by Barry Lopez
During exceptionally heavy snows in Minnesota in 1969, wolves killed almost every foundering deer they came across, leaving many of them wholly uneaten. Hans Kruuk, a Dutch biologist, studied this phenomenon among foxes in England and hyenas in Africa and gave it a name—surplus killing. He believes that a specific sequence of events leads up to an animal’s death and shuts off the predator’s impulse to kill. If the sequence jams—if, say a rare meteorological event like unseasonably deep snows or an excessively dark night interferes, if game animals can’t, or won’t, flee—the predator just keeps killing.
For the wolf, take a moose as an example of prey. The sequence (as established by the wildlife biologist L. David Mech) runs: (1) Wolf senses moose and approaches (the stalk); (2) wolf and moose sense each other (the encounter); (3) wolf charges (the rush); and (4) moose runs (the chase).
But things do not always go this smoothly. A pack of wolves may catch scent of a moose yet ignore it. Wolves and moose may stare at each other intently—then the moose may just walk off. During a chase the moose may be surrounded, seemingly doomed, when suddenly one wolf will break off the chase in mid-stride and snap at the other wolves to drive them off—as though they had selected the wrong moose.
Out of the 160 moose that Mech saw from the air on Isle Royale and judged to be within range of hunting wolves:
29 were ignored,
11 discovered the wolves first and eluded detection,
24 refused to run when confronted and were left alone.
Of the 96 that ran:
43 got away immediately,
34 were surrounded but not harmed,
12 made successful defensive stands,
7 were attacked,
6 were killed,
1 was wounded and abandoned.
It would appear that the wolf is either inefficient or not very serious about killing moose. Or that more is going on than we understand.
There is a difference between the way wolves hunt moose and the way they hunt other animals—mice in meadows, Dall sheep on precipitous slopes, and caribou on featureless tundra. As the size of the prey increases, so does the skill and endurance required of the wolf (as well as the size of the pack) and the chance that he himself will be killed. Cursorial hunting of the moose requires a keen refinement of the wolf’s skills. And it is in such encounters with large animals that the nature of this hunter is most clearly revealed.
To illustrate, begin with a classic case that took place in Wood Buffalo National Park, Alberta, Canada, in 1951. Two buffalo bulls and two cows are lying in the grass ruminating. Three of them are in good health; one cow is lame. Wolves approach and withdraw a number of times, apparently put off by a human observer. At each approach, though, the lame cow becomes agitated and begins looking all around. Her three companions ignore the wolves. When one wolf comes within twenty-five feet, the lame cow gets up on shaking legs to face it alone. It seems clear that prey selection is something both animals play a role in.
Postmortem examination of moose and other large prey confirms a kind of selection. Wolves, as stated, take predominantly the very young, the old, and the injured and diseased—individuals the prey population can conveniently do without (due to senility, contagion, etc.), or ones doomed to imminent death anyway because of injury or parasitic infection. They are, after all, the easiest to catch. (It is often forgotten that wild animals like sheep, elk, moose, and deer suffer, sometimes miserably, from disease and injury, perhaps because most of us experience these animals in zoos where they are cared for. A Canadian biologist once observed a mule deer at the point of death, parasitized by an estimated seven hundred winter ticks. Moose parasitized by winter ticks leave a distinctive trail of bloody beds and showers of red on the white snow where they have shaken. Caribou can suffer terribly from warble flies and nostril flies, and moose are sometimes crippled by hydatid cysts in their lungs. Mech found one moose with fifty-seven of these golfball-sized cysts. Necrotic stomatitis, actinomycosis, and other bone and gum diseases and hoof infections are also prevalent among ungulates.)
Prey animals such as these apparently announce their poor condition to the wolf in the subtleties of a stance, a peculiarity of gait, a rankness of breath, or more obvious signs of physical incapacity, such as wounds, massive loss of hair, or visible infection. Wolves are alert to such nuances; further, by forcing a hunch, so to speak, by making a moose run or testing it, the wolf may realize that its lungs are impacted from the wheezing, labored breathing. It might know that the moose is not going to run very far before collapsing.
The testing of a prey species by a predator has been frequently observed in the field, especially among herd animals like caribou. It occurs so often as to be perfunctory. But hundreds of animals may be chased before a burst of speed brings one down, and the conclusion that some of these chases are not serious is at least plausible.
If the prey runs, it is almost certain to be chased. If it refuses to run, or approaches the wolves, it may be left alone. More signals, perhaps, between predator and prey.
Some animals apparently set themselves up (or are set up) to be killed because they feed or travel alone. Musk oxen, practically invulnerable to attack when standing in a defensive formation together, are easy prey for wolves once they are banished. (Among gregarious species, such lone animals living away from the herd tend to be old or sick or both.)
There’s a logic to all this. The injured, the aged, and the diseased have ways of announcing themselves and are subsequently removed. The young are cropped, which in turn controls the size of the population and perhaps eliminates inferior or maladaptive combinations of genes at the outset.
