TransCanada Highway

Performance of Current Fences and Wildlife Crossing Structures

Though not perfect, these measures have been quite effective in lessening the impact of the highway on wildlife. The fence has reduced the mortality of all species on the road dramatically, in excess of 80 percent, with a reduction of 97% in mortality for ungulates.

On the first phase, it was found that coyotes could dig under the fence and get on the road, so later sections included a buried apron which has largely solved this. The existing and planned fences are not perfect barriers. Small animals can still pass through the fence mesh. Cougars and black bears can and do easily climb the wooden fence posts. (Unclimbable metal posts are significantly more costly.) Finally, the fences require frequent maintenance, as they gradually degrade, and may be knocked over by the elements, falling trees, or vehicles gone astray.

Wildlife underpass at Healy Creek (15 m wide)

It is the good performance of fencing which dictates the need for wildlife crossing structures (WCS's). Without WCS's, the combination of road, traffic and fences would form an almost absolute barrier to wildlife movement, preventing individuals from making optimal use of habitat, and fragmenting and isolating populations and communities. Well-functioning crossings are therefore essential to long-term health of individuals, species, biological communities, ultimately the ecosystem as a whole.

Wildlife overpass at Redearth Creek (50 m wide)

The 23 WCS's which currently exist in Banff on the TCH1 have been monitored for their effectiveness since their construction. Monitoring has entailed regular checking for footprints on sandbars (which cross each structure for this purpose) and by electronic means. Researchers are now collecting hairsnags to collect DNA for more detailed analysis of animal use of the structures.

This research2 has yielded some valuable, if preliminary, insights into the factors leading to successful and functional WCS's. Some findings:

1. Structures are best located between patches of high quality habitat. Because different species have different habitat needs and preferences, a variety of locations is necessary to serve a variety of species.
2. Different species prefer different types of structure design. This tends to correspond to species’ general behaviour and habitat preference. For example, cats, such as cougar and lynx, which live in closed forests, prefer smaller closed structures. Species which live in more open environments, such as grizzly bear and elk, prefer overpasses and large structures. This means that a variety of structures is important, and that the combination of structures ought to be designed for the species prevalent in the region.
3. Despite the above, larger structures tend to get more use by a wider range of species than smaller ones.
4. Human use of WCS's is a major deterrent to animal use. WCS's should not be seen as dual use, and special separate provision should be made for human crossings.
5. It takes time for animals to find and learn to use the structures. For example, elk used the WCS's early, but it took several years before a grizzly bear crossed. Grizzly crossings are now fairly common. Again, this happens at different rates according to the wariness of species and individuals. (Only one species has not yet been found to have used the structures at all: wolverine, the behaviour of which little is known.) As well, it takes time for vegetation cover to take hold on structures. The evaluation of structures should not be based on short-term results.

Notes :

Back to Top
Return to Previous menu