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Grizzly Bear Activity in Response to Traffic Volume and Road Densities

Contributing Editor Dr. Jordan Schaul reports on the first study to examine grizzly bear behavior in response to spatial and temporal variations in traffic patterns using traffic models.

In April, while filming a segment for the BBC series Dangerous Roads with actor Charley Boorman, I reported on the impact of roads on wildlife for Nat Geo News Watch.

Vehicle-wildlife collisions were of particular interest to the producers of the BBC television series.  For the Alaskan version of Dangerous Roads, a camera crew was deployed to follow Charley on a road trip from Anchorage toward Prudhoe Bay along the Seward Highway—one of the most dangerous highways in North America.

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The BBC stopped by the Alaska Wildlife Conservation Center on their trip north to visit with our staff and animals. They asked if we had any “statistics” on the number of orphans that had been brought to the Center as result of collisions with vehicles on the Seward Highway.  Indeed, we provided homes for moose calves, bear cubs and other wildlife, orphaned as a result of road incidents, but not all of the incidents occurred on that particular highway.  Hence, we couldn’t provide a valid estimate.

Grizzly and black bear cubs of the year and older cubs were often brought to our facility, particularly during Spring when offspring were just emerging from hibernacula for the first time or otherwise still dependent on their mothers.  Vehicle collisions either killed their mothers or left the sows in conditions that required they be immediately dispatched (euthanized).

Although a busy time for us, the implications stemming from such vehicle-wildlife incidents have great influence on the conservation of species worldwide, including here in North America where we are relatively adept at managing wildlife in the context of road interactions.

Data on vehicle-associated wildlife mortalities may or may not be astonishing, but wildlife conservationists consider road kill so much a threat to species survival that they have begun looking for solutions through an emerging discipline known as road ecology.

Some of our most iconic species succumb to road-associated incidents. In fact, some species like the woodland caribou are threatened more from road collisions than from habitat loss. And at one point when Florida panthers were truly on the brink of extinction, half of the extant population succumbed to vehicle collisions.

Roads present more than just the potential for dangerous interactions between vehicles and wildlife; they fragment habitat and restrict the movement of wildlife species.  Although, many wildlife management and transportation agencies have worked to mitigate vehicle-associated incidents with wildlife on our roadways, there is still much to learn about the ways in which wildlife interact with roads.

We do know that behavioral responses to roads can be species specific, age specific and even gender specific. We also know that behavior may also shift based on the time of day and season.

What does this all mean for the grizzly bear, since most grizzly bear mortalities occur near roads and current management programs aimed at protecting grizzly bears focus on limiting road densities?

While bears may use roads and roadsides to travel and are sometimes attracted to roads because of the presence of ungulate road kill and other attractants, they also avoid roads because of vehicular activity levels.

To adequately develop effective bear management programs, which have focused primarily on limiting road densities, an understanding of how bears respond to traffic volumes on the roads is also needed, according to a new study.

Although previous studies have used indirect indicators of traffic levels to assess bear activity on and near roadways, it is only recently that investigators have used more precise model estimates of traffic volume to examine the behavior of grizzly bears in response to vehicular activity.

Joe Northrup and his colleagues at the University of Alberta, Edmonton and the University of Calgary documented the response of grizzlies to vehicular traffic in a recent issue of the Journal of Applied Ecology (British Ecological Society). In the paper entitled Vehicular Traffic Shapes Grizzly Bear Behaviour on a Multi-use Landscape the authors noted that roads themselves are not so detrimental to wildlife, and grizzly bears in particular, but that the human use of roads is what needs to be examined.

The authors created models of road use for an entire road network in southwestern Alberta, Canada and documented for the first time the response of grizzly bears to a wide range of spatial and temporal traffic patterns. They hypothesized that “traffic would significantly influence grizzly bear habitat selection and movement near roads, and that bears would avoid roads with higher traffic volumes.”

What they found was that bears avoided roads with high and medium traffic volumes and instead used low traffic volume roads and crossed these low volume roads with greater frequency.  They also found that bears utilized private agricultural land over multi-use public land. The agricultural land was typically higher in road density, but lower in traffic volume.

Northrup said, “the finding that traffic had a greater impact on bear behavior than road density is an important for how we manage bears. Typically management plans focus on limiting road density, but with increasing industrial development in bear habitat, this is becoming difficult. Incorporating measures aimed at reducing traffic, such as access management, into these plans will be an important step for bear conservation.”