But there are elements of the wolf hunt that suggest there is more to it than the simple pathology of diseased prey, or behavior that might be triggered by flight and the wolfs need to eat. In fact, people make a rather curious assumption: that wolves look for moose just to kill them. Nunamiut Eskimos believe that during winter a healthy adult wolf can run down any caribou it chooses, but it doesn’t always do this for reasons known only to the wolf. And perhaps the caribou.
Wolves expend energy carefully, taking every advantage of terrain in chasing prey, moving cross-country in trails broken through deep snow by caribou, and sleeping during the hot hours at midday. When food was scarce one year in Minnesota because of a collapse of the deer population, wolves adapted by ranging far outside their territory for food and by resting a great deal, sleeping as much as twenty hours a day.
It has long been held that wolves use various strategies when hunting, though the data are not yet clear. On occasion they do employ what seems to be conscious strategy, sending out one or two animals to herd prey into an ambush. And they vary their tactics slightly to hunt each species of prey, adapting primarily to terrain and somewhat less to the sort of prey. They prefer to attack sheep from above. They may split up to skirt both sides of an island in a frozen lake and then precipitously flush caribou or deer driven toward the island’s tip. When antelope were abundant on the Great Plains, wolves reputedly lay low in the grass, switching their tails from side to side like metronomes to attract the curious animals close enough to jump them. And they apparently once herded buffalo onto lake ice where the huge animals lost their footing, a practice they still use to bring down elk.
Wolves hunt into the wind, and they quickly incorporate any new roads into their strategies, mostly to conserve energy and to facilitate ambushes. Wolves remain acutely conscious of their energy budgets, letting one wolf break trail in deep snow while the others follow in its footsteps, for example. An intriguing instance of this conservation of energy was observed by Robert Ahgook on March 21, 1970, on the tundra sixty-four miles northeast of Anaktuvuk Pass, Alaska. A lone wolf chased a single caribou for ten kilometers across hard-packed snow into an area of loose powder. Both animals slowed to a walk and then alternated running and walking for three kilometers, the wolf always adjusting to keep the distance between the caribou and itself constant. When t
he two animals emerged from the loose snow and headed down a slight incline, the wolf put on a burst of speed and brought the exhausted caribou down in a space of seventy meters.
Wolves may learn their territories well enough to take advantage of shortcuts and to know where they can drive prey into snow that will founder them; but these, like so many other observations, are being made to conform to a preconceived idea, namely, a single-minded strategy, and this could be a mistake.
Wolves halt chases for no apparent reason (to our human senses). One wolf may insist on attacking a certain individual while the rest of the pack expresses disinterest. A pack on the hunt may investigate tracks less than a minute old but pick up some subtle cue from them and not pursue.
There is no certain outcome after the prey is rushed. The chase may last only a few seconds, it may go on for miles, or it may carry on intermittently for days. With most large game successfully pursued, however, the pathology of death is similar: (1) Massive damage to the animal’s hips breaks its stride; (2) crushing and tearing cause bleeding and induce trauma; (3) harassment tires the animal; (4) disembowelment causes death. With large animals like moose, one wolf may grab the nose or head while the others undercut the animal and mob it to get it off its feet. Smaller animals like sheep, deer, and caribou can be ridden down by a single wolf and killed with a neck or head hold, which appears to suffocate them. In deep, crusted snow, a single wolf may kill a moose. An animal is rarely, if ever, hamstrung.
Once the prey is wounded and has taken its death stand, one or two wolves may harass it—make it exert itself, keep it bleeding—while the others rest, play tag, or otherwise demonstrate a lack of interest. The pack may even depart, leaving one or two animals on a death watch.
Again, once one is reduced to considering those animals that are actually killed, prey selection seems in retrospect very tidy. But this does not account for the animals that are not killed, which is an equally important issue.
One of the central questions about predators and their prey is why one animal is killed and not another. Why is one chosen and another, seemingly in every way as suitable, ignored? No one knows.
The most beguiling moment in the hunt is the first moment of the encounter. Wolves and prey may remain absolutely still while staring at each other. Immediately afterward, a moose may simply turn and walk away (as we saw); or the wolves may turn and run; or the wolves may charge and kill the animal in less than a minute. An intense stare is frequently used by wolves to communicate with each other, and wolves also tend to engage strangers—wolf and human—in stares. I think what transpires in those moments of staring is an exchange of information between predator and prey that either triggers a chase or defuses the hunt right there. I call this exchange the conversation of death, and at the risk of leaving the reader hanging will discuss it further in the next section on Indians where the idea is more comfortable. For the moment let me say simply there is good evidence that signals go back and forth, and there is some other evidence to support the idea of a conversation of death. One researcher found that by arranging his fur-rimmed parka hood in a certain way, he could spook caribou at will. His observations of hunting wolves indicated that wolves seriously intent on a chase approached caribou herds with lowered heads; he deduced that it was his similarity of appearance—head buried below shoulder line in his parka hood—that was putting the caribou to flight. Other researchers have sought additional clues and have speculated that prey selection may be based on an exchange of information between predator and prey, but attempts to support such speculation have fallen short. Wolf hunts are rarely seen, even by field researchers, and when they are the observer is usually in a plane or at such a distance that picking up nuances of behavior is difficult. The best that can be done in such cases is to examine tracks in the snow carefully and to check the carcass and try to put together what happened.
