Wildlife Ecology of western Canada and the Canadian Rockies

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For many visitors to the Rockies, images of grizzlies wandering the high country and elk roaming the townsite leave a lasting impression. The Canadian Rockies is sold as a Mecca for wildlife watchers and animals alike. The reality is slightly different. The Rockies present an unforgiving landscape which limits entry to those animals that are able to tolerate the challenging climate and nearly vertical landscape. There are those animals that seem to be uniquely adapted to the mountain landscape, like the mountain goat and grizzly. Others seem able to tolerate the difficulties imposed by the landscape although they lack any adaptations specific to the mountain environment. For instance, mule and white-tail deer are hampered terribly by even shallow snowpacks. It takes only a small amount of snow to force deer into a bounding gate, which has costs in terms of increased energy expenditures. By yarding up, or staying in small herds and creating regularly traveled pathways, they can help to reduce the challenges of breaking trail.

Elk - Click to Read MoreDespite the hardships these animals and birds endure, the mountains are home to a great variety of species. The trick comes in learning their habits, food preferences and seasonal movements. By taking the time to become familiar with the animals and birds, the chance of spotting some of the more elusive residents is increased exponentially. Despite many claims that most wildlife is nocturnal, this is the exception rather than the rule. Dawn and dusk forms a unique compromise between availability of food and protection from predation. This knowledge alone can ensure that would-be wildlife watchers are out at the right time.

Understanding the wildlife of the Rockies requires patience and persistence. Many animals food preferences change throughout the course of the year, and their location will reflect the availability of these foods. While grizzlies may be partial to avalanche slopes in the spring and early summer, the lure of buffaloberries in the fall will often draw them to the margin of highway and hiking trails, locations where these berries are plentiful. With increased understanding, comes a greater respect for the majesty of the animal and the fragility of the landscape they call home. For any avid wildlife watcher, concern over habitat destruction and increased development is essential. It is incumbent upon this generation to ensure our children have the same opportunities to see wildlife.

Struggling To Survive In A Harsh Landscape

It is a simple equation, animals need habitat to survive. The Rockies offer a combination of ruggedness mixed with a unique collection of landscapes, food sources and climate. The Rockies contains many habitats, most of which have already been discussed earlier in this text. Some animals thrive in the Montane, competing with tour buses and townsites for this limited resource. Others, like mountain goats, eschew the valleys for the freedom of the hills. In order to maintain a healthy ecosystem, it is critical that sufficient habitat, of all types, is protected. The combination of area of land mixed with the quality of habitat will determine a locations carrying capacity. An extensive track of poor quality habitat may be able to support fewer individuals than a smaller area of high quality habitat.

The quality of habitat is not easily measured, and is determined by many factors, some tangible and some less so. For instance, the boundary between two habitats often supports a mixture of species representative of both. This boundary region may be quite extensive, as in the foothills (the boundary between mountain and plain). The increased diversity is usually reflected in an increased productivity

Habitat quality is also affected by disturbances. Forest fires are a normal part of the mountain landscape, but individual fires vary in their impact, extent and in the amount of time the landscape requires to repair the damage left behind. Small fires, such as the prescribed burns lit by the Parks Service, are often quick to respond with vigorous new growth and rapid regeneration. Within a few years, the fire site is exploding with food plants for many animals. On the other hand, in areas that have not had fire for many years, the build up of fuel may result in a very hot, and very extensive fire. In these cases, the soil may be damaged, the seeds of lodgepole pines may be burned and even the underground root system of the aspen may suffer. Such a fire will take much longer to regenerate and the quality of habitat will reflect this slower healing.

How humans interact with the landscape also impacts the quality of habitat. The building of townsites has produced extensive tracts of prime elk habitat, while at the same time adding stress to animals like the grizzly bear and cougar which must move around the periphery of the townsite when traveling to adjacent habitats. In some cases, the worst impact may simply be the removal of land from production by increased development. Communities like Canmore, which is booming at an unprecedented rate, is taking more and more land out of production annually. Growth management strategies and increased pressure from environmental groups are the only hope for rapidly shrinking habitats adjacent to this thriving townsite.

For most species, there are critical habitat which must be maintained, in order to ensure the viability of each species. Critical habitats may become even more important during sensitive times of year. For instance, without adequate winter range, a healthy summer range may be irrelevant. The size and quality of these critical habitats will act as a primary limitation on population size for those animals depending upon them.

