ROADS, RAILS AND GRIZZLY BEARS IN THE BOW RIVER VALLEY, ALBERTA
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The Bow River Valley is one of the most developed landscapes in the world where grizzly bears persist. Since 1994, the authors have recorded over 5,000 radio locations for 51 radio-marked grizzly bears in the Central Canadian Rocky Mountains. The authors present preliminary findings on some aspects of how roads and a railway influenced these bears' movements and behavior. The results suggest that the Trans Canada Highway in Alberta, with its high traffic volume, both inside and outside of Banff National Park, is a barrier to female grizzly bear movement, and a significant filter to male movement. This has occurred despite the construction of 12 underpasses in previously fenced sections and another 10 underpasses and two overpasses along the recently fenced section of the highway in the Park. In contrast, eight females have crossed two-lane, secondary highways in other portions of the study area. Three of these females regularly crossed secondary roads. These secondary highways, in contrast with the Trans Canada Highway, have low traffic volumes during evenings, night and mornings. All three females that crossed the secondary roads were habituated. This raises another problem. Over 80% of 118 recorded grizzly bear mortalities in Banff National Park between 1971-95 were within 500 m of a road. The authors show why certain grizzlies are attracted to near road environments. Most grizzlies, especially long-term survivors, avoid them. Clearly near road environments cause grizzly bears to make difficult choices with little opportunity to learn successful behaviors if they die in the process. This has obvious implications for successful use of highway crossing structures built to mitigate the adverse effects of recent upgrading along sections of the Trans Canada Highway. The authors conclude there is a dynamic tension between road avoidance and attraction.