Grizzly bears are an iconic symbol of North American wildlife, but populations have faced large declines in the past decades. Most grizzly bear deaths occur as a result of human-bear conflict, typically poaching and self-defence kills. And what brings people and bears together? Roads.
A recent study found that 86% of grizzly bear deaths occurred within 500 metres of a road. This phenomenon is especially concerning because new roads are constantly being built for industry and recreation, encroaching deeper into bear habitat and thereby increasing the threat. Eliminating development isn’t realistic, but a better understanding of how roads affect grizzly bears can help us lower the risk.
Past studies have looked at how the distance to road, or road density, impacts grizzly bears. I researched grizzly bears’ risk perception and decision making process around roads. I asked: how can measures of visibility be used to better understand the effects of roads on grizzly bears? This is part of a growing field of sensory ecology, which attempts to better understand animal behaviour in terms of how they collect sensory information.
As part of Dr Nicholas Coops’ Integrated Remote Sensing Studio, I had access to fine resolution landscape data collected from drones and satellites. I used that to build detailed models of areas where roads are visible (viewshed). The availability of airborne LiDAR (light detection and ranging) data – which provides a variety of information, such as topographic and vegetation, integral to accurate visibility modelling – was a key research tool. I used the viewshed model together with location data from GPS collars on grizzly bears in Alberta to assess their movement patterns and habitat selection.
My results showed that visibility was an important predictor of grizzly bear movement decisions, but their use of viewsheds depended on what type of activity they engaged in: resting, foraging, or travelling. While travelling, grizzly bears preferred areas where they could see roads. This supports the idea that they use roads as rapid travel corridors and visually orient themselves along them.
However, while resting or during intense foraging, they avoided areas visible to roads. Avoidance while resting suggests that grizzly bears link areas visible to roads with risk because wildlife typically seek out secure areas for resting. In contrast, perhaps the bears are willing to pass through riskier areas while transiting or searching for new habitat. While the reasons for this risk avoidance response was not part of my research, the behaviour may be associated with an increased likelihood of a negative human-bear interaction if the grizzly bear is visible from a road.
My study was conducted with support from fRI Research in Hinton, Alberta and Natural Sciences and Engineering Research Council of Canada, and partnerships with forestry, mining, and oil and gas companies. I conducted my research with the goal of providing information that could help inform natural resource management and landscape planning for grizzly bears and other wildlife.
For example, my research using vegetation data from LiDAR demonstrated the effectiveness of forest cover at blocking visibility. The Canadian forestry industry has adopted harvesting patterns that mimic natural disturbances to reduce negative effects on wildlife and ecosystems. Another outcome of the research is the reduction of visibility between roads and cutblocks. Vegetative buffers are already used to reduce visibility of cut blocks for aesthetic reasons, and may be effective to reduce risk (or at least risk perception) for grizzly bears and other wildlife that suffer from encounters with people. Visual cover may allow humans and grizzly bears to coexist in closer quarters without negative interactions.
By focussing on sensory information, my research emphasized understanding “the why” of animal behaviour. If we understand why, as well as how, wildlife respond, we can better plan for shared landscapes and coexistence well into the future.
Bethany Parsons is a recent MSc graduate of the Integrated Remote Sensing Studio with Dr Nicholas Coops. She can be reached at bethanymarieparsons@gmail.com.
