Driven by all-powerful geometric progression, any population can grow at a staggeringly high rate. Illustrating its power is a question: Would you rather be given one cent on the first day of the month and allow it to double each day until the end of the month, or be given one million dollars? Answer: Take the one cent. On the thirty-first day of doubling, it will be worth $10,737,418.
Curbing the maximum potential growth of any population, however, is “environmental resistance.” It operates as an unseen pressure pushing down on a population, a sleight of hand that increases the death rate, or decreases the birth rate, or both. It also operates by negative feedback, becoming progressively stronger on a population as it grows, eventually strangling any further increase. Then the population is at “carrying capacity,” its environmentally set maximum size.
Measuring carrying capacity is difficult because it is influenced by so many environmental factors. Food quality, food quantity weather, disease, predation — all can interact differently from one year to the next. All have a greater effect the larger the population. Disease is transmitted faster in a dense population; food runs out sooner when there are more hungry mouths to feed; predators increase when prey is more abundant. So, while each animal in a population lives and dies, and leaves more or fewer offspring because of the interplay of environmental factors on just it, simultaneously, every individual is subject to the influence of population size.
For the wolf, as for other predators, a maximum population is set by the total combined biomass (weight) of its prey, and it is surprisingly low. To start with, a wolf population cannot kill more than about one-quarter of a moose population in any single year without causing a decline in prey. This is because we know that moose populations can grow no faster than this to offset losses under ideal conditions. Ideal conditions, of course, rarely exist. So, already there must be a much greater biomass of prey than of predator.
About 20 per cent of prey is inedible bone and hide. And only about 10 to 15 per cent of what a wolf consumes actually becomes wolf biomass; the rest is lost through digestive inefficiency and the metabolic demands of life.
In addition, not all prey that die goes into wolf stomachs. Other predators such as bears take their share, and scavengers such as ravens can eat prodigious amounts. Furthermore, some carcasses are never found by wolves and end up feeding the myriad microbes waiting in the soil.
I calculate that wolf biomass ranges only between 0.15 and 0.52 per cent of prey biomass, based on studies in Alaska (interior and southcentral), Minnesota, Michigan, and northcentral Canada reviewed by Wisconsin biologist Lloyd Keith. Even the wide swings in moose and wolf numbers reported by Rolf Peterson for Isle Royale National Park in Lake Superior between 1965 and 1988 changed the ratio of wolf biomass to prey biomass only from 0.46 to 0.58 per cent. These figures mean that one 34-kilogram (75-pound) wolf needs between 5,900 and 22,700 kilograms (13,000 and 50,000 pounds) of prey on its range each year. In terms of actual animals, a single wolf must share the land with between 14 and 55 moose, or 86 and 333 deer, to assure it gets the fraction of that needed to stay alive.
This analysis implies that food abundance is of overriding importance to wolf numbers. It is, but only when all else fails. A wolf population may be limited by some other components of environmental resistance. Disease may intervene, or social factors may prevent its increase, even in the presence of abundant prey. Or humans may be lowering wolf numbers. In all the studies quoted except Isle Royale, wolf populations were exploited to some extent by humans.
Wolf dominated systems are not unusual in showing low predator biomass relative to their prey. On the rich Serengeti Plains of East Africa, the biomass of predators is only 0.33 per cent of their prey. Paleontologist Robert Bakker concluded that the average biomass ratio of all modern predatory mammals to their prey is 1 per cent or less (three or four times less than the ratio in predatory dinosaurs).
Nature’s economy is set lean. Behind all the greenery are populations of large carnivores such as wolves adjusted low, living near biological bankruptcy.
BIODIVERSITY is the multicoloured fibre in the tapestry of an ecosystem, each species a thread. Woven so intimately, each thread loses individual identity in the form and character of the fabric. Texture is physiography — rugged, wrinkled, warped, faulted, thrown up in rock ramparts, smoothed by glaciers down to the water’s edge. Patterns emerge, if you stare at the tapestry long enough, from the order imposed on biodiversity by trophic webs and forest succession and species interrelationships.
