The reintroduction of wolves into Yellowstone National Park has had a significant impact on the coyote population, and researchers speculate on the ripple effect this may have on the entire ecosystem.
The day before I arrived, the wolves killed an elk. As is the habit of wolves, they ate heavily and withdrew to lie down and digest. For four coyotes, the abandoned elk carcass was now irresistible: a few rips of elk yield as much sustenance as hours chasing around after voles under the snow. The coyotes were watchful even as they tore at the carcass, and when they caught sight of the wolves streaking toward them, they bolted. The last to react dashed up a hill with two wolves gaining on it. As a third wolf joined in, the chase disappeared behind a rock and stopped. Wolves swarmed to the site, their heads down in a scrum; all that could be seen was a bevy of tails sticking up and wagging. Moments later, one wolf trotted down the hill with the carcass.
They would not eat it. Wolves here in Yellowstone Park have killed dozens, perhaps hundreds, of coyotes, but the purpose appears to be sheer competition. This carcass would be taken care of by the regulars in the Yellowstone cleanup crew: eagles, ravens, magpies, and other coyotes.
The next day, Doug Smith, the park's wolf project coordinator, hiked out to the site. Of the elk carcass, there remained almost nothing: a jaw and two leg bones. It had been a calf, and wolves crush and eat calf bones. Of the coyote, there remained some hide, a leg, and the pelvis with a few vertebrae attached. "The system," Smith says, "is very good at using every shred of available energy. Nothing literally is wasted."
Six years ago, life for coyotes in Yellowstone changed abruptly. Seventy years after exterminating the wolf in Yellowstone, humans brought it back. A wolf is about two to three times the size of a coyote: 80 to 100 pounds or more compared with the average coyote's 25 to 40 pounds. It's also faster, although, as Smith says, a coyote may have more "jukes and jives." Coyote numbers have dropped since the wolves returned, perhaps by as much as half. But any coyote that survives among the wolves has something that was unavailable in pre-wolf days: a year-round supply of elk meat.
Wolves have retaken Yellowstone with the authority that seems wired into them. They operate as a pack, take a territory, and defend it....Coyotes used to have the pick of the place. Now they have had to do what coyotes do supremely well: adapt. They have abandoned the core wolf territories and set up their own territories on the fringes and in between.
The coyote can gulp its food. For every gulp at a wolf kill, the wise coyote spends a lot of time looking over its shoulder. I watched one that must have spent 90 percent of its time scanning for any sign of returning wolves. That coyote had the good fortune to be scavenging on a bull elk, probably 800 pounds, killed the night before. The wolves were so laden with meat in their stomachs--a wolf will eat 20 pounds at a time--that they were in no condition to chase an annoyance such as a coyote; they were what is called "meat drunk." The coyote that died behind the rock might have survived had it been more vigilant. It also made a poor choice: 15 wolves had fed on a 200-pound calf. That probably left the carcass already picked over and the wolves still able to run.
On their own, coyotes in Yellowstone hunt voles and deer mice year-round along with ground squirrels in summer. Before the wolves, they would eat elk only under two circumstances. In springtime, a coyote pair can take a newborn calf during its first few weeks of life....The other time of year coyotes get elk meat on their own is winter, when they scavenge on winterkill....
Now coyotes show up at every wolf kill, usually three or four of them and even five or six; it's no wonder the wolves are proprietary. Killing an elk is not easy work. Hunts can seesaw, one minute a wolf chasing an elk, the next minute a 600-pound elk chasing a wolf. A female elk can put a hoof through a wolf's skull. Researchers calculate that on average a wolf pack kills about 1.8 elk per wolf per month in the winter (less in summer, when the elk are fatter). With the average pack size of 14, there's a pipeline of meat year-round not only for coyotes but also for other scavengers: ravens (which average 35 on a kill), golden and bald eagles (a couple on most kills), magpies, and occasionally grizzlies. As the impact of wolves cascades through the park, researchers can only guess what the consequences may be over time. Fewer coyotes, for example, might mean more small mammals, which might in turn benefit raptors....
Wolves have returned not just to Yellowstone; they have spread into the surrounding national forests and Grand Teton National Park. Thirty-one wolves were released here, brought from Canada in 1995 and 1996. They did so well so quickly that a third release was cancelled. By the end of 2001, the greater Yellowstone area had 21 packs with 220 wolves--10 of the packs with 140 wolves within the park's boundaries....
It took a concerted campaign to eliminate wolves from Yellowstone. Between 1915 and 1926, 136 were killed. Park reports recorded the progress: "Wolves had been very troublesome during the preceding winter and had killed many elk" (1913). "Thirty-six wolves killed in the park this year" (1918). "Wolf den near Tower Falls cleared out; old female killed and five pups brought out alive to Mammoth for exhibition" (1923). "There is believed to be a very limited number of wolves in the park" (1926). In the same era, 4,342 coyotes were killed, but with their famous wiliness, they came back on their own. For decades, without the wolves, Yellowstone's coyotes lived wherever they wanted, and thrived.
It is hard now to imagine Yellowstone without wolves. Before he came here, Smith worked in wolf country for 20 years. He arrived in Yellowstone shortly before the first wolves were released and took a flight over the terrain. "If you've ever been in wolf country and then you've gone to country that doesn't have wolves, it is different," he says. "I looked at it, and I thought something was missing. Now it feels right again. It seems much more alive, much more vibrant."
The place even sounds different. Listen long enough and you can hear the high-pitched, enthusiastic yip yowl of coyotes; the long, keening howl of the wolves.