The snowmobile leaped to life again after about the fiftieth pull, and carried us to within five kilometres of the truck where it died a final time. No amount of pulling or ether in the carburetor made it go, so finally we were forced to walk. Our truck started okay, and as long as we kept the speed over fifty kilometres an hour, much too fast for a winding, ice-covered road, it didn’t stall. We careened our way back to Achray.
One moose donated by the Mathews Lake pack put up an even greater fight. In the Mathews pack was a gigantic wolf whose tracks we had observed periodically for more than two years. We collared other Mathews wolves but never the giant. On March 13, 1991, Mary and I took our new research snowmobile up the snow-filled connector road north from Achray into the Mathews territory. A few kilometres along, we heard the signal of Mathews 4, an adult female, off to the north. Simultaneously, Graham and Lee were circling in the Cessna over the wolf, and we judged the centre of their circle to be about one kilometre from us. We encountered a trail of wolf tracks following a little creek, and among the tracks were those of the Mathews giant.
Every wolf study has its mythical wolf, one that is bigger and stronger than all the rest. We wanted to see him (we assumed a male), and here was an opportunity, so we put on our snowshoes and struck out. Mathews 4’s signal led us farther to the east than we expected, but we kept on it in dense conifers for a while. Late winter sunshine dappled through the trees, softening the snow in the forest openings and making it cling to our snowshoes. Eventually we came to a small marsh-lake where the signal was loud. Approaching very slowly, we parted balsam branches and looked out. Four wolves lay there, one of them dwarfing the rest with its enormous neck and shoulders and deep chest. Two smaller wolves lay flat out on their sides, absorbing maximum warmth from the sun; the other two were up on their haunches, occasionally lifting their heads to look around.
A raven flew by from the south carrying a chunk of red meat in its beak, so we knew the pack had a carcass nearby. Soon two of the wolves stood up and walked slowly to the trees on the south side of the lake. We wanted to photograph the giant wolf, and moved a few steps, but he sensed us immediately. When he stood up, he looked as big as a pony. Together he and his companion loped for the trees, the big wolf occasionally stumbling as he broke through the soft crust.
We snowshoed to where they had been, examined the familiar large tracks, then followed them to their moose. Mathews 4’s signal evaporated as we approached. A few ravens lifted off the carcass, this one a young bull, its body parts scattered under the spruces. Branches were broken all around, many splattered with blood. Where the moose made his last stand the snow was pounded flat. His bone marrow was still rich in fat. Here was a clear case of predation, a moose that otherwise would have lived.
So, too, was the moose at Narrowbag Lake, where evidence at the scene allowed us to reconstruct the attack. The moose had been browsing red maples on a ridge 150 metres from the lake, then lay down under a balsam fir. Some wolves came upon her there, at least one of them making contact, judging from the blood on the snow at the bed-site. She jumped up and plunged down the ridge towards the lake, taking big bounds, mowing down saplings and crashing through brush. But she did not get far. More wolves had been hunting along the lakeshore, and they turned up to meet her. She was dispatched quickly in a clump of firs. A four- or five-year-old, her bone marrow showed only slight pink.
Among other memorable moose kills was one made by the Pretty Lake pack in 1996. Snow-covered Emma Lake glistened in late-afternoon sun as Mary, Tom Stephenson, and I trekked up it. At its north end we heard the signal of Pretty 6 and saw ravens circling overhead. We slipped behind some scraggly jack pines along the shore and I howled. Within seconds, five wolves materialized from some small, lake-edge pines. They looked our way but could not see us. Obviously excited, they milled about, flicking their tails vigorously. First one, then all lifted their heads in a group howl. Then, one by one, they ran across the narrow north end of the lake and into the trees. The moving radio signal showed that they came down through the shoreline trees towards us, but, when they were opposite us, stopped. They either picked up our scent or saw us. We waited to see what would happen next, but nothing did, so we snowshoed the rest of the way to the carcass.