The tapestry in northwest Algonquin Park differs dramatically from that in eastern Algonquin, because one dominant thread is missing — white-tailed deer. Deer threads were there thirty years ago, but they faded. Nature keeps tearing out and reweaving, experimenting with colours, altering patterns, inventing new designs.
We wanted to see how species relationships adjusted in the absence of deer. We were interested in the different patterns the wolf threads would form and, with them, the associated strands of moose, maples, aspen, beaver, and other species with a stake in the large mammal system. Would wolf packs be larger where their prey was predominantly moose? Would pack territories cover more land, adjusting to the lower biomass of ungulate (hoofed mammal) prey? Would wolf mortality be greater when tackling a larger prey? And if so, were any useful evolutionary messages hidden there in the northwest among the high hardwood hills?
Mary and I stuck with the northwest for much of two and a half summers, 1988 to 1990. Student crews took over at times, but we liked to swim in the rapids of the Amable du Fond River and dip water from a particular spring that welled up under a big yellow birch beside a logging road. It was exhilarating dodging the logging trucks there, avoiding the “crazy Frenchmen” driving like hell from the nearby town of Mattawa to the logging cuts in the early morning. Often we were coming the other way, bleary-eyed from lack of sleep after radio-tracking all night. Park officials later required us to equip ourselves with CB radios and issue warnings of our location every half-kilometre, just like the loggers do. Traffic control, even in the wilderness!
We also liked a particular beaver pond full of dead standing trees where we could watch moose any time, and where the biomass of moose exceeded that of any place we knew. Moose tracks made the sandy flat on the pond’s east side look like a gridiron after a game, and the balsam firs around the pond’s edge, pruned from moose browsing, met the standards of a formal garden. Usually, there were wolf tracks too.
Over these summers we managed to collar six wolves. Others tantalized us with their howls and tracks, first here, then there. It was a game, and often we were left thinking that they were studying us. In the end, which occurred surprisingly and suddenly, they donated some good data.
Kiosk is a near-abandoned ghost town along the then-active CNR railway, a few kilometres inside the park in its northwest corner. Mary and I first moved into the Kiosk area the summer after capturing the Nahma wolf, after that year’s riot of birdsong dropped off to only red-eyed vireos singing among the maples on the ridges, after the peepers and treefrogs packed it in for the year. From Kiosk, a circulatory system of both logging roads and canoe routes fan out to the south. We set up camp at the far end of Kioshkokwi Lake, by the rapids, where the tannin-laden waters swirl across big, water-smoothed rocks on their fall into the lake.
Immediately on the very first night, the wolves fed us some false data that took us the rest of the summer to untangle. A worn-out, long-forgotten logging road that we called the Fassett Creek road ran west almost to the northwest corner of the park. Out at the end of it we began our first night’s howling. Waiting for darkness where alders had finally reclaimed the road, watching a pair of olive-sided flycatchers swoop from spruce spire to spire, suddenly we became aware of wolf howls floating to us over the gurgle of a stream. We walked up a bank, waited fifty minutes, and howled back. They gave us a response loud enough for an accurate compass bearing.
The human ear is poor at measuring d
ecibels, but accurate in determining direction. Mary and I both take compass bearings while wolves howl, and rarely do we differ by more than five degrees. Because wolves may howl at any time, day or night, our advice to our crews is that they always wear a compass.
This pack was north of us, but we could not plot a bearing on the map because we were not exactly sure where we were. We entered in our notebook: “22 degrees from somewhere.”
After dark we began the drive back to camp, stopping every kilometre to howl. Wolf answers are classical examples of stimulus-response behaviour, well studied in the field of animal ethology and human psychology. An undefined drive to respond, called “action specific energy,” is drained away by the animal’s response, called the “consummatory act.” Action specific energy might be compared to the water in a flush toilet. The act of flushing is the consummatory act that can’t be repeated until the energy builds up again — or the tank refills. We normally wait at least half an hour before trying for a cross-bearing from another location.
