Skip to content | Skip to institutional links

Common menu bar links

Banff National Park of Canada

Park Management

Trans-Canada Highway Twinning

The Banff Wildlife Crossings Project Report, 2002

RESEARCH

WILDLIFE MOVEMENTS ACROSS THE ROAD

Why Do Animals Choose to Cross at Certain Crossing Structures?

Phase 1 & 2 wildlife underpass analysis

Results from an analysis of phase 1 and 2 underpass use suggest that not all wildlife respond the same to the different underpass features - structural, landscape and human-related. But human influence consistently ranked high as an important factor affecting how wildlife use the passages.

Carnivores (black bears, grizzly bears, cougars, wolves) used underpasses close to drainages or riparian areas, whereas ungulates avoided them. Underpass dimensions had little effect on passage, because animals may have got used to the 12-year old underpasses. Once the animals adapt to the structures, human activity and landscape patterns may play a bigger role in determining how wildlife use the passages rather than the dimensions themselves.

Our results indicated that the best-designed and landscaped underpasses might be ineffective if human activity is not controlled.

Our findings suggest that in a national park such as Banff, the most efficient and probably economic approach to making the structures more effective is to manage human activity near each underpass.

Phase 3A wildlife crossing structure analysis

As a sequel to the above underpass study, we examined a completely new set of underpasses and overpasses (Phase 3A) which animals had little time to become familiar with. Contrary to earlier findings, our results suggested that structural dimensions best explained passage for both large carnivores and ungulate species, while landscape and human-related factors were not as important. Passage by grizzly bears, wolves, elk and deer tended to be at wildlife crossing structures that were high, wide and short in length. Black bears and cougars, however, favoured the opposite - more constricted crossing structures. The patterns we observed match the evolved species behaviours and life history traits, e.g., some species preferring open areas whereas others needing cover.

Our findings underscore the importance of:

(1) Looking at how species change their behaviour in using the crossing structures over time and space, and

(2) Looking at the responses of multiple species because each species responds differently to crossing structures.

Results from these two studies suggest that mitigation strategies need to include human use management and be implemented in the area around the crossing structure as well as the broader landscape, to ensure that crossing structures remain functional over time.

Continuous long term monitoring of crossing structures is needed to capture variability in wildlife populations and therefore reliably determine the strengths and weaknesses of design characteristics for multiple wildlife species.

Cougar (Puma concolor) use of wildlife crossing structures.

In another analysis, we looked at wildlife crossing structure use by a single species using different measurements and analytical techniques. Cougar passage was higher than expected during winter and less than expected during summer. Wildlife crossing structures that received the highest numbers of cougar passages were those located close to high quality cougar habitat. We found the crossing structures were effective for cougars since they used them regularly providing connectivity between habitats on both sides of the highway.

For more information see Chapter 3 in Final Report

How Do Small Mammals Get Across the Highway?

Drainage culverts are common structures in road corridors, yet little is known about whether wildlife use them and whether they provide safe passage and connectivity for terrestrial wildlife. We investigated culvert use by small and medium sized mammals along roads in Banff. During two winters we monitored a variety of culvert types, varying in dimensions, habitat and road features.

We found traffic volume, noise levels and road width were highly important factors affecting culvert use. Passage by American martens, snowshoe hares and red squirrels all increased with traffic volume, the most important variable. Coyote use of culverts decreased with higher traffic volumes. Increasing noise and road width appeared to be negative influences on culvert passage by coyotes, snowshoe hares and red squirrels.

For many small and medium sized mammals, common drainage culverts can help to minimize the potentially harmful effects of busy transport corridors by providing a vital habitat linkage across roads.