The snow that winter was heavy enough to break records, and the big bull had been sinking in hip-deep. Making things worse for him, he had been wading through small pines that were bent over under their load of snow, with a tangle of brush beneath. When the wolves attacked, he ran but was up to his belly. Extracting his hooves for defence was impossible. The wolves killed him with apparent ease.
Moose survive in wolf country because they are a dangerous prey. They do not typically outrun wolves, although they may be able to do that with ideal footing and little to impede them. We once clocked a bull moose with half-grown antlers running down a logging road ahead of us at thirty kilometres an hour over one and a half kilometres. At a gallop for two hundred metres, he made thirty-five kilometres an hour. Wolves reportedly can run as fast or even faster. A cow and calf in January could only make twenty kilometres an hour on a ploughed road. Successful moose, however, stand their ground, as observations from several studies have shown.
In our heavily forested study area, we were not privileged to watch attacks, only assess their outcome. Sometimes the moose wins. Grand Lake 4 was a large adult male weighing in at thirty-six kilograms (eighty pounds). In December 1989, Graham heard his signal from the air on mortality mode. To recover him we snow-mobiled from Achray, across Johnson and Berm lakes, then down Stratton Lake to its east end.
We cut into a high-canopy stand of white and red pines at a point where the snow was shallow enough that we could walk without snowshoes. Grand 4 lay about fifty metres inland, his hindquarters exposed but his midsection and head under a few centimetres of snow. One set of fresh wolf tracks led up to the carcass and then away, and some older tracks were scattered near the shore. We carefully brushed off the snow and examined him.
He had some obvious wounds: scalp cut through to his cranium, and cuts on the right side of his face, top of his hip, and left flank just behind his foreleg. None of these wounds, however, seemed serious enough to be fatal. No human tracks were around, or snowmobile, or moose, or any signs of a fight. He was on his own territory so was not paying the price of trespass.
We carried him to the sled, lashed him on, and drove back. Eventually he ended up in a snowbank by our house, awaiting the reopening of the lab at the University of Guelph after the New Year. Upon autopsy, the cause of death was more apparent: fractured skull, broken ribs.
About the only conceivable way he could have been injured so seriously, considering his prime condition, was by a moose. His wounds were consistent with what would happen if a wolf lost its footing in front of a trampling moose that was standing its ground. He must have travelled some distance before he collapsed.
Grand 4 was not the only loser. In my student years I discovered a dead wolf with massive hemorrhaging on one flank and a ruptured kidney, the victim of a swift kick. Moose, even deer hooves, can be lethal. At both Isle Royale and Denali national parks, research showed that up to 90 per cent of wolf attacks on moose are unsuccessful. Wolves test a moose, then make a tactical decision and often leave.
How predators shape their prey, and prey shape their predators, is an example of co-evolution. Two species are bound together, influencing one another over time, like two clowns with feet and hands tied together doing somersaults at a county fair. One is the driving force for the other. As the prey gets better at escaping, it puts pressure on the predator to get better at catching it. And that, in turn, puts pressure on the prey to improve even more.
Under the constant pressure of co-evolution, everything that is not prey in wolf-dominated ecosystems but large enough to provide wolves with a decent meal has had to come up with some adaptation to avoid predation. It either goes into the ground, climbs trees, is large and fierce, runs fast, kicks, has quills
, or tastes bad. By forcing these adaptations, wolves have structured the characteristics of species that share their ecosystems. Wolves, in effect, have lost out to these non-prey species, failed to make counter-adaptations to catch them.
Other species, however, have less perfect predator defences than do bears, porcupines, and the mustelids (mink, marten, otters, skunks), just imperfect enough to support wolves but still allow their own populations to persist. Beaver stay near water, their means of escape, and the dams they build can be interpreted as adding to their safe foraging range. Moose and deer spend most of their time, like almost all forest ungulates, singly or in small groups; they find safety in dispersion. Savannah and tundra ungulates, in contrast, gather in herds; they find safety in numbers where they can see and not be taken by surprise. Deer deviate from this rule in winter, as discussed in a later chapter. Despite these adaptations, enough moose, deer, and beaver succumb to support a wolf population.
