Wildlife Ecology of western Canada and the Canadian Rockies
Wildlife Quick Search
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.
Despite 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