Since a landscape changes over time, the importance of a particular location will also vary. A single site may vary from open aspen groveland where browsers like elk and deer abound, to dense spruce forest which offers these same animals little edible incentive to remain. Think of a particular habitat as an ever-changing, evolving world. As one area of new growth ages, ideally new areas of new growth will be produced due to disturbances like fire. In this way, the ratio of habitats is maintained and the carrying capacity of the total landscape preserved. 

Factors Affecting Population

Carrying capacity is one critical factor affecting the population of a particular species, but there are many other factors at play, most of which are completely independent of location. For most populations, there is a threshold at which point the population is no longer viable. When numbers drop below this threshold, the rate of birth is no longer sufficient to replace those individuals lost to death or migration. In the Bow Valley, the Bow Valley pack of wolves has been teetering on the brink for several years. As of this writing they are holding on, but the future looks bleak. On the other hand, the Cascade pack seems to be maintaining viable numbers.

It is not as simple as calculating birth and death rates to determine whether a population will survive. Birth rates and death rates are not independent activities, but are often altered by external factors. In bears, the failure of their principle autumn food, buffaloberry, may result in short term reductions in birth rate. Reduction of this critical food at a critical time reduces the bears ability to successfully produce cubs. For decades, the reproductive success of many of our birds of prey was compromised by the effects of DDT use. This pesticide would accumulate in their blood streams and reduce their ability to produce strong shells. When they laid eggs, the simple act of incubation would often result in broken eggs and lost reproductive opportunities. For some animals, a few years of poor reproductive success could threaten the viability of the entire population. For animals like bears which are not prolific producers, it may take several years to replace a year of reduced birth-rate compounded by a few highway fatalities. However, bears also have certain advantages. They mate in the spring, and carry the fertilized egg in the uterus for up to six months. Come autumn, if they are healthy, only then will the egg implant in the uterus and develop. This gives them, along with weasels which have a similar strategy, to more directly alter their birth rate based upon the current conditions. Other animals, like ground squirrels produce large clutches. This enables them to more rapidly repair reductions in population.

When one thinks about mortality rates, the first thing that pops into mind is predation. A population of snowshoe hares is intricately connected to the local lynx population. As populations increase, the reproductive success of the lynx increases, which in turn will produce a subsequent increase in snowshoe hare mortality as these lynx reach hunting age. For animals like lynx, which depend primarily upon a single species, their mortality rate may also follow the availability of prey species. Highway mortality is another critical problem in the Rockies. Fences along major stretches of highway have greatly reduced the numbers of traffic fatalities along these stretches. On an average year, 70 elk die from car and train impacts in Banff National Park alone.

As a population becomes increasingly healthy, and the carrying capacity of the land is exceeded, the health of the population will drop, making the animals susceptible to disease and parasite infestations. Both will occur without overpopulation situations, but the resistance of animals is reduced at times of stress and it is during these times that the infestations will be most severe. Some parasites use an alternate host to facilitate infection. Bighorn sheep are the preferred host of a lungworm (Protostrongylus stilesi). The lungworm uses a land snail as an alternate host. These snails are ingested as the sheep feed, and the lungworm establishes itself in the bighorn.

Starvation is also an important component of the natural system. When the carrying capacity of a habitat is exceeded, perhaps as deer population boom, starvation is bound to ensue. Starvation may also occur simply at the end of a particularly difficult winter when fat reserves are depleted and fresh spring growth is not yet available. In many situations, it is not the starvation that kills the animal, but predators which recognize those individuals most weakened. In conditions of overpopulation, starvation may actually help the population. Since those animals most affected will likely succumb, starvation will result in smaller, healthier populations. It is a way for nature to reduce the population to more manageable levels.

One final factor affecting the viability of populations is dispersal. How well do animals move to new habitats and replace populations which may have been reduced by previous hardship. Recent studies of grizzlies in the Rockies have shown that the genetic diversity of the population has dropped over the last 10 years. This is in direct response to the population being increasingly stressed through development and tourism, and the subsequent reduction in the ability of bears to move freely. As a grizzly attempts to move from the Bow valley to the Spray valley, it must pass through a gauntlet of development. For biologists, the protection of these animal pathways is a priority. To facilitate this movement, Parks Canada recently spent $3,700,000.00 building two overpasses for its large predators along the Trans Canada Highway to the west of Banff Townsite.

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All Material Ward Cameron 2005

 

 

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