Why the prey manages to outstrip the adaptations of the predator and develop immunity, sometimes but not others, is a central question in ecology. If wolves shape their prey by culling the vulnerable, making even faster and fiercer moose and deer, why haven’t wolves always responded by getting better at killing?
They have responded in times past. The characteristics of the prey have forged the characteristics of the predator. This phenomenon is called the Red Queen Effect. In Alice’s Adventures in Wonderland, the Red Queen said, “Now here, you see, it takes all kinds of running you can do to keep in the same place.” The predator has been forced to keep improving to match each improvement in the prey just to maintain the same level of killing efficiency. The Red Queen Effect has been important in the co-evolution of predator-prey systems.
But the wolf has remained relatively unchanged since it first showed up in the fossil record about one million years ago. Making that more remarkable is the dramatic variety of its prey. Environments have changed too, going through glacial and non-glacial periods. Under the influence of changing environmental conditions such as these, you would expect to find the Red Queen Effect, an ever-adapting predator, or else it would fall back and become extinct.
Why the Red Queen Effect has not driven changes in wolves can only be answered speculatively. The wolf owes its success to being a generalist predator. Like the king or queen on a chessboard, it is capable of many moves. Wolves are able through their behaviour to adapt easily from one prey to another. They could shift with the diverse species that paraded through the Pleistocene: various deer, camels, pigs, horses, elk. In contrast, the sabre-toothed tiger could not; like a bishop or a rook, it was limited in its options. It evolved as a specialist on the mammoth, capable with its long, sharp canines of penetrating its tough skin. When the mammoth became extinct, so did it.
Also limiting the never-ending Red Queen Effect is the fact that predation is only one selection pressure working on prey species. Other pressures include unfavourable microclimates, accidents, and the ability to win mates and raise young. Life is a compromise. Getting better at avoiding predation may work a disadvantage in other ways. For a moose, environmental fitness involves surviving cold winters, which it achieves in part through efficient heat retention and a slow metabolism, both a function of being so large. But by being large, moose are less manoeuvrable when attacked by wolves. With such bulk, they also have little chance to stay on top of boreal snows. Large antlers have an advantage in attracting a mate but reduce speed in dense forest. A moose is an environmental compromise, shaped by wolves in some ways, shaped by other factors too. It is left with an average stable vulnerability instead of an ever-improving ability to avoid predation.
The wolf, too, is a compromise, driven in part by the Red Queen to match improvements in its prey’s ability to escape, compromised by other environmental demands. Its long denning period restricts mobility, especially inhibiting for wolves that inhabit tundra where caribou migrate away. Energetic and time investments in pack rivalries limit the wolf’s efficiency as a predator. Its large body size, driven upwards in part by selection for dominance within a pack, demands more energy.
Such a compromised situation for both predator and prey is like a chessboard with only certain squares open. Either the game goes on — the Red Queen — or the players reach a stalemate, and nothing changes for a long time until some drastic environmental event creates new moves.
Moose and wolf have not been locked in co-evolution for long, not much more than a hundred thousand years. Moose are latecomers in evolutionary history. Wolves evolved over longer periods with the ancestors of moose, such as the Gallic elk and the broad-fronted elk, although the latter was much bigger than modern moose and perhaps immune to wolf predation. Roe deer and Irish elk lived in Eurasia; stag-moose, white-tailed deer, and mule deer lived in North America; and caribou, camels, horses, muskoxen, beaver, pigs, red deer (wapiti), and bison lived in both. All have ancient histories. Wolf adaptations to kill moose are mainly a spillover from adaptations to kill these other, older prey.
