studied wolves with biologist Rolf Peterson in Isle Royale National Park in Lake Superior, says one rare species that might benefit from the wolf's presence is the wolverine. "Wolverines are carrion- feeders that often stay at high elevations, even in the winter," he said, adding that they survive by preying on animals that fall off cliffs, get trapped by avalanches or succumb to winter conditions. |
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Smith recounts an incident he observed from a plane last winter. "On one flight, we located the Leopold pack at 8,200 feet where they had killed a bull elk. There was a small band of bulls wintering on a windblown ridge otherwise covered with deep snow. While food was available, escape options were minimal. The partially consumed remains of one or two of these elk might be enough to sustain a wolverine through an entire winter." |
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Nearly 450 beetle species are known to use carcasses in Yellowstone. More than 50 are directly dependent. Derek Sikes, who is studying Yellowstone's beetles while working toward a Ph.D. at the University of Connecticut, asks: "How much biodiversity would vanish if Yellowstone Park lost its great herds of megafauna? The herds themselves are composed primarily of fewer than five species. However, I can name 57 beetle species that might be greatly affected by such a loss." |
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Not all those beetles feed on carrion; many prey on other beetle species. An entire predator/prey community flourishes in miniature on each carcass. We don't know the life history of many of these insects, but the few we do know are as fascinating as any toothsome carnivore. Consider a predatory beetle known only by its scientific name, Aleochara verna. "It has an unusual life cycle that strongly resembles that of the monster in the science fiction movie Alien," Sykes says. "The female adults pierce the skin of living fly larvae (maggots) and deposit their eggs, where they quickly hatch into beetle larvae that slowly consume the living maggot from the inside out, eventually causing its death." |
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Harvard evolutionary biologist Stephen Jay Gould has suggested that natural history is largely a tale of species adaptations to avoid being eaten. Anyone who watches the wolves in Yellowstone can't help but reflect on the incredible complexities created by predation. It's an inexhaustible game of "what ifs" and "maybes." What if the wolves reduced Yellowstone's elk to the point that willows and aspens grew more vigorously along the Lamar River? Perhaps there would then be more beavers and songbirds. What if wolves completely eliminated coyotes? Perhaps raptor numbers would explode. What if the wolves started preying aggressively on bison? Perhaps bison numbers would shrink to worrisome levels. Such thoughts filled my head as I left the Lamar Valley. |
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Approaching a turnout that overlooks where Hellroaring Creek joins the Yellowstone River, I saw a park research vehicle and pulled in. Several times before the wolves arrived I had brought journalists to this very spot to help them visualize how the wolves might use the park. Here in spring, 1916, park officials discovered and destroyed one of Yellowstone's last known wolf dens of that era. Three adult wolves had dug burrows in the open hillside. The female had given birth to six pups. Excellent historical photographs show the den and offer a grim, grainy black-and-white record of their subsequent demise. |
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As I got out of my car, a park researcher told me the Rose Creek pack's alpha male had killed a yearling elk only 15 minutes earlier. Through the spotting scope I saw eight pack members with their noses buried in the carcass. It lay only a few hundred yards from where park officials had destroyed the wolf family eight decades earlier. Like onlookers at a car crash, a tightly bunched throng of 200 elk nervously watched the wolves turning elk molecules into wolf molecules a quarter of a mile down the hill. |
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This endless evolutionary drama between wolves and elk has occurred millions of times on the slopes of Yellowstone. In this play the prey grows ever more difficult to find and catch while the predator becomes ever more skillful at searching and capturing. It's a rhythm from a song as old as time, temporarily interrupted, now restored. |
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Ravens circled the kill, and a golden eagle perched on a giant boulder nearby. Coyotes were visible half a mile away. They would get theirs, and no doubt a grizzly would soon catch a whiff of fresh meat in the spring air. The elk's blood hadn't even soaked into the soil, yet the system was already in motion. |
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Dave Mech got it exactly right when he said in 1986, "Yellowstone is a place that literally begs to have wolves. It's teeming with prey. It used to have wolves. And all of the species that were there originally should be restored." After only three years, it's more obvious than ever that Yellowstone is a perfect place for wolves. They make the landscape sing. The Yellowstone wilderness cannot be truly wild without them. |
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Hank Fischer is Defenders' northern Rockies representative. He lives in Missoula, Montana. |
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