There are some other elements in the wolf hunt that are intriguing, worth noting. Douglas Pimlott mentions a “bystander phenomenon.” Two prey animals are pursued, and while wolves focus on one the other backtracks to watch its companion killed. Murie saw an eagle chase off a wolf that was engaged in a sheep stalk. Mech observed a “sure kill” from the air only to find when the site was examined from the ground that the prey animal had walked off.
The latter point should be well taken: in the past, it was assumed that wolves were basely motivated and bloodthirsty; then in an environmentally enlightened age, it was suddenly assumed that they were noble and wise. So, too, have we analyzed their hunting behavior in human terms, and none of it is worth more than the metaphor it’s couched in. This habit indeed may eventually lead us even further from an understanding of the animal. For my own part, I mean to suggest that there is more to a wolf hunt than killing. And that wolves are wolves, not men.
Before moving on to a discussion of territory, I would like to glance quickly at something else: caching. Wolves occasionally bury parts of a kill. In the Arctic, cold helps to preserve the meat; farther south, a covering of earth and duff keeps some potential raiders at bay. The wolf digs the hole with his paws and covers it by pushing with his nose, perhaps memorizing the smell. But caching is not a very efficient system. Field researchers think that other animals—eagles, weasels, foxes, wolverines—use wolf caches as often as wolves do. Foxes seem especially adept at locating wolf caches. Murie writes about a wolf that killed a Dall lamb and carried off part of the carcass. The ground was covered with enough snow for good tracking and Murie followed him, only to find that a fox had cut the trail ahead of him and was also following. In one place the wolf backtracked for fifteen yards, jumped off the trail eight feet to one side, then wandered about in several loops. At this point the fox tracks circled around as though the fox were confused. The wolf went on across some wet tundra, stepping deliberately into shallow puddles—to destroy his scent, Murie thought. After passing through some woods, he came to a creek, and there the trail ended. The fox sniffed around for the scent before, like Murie, he discovered the tracks downstream about fifteen yards. Three hundred yards and the wolf crossed the stream and drifted into the woods. There, beside a tree, was the cache. By the time Murie got there the fox had raided it and departed.
Such incidents, it seems to me, contribute to the sense of a community of creatures in the woods which we so often lack when we examine a single species.
What land actually constitutes a wolf pack’s territory is difficult to determine. Territories overlap; there are gaps between them; they are even abandoned. Tundra wolves don’t really have year-round territories. During the winter months they wander over vast areas of land in the wake of migrating caribou, centrally locating only during the denning season. Timber wolves, on the other hand, preying on species that migrate less or not at all, tend to have more recognizable territories. In an extreme case, such as on Isle Royale, where the packs are clearly defined and the landmass is exactly known, territories take on an artificial precision.
A given pack territory also changes size and shape with the season, shrinking or shifting a little during the denning period, for example. In winter the wolves may stay in one small area for weeks where a large number of deer have yarded up. Size of territory is also a function of prey density, as are the type of prey available and the number of wolves in a pack. Some wolves—loners—don’t seem to have any territories.
The problem here is not simply one of definition, but one of conceptualization. “Territory” is too frequently understood to mean something rigid and well defined, like a city block. Wolf territories are highly plastic, more or less so depending on factors already mentioned. And this idea, that there is a high probability that in a certain area you will find the members of a certain pack on a regular basis, is tenable. But we are not talking about well-delineated areas patrolled in an orderly fashion by paramilitary creatures—a notion spawned by confusing the idea of territory with the idea of private property.
Wolf territories are defined, albeit rather tempo
rarily, by scent marking and by hunting activities. We get a sense of a territory’s boundaries from the way in which packs double back on themselves at various points in their wanderings. A pack at the edge of its territory might permit a wounded prey animal to escape if it flees across that border into another pack’s territory. A wolf pack is repelled by the fresh scent marks of a neighboring pack. The boundary is defined from both sides of the fence; that it is not an idea to be taken lightly is evidenced by the number of trespassing wolves that are killed.
Wolf packs, everything else being equal, occupy larger territories in the north than wolves in the timbered country in the south do. Game is denser in the south; those packs need less territory to secure the same amount of food. The sheer size of a wolf pack’s territory, therefore, is a relatively minor issue. More important are questions like these: Where do the lone wolves that leave packs every year go? Do they join other packs? If not, how—and where—do they define a new territory? Does a space of, say, 100 square miles suddenly open up? Which leads to the more interesting issue: How does an area where wolves are found absorb an increase in population if the loner is an unstable social entity (as he is) and the pack, as a rule, doesn’t accept strangers and, furthermore, presumably controls contiguous territories? The answer, since loners do indeed find a place to live, can only be that territories are organic and not necessarily exclusive.
The idea of territory is really not very exciting in itself. Its importance lies in the fact that it precipitates such things as interpack communication through scent marking, that as a sine qua non of existence it is a major influence on the control of the wolf population, and that to violate its boundaries can result in death—sometimes.
