Crows (10 page)

Scheming and deception by animals are hot topics in contemporary science. If higher intelligence is a response to the challenges of living in social groups, then brain power should pay off in improved mastery of social situations. Individuals should gain a survival advantage—more food, more sex, longer lives, increased reproduction—by using their brains to outwit and outmaneuver their friends and associates. Put bluntly, this theory predicts that exceptionally smart animals will also be exceptionally tricky. With this provocative idea in mind, a small but gleefully determined band of researchers has begun to look for proof that ravens and other bird brains not only connive and scheme but that they know exactly what they are doing.

On a wintry afternoon in October 1984, researcher and marathon runner Bernd Heinrich made a simple observation that, over the next four years, would engage both his mental and his physical skills. He was at his cabin in western Maine when all of a sudden he heard a hullabaloo of raven cries echoing through the forest. A good mile away, he discovered a group of ravens shouting around a moose carcass. If he had been attracted by the commotion, he thought, surely other ravens would have been drawn to the food source as well. “The birds seemed to be advertising their find,” he noted,
“which meant they would have to share it.” But this behavior didn’t seem to make sense. Why didn’t the noisy ravens just shut up and eat the moose themselves?

As this question took hold of his mind, Heinrich hatched a plan: he would drag carcasses into the forest and watch to see what happened. Over successive winters, he distributed more than 135 piles of meat in the Maine woods, for a total of almost 8 tons, including 3 road-killed deer, 5 moose, 3 cows, 12 calves, 2 sheep, 3 goats, innumerable loads of slaughterhouse offal, and numerous carcasses of small mammals. To prevent coyotes from stealing his baits, he took the precaution of peeing on them, such was his dedication to science. Then, as each offering was put in place, he established an observation post—in a cabin, in a blind, or in dense branches at the top of a tall spruce—and crept into place each morning an hour before dawn so that he could watch the ravens without disturbing them. In all, he spent 1,520 hours making observations.

By the time Heinrich climbed down from his tree for the last time, two general patterns had emerged. When ravens fed on carcasses, they either showed up in ones and twos and scarcely uttered a sound, or else they arrived in congregations of two or three dozen birds, amid a hubbub of raucous calls. By capturing and marking individuals, Heinrich was able to show that the singletons and pairs were adult, mated birds on their territories, whereas the noisy crowds consisted mainly of wandering youngsters. Why the difference? When a lone juvenile landed at a carcass, it was likely to be attacked and chased away by the resident pair, but not so if it showed up with a group. The young ravens found strength in numbers.

And that wasn’t all. It turned out that these gangs of young toughs did not assemble by chance; the ravens actively recruited one another. Heinrich concluded that a special, high-pitched yell uttered by juveniles at carcasses attracts others to the scene and that together the mobs of young ravens are able to descend and feed. In a later set of experiments—inevitably involving the recovery and transportation of another few hundredweight of road kill—he and his colleagues demonstrated that feeding crowds also develop out of communal roosts. Hungry youngsters, eager to feast on something dead, follow the lead of birds that know of a nearby carcass.

Yet even after all these exertions, there was one problem Heinrich still couldn’t crack. When ravens form these shifting alliances, do they consciously plot and scheme, or are they acting on impulse, without thinking? And the same tantalizing perplexity hangs over another aspect of the ravens’ social repertoire. In addition to associating strategically with one another, the birds strike up pragmatic relationships with wolves and other large carnivorous mammals. Long the subject of excited speculation, the wolf-raven partnership was conclusively documented in 2000 by Daniel Stahler, one of Heinrich’s graduate students. As a member of the team responsible for monitoring the reintroduction of wolves to Yellowstone National Park, Stahler
spent several winters following radio-collared packs and watched them make more than two dozen kills. In almost every instance, the predators were accompanied by a retinue of black hangers-on, which hovered overhead or perched on nearby rocks. On the five occasions when ravens were not present at the moment of death, they arrived on the scene within four minutes.

The ravens were purposefully following wolves; that much was obvious. But Stahler and his colleagues also caught a glimpse of an even wilier permutation of the relationship. The ravens sometimes led the wolves to carcasses. (Since ravens cannot slice through animal hides and open bodies, they rely on wolves to do the dirty work for them.) One winter day in 1999, six wolves from a group known as the Druid Peak pack were spotted traveling along one of their regular routes in a snow-covered valley bottom. Overhead, silhouetted against the sky, a cluster of three dozen black, winged forms wheeled in lazy circles. Suddenly, the ravens veered away from the pack and landed some distance off, beside a mound in the snow. Two minutes later by the clock, the lead wolf turned off the well-worn path and, with the rest of the pack in tow, plowed through deep drifts until it reached the spot where the ravens were. There the wolves uncovered a dead elk calf, presumably the same animal that earlier had been seen in the area, injured and bleeding, surrounded by a dark cloud of ravens. Once the carcass had been opened, the ravens landed warily among their wolves, and the co-conspirators fed at the same table.

The
SAME
female
that SNUGGLES up to her mate
at night may
sneak away
the MINUTE his back is turned
and
COPULATE
with a neighbor.

Are ravens tricky? No doubt about it. Do they exploit their social relationships for personal gain? Absolutely. But do they do so intentionally, with full malice aforethought? That is a much more difficult matter. Yet Heinrich, for one, is persuaded that the issue of raven consciousness has to be addressed in the interest of human understanding and good science. “I didn’t start out at all interested in the question of intelligence,” he says. “It was forced upon me by the ravens.”