The Problem of Mountain Bikers

A new report, shown at right, provides perhaps the best available assessment of the impacts of mountain bikers on grizzly bears as well as the hazards to mountain bikers of recreating in grizzly bear country.


Mountain bikers occupy a conceptual middle-ground between pedestrians and people on or in motorized transport. They do not employ noisy mechanized equipment that potentially gives advance warning of their progress, but at the same time they move at potentially high speeds. Unlike people enclosed in hard-sided mechanized vehicles, but like people riding off-road-vehicles (OHV) or on foot, they are exposed to the risks of physical injury from an attacking grizzly bear. Given these provisos, mountain bikers qualify for extrapolation of the results in this report, primarily because of their comparative silence as well as vulnerability.   


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Emblematic of these basics, Brad Treat was killed by a grizzly bear in June of 2016 after essentially colliding with the bear while he was traveling at high speed on a mountain bike along a trail with limited visibility. This incident elevated the profile of risks for both people and bears posed by mountain biking, although a number of similar incidents had highlighted the hazards of mountain biking in Canada as much as 20 years earlier. Concern about risks were also magnified by the fact that mountain biking is becoming more popular in areas occupied by grizzly bears, reflective of the 28% increase nationwide in this activity during the last 10 years.

The few investigations of encounters between bikers and grizzly bears paint a stark picture. Data pooled from all of these reports show that 87% (± 4.6%) of all documented encounters were at distances less than 50 m, and that 52% (± 10%) involved females with young. Of these close encounters, 89% (± 6%) resulted in the biker either being approached or charged by the involved bear. Not surprisingly, of the 41 encounters described by bicyclists interviewed by Matt Schmor, bears were described as being “startled” during 66% of them.

These risk-related figures are far in excess of the averages for other activities by people on foot. The percent of encounters that elicited some kind of aggressive response from involved bears is an astounding 14-times greater for mountain bikers compared to for pedestrians. Even if, compared to pedestrians, a greater number of “encounters” went undetected by mountain bikers, this alone would not account for the magnitude of this disparity. Moreover, the obvious heightened reactivity of bears to mountain bikers is not surprising given that average encounter distances were closer for bikers compared to the average 70-90 m involving pedestrians—and well within the Overt Reaction Distance (ORD) of most grizzly bears.


These results are not unexpected. As Jake and Stephen Herrero noted nearly 20 years ago, mountain biking is a perfect recipe for hazardous close encounters with grizzly bears given that bikers are often traveling silently at comparatively high speeds (11-30 km per hour), which increases the odds of rapid closure prior to detection along with amplified reactivity among even highly tolerant bears. This same point has subsequently been made in several assessments of hazards posed by mountain biking in grizzly bear habitat.


The disproportionately large number of encounters between mountain bikers and female grizzly bears with young is also not surprising. If a person is approaching at high speed, solitary bears are plausibly better able to detect the approach and leave before being seen. By contrast, females with young are predictably challenged and delayed by marshalling their offspring before being able to depart, even if they detect an oncoming bicyclist at a distance. The plausible outcome is an encounter at close range with a highly reactive female grizzly bear mobilized in defense of her young. 


The flip side of this dynamic between mountain bikers and grizzly bears is the likely short- and long-term impacts on involved bears. Greater immediate reactivity on the part of bears almost certainly translates into more rapid and sustained subsequent flight, along with longer-term energetic and physiological costs associated with impaired foraging, increased movements, and displacement of activity to suboptimal times of day.


The weight of evidence unambiguously supports concluding that mountain biking is far more hazardous for involved people and more impactful on affected bears compared to any other pedestrian activity with the exception of hunting. Given this perhaps self-evident verdict, it is not surprising that Parks Canada seasonally or permanently closed trails to mountain bikers several years ago in areas where chances of hazardous encounters were high (for example, the Minnewonka, Mortaine Lake Highline and Bryant Creek trails).

To download the report, clink on this link or click on the image above. For a brief overview of this information, see this video

A New Paper Shows The Disproportionate Impacts of Mountain Biking

Naidoo Burton_2020_Impacts mountain bike

Click on the image above to download the publication

This from the Abstract of Relative Effects of Recreational Activities on a Temperate Wildlife Assemblage by Robin Naidoo and A. Cole Burton, published in the journal Conservation Science & Practice:

"Across 13 species, only two negative associations between recreational activities and wildlife detections were observed at weekly scales: mountain biking on moose and grizzly bears. However, finer-scale analysis showed that all species avoided humans on trails, with avoidance strongest for mountain biking and motorized vehicles."