Banff National Park of Canada
Trans-Canada Highway Twinning
The Banff Wildlife Crossings Project Report, 2002
MONITORING OF THE WILDLIFE CROSSING STRUCTURES
Summary of Wildlife Use
There have been a total of 37,507 through-passes by wildlife at the 10 underpasses we monitor on phase 1 & 2 since November 1996 to November 2003. Elk were the most frequently detected species at the crossing structures, followed by deer, wolves, sheep and coyotes. Among large carnivores, wolves used the structures 2986 times, cougars 587 times, black bears 526 times, and grizzly bears 36 times. There have been 11,175 passages by wildlife at the 13 wildlife crossing structures on phase 3A since November 1997 to November 2003. Among large carnivores, wolves used the structures 254 times, cougars 197 times, black bears 166 times and grizzly bears 50 times. In the 71 months of monitoring 48,682 individual wildlife passes have been detected at the 23 crossing structures. In total, grizzly bears have used the structures 86 times, which is encouraging since the number of grizzly bears using the Bow Valley is low compared to other animals. We know from radio telemetry monitoring that adult female, adult male, and sub adult grizzly bears have all used the crossing structures. We also detected an unmarked adult female grizzly bearaccompanied by a cub using the Powerhouse underpass east of Banff.
Annual Wildlife Crossing Structure Use by Carnivores
From 1996 to present there have been fluctuations in the numbers of animals in the Bow Valley and likewise near the crossing structures. This has resulted in fluctuations in how we might expect wildlife to use the passages and how they actually end up using them.
Individual animals and populations also need time to adapt to newly constructed wildlife crossing structures. For example, each year large carnivores, (wolves, black bears, grizzly bears, and cougars) steadily increased their use of the wildlife overpasses after construction although cougar use declined in 2000-01 when the resident cougar population declined dramatically in the Bow Valley.
Chart showing frequency of wildlife overpass use by grizzly bears, black bears, wolves and cougars for each year of monitoring, 1997-2001.© Tony Clevenger
When Do Animals Use the Overpasses?
By taking pictures of animals with remote cameras as they crossed the overpasses, we had a unique opportunity to study wildlife species' daily patterns of overpass use. We would expect functional overpasses to provide a safe environment for getting across the bustling Trans-Canada Highway. Therefore we would also expect the time different species chose to travel on the overpass to match their normal activity patterns.
The time of day wildlife used the overpasses did appear to match what we know about these species' activity patterns in areas away from human-caused disturbance. Moose, elk, deer, wolves, grizzly bears and black bears tended to used them during the day. Cougars, snowshoe hares and martens used them more at night. Coyotes used the overpasses during day and night. The time grizzly bears crossed the wildlife overpasses coincided with when they crossed roads in our study area .
Chart showing what time of day moose, wolves, cougars, grizzly bears, and other mammals (snowshoe hares and martens) used the overpasses.© Tony Clevenger
Chart showing what time of day elk, deer and coyotes used the overpasses.© Tony Clevenger
Do Animals Prefer Wildlife Overpasses to Underpasses?
It is difficult to compare two different crossing structures because of confounding variables associated with each structure. For example, habitat type and dimensions associated with each structure may vary widely. By looking at structures that are close together we can eliminate some of the confounding variables. A close approximation to a side-by-side comparison can be found in Banff. An underpass is located within 200 m of each of the two overpasses.
When we look at the paired comparison of use, grizzly bears, wolves and all ungulates tended to use wildlife overpasses more than nearby underpasses, whereas cougars preferred underpasses, and black bears do not prefer one over the other.
Chart showing how frequently grizzly bears, black bears, wolves and cougars used overpasses compared to adjacent underpasses.© Tony Clevenger
For more information see Chapter 2 in Final Report
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