Today in Algonquin Park, wolf hunting strategies may be some compromise between what is best to find and kill moose, white-tailed deer, and beaver. Optimum pack sizes and group hunting strategies may not be the same for hunting them all. Of the three prey species, we concluded that wolves were responding primarily not to moose, but to deer (subject of a later chapter).
Graham concluded in his Ph.D. thesis that wolves were not a sufficient, single limiting factor on the moose population, largely because alternative prey provided close to two-thirds of wolf diets. As well, we found only 15 per cent moose calf in summer diets, low compared with other studies. A declining rate of twinning in moose, documented by MNR biologist Mike Wilton, suggested that the population was experiencing some nutritional stress so was near its range carrying capacity. In such cases, losses from wolf predation are largely irrelevant because they just reduce deaths from starvation. Low production because of the lack of twinning roughly balanced some combination of tick-caused deaths, energy-stress, accidental deaths, human killing, and predation.
Killed or scavenged, most moose meat not taken from Algonquin Park by native people is cycled through wolves, despite the immediate or predisposing natural causes of moose deaths. Relatively little is left uneaten, or it is eaten by other things. Moose give their atoms another fling with life, in wolves, before they are handed back to decay organisms and the soil. This gift of life after death, given only because moose can make no effective move to avoid it, is the big herbivore’s lasting contribution to its evolutionary companion.
WOLF WEB
Top Down or Bottom Up
Nothing is more basic to understanding wolf ecology than the drive-it—ride-it conundrum. It generates heated debate and calls for better research design.
At issue is the question of what predominates to control change in an ecosystem. Does the wolf, as summit predator, drive change down through the trophic levels, or does the wolf merely ride change caused by other environmental factors?
Why this conundrum has been so difficult to solve is obvious if you flip to the chapter on predator-prey theory in ecology books. It is full of graphs, tables, examples: functional response to increasing prey numbers, numerical response, principle of inversity, principle of compensation, models of predator-prey relationships, models of multi-equilibrium predator-prey states, relationship of predation to extrinsic factors, to intrinsic factors.… There is no shortage of theory, all looking for field evidence, nor any shortage of field evidence looking for theory.
Rephrasing the conundrum, the choice is between ecosystem control from the top down (wolf driving change in the herbivore, then herbivore driving change in the vegetation) or bottom up (soil and vegetation driving change first). If top down, changes in wolf numbers would precede changes in prey numbers. That is, if wolf numbers go up, then as a consequence prey numbers go down. If bottom up, however, vegetation changes first, then prey, and wolf numbers follow. In the latter case, the wolf is more passively
riding the system.
To detect which population changes first and identify consistency over several cycles requires long-term study. That requirement severely limits the evidence. As well, most studies examine only the controversial wolf-prey link and not the vegetation.
On Isle Royale in Lake Superior, Rolf Peterson has found evidence that the system may run both ways depending upon circumstances. He published a top-down evaluation because he and his students observed changes in wolf numbers influencing moose numbers that in turn influenced the amount of browsing and seedling success of balsam fir. But then a crash in the moose population in 1995 and 1996 was precipitated by a heavy tick infestation, not by wolves. So the answer to the conundrum is not simple.
Where the possibility of conducting a controlled experiment does not exist, such as in studies of top-down or bottom-up control, scientists look for pattern over time or space. It seems reasonable that in very changeable environments, ecosystem control might be bottom up simply because something is continually altering conditions. One place you can expect natural environmental change is in boundary areas between biomes, where one type of ecosystem, such as forest or tundra, grades into another on some knife edge of differing physical conditions such as soil or climate.
Algonquin Park lies between two great biomes: boreal and southern deciduous. The park is range-edge for moose who make it no farther south except at higher elevations in the eastern United States. They need a cold climate. Algonquin is also range-edge for deer who peter out in deeper snows farther north. It is range-edge for gray wolves as well, on the southern fringe of their range in eastern Canada. The park, then, is a tension zone for the large mammal system. On top of that, humans are altering the forest with logging.
Wolf Country Page 13