A response of this type is a reflex action. Wolves benefit enough from howling for it to be favoured by natural selection. From my master’s research, we learned both that individual wolves have characteristic harmonically related overtones in their howls that can serve to identify them, and that wolves can distinguish among these overtones more accurately than humans. Therefore, individuals probably recognize one another’s howls, an advantage for pack animals often separated from one another. Wolves can pinpoint the source of the sound from a distance of well over two kilometres, as shown by the frequency with which they come to the exact place we howled. We also know that excited wolves howl at a higher pitch than normal. Group howls seem to be a spontaneous combustion of excitement, with wolves running around or grouping and jumping together, tails flicking. Undoubtedly there is a lot more encoded in howls known only to wolves.
What wolves think when they hear humans howl is unclear. Often they may respond as a reflex and not think, but other times they clearly do. They come to investigate, sometimes howling back first but often arriving silently. We know this from the increasing signal strength of those wearing radio-collars. That happens between one-third and one-half of the times. Then we are a temporary disturbance, probably of little consequence. Wolves discover us, then leave to continue whatever they were doing.
When humans howl near dens or rendezvous sites in the spring or early summer, however, they may cause a pack to move out, carrying the pups with them. We rarely howl in spring now, unless we know the alpha-female is not present, and we conduct fewer general howling surveys at that season. Instead, throughout the summer, we camp near known rendezvous sites and monitor spontaneous howling.
People travelling in Algonquin, or any wild environment, should consider the immensely more rewarding experience of hearing wolves howl spontaneously without the nagging fear that by howling themselves they have intruded into the wolves’ world. The costs-benefits of howling as a research tool, used when necessary, differ from those of recreational users.
Exactly at midnight on that first night of searching along the Fassett Creek road, we heard wolves again, pups too, closer than before. In our notebook we jotted down 138 degrees from wherever we were, but this time we had just passed an old portage sign so we had a clue.
Never having located more than two packs in one night, so buoyed by success, we continued past our camp. It was wrapped in a light mist from the cool air. If we waited another night to finish covering the area, we could not be sure of the separate identities of packs we heard that may have moved. At 3:55 A.M., we scored the hat trick. By the time we had taken our three cross-bearings, the thin light of day was washing out our headlights.
The following afternoon we puzzled over the topographic map and our notes. Periodically the night before, we had tried to figure out our location from the stars. When we plotted our course, we found to our chagrin that the Fassett Creek road had taken a 180-degree turn in its first few kilometres. After identifying the creek where we had heard the first pack, and the portage where we had heard the second, and drawing our compass bearings on the map, we found they crossed!
Our hat trick was rescinded. The first two packs were the same.
Realizing we could approach the pack from Fassett Creek itself, that evening we drove back to the portage and unloaded our canoe. Fassett Creek meanders out in wide sedge flats with hills rising in the distance. Escorted by myriad mosquitoes, we paddled and poled our way downstream.
The calm air was burdened with light mist. A few hermit thrushes and a white-throated sparrow sang now and then, without vigour because the season was well advanced. We encountered a series of beaver dams that forced us to climb out on each side of the canoe and hoist it across. A moose heard us coming and beat a sloshing retreat to high ground.
In the gathering dusk we waited for the wolves to howl, but they were silent or not there, so after a while we gave a couple of howls ourselves. A lone wolf answered from back in the hills to the west with a series of remarkable treble-pitched howls, each starting with a half-bark. When the wolf stopped, all we could hear was mosquito-hum as before.
We manoeuvred the canoe into a backwater and sat quietly to see if the wolf would investigate. The thrushes fell silent, and the first stars appeared. Fifteen minutes later the wolf howled again with its unusual treble howl, this time much closer, halfway between us and the shore. The tall sedges and grasses completely hid us, and the gentle air currents were not flowing the wolf’s way.
