in the Canadian
Rockies
Bears and
Habitat
Bears and
Roads
Bears and
Science
Roads
and Railways as Barriers
to
Bear
Movements
Bears and
Roads
Roads and railways can present barriers to the movements of bears (and many other wildlife species). The barriers may be physical in cases where high-use roads create a near-impassible wall of traffic, or where they are fenced in an attempt to keep both people and wildlife out of the road corridor. The barriers may also be psychological in the sense that noise, smells, lighting, etc may deter animals from being near roads or attempting to cross them. Whether physical or psychological, the barrier effect of roads contributes significantly to habitat fragmentation.
Black
bears
Rob Serrouya conducted a study to assess the
permeability of the Trans-Canada Highway (TCH) to black bear movements in
the Bow River Valley area of Banff National Park. He compared the black
bear crossings of the TCH to three other parallel, linear features in the
Bow Valley: the 1A Highway, the Canadian Pacific Railway and the Bow
River. The following are selected results of the study:
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there is an inverse relationship between permeability and traffic volume. 1997 data show that 37% of radio-collared bears crossed the TCH less than expected, while only 13% crossed the 1A less than expected. Average daily summer traffic volumes that year for the TCH and 1A were 21 574 vehicles/day and 2 899 vehicles/day respectively.
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the TCH has a “filter” effect on black bears: they do cross it, but not as often as expected.
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learning to use wildlife crossing structures (under- and over-passes) is important: some individuals had learned to use them efficiently and frequently while others had not.
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for females, age/experience is a better indicator of permeability of the TCH than is habitat quality.
(Serrouya 1999)
Grizzly
bears
In five years (1995-1999)
of intensive monitoring of radio-collared grizzly bears in the
Central Rockies Ecosystem, no adult females were documented crossing
the Trans-Canada Highway (TCH). During this same period, 3 adult males and
2 sub-adult males crossed. However, only one of the adult bears made
regular crossings, and both of the sub-adults were habituated bears that
were ultimately removed from the population. These findings led grizzly
bear researcher Dr. Mike Gibeau to conclude that the TCH served as an
effective barrier for females, a filtered-barrier for males, and that
“significant potential currently exists for permanent habitat and
population fragmentation to occur along the Trans-Canada Highway.” 2
Gibeau also looked at landscape and human characteristics at highway crossing points and found that:
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total human access density (i.e., density of roads, hiking and biking trails, etc) around crossing points is a better indicator than is road density alone.
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high frequency crossing zones are characterized by: less than average total access density, closer to a major drainage, more rugged terrain, and higher quality habitat.
(Gibeau 2000)