in the Canadian
Rockies
Bears and
Habitat
Bears and
Roads
Bears and
Science
Habitat
Connectivity
Bears and
Habitat
Human developments and activities such as roads, towns and agriculture can block animal movements and fragment the landscape. In an increasingly fragmented landscape, bears are forced to use smaller and smaller patches of quality habitat. It is essential that bears maintain the ability to move between these habitat patches in order to fulfill daily and seasonal needs. This ‘habitat connectivity’ is, therefore, critical for ensuring the long-term persistence of bears and many other species. While the following research resources refer mostly to grizzly bears and habitat connectivity, the findings are also relevant to black bears.
Why is connectivity
important?
Individual level
In order to meet requirements for feeding, mating,
denning and dispersal, grizzly bears in the Canadian Rockies have very
large home ranges. The Eastern
Slopes Grizzly Bear Project has reported average
male home range sizes of 1172km2 (maximum up to 2910km2). (Herrero and Gibeau 1999)
Preliminary results of the Foothills
Model Forest Grizzly Bear Research Project show female home
range sizes of up 513km2. (The Jasper Booster,April
26, 2000)
Loss of connectivity can significantly affect individual grizzly bears by reducing their ability to efficiently exploit resources within their home range. This can eventually result in compromised reproductive success if: adult males are limited in their ability to access adult females or if adult females fail to build sufficient fat reserves for embryo implantation and development.
Population level
Reduced habitat connectivity can
have significant implications for long-term bear conservation if it
results in regional populations becoming cut off, or isolated, from one
another.
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isolated populations experience little/no emigration. This results in a decreased ability to respond to short- and long-term changes in their habitat (e.g., changes resulting from a forest fire, or from climate change). (Ministry of Environment, Lands and Parks, British Columbia 1995)
- isolated populations experience little/no immigration. (Ministry of Environment, Lands and Parks, British Columbia 1995) Relatively small, isolated populations eventually show reduced genetic variability which is “generally regarded as important in maintaining high levels of fitness and [which] allows for adaptation to a changing environment.” 26
- preliminary results of DNA analysis of grizzly bears in the Central Canadian Rockies “raise concerns about the connectivity of the population as a whole and certainly questions the long held belief that grizzly bears freely move up and down the length of the Rocky Mountains.” 27
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isolated populations and populations that exist along “the fringe” of the species’ distribution in North America are especially vulnerable to the negative impacts of human developments and activities.
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“It is likely that small populations that are isolated due to human presence around the perimeter are increasingly susceptible to being extirpated because they have a relatively large fringe for the area of occupied habitat and it is along the fringe that bears often experience a higher rate of mortality.” 28
How can connectivity be
maintained?
A proposed strategy
Grizzly bear researchers and
land managers believe that existing parks and protected areas alone are
not sufficient to maintain grizzly bears. Reasons for this include:
-
most parks and protected areas are not large enough to maintain sufficient numbers for population viability. Also, many individual grizzly bears have home ranges that include areas inside and outside of parks and protected areas. (Ministry of Environment, Lands and Parks, British Columbia 1995)
- many were initially established to capture scenic or recreational wilderness values – they were not intended to represent a full range of ecological diversity. As a result, for the most part, these areas do not contain prime bear habitat and their boundaries do not reflect natural systems. (Ministry of Environment, Lands and Parks, British Columbia 1995)
- the more intensively visited parks such as Banff National Park, have levels of recreational developments and activity that currently threaten their protected status. (Gibeau and Herrero 1998)
Given these realities, land-use strategies that extend well beyond the borders of parks and protected areas have been proposed to conserve grizzly bears and their habitat. These strategies generally consist of the following components:
-
strictly protected core areas and linkage zones between them. Hunting and resource development would not be allowed in core areas and recreational activities would be managed with the needs of sensitive wildlife species in mind.
- surrounding regions that are carefully managed to allow regulated
resource development with minimal impacts on grizzly bears
(Herrero 1994, Mattson et al 1996, and Ministry of Environment, Lands and Parks, British Columbia 1995)
Other actions that are not directly related to habitat would also have to be implemented in order to make this strategy successful. These include educating people who live in and visit areas occupied by bears, and implementing strict garbage management.
Yellowstone to Yukon: a
vision for the future
The Yellowstone to Yukon
Conservation Initiative (Y2Y)
To accomplish its goal, “Y2Y is working to establish a connected network of protected areas and wildlife habitat linkages (often called corridors) that runs from the Greater Yellowstone Ecosystem in the south to the Yukon’s Mackenzie Mountains in the north. Such a system, combining the principles of conservation biology with local and traditional knowledge, will ensure long-term survival for such North American wilderness icons as the grizzly, wolf, caribou, salmon, wolverine and bald eagle.” 30
“Existing national, state and provincial parks and wilderness areas will anchor the system, while the creation of new protected areas will provide the additional cores and corridors needed to complete it.” 31
“The grizzly bear is a [flagship species] for Y2Y, in part because of its extensive habitat requirements. Studying these requirements will help to define the habitat network that is envisioned by Y2Y.” 32