Three minutes of silence, then almost on top of us, the wolf howled again. We could not see it. By then it was too dark, and to shine the flashlight over the grasses would have meant standing up and becoming visible. So we sat there, breathless. In a minute we heard the wolf in the water, then all was silent.
Five minutes went by before the wolf howled again. It had swum the creek and was on the far side, halfway to shore. Having finished its reconnaissance and discovered the fraud, it launched into a long series of bark-howls. On and on it howled. Finally, its protest over, it disappeared into the night.
We were to hear that wolf with its distinctive voice again. Meanwhile, we found another pack the very next night, ten kilometres to the east, almost between the two-for-one pack that we had named the Fassett Creek pack, and the pack we had heard later that first night that we called the Ratrap Lake pack.
This new pack howled for us near the head of a deeply incised creek valley. The wolves had left plenty of tracks in an abandoned gravel pit nearby. Because we were uncertain of the pack’s identity, and because it was wedged in an unusually small area between the other two packs, we gave these wolves only the temporary name Gravel Pit pack.
For weeks, we tried to catch wolves from all three packs — Fassett Creek, Ratrap Lake, and Gravel Pit — but they were elusive. More than once they investigated a trap set, walked all around it, and left. By late summer, when cicadas droned in the hills and the long-horned grasshoppers fiddled nightly from the meadows, we suddenly realized from our field notes that while we had occasionally heard the Ratrap and Gravel Pit wolves on the same night, never had that happened with the Fassett and Gravel Pit wolves. We had no confirmation that these were separate packs.
The wolves kept their identity a mystery until the last night of the summer. Then, just after midnight, from the edge of a bog three kilometres east of the gravel pit, we heard the same treble voice and bark-howl. It was the Fassett Creek howler well inside the Gravel Pit territory. Its presence there indicated that the Fassett Creek and Gravel Pit packs were the same.
We reinterpreted our data in light of this discovery and were surprised to learn that a whole pack, pups and all, would have moved ten kilometres between Fassett Creek and the gravel pit in mid-July when the pups were so young. Even more surprising was that they had repeated the trip. Maybe they were travelling back and forth to a moose carcass. We found a well-used game trail with wolf scats along it that led from the gravel pit south to a series of mars
hes and bogs that in turn ran west towards Fassett Creek, but our searches turned up no dead moose.
The Fassett Creek and Ratrap Lake packs had yet another surprise, and one disappointment, in store for us. In late August, Mary and I caught and radio-collared a wolf near the gravel pit that we took to be a member of the Gravel Pit pack. We were elated, hoping we could work out winter movements and territory boundaries. But it died in early October. Graham heard the collar on mortality mode and tracked it beyond the boundary of the park. He found it beside a lake, its body only a pile of fur, too decayed to determine the cause of death.
In early September, however, a student crew that had taken over our trapline caught a Ratrap wolf not far from Ratrap Lake. That wolf did give us winter data. Once, Graham and Jenny saw the pack from the air, feeding on a moose at the edge of Manitou Lake. Surprisingly, the lake was well within what should have been the Fassett Creek pack’s territory. In later flights, Graham often located the wolf that far west. Repeated flights looking for the tracks of a different Fassett Creek pack turned out negative.
Our final interpretation was that Fassett Creek and Ratrap Lake packs were the same, but there had been two breeding females and two sets of pups. That happens in wolf packs sometimes, as other studies have shown, but we recorded it rarely. It is unclear why at times the social hierarchy in wolves permits it. In our population, experiencing high annual mortality as we discovered later, perhaps it was uncommon because vacant land was often available.
So, our three packs in one night shrank to two and finally to one. Still, its territory was only average size, 125 square kilometres (plus about 50 per cent for interstices between packs — land they undoubtedly used but where we lacked data points for sampling reasons). With few deer to supplement their moose-meat winter diet, hunting often must have been hard.
Wolf Country Page 4
